How Many Bacteria Does It Take to Cause Illness?

The number of bacteria that makes a person sick is a well-debated topic – but the numbers can be quite small for “ordinary” people for some of the common food pathogens and even lower for those with specific health problems.  Each species has its own “dose” level. For any one person, this number could be on the high side for one type of  bacteria and on the low side for another type of bacteria.

How fast do bacteria increase in number?  There’s no single answer to this question either. The doubling time for each organism is very temperature dependent and very organism specific. The worst case is probably about 20 minutes for a doubling at a very warm temperature. But many organisms are slower.

Source(s):

 Joe Regenstein, Ph.D. Cornell University, Dept. of Food Science