MRSA bacteremia

Bacteremia is the third most common nosocomial infection, with urinary tract infection most common, and pneumonia ranking second (1,2). The most 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 49 U.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) (3). S. aureus was the second most common bacteremia isolate after coagulase-negative staphylococci, accounting for 20% of cases. Most importantly, the proportion of S. aureus bacteremia isolates with methicillin resistance (MRSA) increased from 22% in 1995 to 57% in 2001 (4). In intensive care unit (ICU) patients, 59.5% of all S. aureus isolates associated with nosocomial infections are now methicillin-resistant (5). Overall rates of S. aureus bacteremia are on the rise; this is due to a significant increase in the rates of MRSA bacteremia.