If you think about your sink at all, it's probably when it's clogged, when things won't go down it. Unless you're in a horror movie about pipe-dwelling invaders, you're probably not too concerned about what might be coming up it. But science suggests maybe you should be, because there's new evidence that bacteria can lie in wait in the pipes beneath your sink and, under the right conditions, climb right up into the open.
Well, not your sink so much as sinks in hospitals. The study built on previous research which showed that multidrug-resistant bacteria (aka the much-feared superbugs) could travel from hospital sink traps to infect vulnerable patients. Researchers weren't sure just how this could happen, however: It wasn't clear how the superbugs were traveling from the colonized trap (the curved pipe running from the sink drain, where superbugs were found) to, presumably, hospital workers—who were, ironically, just trying to wash their hands. The problem couldn't be eradicated, no matter how potent the disinfectants used. In one major outbreak, the sinks had to be replaced with models that splashed less.
That suggested droplet dispersion was the culprit. It makes sense, given that the sink is a wet environment where water gets tossed around willy-nilly. But still, water going down the drain shouldn't have helped bacteria come up it. Superbugs in the trap should have stayed in the trap.
It turns out, though, that under the right conditions, the bacteria dwelling in the trap could create a creeping, protective film that allowed them to slowly climb back up the sink. Slowly, in this case, means 2.5 centimeters a day; it took just about a week for the experimental bacteria (E. coli engineered to glow green) to reach the top. Once there, bugs could hitch an easy ride on the splashing water, landing on surfaces up to .76 meters away in the experiment.
Climbing bacteria get splashed around by unwitting hospital workers and find their way to patients: It's an easy—if horrifying—story to understand. But according to the researchers, it could only happen under certain conditions. Most importantly, for the bugs to begin their crawl, they needed nutrients. E. coli in the P-trap of a sink where only water drained tended to stay in the trap.
But of course, more than water goes down a hospital drain. You can imagine bodily fluids, leftover lunch drinks, and other liquids that'd provide substance for growing bacteria. So the researchers mimicked that environment by adding nutrients to the water. Sure enough, the bacteria perked up and started climbing the drain.
Does this mean your sink is filled with super-pathogens just waiting to be fed so they can make their way out into the world? Probably not. But it is a vital contribution to understanding how, in a nominally antiseptic hospital setting, a superbug could travel from sink to patient. The monster was in the pipes all along.