Occurrence of pneumococci with resistance or decreased susceptibility to penicillin in southeast Sweden.

The minimal inhibitory concentrations (MICs) of 14 beta-lactam and non-beta-lactam antibiotics were determined for all pneumococci with intermediate susceptibility (I), (n = 26) or resistance (R), (n = 15) to penicillin G isolated at the Clinical Microbiology Laboratory, University Hospital, Linköping, Sweden during 1994. These isolates accounted for 3% of all pneumococcal isolates. The results were compared with those of 26 penicillin-susceptible isolates. The MICs of all tested beta-lactam antibiotics increased with MICs of penicillin G. The least increase and the lowest MICs of these agents were recorded for cefotaxime and imipenem. 27% of I- and R-strains were multiple-resistant, most often to tetracycline, trimethoprim-sulfametoxazole, erythromycin, chloramphenicol and clindamycin. All strains were susceptible to vancomycin and rifampicin. I-strains belonged to at least 5 different serotypes. However, 12 of the 15 R-strains were serotype 9 and 6 of these were recovered during contact tracing, indicating spread of a single clone within day-care centres.