December 28, 2009

Disinfectants May Cause Superbugs To Resist Antibiotics

New research suggests that disinfectants could effectively train bacteria to become resistant to antibiotics.

Previous studies have shown that bacteria can become inured to disinfectant, but newer research increasingly shows the same process may make them resistant to certain drugs.

Scientists say this can occur even with an antibiotic the bacteria have not been exposed to yet.

The National University of Ireland team, who focused on a common hospital bacterium, said the new revelations mean science must now rethink how infections are managed.

The researchers discovered that by adding increasing amounts of disinfectant to cultures of pseudomonas aeruginosa in the lab, the bacteria learned to resist not only the disinfectant but also ciprofloxacin - a commonly-prescribed antibiotic - even without being exposed to it first.

The study, published in Microbiology, shows that bacteria had adapted to pump out anti-microbial agents -- be they a disinfectant or an antibiotic -- from their cells and the adapted bacteria also had a mutation in their DNA that allowed them to resist ciprofloxacin-type antibiotics specifically.

Pseudomonas aeruginosa is a bacterium most likely to infect those who are already seriously ill and can cause a wide range of infections, particularly among those with weak immune systems such as HIV or cancer patients, as well as people with severe burns, diabetes or cystic fibrosis.

Medical experts can prevent its spread with surface disinfectants, but if the bacteria manage to survive and go on to infect patients, antibiotics are used to treat them.

However, the study warned that bacteria that could resist both these control points could be a serious threat to hospital patients.

Study author Dr. Gerard Fleming said at the high concentration levels generally employed, it was unlikely to be a problem.

"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," he added.

Meanwhile, there is a growing body of research raising concerns about the effects on antibiotic resistance of disinfectants and antiseptics.

A report from the UE, published earlier this year, highlighted the importance of the "appropriate and prudent" use of disinfectants to minimize the risk that bacteria become resistant to both forms of defense.

Treatments in hospitals in Brazil had been compromised earlier this year by a bacterium -- mycobacterium massiliense -- that had developed resistance to a common sterilization fluid and a number of antibiotics used to treat the subsequent infections.

Dr. Gerry McDonnell, a researcher in the field, said it was very significant because it was really the first incident related to resistance to a biocide that led to clinical failure, which is new.

"This really needs to be an area of active investigation and debate. But it's worth bearing in mind that disinfectants may not just be the problem, they may also be the cure," he added.

The disinfecting wipes used to protect against MRSA could in fact spread the bug, as the solution contained was often not sufficient to kill all the bacteria picked up, and hospital staff often used the same wipe to clean more than one surface, according to a recent study.


Image Caption: Pseudomonas aeruginosa bacterial culture on an Xylose Lysine Sodium Deoxycholate (XLD) agar plate. CDC


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