RESUMEN
Resistance of Streptococcus pneumoniae is a worldwide, growing problem. Studies of factors associated with resistance to penicillin have not been conducted in Brazil. The objective of the present study was to evaluate factors associated with infection by S. pneumoniae not susceptible to penicillin. A prevalence study was conducted including all patients with a positive culture for S. pneumoniae in a hospital from July 1991 to December 1992 and the year 1994. Of 165 patients identified, 139 were considered to have clinically relevant infections and 88 percent of them had invasive infections. All infections were community acquired and consisted of pneumonia (44 percent) and of central nervous system (19 percent), pelvic or abdominal (12 percent), upper airway or ocular (12 percent), primary bloodstream (9 percent) and skin and soft tissue (5 percent) infections. Mortality was 25 percent. Susceptibility to penicillin was present in 77.6 percent of the isolates; 21.8 percent were relatively resistant, and one isolate was resistant (minimal inhibitory concentration = 4 æg/ml). Multivariate analysis showed that age below 4 years (odds ratio (OR): 3.53, 95 percent confidence interval (95 percentCI): 1.39-8.96) and renal failure (OR: 5.50, 95 percentCI: 1.07-28.36) were associated with lack of susceptibility to penicillin. Bacteremia occurred significantly less frequently in penicillin-nonsusceptible infections (OR: 0.34, 95 percentCI: 0.14-0.84), possibly suggesting that lack of penicillin susceptibility is associated with lower virulence in S. pneumoniae