Is it safe to directly grow bacteria from hands?

[Benjamin Lee]

My name is Ben and I am a high school student. I am currently conducting a research on the efficacy of 3 different types of hand sanitisers on bacteria (Bacillus subtilis). I would like to ask this question: Is it safe to culture and grow samples of bacteria directly from our hands? This is one of the issues that has deterred me from continuing my research as my teacher is not sure whether it is safe and I was hoping that you would be able to clarify things a bit! Thank you

Best Regards,

Ben

[CharonY]

It is not entirely safe and generally should not be done if the teacher is not entirely comfortable with safety supervision. The reason being that our skin also harbors a number of pathogens. Generally, one can limit their growth somewhat by using the right media, but there are still some that generally can multiply. It is therefore necessary to control exposure and ensure proper decontamination after the experiments. But again, if there is no one with proper training around it is probably better not to do it.

 

My suggestion is to reach out to the local college/university and ask for help. Most are happy to do some level of outreach with highschools.

Edited August 31, 2016 by CharonY

[andycap]

I beg to differ. If pathogens are present on your skin in dangerous amounts then I'd have to ask how you avoid harm when you eat with your hands or cut yourself?

It should be fine so long as you follow aseptic technique & dispose of the culture material as contaminated material. If you don't know what the former is or have access to the latter then don't try.

BTW how are you going to assure yourself that you have B subtilis & not some other bacillus (which could be really interesting!).

[StringJunky]

I beg to differ. If pathogens are present on your skin in dangerous amounts then I'd have to ask how you avoid harm when you eat with your hands or cut yourself?

It should be fine so long as you follow aseptic technique & dispose of the culture material as contaminated material. If you don't know what the former is or have access to the latter then don't try.

BTW how are you going to assure yourself that you have B subtilis & not some other bacillus (which could be really interesting!).

In a culture medium, the pathogens are in an environment that facilitates reproduction; much more so than on the hands.When you eat bacteria there are several mechanisms for dealing with them and keeping their numbers in check; in a culture medium they can run rampant and in that environment there may be pathogens that are dangerous in large numbers, but there are not so many on the hands where the sample was taken from..

Edited September 2, 2016 by StringJunky

[andycap]

Yes we do have protective mechanisms & the culture process does generate large numbers. But I don't see the risk.

If he's trying to culture B subtilis then he won't get E Coli or Pseudomonas (or other Gram negatives) to grow very well. (If present what are they doing on his hands anyway!) The other Gram positives would be Staphs (food poisoning), Streps (sore throat) or other Bacilli sp.

See my comment about aseptic technique.

I assume that Ben, once he's grown the bugs, won't stick his fingers in the culture medium!

However back to the first reply - doing the work in a real laboratory would be a) safer, b) much more rewarding & interesting.

[CharonY]

1) as already pointed out, cultivation massively increases the bacterial titer

2) many media for Bacillus are not selective for Gram+ cells

3) Even if it was, there are plenty Gram+ pathogens as well as Bacillus species.

4) the point was that neither OP nor his teacher were familiar with aseptic techniques nor biosafety (which includes safe disposal). Without proper knowledge or supervision cultivating unknown bacteria always carries a risk. In school it usually appears trivial as there is always someone around to take care of it and prevent something going wrong. But assuming that people will be safe without training is, well, risky.

 

Note that the question was whether it is safe rather then whether it can be done safely.

Edited September 4, 2016 by CharonY

[John Cuthber]

...If pathogens are present on your skin in dangerous amounts...

They typically aren't.

However if you culture lots of them up, they would be present in large amounts.