University of Pittsburgh’s Microbiology Lab Coordinator, Melanie Popa, kindly answered some… University of Pittsburgh’s Microbiology Lab Coordinator, Melanie Popa, kindly answered some basic questions about the topic of “good” versus “bad” bacteria that people encounter:

What determines good and bad bacteria? “Bad” bacteria have many mechanisms for being bad. Some excrete a toxin or even several toxins which will make you sick if you ingest it or have it present in a wound. In some cases, part of the bacteria itself is toxic.

Where can we ordinarily find both types of bacteria?

Bacteria are present in pretty much every place that we’ve looked for them.

How do our bodies react to each type?

Remember that E. coli is a normal inhabitant of all mammalian intestines, so when you have normal E. coli present, as we all do, your body doesn’t react at all. When you get one of the food-borne disease versions, most notably E. coli O157:H7 of the recent spinach-related outbreak, you develop diarrhea and possibly much worse symptoms, like kidney failure. Different disease-causing bacteria will elicit different responses from the host.

Keep in mind that entire courses are taught on this subject, so the provided answers only give a brief background about the differences in bacteria.

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