Infections Caused by Erythromydn-Resistant Streptococcus pneumoniae: Incidence, Risk Factors, and Response to Therapy in a Prospective Study

To evaluate the incidence and the significance of resistance to erythromycin among clinical isolates of Streptococcus pneumoniae, we identified and prospectively followed all hospitalized patients in a 27-month period who had the organism isolated from any clinical sample. Patients who had an infection caused by pneumococci resistant to erythromycin (minimum inhibitory concentration, >1 µg/mL) were compared to those with infections caused by erythromycinsusceptible organisms. The incidence of erythromycin resistance among pneumococci doubled over the study period (from 7.6% in 1988 to 15.2% in 1992). Most strains (94%) showed resistance to multiple antibiotics, including other macrolides. By multivariate analysis, an age of