Increasing resistance to penicillin in Streptococcus pneumoniae in southern Sweden.

The susceptibility to penicillin of 6 prevalent pneumococcal types isolated from nasopharynx in 1992 was compared with that of corresponding types from 1980-82. The 6 types or groups, 6, 9, 14, 15, 19 and 23, constituted 78% of consecutive isolates. 19/204 isolates in 1992 were intermediately resistant (MIC 0.12-1.0 mg/l) in comparison with 1/194 from 1980-82 (p < 0.001). Resistant strains (MIC > or = 2 mg/l) were not found. Of group 15, no fewer than 10/31 isolates were intermediately resistant, which may support the clonal origin and spread of penicillin-resistant pneumococci. At least 5.0% of nasopharyngeal isolates are now intermediately resistant to penicillin. This figure is substantially higher than the 2% earlier reported in Sweden.