serotype distribution of streptococcus pneumoniae carriage in six-month-old infants: a cross-sectional study during 2017-18, tehran, iran

Background: streptococcus pneumoniae is recognized as one of the main pathogens inducing several invasive and non-invasive infections in children. objective: the present study aimed to evaluate the serotype distribution of s. pneumoniae in six–month–old carriers. methods: this study encompassed 600 six-month-old healthy infants whose pharyngeal swap samples were collected and then cultured to isolate s. pneumoniae. twenty- five different serotypes were defined on positive culture samples by multiplex pcr. results: in this study, 13 cases (2.2%) were positive s. pneumonia. the most common isolated serotypes of s. pneumoniae were serotypes 23f (n = 6, 1%) and 3 (n = 3, 0.5%), respectively. notably, the most frequent serotype in formula-fed infants (n = 300) was serotype 23f (n = 5, 1.7%); however, serotype 3 (n = 3, 1%) was the most frequent one in breastfed participants (n = 300). according to the findings, the overall coverage of pcv10, pcv13, and ppsv23 on the s. pneumoniae serotypes at the age of six months was 50%, 73%, and 85%, respectively. conclusions: at this age, the type of feeding could not significantly affect the frequency rate of s. pneumoniae colonization, while the serotype distributions in the two breastfed and formula-fed groups were different.