chapter  12
28 Pages

Reducing the Risk of Nosocomial Dissemination of Methicillin- Perspective /

ByCharles E. Edmiston, Jr. and Nathan A. Ledeboer

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).