- Background: Respiratory viruses and S. pneumoniae are known to be co-pathogens in childhood pneumonia. However, it is unclear whether all pneumococcal serotypes are equally prone to such interaction. We attempted to determine association between carried pneumococcal serotypes and respiratory viruses during childhood community-acquired alveolar pneumonia (CAAP). Methods: The study was conducted during RSV seasons, before pneumococcal vaccine introduction. Children <5 years diagnosed with CAAP, with positive pneumococcal nasopharyngeal cultures from whom viral diagnostic tests were obtained were enrolled. Viral detection was done by culture, direct immunofluorescence assay (DFA) or PCR. Adjusted Odd Ratios (ORs) for serotype-specific carriage rates by presence of specific viruses were calculated: Single RSV-positive (RSV[+]); other respiratory viruses (ORspVs[+]); and no respiratory virus (RspVs[-]). We compared "invasive" and "non-invasive" pneumococcal serotypes according to previous publications. Results: "Invasive" serotype colonization was significantly lower in RSV(+) vs. RspVs(-) CAAP (OR= 0.18, 95% CI 0.05-0.60). While colonization with "non-invasive" serotypes tended to be higher in RSV(+)(OR=2.39;95% CI 0.98-5.79). Conclusion: We found an inverse relationship between pneumonia-associated invasive pneumococcal serotypes and RSV detection during CAAP. This finding may lead to better understanding of the interaction between respiratory viruses and S. pneumoniae in CAAP pathogenesis.