Scientists in the Republic of Ireland have found that the growth of superbugs may be fuelled by disinfectants designed to keep bacteria out of homes and hospitals.
The study found that the bugs turned into hardy survivors when an increasing amount of disinfectant was used.
The researchers raised concerns over the spread of hospital bugs as the bacteria involved, Pseudomonas aeruginosa, also developed a resistance to a commonly prescribed antibiotic, ciprofloxacin.
People with weak immune systems, and those who suffer from diseases such as cystic fibrosis and diabetes are vulnerable to the bug.
The scientists, led by Dr Gerard Fleming from the National University of Ireland in Galway, found that the 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 them resist ciprofloxacin-type antibiotics.
Disinfectants are commonly used in homes, workplaces and hospitals to kill bacteria on surfaces, while antibiotics are administered to infected patients. Bacteria that can resist both these control points could be a serious threat in hospitals, said the scientists.
The study, reported in the January issue of the journal Microbiology, showed that exposure to small non-lethal amounts of disinfectant encouraged the survival of resistant bacteria.
Dr Fleming said: "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 stressed the importance of studying environmental factors that might promote antibiotic resistance. 
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