Introduction and clonal spread of penicillin- and trimethoprim/sulfamethoxazole-resistant Streptococcus pneumoniae, serotype 9V, in southern Sweden

As part of an intervention project, all patients in Malmohus county with a culture positive for penicillin-resistant pneumococci, MIC greater than or equal to 0.5 mg/L (PRP), have been registered since January 1995, Nasophary ngeal specimens were obtained from family members and close contacts of ide ntified carriers. Children were denied attendance at regular day-care until PRP-negative, In 1995 and 1996, PRP were isolated from 882 individuals, 36 4 of whom had clinical infection and the remaining of whom were asymptomati c carriers. In 49%, the PRP were of serogroup 9, with MIC of penicillin 0.5 -2.0 mg/L and resistance to trimethoprim/sulfamethoxazole. Further analyses with serotyping and genetic fingerprinting suggested strongly that most of the isolates belonged to a single serotype 9V clone. Month by month, an ap parently continuous spread appeared from one municipality to a neighboring one. In most communities, the serotype 9V PRP appeared and disappeared with in a few months. The active procedures of the intervention project may have limited the spread of the clone in the county.