Penicillin-nonsusceptible Streptococcus pneumoniae at San Francisco General Hospital

Positive pneumococcal cultures of specimens from adult inpatients at San Fr ancisco General Hospital (SFGH) during the period of 11 August 1994 through 31 December 1996 were identified retrospectively. Of the isolates recovere d, 15.5% were not penicillin-susceptible (MIC, greater than or equal to .1 mu g/mL). A case-control study was performed to evaluate risk factors for c olonization or infection with penicillin-nonsusceptible Streptococcus pneum oniae (PNSP) and outcomes. Cases (n = 65) were adult inpatients with a posi tive culture for PNSP, and controls (n = 411) were adult inpatients with a positive culture for penicillin-susceptible pneumococci (PSSP) and no evide nce of PNSP. Cases were less likely to have pneumococcal bacteremia (15.4% versus 39.4%; P < .001) and less likely to have pneumonia (50.8% versus 68. 9%; P = .006). In a multiple logistic regression model, recent hospital adm ission and absence of bacteremia were independent predictors of penicillin- nonsusceptibility. Human immunodeficiency virus infection, mortality, and l ength of hospitalization were not significantly different among cases and c ontrols. These data suggest that PNSP may be less virulent (cause less pulm onary infection) and/or less invasive (cause fewer bloodstream infections) than PSSP at SFGH.