Antibiotic-resistant isolates of Streptococcus pneumoniae from clinical specimens: a cluster of serotype 19A organisms in Brooklyn, New York.

Ten of 294 isolates of Streptococcus pneumoniae from patients enrolled in a Veterans Administration Cooperative Studies Program trial of pneumococcal vaccine efficacy were moderately resistant or resistant to penicillin. Nine of these organisms were serotype 19A isolated from patients at the Brooklyn (New York) V.A. Medical Center over an 18-month period (March 1983-November 1984). The minimal inhibitory concentration of penicillin for these pneumococci ranged from 1.0 to 2.0 micrograms/ml by the agar dilution technique and from 4.0 to 8.0 micrograms/ml by tube dilution. These organisms were resistant also to other beta-lactam antibiotics and to tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole. They were sensitive to erythromycin, clindamycin, vancomycin, and rifampin. The epidemiological source of these isolates was not discovered. However, it is possible that a focus of multiple antibiotic-resistant serotype 19A S. pneumoniae is present in Brooklyn.