Risk factors for nasopharyngeal carriage of resistant Streptococcus pneumoniae and detection of a multiply resistant clone among children living in the Yukon-Kuskokwim Delta Region of Alaska

Background. Children <2 years old living in the Yukon-Kuskokwim Delta (YKD) region of Alaska have one of the highest pneumococcal bacteremia rates of in the world. Methods, To determine the prevalence of and risk factors for infection with intermediate or resistant Streptococcus pneumoniae in the YKD, we cultured nasopharyngeal secretions of healthy children less than or equal to 5 years old, reviewed their hospital records and administered questionnaires to accompanying parents. Results. Of 185 children evaluated we obtained 95 pneumococcal isolates; drug susceptibility patterns and serotyping results were available for 92. Of these, 33 (36%) were intermediate or resistant to at least one drug class tested; 27 isolates were intermediate (minimum inhibitory concentration 0.1 to 1.0 mg/l) and none were resistant to penicillin. Compared with other isolates, capsular serotype 6B isolates were more likely to be intermediate or resistant to at least one drug (relative risk, 5.3; P < 0.001) and to more than one drug (relative risk, 17.0; P < 0.001), The majority of 6B isolates had identical pneumococcal surface protein A patterns. Carriage of intermediate or resistant pneumococcus was associated with age <2 years (relative risk, 3.0; P < 0.001) but not with antibiotic use or other evaluated risk factors. Conclusions. Young age but not antibiotic use was associated with carriage of intermediate or resistant S. pneumoniae in the YKD region of Alaska. Much of the intermediate or resistant pneumococcus in the YKD may have resulted from the proliferation of a single capsular serotype 6B clone.