Determination of Streptococcus pneumonia Serotypes Isolated from Clinical Specimens: A Step Toward the Production of a Native Vaccine in Iran

Abstract

Background: Streptococcus pneumoniae remains a major cause of invasive streptococcal diseases among all age groups, particularly infants and the elderly. Objectives: This study aimed to recognize and determine S. pneumoniae serotypes isolated from clinical specimens by multiplex polymerase chain reaction (PCR). Methods: A total of 105 pneumococcal strains were collected from nonvaccinated cases within the age range of 10 days to 92 years from five provinces of Iran within June 2017 to August 2019. The strains were cultured on blood agar. Biochemical analyses and molecular tests were performed for the primary identification of bacterial isolates. Capsular typing was carried out by multiplex PCR assay. Primers that target the capsular polysaccharide site were used in this study. Results: Out of 130 studied clinical specimens, 105 isolates of S. pneumoniae were detected and identified. The most frequently isolated capsular types were 6B, 14, 19A, and 1. Serotype distribution consisted of 83.5% of vaccine serotype and 16.5% of nonvaccine serotype. The serotype 6B was significantly more frequent (P < 0.05) among the invasive clinical isolates (75%) compared to that among their noninvasive counterparts (25%). The distribution of 13-valent pneumococcal conjugate vaccine (PCV-13) serotypes in invasive pneumococcal disease (IPD) and non-IPD revealed 83% and 84% of the isolated serotypes, respectively. Moreover, 83.5% of all the serotypes identified in the study were covered by PCV-13 serotypes. Conclusions: The common serotypes of invasive and noninvasive groups in Iran are covered by PCV-13.