Heterotrophic plate count levels in potable water should be
<500 CFU/mL
. These levels may increase on occasion, but counts consistently >500 CFU/mL would indicate a general decrease in water quality.
Is heterotrophic plate count same as total plate count?
Colony counts of heterotrophic bacteria, referred to as HPC, provide an indication of the general load of aerobic and facultative anaerobic bacteria of a water sample. This indicator is also known as standard plate count (SPC), aerobic plate count (APC) and total plate count (TPC).
How do you calculate heterotrophic plate count?
To compute the heterotrophic plate count for pour plate, spread plate, and membrane filter methods (CFU/mL),
divide either the total or average number of colonies per plate by the sample volume
. (Use the average number of colonies if duplicate plates of the same dilution.)
How is plate count calculated?
For example, suppose the plate of the 10^6 dilution yielded a count of 130 colonies. Then, the number of bacteria in 1 ml of the original sample can be calculated as follows:
Bacteria/ml = (130) x
(10^6) = 1.3 × 10^8 or 130,000,000.
How do you calculate CFU ml?
- 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 a CFU count?
A colony forming unit, or CFU, is
a unit commonly used to estimate the concentration of microorganisms in a test sample
. The number of visible colonies (CFU) present on an agar plate can be multiplied by the dilution factor to provide a CFU/ml result.
What is an acceptable aerobic plate count?
Counts outside the normal
25-250 range
may give erroneous indications of the actual bacterial composition of the sample. Dilution factors may exaggerate low counts (less than 25), and crowded plates (greater than 250) may be difficult to count or may inhibit the growth of some bacteria, resulting in a low count.
What is the difference between aerobic plate count and total plate count?
The APC term stands for aerobic plate count, but again is interchangeable with the others. Other terms used more historically are Standard Plate Count, Mesophilic Count or Total Plate Count these too generally refer to aerobic bacteria able to grow at average temperatures (e.g. 30 to 40°C).
How do you reduce heterotrophic plate count?
Activated carbon
is another method of reducing Heterotrophic bacteria. Activated carbon adsorbs dissolved organics, which heterotrophs use as food, essentially starving them.
What is CFU per mL?
cfu stands for colony-forming unit. This means that cfu/g is colony-forming unit per gram and
cfu/ml is colony-forming unit per millilitre
. … They give you the results of the number of colony-forming units, for the number of grams or millilitres of test material that they put on the petri dish.
What is standard plate counting?
The Standard Plate Count (SPC) means
the colony count of the mesophilic bacteria growing under aerobic condition on
standard methods agar (Plate Count Agar), and SPC becomes the representative index indicating the degree of the microbial contamination of the food.
What is pour plate technique?
Pour plate method is usually the
method of choice for counting the number of colony-forming bacteria present in a liquid specimen
. Because the sample is mixed with the molten agar medium, a larger volume can be used than with the spread plate. … Each colony represents a “colony-forming unit” (CFU).
What advantages does the direct count have over the plate count method?
Advantages of Direct Microscopic Count
Rapid, Simple and easy method requiring minimum equipment
. Morphology of the bacteria can be observed as they counted. Very dense suspensions can be counted if they are diluted appropriately.
What is the formula of dilution factor?
For dilution factor you should
divide the volume of your final solution by the weight of sediment used
. For example 50mL/1g=50. That means you should multiply the AAS values by 50.
What is a dilution factor of 2?
A two-fold dilution
reduces the concentration of a solution by a factor of two that is reduces the original concentration by one half
. A series of two-fold dilutions is described as two-fold serial dilutions. In this manual, two-fold serial dilutions are carried out in small volumes in microwell plates.
How do you calculate dilution?
Dilution calculations can be performed using the formula
M
1
V
1
= M
2
V
2
. A serial dilution is a series of stepwise dilutions, where the dilution factor is held constant at each step.
