Nasopharyngeal carriage of Streptococcus pneumoniae in Gambian villagers

Background. To prepare for the introduction of a pneumococcal conjugate vaccine of restricted valency, we studied the nasopharyngeal carriage of Streptococcus pneumoniae in Gambian villagers. Methods. A cross-sectional survey was conducted in 21 villages after a census. We recorded demographic characteristics, information on medical history, and data on possible risk factors for carriage from subjects. We collected a nasopharyngeal swab specimen from each subject for isolation and serotyping of S. pneumoniae and for antibiotic susceptibility testing. Results. The prevalence of S. pneumoniae carriage among 2872 villagers was 72%. It was highest among infants ( i.e., children aged < 1 year; 97%); the rate was 93% among babies aged < 1 month and decreased with increasing age (P < .001). Prevalence of carriage was linked to proximity to another village. Sixty-three percent of isolates P < .001 recovered from children aged < 5 years were covered by the 7-valent vaccine or were of a vaccine-related serotype, compared with 43% of isolates overall. Forty-three isolates ( 14.3%) tested were initially penicillin resistant; none had high-level resistance, and 4 had intermediate resistance. The rates of resistance to other antibiotics were as follows: trimethoprim-sulfamethoxazole, 39%; tetracycline, 32.3%; chloramphenicol, 6.3%; cefotaxime, 0.3%; and erythromycin, 0%. The rates were highest for isolates of vaccine serotypes. Conclusions. Pneumococcal carriage rates among Gambian villagers are very high. A pneumococcal conjugate vaccine of restricted valency should reduce the pool of antibiotic-resistant pneumococci. The large reservoir of pneumococci of nonvaccine serotypes will require close monitoring when the vaccine is introduced.