I’m curious to learn the typical order of magnitude of the number of organisms (per square cm, say) found on the surface of a contaminated piece of chicken (or beef, etc). I understand this is going to be highly variable, but, for example, what order of magnitude of salmonella bacteria might I expect to find on the surface of a piece of severely infected chicken? Same goes for E-coli on beef or spinach – a million? 10^12? I have my own crude back-of-the-envelope guesses, but I’d like an informed opinion here.
That depends on how contaminated it is. It’s rare to find more than 10 million or so organisms per square cm, even when you’re growing it on purpose, although some organisms can develop complex support structures holding slightly more than that. If you’re not looking at obviously contaminated food, the concentration is likely to be no more than 100,000 per sq. cm, and most tainted products that temporarily pass the smell test are below 1000 – but they’re going to grow.
How about salmonella specifically? I only ask because I read that it typically takes ingestion of greater than 100K salmonella bacteria to cause human symptoms. This is consistent with your above answer, but I’m still thinking “wow, you’ve got to really be quite sloppy in order to have a chance of getting infected.”
A square centimeter is pretty damn small compared to most food items. With a fairly inconspicuous concentration of 1000 organisms per sq. cm, a single large chicken breast could harbor more than 100K on its surface.
Well, I hear you, but all I’m saying is, for example, one would have to take that (quite large) chicken breast, rub all sides of it onto a plate with vigor, and then forget to wash the plate and use it for something else, and earnestly lick every square centimeter of the plate, in order to actually consume all those 100K bacteria.
I agree that it would probably be pretty easy to get salmonella with there being a concentration as high as 100K organisms per sq. cm. But I find it interesting that you could do a half-assed job of washing the raw chicken plate (ie remove only 99% of the bacteria) and then be pretty sure that you won’t possibly get salmonella by eating off the plate (although I don’t condone such a thing).
On a related note which will freak out the germophobes …
How many organisms per cm[sup]2[/sup] are typical on uncontaminated food? I kill my chicken, defeather it, rinse it, slice off a breast & set it in my pan. How many “bugs” of all types on it?
How many on my hand after washing but just before I touch the chicken?
Oh, that. The majority of the time, salmonella is not ingested in the form of uniformly contaminated foodstuffs, but by contamination of food with microbe-rich material, like manure. I also checked the 100K story, and it’s not true; some serotypes of salmonella can cause illness after ingestion of as few as 20 cells. However, the more one ingests, the more likely (and more rapid) the onset of gastroenteritis becomes.
LSLGuy, a breast from a freshly killed chicken, handled by the best hygienic practices, shouldn’t have any bacterial contamination; it’s the exterior surface, including the gut, that gets colonized. Your kitchen, on the other hand, probably doesn’t meet those standards. Uh, no offense – neither does mine.