Preventing Nosocomial Spread of MRSA is in Your Hands

Posted 01/26/2004
Teri Capriotti
Introduction
Antibiotic-resistant bacteria have become the scourge of the practices of
medicine and nursing, particularly in the hospital setting. Pharmacologic
innovations can barely keep pace with the development of drug resistance among
strains of bacteria. One of the most troublesome bacterial strains is
methicillin-resistant Staphylococcus aureus (MRSA). MRSA infections can lead to
death, predominantly in hospitalized, debilitated patients. Health care
providers may be confused about the contagion and transmission of this pathogen.
Particularly in hospital settings, nurses must be knowledgeable about the
epidemiology of MRSA to prevent its spread. The hardy S. aureus bacterium has
developed resistance to every antibiotic in its path, beginning with penicillin
60 years ago.
The Natural History of MRSA
The discovery of penicillin in 1940 dramatically reduced the incidence of
bacterial infections around the world. This single antibiotic was effective
against a broad spectrum of bacteria for years, until S. aureus developed the
ability to produce beta-lactamase, an enzyme that destroys penicillin. S. aureus
develops resistance to antibiotics through plasmid-mediated genetic mutations
(Chambers, 2001). These mutations confer S. aureus with a remarkable ability to
adapt to changing antibiotic environments. The resiliency of S. aureus motivated
pharmacologists to create a class of semi-synthetic penicillins that could
withstand beta-lactamase. These antibiotics became known as beta-lactam
penicillins, with methicillin as the prototype. For years, infections with S.
aureus were reliably eradicated with methicillin and its analogs, nafcillin and
cloxacillin. However, the resourceful bacterium soon became able to resist these
beta-lactam antibiotics, and the first strain of MRSA was
identified in 1961. Since the mid-1980s, antibiotic resistance among nosocomial
S. aureus isolates has been increasing appreciably.

In addition to methicillin, strains of S. aureus have developed resistance to
other antibiotics. MRSA is resistant to cephalosporins, erythromycin,
clindamycin (Cleocin®), gentamycin, trimethoprim-sulfamethoxazole (Bactrim®),
and ciprofloxacin (Cipro®). Vancomycin, a glycopeptide antibiotic, was relied
upon until recently to eradicate MRSA infection. As expected, strains of
vancomycin-resistant S. aureus (VRSA) have been isolated and are fast becoming a
new treatment challenge (Hiramatsu, 2001).








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