Killing bacteria

Let’s say that I am in desperate need of a toothbrush and a stranger,. let’s again say, with the flu, gives me his. If I boil it for, let’s say, 5 minutes. Is like a new toothbrush free from any and all bacterias?

For a complete sterilization - killing off all viruses, bacteria, and fungi, including their spore forms - boiling won’t cut it. You would need to steam-treat the toothbrush using something like an autoclave, assuming the toothbrush can handle about 125C for ten minutes.

Boiling it in water for 15 minutes will likely be enough to kill off a big majority of pathogenic bacteria and viruses, so if you’re desperate to use the guy’s toothbrush, leave it in the boiling water longer.

Soaking it in bleach for an hour or so will help. But while you are waiting for it to disinfect, you can always go out and buy a new brush.

Yes, well I mean what pathogen is going to be in an ambulatory (walking…) guys mouth AND survive boiling for 5 minutes ?

Even if you remove all the bacteria, that won’t help you with the flu. Flu is caused by a virus, not bacteria.

That said, boiling does kill flu viruses too, apparently.

A few, potentially. The major groups of spore-forming pathogens include Bacillus and Clostridium. This includes anthrax, botulism, tetanus, and a number of common bacteria that cause food poisoning or GI infections. AFAIK, these bacteria wouldn’t normally colonize the mouth. And some of them (e.g. botulism, tetanus) are pretty ubiquitous in the environment, so you’re already ingesting some of their spores without a problem. They’re only dangerous in high doses or if something is wrong with your body’s natural defenses.

I think that most of the common pathogenic bacteria that might be found in the mouth do not form spores, and would killed by a thorough bleaching or boiling. And I’m not aware of viruses that can survive such treatments. Viruses tend to be a bit more delicate, and conveniently they also tend to cause a lot of the most easily transmissible diseases like the flu or the common cold.

FWIW, I would be comfortable using the boiled toothbrush of someone who has the flu.

boiling could destroy the brush.

a bleach soak would be better.

It should also be washed thoroughly with some soap and water first to remove any toothpaste or other residue that might inhibit the bleach’s anti-microbial action.

Chuck it in a pot of water and place it on the stove, by the time it reaches a boil it’ll be safer than the sponge you used to wash the pot.

Why the x minutes of time? Are some bacteria more heat resistant than others? Because of thickness of different biological layers among one or another? Some kinds of different death temperatures…what/why are they?

Absolutely. Gram-positive bacteria (streptococcus and staphylococcus for example) tend to be more resistant to environmental stresses than gram-negative (E. Coli and pseudomonas spp.) I’m sure the thicker peptidoglycan has something to do with it but there’s also a class of proteins called heat shock proteins (natch) that are expressed as temps rise and protect critical structures. Could be differences between bacterial spp in how effectively they work. The ultimate in heat resistance are the Archeabacteria which have been found happily munching on methanogens and sulfur compounds in boiling hot springs and deep ocean black smokers.

If a stove or bleach are unavailable, this blurb suggests that nuking in a microwave for 4minutes will do the trick.


How effective would it be to immerse the brush in a typical 3% solution of hydrogen peroxide? For how many minutes?

A college friend boiled his toothbrush after it fell into the toilet. The boiling water caused the toothbrush to twist itself into a corkscrew shape, after which he kept it on display in his bathroom as a curio. Visitors would puzzle over its intended purpose.

All things considered, I think you’d be forgiven if you skipped a brushing.

OP here. Thanks for all the comments. Actually the item in question is a toothbrush holder which I bought on ebay. Photo here:


Boiling it as we speak.

A holder? I’d have swiped it a couple times with a Clorox wipe and called it a day. Bacteria and viruses live a lot longer on damp surfaces, so a toothbrush would collect bugs pretty well. Hard surfaces like that toothbrush holder really don’t keep most microbes alive very long.

Let us know how you feel after you you use it. If you don’t post, we’ll assume you’re dead because you didn’t boil it long enough.