Germs can develop antimicrobial resistance. It is a problem serious enough to deserve an FAQ page on the WHO website (http://www.who.int/mediacentre/factsheets/fs194/en/).

But how about surfactant resistance? We wash our body, our dishes, our clothes, and pretty much anything that is washable with soap/detergent, which means surfactants.

So can germs develop surfactant resistance in a way that is harmful to human health? If so, is there any recorded experiment about it? If not, why not?

  • $\begingroup$ Against detergents this is hardly possible (ok, never say never for bacteria but still), since detergents destroy the membranes of the cells. I don't think bacteria will have enough time to develop resistance mechanisms against it. $\endgroup$ – Chris Jan 20 '14 at 7:48

Never say never indeed!

There are a few sorts of answers to this question 1) Bacteria can develop resistance. These researchers did a screen for Staph and Pseudomonas which survived a detergent/soap treatment and indeed were able to select for many strains. I'm not sure that their explanation of why they are resistant is a final answer, especially for the Pseudomonas strains which have no hypothesis at all.

2) Nearly all bacteria do this all the time #1 Most bacteria can go into spore or plaque forms which basically hibernate. These plaque colonies are matrices of crosslinked bacteria and are resistant to extremes of conditions in the environment or lack of food.

3) Nearly all bacteria do this all the time #2 Resistance is a relative term. Alcohol sanitizers kill 99.9% of bacteria. that 0.1% can come back to full strength in a relatively short period of time. its still millions of individuals surviving. resistant bacteria have a higher proportion of survivors and might improve the bounce back rate little or not at all. So resistance is a term which you need to define for a given situation.

Surfactant resistant bacteria can be nearly any sort of bacteria and a certain percentage of them are ready for a scrub down at any given time. To get a surface completely free of bacteria takes a good deal of work.

As far as a danger to human health - resistance to being killed by soap is a real problem because the few of them which also have resistance to antibiotics and are pathogenic will be pretty much unstoppable. Its not likely that surfactant resistance will itself make a bacteria pathogenic (never say never!) but if such a 'triple threat' emerges we'd all be in trouble.

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    $\begingroup$ I agree, I did a "death of kitchen bacteria" project and subjected pieces of sponge to different treatments. One of them was washing with lots of detergent and soap. When I grew the bacteria remaining on the sponge after the treatment, I found that it was not very effective. $\endgroup$ – biogirl Jan 20 '14 at 14:22

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