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A while back I heard an NPR story about bacteria growing in reusable grocery bags, and now there's a piece from WaPo's health blog about bacteria fround on 3-D glasses you get at movie theaters:

In its July issue, Good Housekeeping magazine tested seven pairs of 3-D glasses, three that were wrapped and four unwrapped, and found that none of them were bacteria-free.

Well, duh. Bacteria are everywhere! When working with cell culture in lab, everything is done in a special "hood," a box with fans and filters specifically designed to prevent anything outside from getting in, I wear gloves, and spray everything with ethanol, and I even have high doses of antibiotics in the media. Stuff still gets contaminated every once in a while.

What matters is what kinds of bacteria are present, and if they are actually pathogenic. The NPR story goes to great lengths to explain that the bacteria found in the grocery bags are basically benign, but the WaPo piece...

While most of the bacteria (collected via swabs that were sent to an independent lab) was deemed harmless, one set of glasses bore Staphylococcus aureus bacteria, which can cause pinkeye and other infections.

And some strains of E. coli can cause severe food poisoning, but there's billions of non-pathogenic E. coli in your gut right now. They then say you should wipe the glasses with alcohol swabs, but in the very next sentence is

Even if you don't think to take any such measures, though, your risk of getting sick from movie glasses is pretty low[...]

Ugh. So, there are bacteria in your grocery bags and on your 3-D glasses, which are harmless, but you should wash them anyway, but if you don't it doesn't matter. My take: after you wipe the glasses with alcohol swabs, you'll probably just re-contaminate them with the S. aureus that's already on your nose.