Characterization of a multidrug-resistant clone of invasive Streptococcus pneumoniae serotype 6B in Alaska using pulsed-field gel electrophoresis andPspA serotyping

Antimicrobial susceptibility, pneumococcal surface protein A (PspA) serotyp ing, and pulsed-field gel electrophoresis (PFGE) were used to evaluate clon al relatedness among 66 invasive isolates of Streptococcus pneumoniae serot ype 6B collected during 1982-1996 from patients in Alaska. Thirty-seven (56 %) of the isolates had penicillin minimal inhibitory concentration values g reater than or equal to 0.125 mu g/mL and were resistant to at least 1 othe r antibiotic. Fourteen PspA serotypes were observed; PspA 16 was the most c ommon (35%), Forty-five (68%) of the 66 isolates shared common and highly r elated PFGE patterns using 3 enzymes. Twenty-six (58%) of the isolates with common PFGE patterns were from Native Alaskan children less than or equal to 2 years of age residing in 1 region of Alaska. The PFGE patterns of Alas kan serotype 6B were distinct from those of the South African 6B-8 and Span ish 6B-2 multidrug-resistant clones, suggesting that the Alaskan 6B isolate s were distinct from these other pneumococcal 6B clones but genetically rel ated to them.