What is the research methodology for measuring bacteria?

I am currently writing a proposal for a research project. In my project I am trying to determine the amount of bacteria that is contained when exposed to two different types of topical antiseptics. I know that I will have to use Petri dishes and grow the bacteria, however, I am not completely sure how to go about it. I also need to know the specific name of the method that I would use in order to measure that amount of bacteria that would (or would not) grow. Thanks so much!What is the research methodology for measuring bacteria?
Please see the web page for more details on Growth medium. The number of bacteria is usually counted on high power field. High Power Field (HPF) when used in relation to microscopy references the area visible under the maximum magnification power of the objective being used. Often, this represents a 400x magnification level when referenced in scientific papers.What is the research methodology for measuring bacteria?
Bacterium are exposed to agar and incubated. You then count "Colonies" of bacteria. See writeup at attached link.What is the research methodology for measuring bacteria?
Hi,



The best way to quantify bacteria on Petri dishes, is through the Colony Forming Units (CFU) method.



This method consists in the serial dilution of a suspension of bacteria. First, you have to dilute the bacteria 10 times in a certain volume (for example 100uL of bacteria in 900uL of water or PBS). Then, from this dilution, you take another 100uL and dilute it again, in 900uL of water or PBS. By repeating this several times, you are doing a serial dilution. In the last dilution discard 100uL.



Then, from each one of the dilutions, you transfer a small volume (5 or 10uL) to the Petri dish containing the culture medium specific to grow your bacteria of interest.



Incubate the Petri dish in the appropriate incubator at the optimal temperature and atmosphere.



Finally, after a few days (depending on the species of bacteria), you will see bacterial colonies on the areas where you put the 5/10uL drop. You will select the nicest drop to count (ideally, between 30 to 300 colonies).



You count the colonies and make the dilution calculations.



In the end, by comparing the number of colonies on the treated bacteria versus the untreated bacteria, you will be able to determine if the drugs you are tersting have an effect on the killing or growth of the bacteria.



If you do this in triplicates the results will be more consistent.



I hope this helps. Good luck!