BACKGROUND AND OBJECTIVES: Many surface proteins are implicated in nasopharyngeal colonization and pathogenesis of Streptococcus pneumoniae. Some of these factors are candidate antigens for protein based vaccines. New vaccine designs focus on the surface proteins (e. g., pspA and pspC) and also cytolysin, and pneumolysin. In this study, 3 key virulence genes, lytA, pspC, and rrgA, which encoded surface proteins, were detected among S. pneumoniae isolates. MATERIALS AND METHODS: A total of 260 nasopharyngeal swabs were collected from healthy children under 6 years old attending day care centers in Mashhad, Iran. Isolates of S. pneumoniae were confirmed by optochin susceptibility and colony appearance and also by PCR for cpsA gene. The presence of lytA, pspC, and rrgA genes were also detected by PCR. RESULTS: A total of 59 isolates were confirmed as S. pneumoniae. Among these isolates, 50 (84.74%), 19 (32.20%), and 2 (3.38%) were positive for lytA, rrgA, and pspC genes respectively. The presence of these genes among S.pneumoniae isolates were as follows: 1) rrgA, lytA, pspC (1 isolate), 2) rrgA, lytA(17isolates), 3) pspC (2 isolate), 4) lytA (50 isolates). CONCLUSION: cpsA gene was specific for detection of S. pneumoniae isolates which were colonized in nasopharynx. The lytA gene was the most frequent gene among the S. pneumoniae isolates, and combination of rrgA, lytA was the most observed pattern. Thus, it is important for future monitoring of vaccine formulation in our country.

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