Antimicrobial resistance with Streptococcus pneumoniae in the United States, 1997-98

From November 1997 to April 1998, 1,601 clinical isolates of Streptococcus pneumoniae were obtained from 34 U.S. medical centers. The overall rate of strains showing resistance to penicillin was 29.5%, with 17.4% having inter mediate resistance. Multidrug resistance, defined as lack of susceptibility to penicillin and at least two other non-beta-lactam classes of antimicrob ial drugs, was observed in 16.0% of isolates. Resistance to all 10 beta-lac tam drugs examined in this study was directly related to the level of penic illin resistance. Penicillin resistance rates were highest in isolates from middle ear fluid and sinus aspirates of children <5 years of age and from patients in ambulatory-care settings. Twenty-four of the 34 medical centers in this study had participated in a similar study 3 years before. In 19 of these 24 centers, penicillin resistance rates increased 2.9% to 39.2%. Sim ilar increases were observed with rates of resistance to other antimicrobia l drugs.