The emergence of
vancomycin-intermediate and vancomycin-resistant Staphylococcus aureus.
Clin Microbiol
Infect. 2006; 12 Suppl 1:16-23 (ISSN: 1198-743X)
Appelbaum PC, Hershey Medical Center, Hershey, Pennsylvania,
USA.
Methicillin-resistant Staphylococcus
aureus (MRSA) is well-recognised as a major cause of infection in the
healthcare setting but, even more worryingly, is now emerging in the
community. The glycopeptides-notably vancomycin-have traditionally
been the mainstay of treatment of MRSA but overuse has led to the
emergence of vancomycin-intermediate and vancomycin-resistant MRSA
(VISA and VRSA, respectively). Although the mechanisms underlying
vancomycin resistance are not yet fully understood, changes to the
bacterial cell wall-the site of action of the glycopeptides-are
believed to be key. Recent evidence also supports the transfer of
genetic material among bacteria as contributing to the development of
VRSA. Based on the cases identified to date, risk factors for the
development of VRSA may include older age, compromised blood flow to
the lower limbs, and the presence of chronic ulcers. The true extent
of the problem, however, remains to be determined-it is likely that
many cases of VISA and VRSA infection go undetected because of
suboptimal screening programmes and possible limitations of automated
and non-automated detection methods. Effective screening directed at
those patients considered to be most at risk should therefore be a
priority. Not surprisingly, the spread of MRSA from the hospital to
the community setting, coupled with the emergence of VISA and VRSA,
has become a major cause of concern among clinicians and
microbiologists. The treatment options available for these infections
are now severely compromised and thus new classes of antimicrobial
agents effective against MRSA, VISA and VRSA are urgently required.
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