THURSDAY, Oct. 16 (HealthDay News) -- Improper use of chemical disinfectants might actually make the bacteria they are trying to kill stronger and more resistant over time, a new report says.

When these chemicals, called biocides, are used at lower-than-lethal concentrations, the bacteria can survive and eventually become resistant to the chemical and antibiotics, according to a paper published in the October issue of Microbiology.

In experiments done on the potentially lethal bacterium Staphylococcus aureus, researchers found the samples mutated when exposed to low concentrations of several biocides and dyes regular used in hospitals for disinfecting. The mutated bacterium had increased numbers of efflux pumps, which remove toxins from its cells. The pumps eliminate antibiotics from the cell and can make the bacteria resistant to those drugs.

"Pathogenic bacteria with more pumps are a threat to patients, as they could be more resistant to treatment," author Dr. Glenn Kaatz, head of infectious diseases for the Department of Veterans Affairs Medical Center in Detroit, said in a society news release.

If the surviving bacteria are exposed repeatedly to biocides, they may build up resistance to disinfectants and antibiotics. Such bacteria contribute to hospital-acquired infections.

"Careful use of antibiotics and the use of biocides that are not known to be recognized by efflux pumps may reduce the frequency at which resistant strains are found," Kaatz said. "Alternatively, the combination of a pump inhibitor with an antimicrobial agent or biocide will reduce the emergence of such strains and their clinical impact."

More information

The Alliance for the Prudent Use of Antibiotics has more about antibacterial agents.