Geographic, demographic, and seasonal differences in penicillin-resistant Streptococcus pneumoniae in Baltimore

We examined the epidemiology of invasive penicillin-resistant Streptococcus pneumoniae (PRSP) infections among residents of the Baltimore metropolitan area from 1995 through 1997. During this period, the proportion PRSP cases increased 42%, from 5.7% to 8.1% of cases. PRSP rates were highest among p ersons aged <5 and <greater than or equal to>65 years, black patients, and urban dwellers. However, the proportion of PRSP cases was higher among whit e persons (10%) than it was among black persons (5%) and among residents of suburban counties (10%) versus urban counties (6%). PRSP cases were more c ommon in November-April (8%) than they were in May-October (5%), particular ly for persons aged greater than or equal to 65 years (10% vs. 1%). By use of logistic regression, white race, suburban residence, and winter respirat ory season were found to be independent predictors of infection with PRSP. The incidence of PRSP is increasing in Baltimore, and the seasonality of PR SP suggests that recent antibiotic use, which is more common in winter mont hs, may rapidly affect the prevalence of resistant pneumococcal infections.