The use of a commonly prescribed antibiotic is a major contributor to
the spread of infection in hospitals by the 'superbug' MRSA, according
to new research. The study also found that increasing measures to
prevent infection -- such as improved hygiene and hand washing --
appeared to have only a small effect on reducing MRSA infection rates
during the period studied.
MRSA -- methicillin-resistant Staphylococcus aureus -- is a
bacteria that causes hospital-acquired infection and is resistant to all
of the penicillin-type antibiotics frequently used in hospitals to
prevent and treat infection. It can cause serious infections of the
skin, blood, lungs and bones.
The researchers -- led by St George's, University of London --
tracked MRSA infection over 10 years from 1999 to 2009 at St George's
Hospital, looking at how it has adapted to survive in a hospital
environment and at factors that affected its prevalence. They found that
a significant drop in MRSA rates coincided with a reduction in hospital
prescriptions of ciprofloxacin, the most commonly prescribed antibiotic
of the fluoroquinolone family.
Over a short period of the study, ciprofloxacin prescriptions fell
from 70-100 daily doses for every thousand occupied beds to about 30
doses. In the same period, the number of patients identified by the
laboratory to be infected with MRSA fell by half, from an average of
about 120 a month to about 60. Following this, over the last two years
of the study both the drug prescription level and MRSA rates remained at
these reduced levels. Symptoms of MRSA infection can range from very
mild to severe, but it is not known how many of the cases examined in
the study were serious.
The study -- published in the Journal of Antimicrobial Chemotherapy
-- looked at whether other factors such as improved infection control
measures may have contributed to this decrease in infection. However,
during a four-year period when more stringent infection control policies
were introduced -- including improved cleaning and hand washing, and
screening patients for MRSA on arrival at hospital -- the only major
reduction in MRSA infection rates coincided with the reduction in
ciprofloxacin prescriptions.
Lead author Dr Jodi Lindsay, a reader in microbial pathogenesis at St
George's, University of London, said: "Surprisingly, it wasn't hygiene
and hand washing that were the main factors responsible for the decrease
in MRSA in the hospital. Rather, it seemed to be a change in the use of
a particular group of antibiotics. Hand washing and infection control
are important, but they were not enough to cause the decrease in MRSA we
saw."
Dr Lindsay said the study suggested that MRSA relies on ciprofloxacin
-- and fluoroquinolones in general -- to thrive in hospitals, as well
as penicillin-type drugs, which was already assumed. The fluoroquinolone
group of antibiotics have a similar enough mechanism of action to
assume that the effect would be the same for them all.
She added that the findings suggest the most effective way to control
MRSA and other hospital-based superbugs is to continue finding
alternative ways to use antibiotics, rather than simply focusing on
infection control techniques.
As well as identifying factors that influenced prevalence, the
researchers identified the strain of MRSA that has become dominant. This
strain -- CC22 -- has thrived by developing and maintaining multi-drug
resistance, and becoming more fit to survive on hospital surfaces than
other strains.
Dr Tim Planche, consultant microbiologist at St George's Healthcare
NHS Trust and one of the co-authors of the study, said: "The Trust
currently has infection rates among the lowest in London, having
successfully driven acquisitions down over the past five or six years
using a combination of both tough hygiene regimes and careful selective
use of antibiotics. These findings, however, provide valuable insight
and certainly warrant further investigation, which could lead to the
development of even more effective infection control strategies in
future."
Dr Lindsay said that studying the dynamic of how MRSA bacteria
strains continue to evolve in hospitals in response to changing practice
and interventions, such as infection control and antibiotic
prescribing, will be essential to determine which interventions work,
which are cost effective, and which are likely to have the best
long-term outcomes.
She added: "But it seems that we now have an excellent opportunity to
control superbugs in hospitals by re-examining how we prescribe
antibiotics and ensuring we're using them in the most effective way
possible."
Journal Reference:
- G. M. Knight, E. L. Budd, L. Whitney, A. Thornley, H. Al-Ghusein, T. Planche, J. A. Lindsay. Shift in dominant hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) clones over time. Journal of Antimicrobial Chemotherapy, 2012; 67 (10): 2514 DOI: 10.1093/jac/dks245
Courtesy: ScienceDaily
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