Risk factors and predictors of mortality of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in HIV-infected patients.
OBJECTIVE
To define the incidence, risk factors and short-term predictors of mortality of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in HIV-infected patients.


METHODS
All HIV-infected subjects with S. aureus bacteraemia were consecutively enrolled in a case-control study between January 1, 1991 and December 31, 2000 and prospectively followed up.


RESULTS
In the study period, 129 of 419 (31%) HIV-infected patients with bacteraemia had a diagnosis of S. aureus bacteraemia. The comparative analysis of incidence of S. aureus bacteraemia in the period 1991-96 and 1997-2000 showed a significant decrease (P < 0.001). The same trend was observed for MRSA bacteraemia (P = 0.002). The analysis of antimicrobial resistance showed that among 129 S. aureus strains, 88 (68%) were methicillin susceptible and 41 (32%) were methicillin resistant. The majority of MRSA bacteraemia was hospital acquired (78%). Previous administration of beta-lactams (P < 0.001), multiple previous hospital admissions (P < 0.001) and low numbers of CD4+ peripheral cells (P < 0.001) were found to be independent risk factors of methicillin resistance at multivariate analysis. The mortality rate was 34% in the cases and 11% in the controls (P = 0.002). Multivariate analysis indicated that a high Acute Physiology and Chronic Health Evaluation (APACHE) III score (P < 0.001) and high HIV viraemia (P = 0.02), but not methicillin resistance, predicted an increased risk of death in patients with S. aureus bacteraemia.


CONCLUSIONS
Individual exposure to beta-lactams, in association with a history of multiple hospitalizations and low CD4+ cell number, plays a pivotal role as a risk factor for the development of methicillin resistance in HIV-infected patients. Methicillin resistance does not influence the outcome of S. aureus bacteraemia when included in a multivariate analysis.
Department of Infectious Diseases and Microbiology, Catholic University, Largo A. Gemelli 8, 00168 Roma, Italy. tumbarello@rm.unicatt.it
Mario
M
Tumbarello
Katleen
K
de Gaetano Donati
Evelina
E
Tacconelli
Rita
R
Citton
Teresa
T
Spanu
Fiammetta
F
Leone
Giovanni
G
Fadda
Roberto
R
Cauda
D018806:APACHE; D000328:Adult; D016470:Bacteremia / Q000150:complications / Q000382:microbiology / Q000401:mortality*; D018791:CD4 Lymphocyte Count; D016022:Case-Control Studies; D017714:Community-Acquired Infections / Q000382:microbiology; D003428:Cross Infection / Q000382:microbiology; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000821:virology; D015497:HIV-1 / Q000302:isolation & purification*; D006785:Hospitals, University; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000150:complications* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification