Relationship Between Prevalence of Pneumococcal Serotypes and Their Neuraminidases in Carriers, Predictive Facts?

Streptococcus pneumoniae is one of the leading causes of morbidity and mortality worldwide that mainly colonizes the upper respiratory tract in children and produces invasive infections such as meningitis, bacteremia, pneumonia, and otitis media. Pneumococcus species harbor a number of virulent genes that influence disease severity. Neuraminidase is a virulence factor that cleaves sialic acid. Pneumococcal nasopharyngeal carriage is common among healthy individuals and is considered an important transmission source. This topic, however, is less regarded in research from Iran. Therefore, the current study aimed at investigating the prevalence of pneumococcal nasopharyngeal carriage among Iranian children under six years of age. The study also aimed at determining the frequency of pneumococcal serotypes and the neuraminidase virulence genes (nanA, nanB, and nanC) among carriers. A total of 384 nasopharyngeal samples were collected from children under six years of age referred to healthcare centers of six provinces in Iran, including Tehran, Fars, Ardebil, Lorestan, Khorasan, and Sistan va Baluchistan from 2013 to 2016. Of these, 92 carriers were identified (24.0%; 95% confidence interval [CI]: 20.0, 28.5%). Identified pneumococcal serotypes included 6A/B (14.1%), 14, 3, and 19A (each 12.1%), 4, 19F, 23F (each 5.4%), 11 (4.3%), 18C, 22F, 9V, 19, 12, and 33F (each 2.1%), 5, 12F (each 1.1%) and non-typable (14.1%). Frequency of neuraminidase nanA, nanB, and nanC genes among 92 carriers was 100% (95% CI: 96.0, 100%), 85.9% (95% CI: 77.3, 91.6), and 62.0% (95% CI: 51.8, 71.2), respectively. The results showed that about 25% of children (n = 92) were pneumococcus carriers. A wide range of serotypes, some of which are known as virulent, were seen in the population. Prevalence of neuraminidase genes was also considerable.