Lighthouse ActiveCount100 Operating Manual
248083444-1 Rev 2
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Interpret Results
Microorganism Sampling Principles
Microorganisms can be found in droplets suspended in air for long periods, and can contaminate
hygiene-sensitive environments. These droplets fall and settle on surfaces, potentially causing
infections in medical facilities and contamination in manufacturing facilities.
MPN (most probable number) is a well established method to estimate the number of viable
microorganisms in a monitored area. To derive MPN, ActiveCount100 uses the principle that
statistically assumes an increasing number of organisms enter the same hole in the sampling
head as the number of organisms per sample rises.
After sampling, incubate the petri dish to determine the number of Colony Forming Units (CFU).
Then, refer to the Feller Conversation Table in Appendix B to find the Most Probable Number
(MPN) of microorganisms.
As an example, if an incubated agar sample contains 5 CFUs, the Feller Conversion Table shows
the MPN is 5.
Summary of Contents for ActiveCount100
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