Research leader Dr. Glenn Kaatz says that low levels of the chemicals called biocides can make the potentially lethal bacterium Staphylococcus aureus remove toxic chemicals from the cell even more efficiently, potentially making it resistant to being killed by some antibiotics.
"Bacteria like Staphylococcus aureus make proteins that pump many different toxic chemicals out of the cell to interfere with their antibacterial effects," said Kaatz.
"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," he added.
During the study, the researchers exposed S. aureus taken from the blood of patients to low concentrations of several biocides and dyes, which are also used frequently in hospitals.
They studied the effect of exposure on the bacteria and found that mutants that make more efflux pumps than normal were produced.
"We found that exposure to low concentrations of a variety of biocides and dyes resulted in the appearance of resistant mutants," said Kaatz.
"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," he added.
If bacteria that live in protected environments are exposed to biocides repeatedly, for example during cleaning, they can build up resistance to disinfectants and antibiotics. Such bacteria have been shown to contribute to hospital-acquired infections.
If these chemicals are used at the correct strength, biocides kill bacteria and other microbes.