home Miscellaneous Shades of Grey in Sterility

Shades of Grey in Sterility

It’s always hard, especially in today’s world, to find the shades of grey in any topic. Everything in media is portrayed as black and white because, frankly, it’s more striking. Similarly, most people are interested in either really beneficial microbes that can be used therapeutically or the pathogens that can kill us.

We have studies such as this one from Kadaifciler and Cotuk that talks about microbial contaminants in dental unit waterlines. This also affects indoor air quality since the water disperses bioaerosols upon being dispensed. Sounds pretty bad…indoor air is definitely not where you’d want water contaminants to end up. But if something like this hit the newsstands, there would probably be an uproar that would lead to over-sterilization. If you kill all the microbes, you’re safe, right?

Not really. As was mentioned in an earlier post this week, being fully sterile is a terrible idea. Most of the time, the reason we don’t die of plague is because beneficial microbes that call our bodies “home” are able to outcompete pathogens. Sterility is not selective (although natural selection at work in/on your body is). It won’t differentiate between microbes that help you live and those that help you die or become ill. An incredibly popular topic of discussion on this blog and in the microbiology sphere is antibiotic resistance and the apparent overmedication that causes it. A comprehensive outline of antibiotics and microbes in medicine can be found here from Bérdy, suggesting that research is starting to move away from purely using antibiotics to solve our germ problems.

So if you want your body to have a hardy immune system, you need to colonize with lots of stuff right? Microbial diversity galore? It’s definitely a factor, but you need to colonize with the right stuff. You can’t just lick every surface you find and expect your immune system to benefit somehow. Research on how children derive and develop their immune systems is incredibly helpful in determining an “optimal” balance of microbes. Kaplan et al wrote on the role of microbes in developing immune responses. From conception, the colonization begins, although the last few months of pregnancy and first few months of life are pivotal.

The question is where is that sweet spot of not being too sterile but not being unhygienic? I personally care because one day I’ll probably have kids, and I’ll want to know how much is too much germ exposure and how much is too little? Should I stop them from playing with potentially sick children or will that actually be beneficial to their immune system. Should I let them lick a cat or put a pacifier that just fell on the floor in their mouth? This is what built environment research is helpful for determining. How many microbes and which ones do we ideally want in our living spaces? How many and which ones do we want on our bodies to optimize our health? These aren’t easy questions and they probably won’t be answered anytime soon, but they are interesting and relevant to our lives.

Shades of Grey


Alex Alexiev

Alex Alexiev is a recent UC Davis graduate with a BS in microbiology working in Jonathan Eisen’s lab on aquariums as part of the microbiology of the built environment.

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