Question

You have performed a serial dilution of an unknown sample and counted 46 cfu on a countable plate that was marked as a 10-8 dilution and you used 0.1 ml to inoculate the plate. what is the population density of the original sample

Answer 1

books.google.co.in

Food microbiology laboratory

Lynne McLandsborough

CRC Press, 2004

In order to truly understand food microbiology, it is necessary to have some experience in a laboratory. Food Microbiology Laboratory presents 18 well-tested, student-proven, and thoroughly outlined experiments for use in a one-semester introductory food microbiology course. Based on lab experiments developed for food science and microbiology courses at the University of Massachusetts, this manual provides students with hands-on experience with both traditional methods of enumerating microorganisms from food samples and" rapid methods" often used by industry. It covers topics such as E. coli, Staph, and Salmonella detection, as well as the thermal destruction of microorganisms, and using PCR to confirm Listeria monocytogenes. All parameters and dilutions presented in the text have been optimized to ensure the success of each exercise. An instructor's manual is also available with qualifying course adoptions to assist in the planning, ordering, and preparation of materials. This valuable text features well-established laboratory exercises based upon methods published in the FDA Bacteriological Analytical Manual. It provides the backbone for any laboratory session and may be customized with test kits to reflect the emphasis and level of the class.

Answer 2

The CFU/ml can be calculated using the formula: cfu/ml = (no. of colonies x dilution factor) / volume of culture plate. For example, suppose the plate of the 10^6 dilution yielded a count of 130 colonies.