Nasopharyngeal Carriage, Antibiotic Resistance and Serotype Distribution of Streptococcus Pneumoniae among Healthy Adolescents in Zahedan

Background: Colonization of nasopharynx by Streptococcus pneumoniae can lead to pneumococcal diseases. This study was performed to determine the carriage rate of nasopharyngeal S. pneumoniae in adolescents, antibiotic susceptibility and serotype prevalence in Zahedan, Iran. Methods: Nasopharyngeal specimens from 865 adolescents (age range: 10-19 years old) attending eight schools in Zahedan, Iran, were collected and assessed by standard procedures to recover S. pneumoniae. The serotyping was carried out by latex agglutination test and the minimum inhibitory concentrations (MIC) of penicillin as well as other commonly used antibiotics were determined by a broth dilution method. Results: Pneumococci were recovered from 15.7% (136/865, 95% confidence interval (CI) 12.3-18.9) of total samples which 119 isolates were typable with the available antisera. 1, 19A, 15C, 9V, 11A and 19F were found as the most frequent serotypes. Ninety three pneumococcal isolates were sensitive to penicillin. The MIC values of antibiotics tested were (μg/ml): penicillin 0.01-4, cefotaxime 0.01-4, ceftriaxone 0.02-128, chloramphenicol 0.08-32, ciprofloxacin 0.06-16, erythromycin 0.01-128, tetracycline 0.08-128 and vancomycin 0.02-1. Conclusion: A clear diversity was seen in the serotype distribution of the S. pneumoniae isolates and most of the antibiotic resistant strains belonged to few serotypes. Healthy adolescents in Zahedan, Iran commonly show pneumococcal carriage and antibiotic resistance.