Initial microbiologic studies did not affect outcome in adults hospitalized with community-acquired pneumonia

Microbiologic studies (MBSs) fail to identify a specific pathogen in more t han 50% of patients with community-acquired pneumonia (CAP). The 1993 Ameri can Thoracic Society guideline (ATS-GL) for the management of CAP advised s electing initial antibiotic regimens based on severity of illness and comor bidities. Our study evaluated the role of initial MBS in adult patients hos pitalized with CAP and treated according to the ATS-GL. In 184 patients hos pitalized at our facility for CAP in 1996, and treated according to the ATS -GL, 25 (14%) failed to respond to initial antibiotic regimens. In these no nresponders, there was no difference in mortality between those in whom ant ibiotics were changed empirically, and those with MBS-guided changes. We co nclude that initial MBS may not be warranted in many adult patients admitte d for CAP. Exceptions include patients with conditions that predispose to l ess common, more resistant pathogens.