Antimicrobial resistance of Streptococcus pneumoniae

The increasing number of Streptococcus pneumoniae isolates identified as relatively or fully resistant to penicillin or fully resistant to otherantimicrobials in the United States supports the needto monitor for this resistance. Thus, 5459S. pneumoniae isolates submitted to the Centers forDisease Control in 1979-1987 by 35 hospitals in a hospital-based pneumococcal surveillance system were evaluated. TheMICtopenicillin orampicillin was ~0.1 JLg/ml for274(5%) isolates; 1 had an MICof4.0 JLg/ml to penicillin. Seventeen (0.3%)were resistant to erythromycin (MIC, ~8 JLg/ml), 157(29%) were resistant to tetracycline (MIC, ~16 JLg/ml), and 34 (0.6%)were resis-tant to sulfamethoxazole/trimethoprim (MIC, ~76 and 4 JLg/ml). Isolates relatively resistant to penicillin represented 1.8 % ofisolates in 1979, 8 % in 1982,and 3.6 % in 1987. Sixty-five multiply resistant isolates were identified. Pneumococci fromthe southwestern United States (region 4) were morelikely to be relatively resistant to penicillin. Using logistic regression analysis, sero-types14and 19A,isolates from region 4, and isolates from middle earfluidwere associated with penicillin resistance (P ~.008, X:. These dataconfirmthat antimicrobial resistance among pneu-mococcal isolates remained at low levels in the United States through 1987. Streptococcus pneumoniae is a major cause of morbidit