In hospitals, can disinfectant create super bugs?

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In hospital settings, disinfectants are regularly used to prevent the spread of bacteria and prevent infection, but a new study published in the January issue of the journal Microbiology, suggests that too much exposure to a disinfectant may actually cause harm by creating bacteria that can not only resist the cleaning product, but some antibiotics as well. A team of microbiologists from the National University of Ireland in Galway examined the effects of disinfectant on the bacteria Pseudomonas aeruginosa, which has been known to cause some hospital-acquired infections and can be particularly dangerous for people with weakened immune systems or those with conditions such as diabetes or cystic fibrosis. Researchers found that when they increased exposure to the disinfectant in lab cultures, the bacteria adapted to withstand the disinfectant. What’s more, exposure to the disinfectant also caused the bacteria to resist the commonly prescribed antibiotic ciprofloxacin, despite the fact that the researchers had never exposed the bacteria to this drug.

The microbiologists explain that Pseudomonas aeruginosa was able to withstand the effects of both the disinfectant and antibiotic by adapting to more effectively flush them out of bacterial cells. The researchers also found that, if overly diluted disinfectant was applied to the adapted bacteria, it was far more likely to survive than bacteria that had not been steadily exposed to high levels of disinfectant. This finding may indicate that if some incorrectly diluted hospital disinfectants are applied to surfaces containing the “super bug,” it could even promote the bacteria’s growth.

Of course, the most alarming finding for researchers was that the bacteria became antibiotic-resistant, even without ever being exposed to the ciprofloxacin. This research raises interesting questions not only for future study, but for practical application in hospitals—perhaps something as simple as using multiple types of disinfectant could thwart the evolution of some antibiotic-resistant bugs and reduce the incidence of hospital-acquired infections, the researchers suggest.