Serotyping of Streptococcus pneumoniae isolated from Tehran by Multiplex PCR: Are serotypes of clinical and carrier isolates identical?

Streptococcus pneumoniae is the most common cause of invasive infections among both young children and elderly people. Common serotypes causing invasive diseases and the emergence of carriers of Streptococcus pneumoniae in Iran is not yet known. Past-vaccine surveillance studies of serotype prevalence patterns in Iran are necessary to monitor the epidemiology of Streptococcus pneumoniae. Because of variation of pneumococcal serotypes in different geographical regions, in this study we evaluated common serotypes causing pneumococcal infections and healthy carrier children in Tehran by Multiplex PCR. A total of 150 nasopharyngeal swabs were collected from healthy children in Tehran between December 2011 and August a2012, and 100 clinical samples were collected. Identification was performed by biochemical and molecular tests. Serotyping was done by multiplex PCR. We designed primers based on the sequences available for the routine capsular types and combined them into six multiplex PCR. From 150 nasopharyngeal swabs, 40 isolates of Streptococcus pneumoniae were identified after identification tests. Thirty six clinical isolates were also detected among clinical samples. Four serotypes (19A, 6, 3, 23F) of S. pneumoniae accounted for 55.7% of both sets of strains isolated from nasal carriage and clinical samples. Serotype 19A was the most common serotype among both groups. The multiplex PCR approach was successfully adapted to identify serotypes from more than 91% of the isolates tested. Among S. pneumoniae isolates in Tehran, the most prevalent serotypes were similar among carriage and invasive isolates. Continued monitoring of common serotypes of Streptococcus pneumoniae is essential for future vaccine formulation in Iran.