Why are Miles Misra plates useful?
The Miles and Misra Method (or surface viable count) is a technique used in Microbiology to determine the number of colony forming units in a bacterial suspension or homogenate. The Miles and Misra method has been shown to be precise.
What are the advantages and disadvantages of spread plate method?
It is useful for the samples having heat sensitive microbes. 2. No subsurface colonies appear in spread plate so isolation of the organism is easy. Volume no greater than 0.1 ml can be spread on the nutrient agar plate because it would not soaken well and may result colonies to coalesce as they form.
What is drop plate method?
The drop plate (DP) method can be used to determine the number of viable suspended bacteria in a known beaker volume. Less time and effort are required to dispense the drops onto an agar plate than to spread an equivalent total sample volume into the agar.
How do you calculate colony forming units?
- To find out the number of CFU/ ml in the original sample, the number of colony forming units on the countable plate is multiplied by 1/FDF. This takes into account all of the dilution of the original sample.
- 200 CFU x 1/1/4000 = 200 CFU x 4000 = 800000 CFU/ml = 8 x 10.
- CFU/ml in the original sample.
What is viable plate count?
The viable plate count, or simply plate count, is a count of viable or live cells. It is based on the principle that viable cells replicate and give rise to visible colonies when incubated under suitable conditions for the specimen.
What are the disadvantages of spread plate technique?
Limitations. Strict aerobes are favored while microaerophilic tends to glow slower. Crowding of the colonies makes the enumeration difficult. Accurate dilutions using pipettes should be made.
Why is spread plate method used?
The spread plate method is a technique to plate a liquid sample containing bacteria so that the bacteria are easy to count and isolate. A successful spread plate will have a countable number of isolated bacterial colonies evenly distributed on the plate.
How do you calculate the number of bacteria?
How to calculate the number of bacteria in a population
- Example.
- The mean division time for bacteria population A is 20 minutes.
- In order to answer this, you can split the calculations into two sections.
- If the bacteria grow for six hours, each bacterium will divide 3 times per hour × 6 hours = 18 times.
What is normal CFU mL?
Laboratory Tests For that reason, up to 10,000 colonies of bacteria/ml are considered normal. Greater than 100,000 colonies/ml represents urinary tract infection. For counts between 10,000 and 100,000, the culutre is indeterminate. Sensitivity refers to the antibiotics tested to be effective in stopping the bacteria.
What are the disadvantages of viable plate count method?
There are several drawbacks to the viable count method. The major disadvantage is that it is selective and therefore biased. The nature of the growth conditions, including the composition and pH of the medium used as well as the conditions such as temperature, determines which bacteria in a mixed population can grow.
What are the disadvantages of plate count assays?
among these disadvantages are: (1) the length of time required for incubation, 48 hours being the shortest; (2) large amount of glassware and culture medium required, as well as other expensive equipment, and (3) the paucity of details regarding the kinds of organisms present.
Which is better pour plate or spread plate?
Although you don’t need spreaders, I see only one real advantage of pour plates in comparison with standard spread plates: If you bacteria don’t like oxygen, they would be better off in the media, where there is less oxygen, than on the agar surface.
How is the miles and Misra method used?
Miles and Misra method. The Miles and Misra Method (or surface viable count) is a technique used in Microbiology to determine the number of colony forming units in a bacterial suspension or homogenate.
When did miles and Misra invent surface viable count?
This is a type of surface viable count technique. In 1938 Miles and Misra invented this method. In this method, Miles and Misra used dilution of S.pneumoniae on blood agar plate. To learn this technique completely, let us understand what is its pre-requirements of materials, its method, its advantages and disadvantages.
When did miles and Misra invent the CFU method?
Determining Bacterial CFU : A technique used in Microbiology to determine the exact number of cfu that is colony forming units in a bacterial suspension or homogenate is known as The Miles and Misra Method. This is a type of surface viable count technique. In 1938 Miles and Misra invented this method.