The total count includes dead cells as well as living cells.
- What Are Some Advantages And Disadvantages Of The Serial Dilution Agar Plate Technique (3 Pts)
- What Are Some Advantages And Disadvantages Of The Serial Dilution Agar Plate Technique
- Advantages And Disadvantages Of The Serial Dilution Agar Plate Techniques
What is a physical or chemical procedure to destroy microbial life?
Where is the cervical cryotherapy procedure performed?
The procedure is usually performed in an outpatient setting. Read More
What is a surgical procedure performed on the pharynx?
Tonsillectomy is a surgical procedure performed on the pharynx. Read More
What is the medical term meaning procedure performed for definitive treatment of the principal diagnosis?
The procedure performed for definitive treatment of the principal diagnosis is called the _____________ procedure Read More
What procedure is performed to treat craniostenosis?
Craniectomy is a procedure performed to treat craniostenosis or to relieve increased intracranial pressure Read More
A procedure performed through the skin is called what?
Which procedure is performed last when installing a new motherboard?
When installing a motherboard, the procedure that is performed last is connecting the peripheral device. Read More
Did you have any discoloration or markings left on the outside of your nose after the procedure?
Please be more specific about the procedure. What procedure was performed? Read More
What is the type of procedure that is performed independently of and is not immediately related to other services?
What is aseptic technic and why is it necessary?
aseptic technique is the procedure in which work is done in microbial free environment and is necessary for the prevention of infections to the human beings e.g. doctor or patient or other hospital workers and to the microbiologist it is also done for preventing the contamination in microbial culture grown in laboratory Read More
When was the first liposuction procedure performed?
What procedure is often performed with laminectomy?
What procedure is often performed with a laminectomy?
When a laminectomy (removal of a lamina) is performed, an arthrodesis (surgical of joints) is also performed. Read More
What is an emergency procedure performed to gain access to the airway below the blockage?
The emergency procedure is called a tracheotomy. Read More
A colostomy is a surgical procedure performed on this structure?
A colostomy is a surgical procedure performed on the large bowel, an opening is made in the bowel which is sutured to the skin in the abdominal wall and colostomy ba Read More
What is a procedure commonly performed in conjunction with a pylorplasty?
Where can a colonoscopy be performed?
Colonoscopy can be performed either in a physician's office or in an endoscopic procedure room of a hospital. Read More
What procedure was performed by dr christian bernard?
He performed the first sucessful heart trans plant. Read More
Where is penile implant surgery performed?
The procedure is performed in a hospital with the patient under general anesthesia. Read More
Can septoplasty surgery be performed as an out-patient procedure?
Septoplasty surgery can be performed as an out-patient procedure in fact this is the normal. The surgery can last one to two hours and is done with general anesthesia. Read More
How does massage therapy work during a surgical procedure?
There is no massage therapy work that is performed during a surgical procedure. Read More
Where can the procedure of spinal fusion be performed?
A spinal fusion procedure can only be performed at a hospital with a specialized surgeon. Due to the risk involved with the surgery it is considered a last resort in the spectrum of possible treatments. Read More
When is a hysteroscopy not performed?
The procedure is not performed on women with cervical cancer, endometrial cancer, or acute pelvic inflammation. Read More
What does the word automated mean?
An action performed by automatic procedure. Read More
What is the medical term meaning procedure performed with a stethoscope?
How is Arthroscopy performed?
The procedure is performed by inserting a specifically designed illuminated device into the joint through a small incision Read More
Who performs femoral hernia repairs?
This procedure is performed by a general surgeon. Read More
What is the name of the procedure that is performed to check the intraocular pressure of the eye?
What procedure is performed if a radiopaque material is injected into the blood vessels?
What surgical procedure might be performed on a 40 year-old obese man to treat sleep apnea?
uvulopalatopharyngoplasty, or UPPP procedure. This procedure is performed to enlarge the airway by removing or shortening the uvula and removing the tonsils and adenoids, if present, as well as part of the soft palate or roof of the mouth. Read More
How is a tubal ligation diagnosed?
A tubal ligation isn't diagnosed..it's performed. It's a surgical procedure performed by a Gynaecologist. Read More
What procedure performed to examine and treat a portion of the digestive system?
Endocscopy is a common procedure performed to examine and treat a portion of the digestive system. In endoscopy, a 'scope' or camera is inserted into the digestive tract to examine its structures. Read More
What is a Loop electrosurgical excision procedure?
Loop electrosurgical excision procedure (LEEP)-- Cone biopsy performed with a wire that is heated by electrical current. Read More
How is arthoscopy performed on knee?
Arthroscopy of the knee is performed through a sophisticated procedure where a small scope is inserted into the knee joint in order to repair the damaged cartilage and other ligaments. It is also performed as a diagnostic procedure to rule out the other knee problems in the knee joint. Read More
What type of anesthesia would be most appropriate for a surgical procedure performed on a very small area of the body?
Local anesthesia would be most appropriate for a surgical procedure performed on a very small area of the body, as in dental procedures. Read More
What type of procedure was performed when a radiopaque material was injected into the blood vessels?
Which procedure is performed to affix sagging breasts in a more elevated position?
Which procedure is performed to open a partially blocked coronary artery?
FESS is a surgical procedure that is performed to?
enlarge the opening between the nose and sinus. Read More
What is the Medical term timeout mean?
A 'timeout' was performed in the room prior to procedure Read More
Is liposuction common?
It is the most commonly performed cosmetic procedure in the United States. Read More
Where is cataract surgery generally performed?
Surgery to remove cataracts is generally an outpatient procedure. A local anesthetic is used and the procedure lasts about one hour. Read More
What is a modifier involving insurance claims?
Importance of Using Proper Modifiers: 1. The physician performed multiple procedures 2. The procedure performed was bilateral 3. The E/M service was done on the same day of the procedure 4. The procedure was increased or decreased 5. The procedure has both professional and technical component 6. The procedure was performed by other provider (Anesthesiologist, Surgeon Physical Therapist, Speech Pathologists etc.) 7. Procedure on either one side of the body was performed 8. The E/M… Read More
How is plastic surgery performed?
It depends on the procedure. Some are quite simple and others are much more complicated. These procedures are performed by a licensed surgeon. Read More
Can a failed root canal be fixed once there is a post?
Often a surgical procedure (apicoectomy) can be performed, which removes the infected area. The procedure can weaken the remainder of the tooth. Read More
What is the cpt code for repeat radiology procedure performed by the same physican?
What does aseptic technique mean?
it means a procedure that is performed under completly sterile conditions Read More
What is the procedure performed prior to transplanting an organ from one individual to another?
In prenatal diagnosis the newest procedure that can be performed early in pregnancy involves sampling the?
Does insurance cover a scrotum tuck?
Only if the procedure is performed by Michael Greaves, MD. Read More
serial dilution can give the relation b/w the consenteration andthe growth of bacteria
Advantages of spread plate method?
There a few advantages of using the spread plate method. One of the advantages of using the spread plate method is it is better for isolating the bacteria colonies. It also is helpful in isolating organisms. Read More
Compare the pour plate and streak plate methods of isolating bacteria?
A streak plate method involves the rapid moving method for separating bacteria in a mixed population. A pour plate method, meanwhile, involves the dilution of a mixed population of bacteria into tubes of nutrient agarmedium, which is then poured into a petri dish for incubation. Read More
What are the method of estimating microbial population in soil?
Serial Dilution Plate Technique is the method to estimate soil microbial population by Dhinga & Sinclair in 1993. Read More
What is the differences between a streak plate technique and a serial dilution technique?
what is serial dilution and spread plate technique Read More
What are Advantages of pour-plate method over streak plate method?
The pour plate method requires somewhat less skill than that required for a good streak plate; a disadvantage, however, is that it requires more media, tubes, and plates. Read More
What advantages does the streak plate method have over the pour plate method?
The streak plate method makes it easier for colonies of bacteria to grow. It also generally leads to individual colonies that look like small dots, rather then simply a mat of bacterial growth. Read More
Advantages of pour plate method over other methods of bacterial colony?
What are the advantages and disadvantages of spread plate method in pure culture method?
The spread plate method is used in microbiology to grow colonies of yeast. It is advantageous compared to the pure culture method because it is easier to isolate specific colonies, however less colonies have a chance of surviving. Read More
Who invented serial dilution method?
What are the limitations and advantages of standard plate count?
this method is suitable for non aggregated cultures but the nature of the reaction must not be mycelial . Read More
What are the major sources of error in the serial dilution and plate techniques?
What is the purpose of using streak plate technique?
What are the advantages and disadvantages of pour plate technique?
Some advantages of pour plate technique are: it counts only living cells and it is a standardized test, which is used worldwide. Some disadvantages of this method are: it generally takes a long time to incubate bacteria and osmotic shocks can occur. Read More
What are the advantages and disadvantages of deductive method?
What are the advantages of organization and method team?
advantages of organisation and method team Read More
Does the streak plate method work better than the pour plate method?
What does a metal plate in the skull do?
what are the advantages of a metal plate Read More
Serial dilution method for bacterial growth measurement?
bacterial cell numbers needs reducing ,which is done by repeatedly diluting the amount of you have in your sample. A small amount of bacterial sample is mixed with a diluent solution(such as sterile broth), and then dilution are made. by adding small amount of diluted bacteria samples then spread onto the agar plate by L-shaped glass rod. Read More
What are the Advantages of poaching method?
What is the advantages of streak plate method?
Streak plating allows for the formation of individual colony forming units for isolation by reducing the number of bacterial cells with each streaked quadrant. Read More
Advantages of rast method?
there are no advantages. your a silly moo. Read More
Who developed the culture plate method to identify pathogens?
Rober Kock developed the culture plate method to identify pathogens. Read More
Who developed the culture plate method of identify pathogens?
Robert Koch developed the culture plate method to identify pathogens. Read More
Advantages of observation method?
There are a great many advantages of using the observation method. You can see what works and does not work for example. Read More
What are the advantages of audio visual method?
What is the difference between a heavily seeded plate and a sparsely seeded plate?
Heavy seeded plates means a agar plate having inoculum in large quantity it is generally done by spreading method with low dilution or concentrated inoculum and is done for the need of large no. of colonies generally in industrial purpose. Sparsely or low seeded plate are those which contain very diluted spreaded inoculum or little streaking inoculum it is generally done for examine and study purpose for understanding the physiology and morphology of microbe. Read More
What are the tests to confirm coliform bacteria in cow milk?
Violet Red Bile Agar and MPN are the tests that are used to confirm coliform in cow milk. The plate count method takes 24 hours to perform and can use 1.0 ml of 1:10 dilution and has a very high sensitivity. Read More
A colormertric method calls for the use of 0.1ml serum 5ml of reagent and 4.9ml of water what is the final dilution?
What are the advantages and disadvantages of the Height of Collimation method in surveying?
the advantages of this method was that it is more quick and less calculation needed and the disadvantages, it less accurate compare to the rise and fall method. Read More
What are the advantages of the high low method?
what are the usefulness of high low method Read More
Advantages and disadvantage of project method?
Advantage and disadvantage of project method Read More
What are advantages aluminium plate in electrocoagulation compared to ferum plate?
What is advantages and disadvantages of distillation method?
The distillation method's advantages are that it will make a pure result. The disadvantages are that the method is time consuming and is not cheap. The distilled method as a result is avoided unless needed. Read More
What are the advantages and disadvantages of using the polygon method?
One of the main advantages of using the polygon method is speed. The main disadvantage to this method is the fact that it cannot adequately represent curved items. Read More
What Are Some Advantages And Disadvantages Of The Serial Dilution Agar Plate Technique (3 Pts)
Do both the spread-plate and pour-plate method in a experiment produce similar bacterial counts or are they vastly different?
Both Spread-plate and pour plate method don't give the same results. Because in the case of spread plate method the inoculmn used for inoculation can't be spread in a exact volume. A little inoculmn remains stick with the spreader after spreading. On the other hand, in pour plate method it doesn't happen. So mostly, through comparing the counts by both methods, less counts are obtained in spread plate method. I am Working as a Sr… Read More
What are the advantages of doing turbidity method over standard plate count method?
Turbidity takes less time to perform; therefore, it takes less time to obtain the results. However, the concentration of the tube needs to be 10^7 or greater. Plate count method takes time to incubate and takes a longer time to prepare. It does not require the concentration to be that high because you are diluting the sample. Plate count accounts for live microorganisms only, as turbidity accounts for both live and dead because your just… Read More
What does CPT code 87186 stand for?
Susceptibility studies, antimicrobial agent; microdilution or agar dilution, each multi-antimicrobial, per plate Read More
What are the advantages of frying?
What are the advantages of gauss elimination method?
What are the disadvantages and advantages of using the polygon method and the component method?
The disadvantages of the polygon method include a lack of accuracy as well as detail. Advantages include its ease of use. The component method is much more exact, but is tougher to achieve. Read More
What are the advantages and disadvantages of the percent of sales method?
What are the disadvantages of the percent of sales method Read More
How do you measure bacterial growth quantitatively in an Agar plate?
When bacteria is grown in an Agar plate, one quantitative method to measure growth is using a counting chamber. Another method is using viable plate counts. Read More
The advantages of using the scientific method When studing environmental issues?
The advantages of using the scientific method when studing environmental issue? Read More
What are the disadvantages using streak plate method?
Streak Plate method cannot be used for the enumeration of the approximate number of bacteria in the given sample. It can used only for obtaining isolated colonies in Pure culture. This is because, In streak plate method, 1. the amount of inoculum added is not a measured quantity. 2. colony count method cannot be applied on streak plate, since except in the fourth quadrant, isolated colonies are not formed. Thus Streak plate method can be… Read More
How do you calculate dilution ratio?
A dilution ratio is a shorthand method to represent a dilution performed using integer ratios of solvent. For example let's say you have 100mL of an aqueous 1M solution. Transfer 25mL of this solution to a 100mL volumetric flask, and dilute with water to the 100mL mark. This solution is now 0.25M, a 1:4 dilution. I have seen this mistakenly reported as a 1:3 dilution, adding the two integers together to get the new solution… Read More
What are the advantages and disadvantages of the calibration method and the method of standard additions?
Why are plates of agar dried before being used for the preparation of dilution streak plates?
Agar plates are dried before using dilution streak plate because it prevents movement of motile bacteria. You can also isolate bacteria better by drying agar plates beforehand. Read More
What are the advantages of modern method of irrigation?
Advantages and disadvantages of preference share?
Some of the advantages of the preference share is the absence of the fixed regular income and less capital loses. Some of the disadvantages includes the dilution of claim over assets and the high rate of dividends. Read More
Who developed the culture plate method?
the total count includes dead as well as living cells
What is the differences between a streak plate technique and a serial dilution technique?
what is serial dilution and spread plate technique Read More
What are the advantages of dilution plate method?
serial dilution can give the relation b/w the consenteration and the growth of bacteria Read More
Who invented serial dilution method?
Why doing serial dilution?
Serial dilutions allow you to obtain different concentrations of the same organism. Read More
What tests determine an unknown bacteria?
What are the major sources of error in the serial dilution and plate techniques?
What is serial dilution?
Serial dilution is usually 1/10 dilution. Therefore after a series of dilutions, you have a logarithmic curve of concentration (log10). Basically, if diluting 1/10 and starting off with 1 molar solution, first dilution = 0.1M, 2nd = 0.01M, 3rd = 0.001M. If making a 0.001M solution involved weighing out 0.005g of a salt for example, the error in making this solution out would be very large in comparison to weighing out 5g (1M) and diluting… Read More
What is the purpose of serial dilution?
A common design for estimating the concentrations of compounds in biological samples is the serial dilution assay, in which measurements are taken at several different dilutions of a sample, giving several opportunities for an accurate measurement. Curren tly, serial dilution is a standard tool in the fields of toxicology and immunology. Serial dilution helps to choose a dilution which is relevant to our experiment. Often the standard which is given to you in the lab… Read More
Use of test tube?
In microbiology it is mainly used for either serial dilution and for slant prepration for culturing microbes Read More
How can you prepare solution 0.2 ppm from 1000 ppm?
dilute it 1 in 5000. likely best done with a serial or step dilution Read More
Advantages and disadvantages of preference share?
Some of the advantages of the preference share is the absence of the fixed regular income and less capital loses. Some of the disadvantages includes the dilution of claim over assets and the high rate of dividends. Read More
Disadvantage of venture capital?
There may be several disadvantages of venture capital; however, a disadvantage to one entrepreneur may be an advantage to another entrepreneur. Focusing however on disadvantages of venture capital: (i) dilution of ownership, (ii) dilution in control, (iii) necessity of having representatives of the venture capital participate in corporate governance, (iv) increased risk of venture capital take over of the business. Read More
What are the advantages and disadvantages of a serial port?
the speed of serial ports are slow. but we can send data on long distances as serial cable have low cost. Read More
How do you prepare 1 is to 100 dilution in small volume?
Your best bet is a serial dilution, i.e. get 2 10ml volumetric flasks and take 1ml of your solution to be diluted, and make to 10ml with solvent, mix this, then take 1ml of the resulting 10mls and dilute that to 10ml. 2x 10 times dilutions is 100x dilution. Alternatively if you have less to start with, use micro pipettes Read More
What are the method of estimating microbial population in soil?
Serial Dilution Plate Technique is the method to estimate soil microbial population by Dhinga & Sinclair in 1993. Read More
Definition of dilution and dilution factor?
As I understand it, the dilution refers to the dilution ratio. If you add 1 part of something to 4 parts of something else, the dilution ratio is 1 to 4. The dilution factor counts all the parts and expresses the same thing as 1 out of 5. Read More
What are the disadvantages of connecting database to the internet?
What is the effect of dilution on viscosity of oil?
dilution will reduce the viscosity The effect of dilution on viscosity of oil is that it will decrease. Read More
12 Distinguish between dilution and dilution factor?
As I understand it, the dilution refers to the dilution ratio. If you add 1 part of something to 4 parts of something else, the dilution ratio is 1 to 4. The dilution factor counts all the parts and expresses the same thing as 1 out of 5. Read More
Distinguish between dilution and dilution factor?
Dilution is the process of making a less concentrated solution and dilution factor is the amount of solvent required to make a certain concentration of solution. Read More
What is infinite dilution?
Infinite dilution means such a large dilution so that when you add more solvent there is no change in concentration. Read More
What sentence has the word dilution in it?
What does 0 percent dilution mean?
What are the disadvantages of a serial port?
The disadvantages of serialports are that the burger comes from burger king and the fries are from mcdonalsd . the drink is from pak supermarket and then it becomes a meal. Read More
How does the number of moles of solute before a dilution compare with the number of solute after the dilution?
Before the dilution the number of moles is higher. Read More
What does dilution rate RTU mean?
What is the equation for a dilution?
To prepare 300 ml of a 115 dilution from a 13 dilution you need to add ml of the 13 dilution to ml of diluent?
What is the difference between dilution and diffusion?
what is the difference between a diffusion and a dilution Read More
How does dilution affect concentration of a solution?
Dilution reduces the concentration of a solution. Read More
What is titer?
In terms of chemistry, a titer is a specific way to express a solution's concentration. The process of titer testing uses serial dilution to obtain quantitative information that is either negative or positive. Read More
What is another term for dilution?
Dilution may also be described as 'watering down' or 'mixing', as well as 'diffusing', although none are exact synonyms of dilution. Read More
What is dilution factor?
In chemistry and biology, the dilution factor is the total number of unit volumes in which the material is dissolved. As I understand it, the dilution refers to the dilution ratio. If you add 1 part of something to 4 parts of something else, the dilution ratio is 1 to 4. The dilution factor counts all the parts and expresses the same thing as 1 out of 5. Read More
What is helium dilution technique?
How is FRC measured by helium dilution, in specific detail. Read More
What is the major disadvantage of microbial counts performed by methods other than the serial dilution-agar plate procedure?
Read More
What dilution to make 50percent acetone control?
What is the key to remember when considering the dilution of a solution?
To remember that only water is added in the dilution. Read More
Why is saline used in bacterial serial dilution?
Because the osmotic pressure of 'plain' water can be too much for bacteria, causing them to pop, and throw off your colony counts during your serial dilutions. A buffered saline solution keeps the bacteria at their usual osmotic pressure. Typical saline is 0.85%. Read More
What is a dilution series?
the dilution of two or more solutions of sulfate and chemical microbial sists of plaque Read More
What is the key idea to remember when considering the dilution of a solution?
To remember that Only water is added in the dilution. Read More
Why is dilution necessary in a pure culture?
if a sample is plated without dilution, then there wont be any isolated colonies. So dilution is necessary for getting isolated colonies, from which pure culture shall be obtained. Read More
Why moles solute before dilution equals moles solute after dilution?
This assumes you are using water (or whatever the original solvent is) to do the dilution so you are not adding more solute, only more solvent, Read More
Why is ringer solution used for serial dilution?
Ringers solution contains a salt content similar to what is found in the cells of a bacteria. This prevents the bacteria under going osmotic stress and subsequent bursting of the cell walls. Read More
Is the concentration change after dillution?
Yes, the concentration changes after dilution. By definition dilution means to lower the concentration. Read More
What is the molar conductivity of kcl in infinit dilution?
what is the literature value of KCl molar conductivity at infinite dilution Read More
Serial dilution method for bacterial growth measurement?
bacterial cell numbers needs reducing ,which is done by repeatedly diluting the amount of you have in your sample. A small amount of bacterial sample is mixed with a diluent solution(such as sterile broth), and then dilution are made. by adding small amount of diluted bacteria samples then spread onto the agar plate by L-shaped glass rod. Read More
What happens to the volume and dilution of urine when alcohol is consumed?
Igi for pc free download. Decreased ADH production increases urine volume and dilution. Read More
What is the formula used to calculate dilution ratios?
A dilution ratio is normally used for a mixture of two fluids: an active component and a carrier solvent. The dilution ratio is the ratio of the volume of the solvent to the volume of the active component. Read More
How do you use the word dilution in a sentence?
The approved dilution is published on a list of disinfectants under the animal health act 1981. Read More
What does dilution and concentration mean?
dilutionis the process of reducing theconcentrationof a solute in solution Read More
What are the advantages and disadvantages of a serial port?
the speed of serial ports are slow. but we can send data on long distances as serial cable have low cost. Read More
What are the advantages of serial port communication?
What are the advantages of disabling a serial port?
Other than freeing up a hardware interrupt (which, in today's computers is really unnecessary anyway), there are no inherent advantages in disabling a serial port. Read More
What are the disadvantages of connecting database to the internet?
What are the disadvantages of a serial port?
The disadvantages of serialports are that the burger comes from burger king and the fries are from mcdonalsd . the drink is from pak supermarket and then it becomes a meal. Read More
What are the advantages of parallel communication over serial communication?
What is the advantages of serial?
A serial connection is used to connect one router to another in a network. In serial verses parallel, Serial only require 2 wires, so is cheaper and easier to use. Read More
What is disadvantages of serial dilution?
the total count includes dead as well as living cells Read More
What is a Zero Slot LAN and Its Advantages Disadvantages?
A zero-slot LAN is a local-area network (LAN) that uses existing serial and/or parallel communication ports on the computers in the network instead of requiring network interface cards (NICs) that would occupy an expansion slot. Advantages It leads to transmitting between computers over a serial or parallel port, thus freeing up an expansion slot normally used by LAN cards (NICs). Disadvantages Zero-slot LANs are typically slower than LANS that use NICs and are limited to… Read More
Advantages in serial monogamy?
Monogamy means the practice of having only one wife Read More
What are the advantages of serial file organisations?
Serial file organization provides indexed categorization of data, which many users find helpful. Another benefit of serial file organization is easy access to files. Read More
What are the advantages of a parallel port over a serial port?
Multiple bits can be transfered per cycle. Read More
What are the advantages of serial communication?
Can span longer distance, fewer data paths, flexibility in design, error detection, Read More
What are the advantages of dilution plate method?
serial dilution can give the relation b/w the consenteration and the growth of bacteria Read More
What is the age of a Colt Frontier Buntline 22 serial number G719707?
you will have to call Colt. the sn you list does not follow the standard numbering procedure. Read More
What are the advantages and disadvantages of serial mouse?
As opposed to having a proprietary bus mouse (only found in very old computer systems), a serial mouse allows you to use a standardized interface and protocol, meaning you can easily replace the mouse if it breaks. The disadvantages of a serial mouse are: It occupies the serial port, barring it from use for other devices, such as a modem. If you only have one serial port and no internal modem, you cannot use a… Read More
How do I find my laptop serial number from the dard disk I am using an Acer 6930G laptop running windows vista I want to know the procedure of reading the computer serial number from the software?
Where is the number you get when you bye a software?
When you buy Software you will need to tell the manufacturer that you now own the item - registration. For most Software packages is part of the installation procedure. Some Games use a serial number on the back of the physical package or printed on the last page of the Users Manual. If you are asked for that serial number the screen will remind you were to find it. Internet access is becoming a big… Read More
Advantages of serial over parallel data transmission?
What are the advantages and disadvantages of parallel and serial communication?
Serial Data Transmission Parallel Data transmission Advantages Disadvantages Advantages Disadvantages Used over long distances Slower to send data Faster than serial Not reliable over long distance Reduces requirement of wiring Data may arrive at different times Read More
Which procedure is used to access a Cisco 2960 switch when performing an initial configuration in a secure environment?
Use the console port to locally access the switch from a serial or USB interface of the PC. Read More
What are the advantages of serial access?
Serial access, also known as sequential access, are usually much cheaper to produce. This also makes it possible to get more data capacity given both a set price and a set physical limit. Hope that's okay. (: Read More
What is the medical term meaning an imaging procedure that displays continuous motion of internal structures and immediate serial images?
Ultrasound displays continuous motion images of internal structures. endoscopy Read More
What is the major disadvantage of microbial counts performed by methods other than the serial dilution-agar plate procedure?
Read More
What does the term USP stand for in computers?
If you truly mean USP, then it could mean Universal Storage Platform, Universal Serial Port, User Stored Procedure, or Universal Service Protocol. Otherwise, if you mean USB, that means Universal Serial Bus, and a UPS would be an Uninterruptible Power Supply. Read More
What are the advantages of USB ports relative to parallel and serial ports?
The serial and parallel ports are slow,have limited expandability and don't carry their own charge of electricity.these ports work fine for connecting Printers, Mice and keyboards to PC but all these device will perform better if connected to a USB port Read More
What are some advantages and disadvantages of serial communication?
In Parallel Transmission, every bit needs a wire to transfer data from one place to another. For instance, n number of bits need n number of wires. Advantage: Its transfer speed is theoretically higher than with serial, since entire bytes or more can be transmitted at once. Disadvantages: Cross-talk can be a problem at higher rates of speed. That is why PATA drives cannot be clocked past 133 MB/S. Also, there can be many wires… Read More
What is most popular TV serial in US?
Its a serial called FRIENDS Its a serial called FRIENDS Its a serial called FRIENDS Read More
What are the advantages of using unshielded twisted pair cable?
One primary advantage of UTP over STP or Fiber is cost. Twisted pair is also more simple to use in many applications (telephone, serial data, etc.) than fiber. Read More
What is a Serial?
What are the types of serial technologies?
Assuming that by serial technologies you mean serial communication, here are some: USB - Universal Serial Bus RS232C - The original serial protocol Read More
What is the homophone for cereal?
serial serial number, serial killer, etc. Read More
What is the age of a Smith and Wesson revolver serial?
No serial number provided. Serial # 426742 Read More
What is a serial processer?
What is the homophone for serial?
What is the advantages and disadvantages of transaction processing system?
The advantage is that usually transaction processing is really fast, it takes up usually a few seconds, however, if there a lot of files in queue, the time taken to process data might take a long time. Another advantage is that it makes the process of boking more fair as files are processed in order in which they had been queued. (e.g. ticket booking) The disadvatages is that there is a chance of double booking… Read More
What are the advantages and disadvantages of frame relay?
* Reasonable WAN speed (64kbps -- 1.5Mbps) * ** When T1 or Fract. T1 is the transport * Buy bandwidth only when you need it **** * One serial port at the central site can support multiple incoming PVCs * Telco is responsible for insuring connectivity * No educational tariff is currently available in Alabama. * Full T1?s are almost always less expensive than Frame Relay (due to the edu. Tariff) * More difficult to… Read More
Who was the first serial rapest?
As is true of serial murder, serial rape is as old as the human race. Read More
What year was smith and Wesson model 36--serial?
Impossible to answer without a serial number. Read More
When was colt frontier made serial?
Can't be answered without the serial number. serial #166043f Read More
Is sindhu bhairavi serial a remake serial?
yes a remake serial of UTTARAN IN COLOURS TV Read More
What is the age of a Colt Mark IV combat elite serial serial?
What year is Ferguson tractor TO 30 serial No 129226?
Your Fergie is a 1954. serial # 60001 to 72679 is 1951 serial # 72680 to 108644 is 1952 serial # 108645 to 125958 is 1953 serial # 125959 to 140000 is 1954 Read More
A sentence for serial?
Is the telegraph a serial or parallel device?
What year was 12ga serial?
What is this browning serial?
When was your model 51 featherlight made serial serial?
Without the serial number, the question can't be answered Read More
Why is ubs put an improvement over serial parallel parts?
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Abstract
The primary aim of this study was to evaluate the level of agreement of the E-test for in vitro antimicrobial susceptibility testing of Campylobacter coli using the agar dilution technique, which is the approved method. A convenience sample of 80 Ontario swine farms was chosen for this study; each farm was visited from January to June 2004. A total of 233 isolates of C. coli were tested for susceptibility to 10 antimicrobials by agar dilution and the E-test. Performance of the tests was evaluated using 7 quality control strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Campylobacter jejuni ATCC 33560, and Campylobacter coli ATCC 33559 for the E-test and E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and C. jejuni ATCC 33560 for the agar dilution test. Weighted Cohen’s kappa and prevalence-adjusted bias-adjusted kappa (PABAK) tests were used for statistical analysis. The E-test and agar dilution test results had a strong agreement when resistance to streptomycin and tetracycline were evaluated (weighted kappa: 0.68 and 0.66, respectively). However, marked disagreement was detected when testing susceptibility to nalidixic acid and ampicillin (0.15 and 0.22, respectively). Almost perfect agreement was detected by PABAK when testing susceptibility to gentamicin (0.99). Agreement was found to be moderate for ciprofloxacin, azithromycin, clindamycin, erythromycin, and chloramphenicol. Although the level of agreement between the E-test and agar dilution depended on the antimicrobial being tested, the E-test always detected a lower proportion of resistant isolates compared to agar dilution.
Résumé
L’objectif principal de cette étude était d’évaluer le niveau d’agrément de deux méthodes in vitro de détermination de la sensibilité aux antibiotiques des Campylobacter, soit le E-test et la méthode de dilution en gélose qui est la méthode approuvée. Un échantillon de convenance de 80 fermes porcines ontariennes a été choisi pour cette étude; chaque ferme a été visitée durant la période de janvier à juin 2004. Un total de 233 isolats de C. coli a été testé pour leur sensibilité à 10 antimicrobiens par dilution en gélose et E-test. La performance des tests a été évaluée à l’aide de 7 souches de contrôle de qualité : Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Campylobacter jejuni ATCC 33560 et Campylobacter coli ATCC 33559 pour le E-test et E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 et C. jejuni ATCC 33560 pour la méthode de dilution en gélose. Pour les analyses statistiques, un test de kappa de Cohen pondéré et un test de kappa ajusté pour la prévalence et ajusté pour le biais (PABAK) ont été utilisés. Le E-test et le test de dilution en gélose avaient un accord marqué lorsque la résistance à la streptomycine et la tétracycline était évaluée (kappa pondéré : 0,68 et 0,66, respectivement). Toutefois, un désaccord marqué a été détecté lorsque la sensibilité à l’acide nalidixique et à l’ampicilline était testée (0,15 et 0,22, respectivement). Un accord presque parfait a été détecté par PABAK pour la sensibilité à la gentamycine (0,99). L’accord s’est avéré modéré pour ce qui est des antimicrobiens suivants : ciprofloxacin, azithromycine, clindamycine, érythromycine et chloramphénicol. Bien que le degré d’accord entre le E-test et la méthode de dilution en agar dépende de l’antimicrobien testé, le E-test détectait toujours une plus faible proportion d’isolats résistants comparativement à la méthode de dilution en gélose.
(Traduit par Docteur Serge Messier)
Introduction
The emergence of antimicrobial resistance is a global problem that encouraged the establishment of the National Antimicrobial Resistance Monitoring System (NARMS), proposed by the United States Food and Drug Administration (FDA), to monitor the occurrence of antimicrobial resistance. Resistance has been observed and reported among many bacterial species, including Campylobacter spp. The agar dilution procedure is a technique approved by the Clinical and Laboratory Standards Institute (CLSI), for antimicrobial susceptibility testing of Campylobacter spp. However, there are no internationally agreed upon susceptibility criteria for Campylobacter spp. and breakpoints used by NARMS are provisional. For this reason, other techniques for testing antimicrobial susceptibility in Campylobacter spp. have been performed, including disk diffusion, broth microdilution, and the E-test.
Disk diffusion refers to the diffusion of an antimicrobial agent of a specified concentration from disks, tablets, or strips, into solid culture media seeded with a standardized bacterial inoculum; results are based on the size of the inhibition zone (). Disk diffusion has been reported to be the simplest and most cost-effective method for testing antimicrobial susceptibility; however, it requires standardization and involves the manual measurement of zones of inhibition making it impractical for some laboratories (,).
Broth microdilution is a technique in which standardized suspensions of bacteria are tested against varying concentrations of an antimicrobial agent in a standardized liquid medium (). Although this technique has been recommended for antimicrobial susceptibility testing of Campylobacter coli (), it involves the use of special equipment and commercially prepared antimicrobial panels that make it a costly option ().
In order to detect emergence of antimicrobial resistance it is important to use a practical, consistent, and standardized method that will allow comparison with national or international monitoring data. Agar dilution involves the incorporation of an antimicrobial agent into an agar medium in a geometrical progression of concentrations, followed by the application of a defined bacterial inoculum to the agar surface of the plate (). Some of the advantages offered by the agar dilution technique include: accurate determination of minimum inhibitory concentrations (MICs) when a full dilution range of the antimicrobial is used; the ability to test many organisms against a series of dilutions of a single antimicrobial at the same time; the potential to extend the antimicrobial concentration as far as required; and the possibility to be adapted to semi-automation (,). The agar dilution method has been known as the gold standard technique of antimicrobial susceptibility testing; however, it is rarely performed in routine laboratories due to the large amount of manual handling needed to run it. This technique requires extensive training of personnel and may be more expensive and labor-intensive, when testing many organisms against many antimicrobials, than other testing methods (,). The E-test might be a reliable alternative method for performing antimicrobial susceptibility of Campylobacter spp. (,) since quantitative data may be obtained. Plastic strips carrying a continuous gradient of antimicrobial agent are placed on the surface of an inoculated agar plate; the antimicrobial diffuses into the agar generating the MIC values of a given antimicrobial. The E-test method is less laborious, less expensive when testing a limited number of antimicrobials (≤ 3) per microorganism, and easier to perform than the agar dilution technique, thus making it an attractive alternative for antimicrobial susceptibility testing (). However, it is important to validate this method before making any recommendations for testing antimicrobial susceptibility of C. coli.
Campylobacter spp., primarily C. jejuni and C. coli, account for the highest annual average incidence rate of human gastroenteritis worldwide (), generally, the disease is self-limiting but in severe cases antimicrobial therapy is required. Since an increased number of Campylobacter strains that are resistant to several antimicrobials have been isolated from clinical samples in many countries (), there is a concern that antimicrobial use in food animals may select for resistance. Pork is considered a possible source of Campylobacter, especially C. coli, as a result of carcass contamination at slaughter. Previous studies have demonstrated that in Ontario almost 100% of the pigs carry Campylobacter coli as a normal inhabitant of their gastrointestinal system (). For this reason, it is important to determine the existing profile of antimicrobial susceptibility of Campylobacter isolates from healthy pigs in Ontario through surveillance programs. However, the lack of a standardized technique to measure antimicrobial susceptibility in Campylobacter isolates has been a limitation in achieving this goal. The objective of this study was to evaluate the level of agreement between the E-test and the agar dilution procedure using isolates from commercial farms.
Materials and methods
A convenience sample of 80 Ontario swine farms was selected for collection of fecal samples; an attempt was made to include a wide variety of farm type, size, and geographical distribution. All the farms were visited between January and June 2004. The 1200 fecal samples collected from hogs that were close to market weight were used to establish the pattern of antimicrobial resistance in Campylobacter isolates recovered from swine in Ontario (). Campylobacter was isolated from 1194 of the 1200 samples; those identified as C. coli (n = 1185) were stored at −70°C for further susceptibility testing.
For the E-test, 240 isolates were randomly selected from the 1185 frozen isolates using a phone book as random number table. The phone book was randomly opened and the last 3 digits from the 1st number on the right page were used as the starting point. Appropriate numbers were then selected by moving down the columns in the phone book; these numbers were used to identify the 240 isolates.
The original results from the main study were used for the agar dilution testing (). Isolates were grown on Mueller-Hinton Blood Agar (MHBA) plates with antimicrobials (cefoperazone and VTP: vancomycin, trimethoprim, polymyxin B solution). The isolates were supplemented with 5% defibrinated sheep blood at 37°C for 48 h in a microaerophilic environment for 2 passages and adjusted to turbidity equal to a 0.5 McFarland standard: 233 isolates were recovered. Antimicrobial breakpoint concentrations were based on the National Committee for Clinical Laboratory Standards (NCCLS) approved standard for members of the Enterobacteriaceae family (M31-A), listed by the FDA, and used by NARMS. Susceptibility of C. coli was tested against a range of antimicrobials: ampicillin, azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid, streptomycin, and tetracycline.
Agar dilution test
Suspensions were dispensed into the wells of a cold Cathra Replicator 36 well plate (Oxoid, Nepean, Ontario) beginning by filling the 1st well with 300 μL of India ink. Each of the next 3 wells was filled with 300 μL of 1 of 3 reference strains (E. coli ATCC 25922, P. aeruginosa ATCC 27853, and C. jejuni ATCC 33560), and the last 33 wells were filled with C. coli isolates. Isolates were spotted onto Mueller Hinton Blood Agar (MHBA) plates containing the antimicrobial agents tested (Oxoid). Determination of the MICs for this test was based on plates holding concentrations of antimicrobials close to the resistance breakpoints, rather than a full dilution range (Table I). Each of the inoculated agar plates were dried at room temperature and microaerophilically incubated at 42°C for 48 h. The MICs were read as the lowest concentration of the antimicrobial at which there was no visible growth.
Table I
Minimum inhibitory concentration (MIC) breakpoints used to test agreement between agar dilution (AD) and E-test for 10 antimicrobials for 233 Campylobacter coli isolates recovered from 80 swine farms in Ontario
Minimum inhibitory concentration (MIC)a breakpoints | |||||
---|---|---|---|---|---|
Antimicrobial | Codes | Susceptible ≤ μg/mL | Intermediate = μg/mL | Resistant ≥ μ/mL | |
I | Ciprofloxacin | CIP | 1 | 2 | 4 |
II | Azithromycin | AZM | 0.25 | 2 | |
Clindamycin | CLI | 0.5 | 2 | 4 | |
Erythromycin | ERY | 0.5 | 4 | 8 | |
Nalidixic acid | NAL | 4 | 16 | 32 | |
III | Ampicillin | AMP | 8 | 16 | 32 |
Chloramphenicol | CHL | 8 | 16 | 32 | |
Gentamicin | GEN | 4 | 8 | 16 | |
Streptomycin | STR | 32 | 64 | ||
Tetracycline | TCY | 4 | 8 | 16 |
E-test
Following suspension of C. coli colonies in Mueller Hinton Broth (MHB) to produce the required turbidity of 0.5 McFarland standard, the suspension was swabbed onto Mueller-Hinton Blood Agar plates supplemented with 5% laked horse blood (MHLHB) 3 times by rotating the plate approximately 45° each time. Plates were dried in a biohood at room temperature, and 2 E-test strips containing a predefined gradient of the antimicrobials were placed on each plate. The E-test strips were placed onto inoculated agar surfaces with the minimum inhibitory concentration (MIC) scales facing upwards. The 1st strip was placed on one half of the surface, and the 2nd was placed in an anti-parallel orientation to the 1st strip. Plates were incubated in an inverted position at 37°C under microaerophilic conditions for 48 h. The MICs were read according to the E-test reading guide: where the edge of the inhibition ellipse intersects the side of the strip (AB Biodisk, Solna, Sweden).
For each set of samples, the following quality control strains were tested to check the performance of the E-test: E. coli ATCC 25922, S. aureus ATCC 29213, C. jejuni ATCC 33560, and C. coli ATCC 33559. For E. coli and S. aureus, 1 set of MHLHB plates was inoculated at 37°C under aerobic conditions for 24 h, and a 2nd set was incubated microaerophilically at 37°C for 48 h. For C. jejuni and C. coli, 1 set of inoculated MHLHB plates containing the E-test strips was incubated at 37°C under microaerophilically conditions for 48 h.
Data handling and statistical analysis
Data were entered into an Excel spreadsheet (Microsoft Excel 2000; Microsoft, Redmond, Washington, USA) and subsequently imported into Intercooled STATA 8.2 (Stata, College Station, Texas, USA) for statistical analysis. Percentage of agreement or exact agreement was calculated for 3 different tables, by dividing the sum of the diagonal matrix by the total number of observations in each table. The 1st table maintained the 3 original categories [S, I, R]; afterwards, data were collapsed into 2 × 2 tables in 2 different ways: intermediate susceptibility was 1st classified as resistant [S, (I + R)], and then as susceptible [(S + I), R]. To assess the degree of agreement between the tests, and correct for any chance-expected agreement, a Cohen’s weighted kappa statistic was calculated. Weighted kappa is an appropriate measure of agreement for ordinal data because it attaches greater emphasis to large differences between ratings than to small differences.
What Are Some Advantages And Disadvantages Of The Serial Dilution Agar Plate Technique
One problem of the kappa coefficient, however, is that its interpretation is not straightforward. There are some factors such as prevalence and bias effects that may influence the magnitude of kappa; if bias and prevalence effects are present, the kappa coefficient may be larger or smaller than the PABAK, depending of the size of PI and BI (8,). Kappa was adjusted for high or low prevalence using the 2 × 2 tables by computing the average of the 2 concordant cells and substituting these values for the actual values in those cells (). Similarly, an adjustment for bias was achieved by substituting the mean of the disconcordant cells for those actual values. The kappa coefficient that results is referred to as prevalence-adjusted bias-adjusted kappa (PABAK) (). The PABAK coefficient was used to investigate the likely effects of prevalence and bias alongside the true value of kappa. The PABAK coefficient chosen for each antimicrobial was that from the 2 × 2 table showing the closer percentage to that detected by weighted kappa (Table II).
Table II
Adjusted reliability measures to test agreement between agar dilution (AD) and E-test for 10 antimicrobials for 233 Campylobacter coli isolates recovered from 80 swine farms in Ontario
Categories | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Agreement (%) | S, I, R | S, (I + R)a | (S + I), Rb | |||||||||
Antimicrobial | A | Ba | Cb | Weighted kappa | Kappa | PI | BI | PABAK | Kappa | PI | BI | PABAK |
Ciprofloxacin | 96 | 96 | 97 | 0.45 | 0.36 | 0.93 | 0.04 | 0.92 | 0.49 | 0.95 | 0.03 | 0.95 |
Azithromycin | 73 | 73 | 73 | 0.25 | 0.25 | 0.59 | 0.27 | 0.46 | 0.25 | 0.59 | 0.27 | 0.46 |
Clindamycin | 73 | 81 | 83 | 0.50 | 0.18 | 0.75 | 0.19 | 0.62 | 0.57 | 0.45 | 0.14 | 0.67 |
Erythromycin | 78 | 91 | 85 | 0.58 | 0.13 | 0.89 | 0.09 | 0.82 | 0.62 | 0.49 | 0.13 | 0.71 |
Nalidixic Acid | 15 | 18 | 82 | 0.15 | 0.02 | 0.07 | 0.82 | −0.62 | 0.34 | 0.70 | 0.14 | 0.65 |
Ampicillin | 27 | 33 | 79 | 0.22 | 0.05 | 0.03 | 0.67 | −0.34 | 0.35 | 0.66 | 0.17 | 0.58 |
Chloramphenicol | 75 | 75 | 97 | 0.17 | 0.03 | 0.64 | 0.25 | 0.5 | −0.007 | 0.97 | 0.02 | 0.95 |
Gentamicin | 99 | 99 | ~100 | 0.00 | 0.00 | 0.99 | 0.00 | 0.98 | 0.00 | 0.99 | 0.00 | 0.99 |
Streptomycin | 84 | 86 | 85 | 0.68 | 0.66 | 0.41 | 0.14 | 0.72 | 0.66 | 0.37 | 0.09 | 0.71 |
Tetracycline | 76 | 84 | 79 | 0.66 | 0.67 | 0.25 | 0.16 | 0.68 | 0.58 | 0.12 | 0.20 | 0.57 |
A — susceptible, intermediate and resistant categories; PI — preference index; BI — bias index; PABAK — prevalence-adjusted bias-adjusted kappa.
The interpretation used for Cohen’s kappa coefficient was as follows: poor agreement below 0.20, fair from 0.21 to 0.40, moderate from 0.41 to 0.60, substantial from 0.61 to 0.80, and almost perfect agreement from 0.81 to 1.00 (8).
Results
The prevalence of resistance detected by each test, weighted kappa indices with their respective 95% confidence intervals (CI) and classification by categories are presented for each of the 10 antimicrobials in Table III. Although the agar dilution test classified a higher proportion of isolates as resistant compared to the E-test, the E-test produced results highly comparable to the agar dilution method. In general, near perfect agreement between the E-test and agar dilution was observed when testing C. coli susceptibility against gentamicin. Agreement on resistance was substantial for streptomycin and tetracycline, moderate for ciprofloxacin, clindamycin, erythromycin, and chloramphenicol, and fair for azithromycin. The 2 tests disagreed when testing nalidixic acid and ampicillin. The percentage of resistance and MICs detected by both the E-test and the agar dilution method are presented in Table IV.
Advantages And Disadvantages Of The Serial Dilution Agar Plate Techniques
Table III
Agreement between agar dilution (AD) and E-test for 10 antimicrobials for 233 Campylobacter coli isolatesa
% Resistance | Test | Number of isolates in the following Categories | ||||
---|---|---|---|---|---|---|
Antimicrobial | AD | E-test | Weighted kappa | 95% CI | Similar | Different |
Ciprofloxacin | 4% (9) | 1% (3) | 0.45 | 0.12–0.78 | 223 | 10 |
Azithromycin | 93% (217) | 66% (154) | 0.25 | 0.15–0.36 | 170 | 63 |
Clindamycin | 82% (190) | 67% (157) | 0.50 | 0.39–0.60 | 169 | 64 |
Erythromycin | 81% (189) | 68% 159) | 0.58 | 0.48–0.68 | 182 | 51 |
Nalidixic Acid | 22% (52) | 8% (19) | 0.15 | 0.08–0.21 | 35 | 198 |
Ampicillin | 28% (64) | 11% (25) | 0.22 | 0.14–0.30 | 62 | 171 |
Chloramphenicol | 2% (5) | 0.4% (1) | 0.17 | 0.07–0.28 | 175 | 58 |
Gentamicin | 0% | 0.4% (1) | 0.00 | -- | 231 | 2 |
Streptomycin | 73% (170) | 64% (150) | 0.68 | 0.58–0.77 | 195 | 38 |
Tetracycline | 66% (154) | 46% (108) | 0.66 | 0.57–0.75 | 176 | 57 |
Table IV
Distribution of antimicrobial minimum inhibitory concentrations (MICs) in 233 Campylobacter coli isolates from swine in Ontario
Discussion
It has been suggested that a McNemar’s X2 test should be used to evaluate any evidence of agreement between tests before assessing the magnitude of such agreement using kappa. A significant result from the McNemar’s X2 test would indicate serious disagreement and thus kappa would be of little value (8). However, a correlation coefficient, like McNemar’s X2 test, is a measure of association that measures the strength of a relation between 2 variables and not the agreement between them (,). For this reason, the significance of McNemar’s X2 was not considered in our analysis.
The Cohen’s kappa coefficient is an adequate method to measure agreement because it measures not only the percentage of agreement, but also the percentage of agreement beyond chance (). One of the advantages is that the kappa coefficient can be used for scales with more than 2 categories; however, unweighted kappa is inappropriate for ordinal scales because it treats all disagreement equally. A weighted kappa coefficient was chosen as the most appropriate measure of agreement in our analysis (ordinal data: S, I, R) because it attaches greater emphasis to large differences between categories (S vs R) rather than to small differences (S vs I; I vs R) (,).
There are limitations to the interpretation of the kappa coefficient if the prevalence of resistance is either lower than 20% or higher than 80% (). In this study, the prevalence of resistance, determined by at least one test, was either lower than 20% or higher than 80% for all antimicrobials tested except streptomycin and tetracycline. The strong dependence of kappa on the prevalence complicates its interpretation as an index of agreement for most of the antimicrobials tested. The prevalence of resistance detected for streptomycin and tetracycline using either the E-test or agar dilution was categorized as moderate (lower than 80% but higher than 20%), and therefore, for these 2 antimicrobials, assumptions can be made for the use of the E-test and the agar dilution method interchangeably for most practical purposes.
Since the degree of resistance was categorized as high to moderately high for several antimicrobials agents including ciprofloxacin, azithromycin, clindamycin, erythromycin, nalidixic acid, ampicillin, chloramphenicol, and gentamicin, it is important to consider the factors that may influence the magnitude of kappa such as prevalence and bias effects, to evaluate the performance of the test. Prevalence effect occurs when the overall proportion of positive (resistant) results is substantially different from 50%, and it can be expressed as prevalence index (PI); a large PI indicates that the kappa coefficient has been lowered (13). The bias effect expressed as bias index (BI) is defined as the extent to which the tests disagree on the proportion of resistant (or susceptible) isolates; a large BI value will indicate an inflated kappa coefficient (). A large PI was observed for ciprofloxacin, clindamycin, chloramphenicol, and gentamicin, indicating that the values of kappa may be underestimated. Adjusted kappa (PABAK) indicates that the agreement observed for these antimicrobials is in fact affected by PI and for this reason, it can be assumed that real agreement is higher than that detected by weighted kappa. However, the PABAK coefficient is presented in addition to, rather than in place of, the obtained value of kappa, because it gives an indication of the likely effects of prevalence and bias index along the true kappa value (). A moderate agreement was declared between the tests with ciprofloxacin, clindamycin, and chloramphenicol. The PABAK coefficient gave an indication that the apparently poor agreement observed for chloramphenicol was underestimated.
Poor agreement was observed for nalidixic acid and ampicillin; although large BIs were detected for these 2 antimicrobials, adjusted kappa confirmed this observation.
Since PI observed for azithromycin and erythromycin were not significantly different from 50% (0.59 and 0.49, respectively), it was assumed that the weighted kappa coefficient, which indicated fair and moderate agreement, respectively was an appropriate interpretation.
The CSLI recently approved the agar dilution test as a standardized in vitro antimicrobial susceptibility testing method for Campylobacter for the following antimicrobials: ciprofloxacin, erythromycin, and gentamicin (). Moderate agreement was observed in this study when antimicrobial susceptibility was tested using these antimicrobials. The lack of standards for testing accepted resistance breakpoints for Campylobacter spp. for some antimicrobials used in this study makes it difficult to declare a best method for testing antimicrobial susceptibility of Campylobacter isolates.
The E-test is considered to be an acceptable alternative for testing the antimicrobial susceptibility of Campylobacter spp. depending on the antimicrobial being tested. It has been reported that the E-test is a less tedious, time-consuming, and expensive method than the agar dilution (), because multiple antimicrobials can be evaluated on a single plate containing a single isolate. The results of this study validate the E-test as an optional method for testing the antimicrobial susceptibility of Campylobacter spp. for all the antimicrobials used except for nalidixic acid and ampicillin. However, it is important to remember not only that the E-test underestimates the prevalence of antimicrobial resistance when compared to the agar dilution test, but also that not all antibiotic-containing E-test strips are approved by the FDA.
A high level of disagreement between the E-test and agar dilution was seen with nalidixic acid and ampicillin; therefore, the agar dilution test should be the preferred method for testing antimicrobial susceptibility of Campylobacter against these 2 antimicrobials. The major disadvantage of the agar dilution test is the preparation of serial dilutions of antimicrobials incorporated into agar plates. However, the endpoint of the agar dilution test is easier to interpret than the E-test endpoint. The E-test endpoints may be difficult to interpret because some strains produce feathery or swarming edges at the intersection with the E-test strip ().
The MICs obtained in this study with the agar dilution method were only estimates, as plates with concentrations of antimicrobials close to the resistance breakpoints were used instead of a specific MIC value generated by the E-test. Our study showed that the E-test tends to define lower MICs than the agar dilution test, as in other studies (,,). Further multicenter laboratory evaluations of the E-test have been recommended in order to establish the efficiency of this technique for Campylobacter susceptibility testing ().
Since there is international concern regarding the transfer of bacterial resistance from animals to humans, susceptibility data from laboratories in different countries should be comparable. However, different regulatory agencies utilize different methods with different breakpoints. Standardization of antimicrobial susceptibility testing methodologies, and accepted breakpoints for determining resistance of Campylobacter spp. offers the opportunity to obtain higher quality data in epidemiological surveillance of antimicrobial drug resistance, as MIC values may be monitored over the years to detect trends and changes. Likewise, different mechanisms producing resistance could be detected by evaluating the MIC distribution of the bacteria against different antimicrobials. Since results from the agar dilution method were only estimates, our results only provided qualitative information, such as whether the organism was susceptible or resistant to an antimicrobial agent and did not provide any kind of quantitative data concerning the level of susceptibility. Interpretative issues regarding the comparison of susceptibility data may arise as a result of using qualitative data or dichotomization rather than MICs. Although qualitative data are clinically valuable, they cannot be use for the purpose of monitoring shifts in susceptibility to antimicrobial agents. The aim of surveillance programs is to monitor antimicrobial susceptibility changes in target bacterial pathogens; however, since there is no standardization and harmonization of laboratory methodologies for the detection of antimicrobial resistance, susceptibility testing data between laboratories within and between countries cannot be compared. Comparable results from antimicrobial susceptibility tests (AST) may arise from quantitative data. Results from AST should be reported quantitatively rather than qualitatively, providing the minimal concentration of an antimicrobial required to inhibit the growth of the microorganism (MIC). This approach would facilitate the detection of small changes in antimicrobial susceptibility over time. The agar dilution test provides quantitative results when all serial dilutions of antimicrobials are used, improving the identification of MIC endpoints and the possibility of extending the antibiotic concentration range as far as necessary. Further studies are needed to determine whether agar dilution and E-test produce more comparable results when all the antimicrobial dilution ranges available for the agar dilution test are used.
In conclusion, the level of agreement between the E-test and agar dilution depends on the antimicrobial being tested. The E-test consistently detects a lower proportion of resistant isolates than agar dilution. Either the agar dilution test or the E-test may be used for testing Campylobacter spp. susceptibility to certain antimicrobials, but under conditions of this study there was marked disagreement between the 2 tests for ampicillin and nalidixic acid.
Acknowledgments
This work was supported by Ontario Pork, Ontario Ministry of Agriculture Food and Rural Affairs (OMAFRA), the Public Health Agency of Canada, and the University of Guelph-OMAFRA Animal Research Program.
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Footnotes
This article is part of a master’s thesis, University of Guelph, 2005.