Disinfectants designed to keep bacteria out of homes and hospitals could be fuelling the growth of superbugs, a study suggests.
Scientists found that exposing infectious bacteria to increasing amounts of disinfectant turned the bugs into hardy survivors.
Not only did they become immune to the cleansing chemicals, but they developed resistance to a commonly prescribed antibiotic, ciprofloxacin.
This was despite the bugs not having previously encountered the drug.
The findings could have important implications for controlling the spread of hospital infections, the researchers believe.
Scientists in the Republic of Ireland carried out the tests on Pseudomonas aeruginosa, a bacterium that causes a wide range of infections in people with weak immune systems.
Sufferers of diseases such as cystic fibrosis and diabetes are also vulnerable to the bug, which is responsible for many hospital-acquired infections.
The scientists, led by Dr Gerard Fleming from the National University of Ireland in Galway, found bacteria adapted to disinfectant exposure by improving their ability to pump antimicrobial agents out of their cells.
They also developed a DNA mutation that helped to resist ciprofloxacin-type antibiotics.
The study will be reported in the January issue of the journal Microbiology.