PURPOSE: Staphylococcus aureus (SA) pneumonia remains associated with substantial morbidity and mortality. The implications of bacteremia complicating SA pneumonia are poorly understood.
METHODS: We retrospectively identified (Jan 2004-Dec 2007), all patients admitted to the hospital with SA pneumonia necessitating mechanical ventilation. All subjects underwent lower airway and concurrent blood cultures. The prevalence of bacteremia served as a primary endpoint. We assessed the impact of bacteremia on mortality and length of stay (LOS) via either logistic regression or a Cox proportional hazard’ s model, respectively. In both models we controlled for multiple co-variates (eg, demographics, severity of illness, co-morbidities, appropriateness of initial antibiotics). We subsequently developed a prediction rule to identify subjects likely to suffer from concurrent bacteremia based on variables assessed at time of presentation.
RESULTS: The cohort included 59 patients (mean age 58.0 ± 17.4 years, 59.3% Methicillin resistant). Bacteremia complicated nearly 20% of cases. Mortality was higher in bacteremia (39.1% vs. 8.3%, p=0.007). Three variables were independently associated with mortality: age, vasopressors use, and bacteremia. Bacteremia conferred a 6 fold increase in the risk for death (AOR: 5.96, 95% CI: 1.08-33.10). Bacteremia correlated with a 5 day longer LOS &, the adjusted hazard ratio for remaining hospitalized if bacteremic was 2.65 (95% CI: 1.14-6.18). For the clinical prediction rule, we assigned points as follows: 2 points -- prior antibiotic therapy (last 30 days); 1 point -- acute lung injury; 1 point -- vasopressors. As the score increased, the prevalence of bacteremia increased (p<0.001). As a screening test, the score performed well (area under the receiver operating curve of 0.83 (95% CI: 0.72-0.94)).
CONCLUSION: Bacteremia often arises in S. aureus pneumonia in the ICU and is associated with both increased morbidity and mortality. Several clinical features identify patients with S. aureus pneumonia likely to suffer from bacteremia.
CLINICAL IMPLICATIONS: For patients with SA pneumonia at potentially high risk for bacteremia, physicians should recognize that these subjects face poor outcomes and should focus on optimizing their resuscitation, ventilatory management, and antibiotic therapy.
DISCLOSURE: Andrew Shorr, Grant monies (from industry related sources) Astellas, GSK, J and J, Pfizer, Sanofi; Consultant fee, speaker bureau, advisory committee, etc. Astellas, BI, Covdien, Cadence, Canyon, GSK, J and J, Medicines Co. Merck, Pfizer, Sanofi, Theravance; No Product/Research Disclosure Information