ABSTRACT
Staphylococcus aureus has been recognized as a major microbial pathogen
for well over 100 years, having the capacity to produce a variety of sup-
purative and toxigenic disease processes (Table 1). Many of these infec-
tions are life threatening and have exhibited enhanced virulence in
hospitalized patients or individuals with selective risk factors such as
diabetes. Within the last 40 years, strains of methicillin-resistant S. aureus
(MRSA) have rapidly spread throughout the health care environment such
that it is estimated 20% to 60% of S. aureus isolates recovered from
hospitalized patients express methicillin resistance (1). Furthermore, a
recent study conducted by the Centers of Disease Control and Prevention
(CDC) reported that the rate of hospitalization because of MRSA in the
United States was highly variable with the rate for MRSA hospitalization
in patients under the age of 14 to be 13.1 per 1000 patient discharges,
while the rate for patients above 65 years of age was found to be 63.6 per
1000 patient discharges (2). MRSA has become a significant clinical
pathogen in part because of three factors: (i) an intrinsic pathogenicity
mediated by specific (and often unique) virulence factors, (ii) high
frequency of nosocomial dissemination and acquisition within the health
care environment, and (iii) limited therapeutic options. Designated strains
of hospital-acquired MRSA (HA-MRSA) in addition to expressing resis-
tance to the b-lactam antimicrobial agents are often resistant to other common anti-infectives such as erythromycin, tetracycline, and clinda-
mycin. Recent studies have documented that in addition to increased
patient morbidity there is a significant economic burden associated with
MRSA infections because of increased length of stay (LOS) and higher
related health care costs (3,4).
