Penicillin resistance and serotype distribution of Streptococcus pneumoniae in nasopharyngeal carrier children under 5 years of age in Dar es Salaam, Tanzania

This study aimed to determine the magnitude of nasopharyngeal carriage, antimicrobial resistance and serotype distribution of Streptococcus pneumoniae in healthy children under 5 years of age in Tanzania. Nasopharyngeal swabs were obtained from 300 healthy children attending a child health clinic at Muhimbili National Hospital in Dar es Salaam, Tanzania. S. pneumoniae was isolated and identified using conventional methods. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disc diffusion method. Penicillin MICs and serotypes were determined by an agar gradient diffusion method and the Quellung reaction, respectively. A total of 105 samples (35.0%) were positive for S. pneumoniae and 115 serotypes were detected (ten specimens yielded two serotypes each). Overall, 78 of 115 isolates (67.8%) were penicillin-non-susceptible pneumococci (PNSP). The resistance levels of S. pneumoniae to trimethoprim-sulfamethoxazole, tetracycline, erythromycin, chloramphenicol and ceftriaxone were 82.6, 10.4, 6.0, 3.5 and 0.0%, respectively. Multidrug resistance was detected in 19 isolates (16.5%). The most prevalent serotypes were 19F (n=25, 21.7%), 6B (n=15, 13.0%), 9V (n=14, 12.2%) and 13 (n=14, 12.2%). Of the 64 pneumococcal isolates potentially covered by the seven-valent pneumococcal conjugate vaccine (PCV7), 44 (68.8%) were PNSP. A high prevalence of PNSP, common pneumococcal serotypes circulating worldwide, was found, and many of the resistant pneumococci strains are covered by the PCV7. These findings indicate that the carriage rate of such resistant strains could be influenced by an appropriate vaccination programme in the study setting and by reinforcing regulations on the rational use of antimicrobial agents.