Disinfectants can make bacteria stronger

Chemicals used to kill bacteria could potentially be making it more resistant

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Monday, 06, Oct 2008 08:25

Chemicals use to kill bacteria could potentially be making them more resistant, scientists claim.

Low levels of these chemicals, called biocides, can make the lethal bacterium Staphylococcus aureus remove toxic chemicals form the cells even more efficiently, potentially making it resistant to being killed by some antibiotics, a report published in the journal Microbiology today.

Biocides are commonly used in disinfectants and antiseptics to kill microbes while sterilising medical equipment and decontaminating skin before surgery in hospitals.

Researchers claim that while at correct levels biocides do kill bacteria and microbes, if lower levels are used the bacteria can survive and become resistant to treatment.

"Bacteria like Staphylococcus aureus make proteins that pump many different toxic chemicals out of the cell to interfere with their antibacterial effects," said Dr Glenn Kaatz, from the department of veterans affairs medical centre in Detroit.

"These efflux pumps can remove antibiotics from the cell and have been shown to make bacteria resistant to those drugs. We wanted to find out if exposure to biocides could also make bacteria resistant to being killed by the action of efflux pumps."

"We found that exposure to low concentrations of a variety of biocides and dyes resulted in the appearance of resistant mutants," he added. "The number of efflux pumps in the bacteria increased. Because the efflux pumps can also rid the cell of some antibiotics, pathogenic bacteria with more pumps are a threat to patients as they could be more resistant to treatment."

Researchers claim that bacteria which build up resistance to biocides can contribute to hospital-acquired infections.

"Careful use of antibiotics and the use of biocides that are not known to be recognised by efflux pumps may reduce the frequency at which resistant strains are found," said Dr Kaatz.

"Alternatively, the combination of a pump inhibitor with an antimicrobial agent or biocide will reduce the emergence of such strains and their clinical impact."