Predicting methicillin resistance and the effect of inadequate empiric therapy on survival in patients with Staphylococcus aureus bacteremia.
BACKGROUND
The restriction of vancomycin hydrochloride use is recommended as a measure to decrease the emergence of vancomycin resistance in gram-positive organisms; however, vancomycin also is the treatment of choice for methicillin-resistant Staphylococcus aureus (MRSA) infections. If vancomycin use is restricted to patients with documented infections due to methicillin-resistant organisms, then patients with MRSA infections may not initially receive vancomycin. This study was performed to determine factors that predict MRSA bacteremia and if ineffective empiric antibiotic therapy increased the risk of death in patients with S aureus bacteremia.


METHODS
We conducted a retrospective cohort study of all patients with clinically significant S aureus bacteremia (132 episodes in 128 patients) diagnosed between October 1, 1995, and January 1, 1998, at an urban acute care Veterans Affairs medical center (approximately 200 acute care beds) in Baltimore, Md. During the study period, vancomycin was a restricted antibiotic. Empiric use had to be approved by an attending physician specializing in infectious diseases.


RESULTS
Compared with patients who had methicillin-sensitive S aureus bacteremia, patients with MRSA bacteremia were significantly older (70 vs 58 years; P<.01), more likely to have a history of MRSA (47% vs 6%; P<.01) and a nosocomial infection (76% vs 50%; P<.01), and less likely to use injection drugs (8% vs 32%; P<.01). In addition, compared with patients who had methicillin-sensitive S aureus bacteremia, patients with MRSA bacteremia were significantly less likely (45% vs 98%; P<.01) to receive effective antibiotic therapy during the first 48 hours of hospitalization. However, the risk of death due to ineffective empiric therapy was less than 1 (relative risk, 0.82; 95% confidence interval, 0.36-1.88) and did not change significantly when adjusted for age, occurrence of sepsis, or nosocomial infection.


CONCLUSIONS
The results of this study support the safety of the restriction of vancomycin use in patients with clinically significant S aureus bacteremia. However, patients with a history of MRSA are more likely to have future MRSA infections and should receive empiric therapy using vancomycin for possible S aureus infections, particularly for nosocomial infections.
Roghmann
M C
MC
Veterans Affairs Maryland Health Care System and the Department of Medicine, University of Maryland School of Medicine, Baltimore, USA. mroghman@medicine.umaryland.edu
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D000890:Anti-Infective Agents / Q000008:administration & dosage*; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology*; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000382:microbiology; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012306:Risk; D012720:Severity of Illness Index; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D016019:Survival Analysis; D014640:Vancomycin / Q000627:therapeutic use*
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D014640:Vancomycin