Use of disinfectants may promote bacterial resistance to antibiotics
13 January 2010
Using disinfectants could cause bacteria to become resistant
to both the disinfectant and also antibiotics they have not been exposed
to, according to research conducted by the University of Ireland.
The findings, published in the January issue of Microbiology
, could have important implications for how the spread of
infection is managed in hospital settings.
Researchers from the National University of Ireland in Galway found
that by adding increasing amounts of disinfectant to laboratory cultures
of Pseudomonas aeruginosa, the bacteria could adapt to survive
not only the disinfectant but also ciprofloxacin — a commonly-prescribed
antibiotic — even without being exposed to it.
The researchers showed that the bacteria had adapted to more
efficiently pump out antimicrobial agents (disinfectant and antibiotic)
from the bacterial cell. The adapted bacteria also had a mutation in
their DNA that allowed them to resist ciprofloxacin-type antibiotics
Pseudomonas aeruginosa is an opportunistic bacterium that
can cause a wide range of infections in people with weak immune systems
and those with diseases such as cystic fibrosis (CF) and diabetes.
P. aeruginosa is an important cause of hospital-acquired
infections. Disinfectants are used to kill bacteria on surfaces to
prevent their spread. If the bacteria manage to survive and go on to
infect patients, antibiotics are used to treat them. Bacteria that can
resist both these control points may be a serious threat to hospital
Importantly, the study showed that when very small non-lethal amounts
of disinfectant were added to the bacteria in culture, the adapted
bacteria were more likely to survive compared to the non-adapted
Dr Gerard Fleming, who led the study, 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.”
Dr Fleming also stressed the importance of studying the environmental
factors that might promote antibiotic resistance. “We need to
investigate the effects of using more than one type of disinfectant on
promoting antibiotic-resistant strains. This will increase the
effectiveness of both our first and second lines of defence against
hospital-acquired infections,” he said.
1. PH Mc Cay, AA Ocampo-Sosa and GTA Fleming. Effect of subinhibitory
concentrations of benzalkonium chloride on the competitiveness of
Pseudomonas aeruginosa grown in continuous culture. Microbiology
; 156: 30-38.