ABSTRACT
Bacteremia is the third most common nosocomial infection, with urinary
tract infectionmost common, and pneumonia ranking second (1,2). Themost
common causative pathogens for bacteremia are gram-positive pathogens,
accounting for 65% of cases, including coagulase-negative staphylococci
and Staphylococcus aureus (Table 1). The SCOPE project examined 24,179
cases of nosocomial bacteremia in 49U.S. hospitals between 1995 and 2002,
and documented a 10% increase in bacteremia due to gram-positive cocci,
with a concomitant 10% decrease in the percentage of bacteremia due to
gram-negative bacilli (from 33.2% in 1986 to 23.8% in 2003) (4). S. aureus
was the second most common bacteremia isolate after coagulase-negative
staphylococci, accounting for 20% of cases. Most important, the proportion
of methicillin-resistant S. aureus (MRSA) bacteremia isolates increased
from 22% in 1995 to 57% in 2001 (3). In intensive care unit (ICU) patients,
59.5%of all S. aureus isolates associatedwith nosocomial infections are now
methicillin resistant (5). In a U.S. study by the Surveillance Network, annual
rates of MRSA were shown to have increased steadily during 1998-2005,
with rates of up to 59.2%among S. aureus isolates in clinical specimens from
non-ICU patients. In the same study, MRSA constituted 49.1% of blood-
stream S. aureus isolates from inpatients and 41.4% of such isolates from
outpatients (6). Overall rates of S. aureus bacteremia are on the rise; this is
due to a significant increase in the rates of MRSA bacteremia.
