ABSTRACT
Aims: Streptococcus pneumoniae is the most common bacterial respiratory pathogen that can lead to invasive diseases such as pneumonia, bacteremia, and meningitis. The interaction of S. pneumoniae with host respiratory epithelial cells is crucial in the colonization of human respiratory tract and involve in the virulence. The aim of the study is to investigate the adherence of S. pneumoniae and the effect of serotypic variation on neuraminidase genes (NanA and NanB) after interaction of A549 human lung epithelial cells with S. pneumoniae serotypes. Methodology and results: Six different serotypes of S. pneumoniae were used (1, 3, 5, 19F, 23F, and 14). A549 human lung epithelial cells were inoculated with pneumococcal strains of different serotype for 3 hours. The number of adherent bacteria was determined by serial dilution followed by spread plate technique on tryptic soy agar supplemented with 5% sheep blood. Bacterial RNA was harvested from the infected A549 cells. The differential expression level of neuraminidases was observed by quantitative real-time PCR (qRT-PCR). Based on bacterial adherence assay, serotype 14 showed highest adherence, meanwhile, serotype 23F showed lowest adherence. This suggests that serotype 14 has a better affinity to adhere to A549 cells as compared to serotype 23F. Higher NanA gene expression was observed in serotype 5, 23F and 19F, while lower expression in serotype 14. In contrast, NanB gene shows low-level expression in serotype 23F and 19F, while higher expression in serotype 14. This postulates that NanA and NanB gene may have different functions in the pathogenesis of S. pneumoniae. Conclusion, significance and impact of study: Our finding on differential expression of neuraminidase gene of S. pneumoniae of various serotypes on A549 cells might give a better understanding of host pathogen interaction between bacteria serotypes and host cell.