Disinfectants may fuel growth of superbugs

Using disinfectants may cause the growth of superbugs, which are resistant to both the disinfectant and antibiotics designed to kill them, scientists have warned.

Scientists from the National University of Ireland added increasing amounts of disinfectant to cultures of the bacterium Pseudomonas aeroginosa. Through time the bacteria learned to adapt to survive not only to the disinfectant but also a common antibiotic called ciprofloxacin, without ever being in contact with it.

As well as being a cause of hospital acquired infections, Pseudomaonas bacteria cause infections in people with weakened immune systems, such as those with AIDS, cystic fibrosis and cancer.

The scientists found the adapted bacteria were better at pumping out disinfectants and antibiotics from their cells. They also had a mutation in their DNA which made them resistant to the antibiotic.

The adapted bacteria were also more likely to survive when weaker concentrations of disinfectant were used compared with normal bacteria. This could make them more of a danger in a hospital setting.

Dr. Gerard Fleming, who led the study, said, "In principle this means that residue from incorrectly diluted disinfectants left on hospital surfaces could promote the growth of antibiotic-resistant bacteria.

"What is more worrying is that bacteria seem to be able to adapt to resist antibiotics without even being exposed to them."

Dr. Fleming also stressed the importance of studying environmental factors that might promote antibiotic resistance.

"We need to investigate the effects of using more than one type of disinfectant on promoting antibiotic-resistant strains. This will increase the effectiveness of both our first and second lines of defence against hospital-acquired infections," he said.

The study is published in the January 2010 issue of the journal Microbiology.

This article was published on Tue 29 December 2009