PURPOSE: Initial choice of antimicrobial therapy is critical for improved survival in the setting of both community-acquired (CAP) and healthcare associated pneumonia (HCAP). Although bacteremia is known to worsen clinical outcomes in the setting of both CAP and HCAP, it is unclear how its presence may mediate the effect of inappropriate initial antibiotic (IIA) on hospital death.
METHODS: We examined pneumonia hospitalizations over a three year period. The diagnosis of pneumonia required signs and symptoms of infection along with radiographic evidence of an infiltrate. Hospital death served as the endpoint and IIA was the primary exposure of interest. HCAP was present if a patient met one of the following criteria: recent hospitalization, nursing home residence, chronic hemodialysis, or immunosuppression.
RESULTS: Of the 639 pneumonia patients, 431 (67.4%) had HCAP. Bacteremia was present in 133 (30.9%) and 78 (37.5%) of the patients with HCAP and CAP, respectively. Among patients with HCAP and no bacteremia, mortality was significantly higher with IIA than with appropriate treatment (28.4% and 15.7%, respectively, p=0.012), but no significant difference was seen in the presence of bacteremia (47.1% and 32.3%, respectively, p=0.123). This pattern was reversed in the setting of CAP, where a substantial mortality difference was observed in the presence of bacteremia in IIA vs. appropriate treatment (62.5% and 5.7%, respectively, p<0.001), and no difference in the absence of bacteremia (10.5% and 7.2%, respectively, p=0.640).
CONCLUSION: Bacteremia modifies the effect of IIA on mortality differentially in the presence vs. absence of bacteremia such that in CAP IIA increases the risk of death when bacteremia is present and not when it is absent, while in HCAP IIA increases the risk of death when bacteremia is absent and not when it is present.
CLINICAL IMPLICATIONS: Our results are indicative of the differential epidemiology and the possible differences in the virulence of the organisms likely to cause CAP vs. HCAP and underscore the importance of early institution of appropriate coverage in both CAP and HCAP.
DISCLOSURE: Marya Zilberberg, None.