B-250. Viral Infection of Respiratory Epithelial Surfaces Enhances Adherence of Streptococcus pneumoniae and Moraxella catarrhalis and Is Influenced by the Polymicrobial Environment

A. Krishnamurthy1, J. M. Kyd1, A. W. Cripps2;
1Central Queensland Univ., Rockhampton, AUSTRALIA, 2Griffith Univ., Gold Coast, AUSTRALIA.

Background- The human respiratory tract is colonised by multiple species of bacteria at any given time. The bacterial adherence to various mucosal and epithelial surfaces is considered as an important step in its colonisation. Bacteria such as Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis are well known to cause respiratory tract infections in humans. Moreover, respiratory viruses are recognised as major triggers in enhancing bacterial adherence, colonisation and translocation through the epithelial barrier. We speculated that the co-presence of different microbes would affect bacterial adherence, a factor associated with the virulence of the bacteria. In this study, we investigated how different microbes interact with each other and the host to cause infection in a polymicrobial environment. Methods- In vitro cell culture models; A549 (human lung epithelial cell line) and BEAS-2B (human bronchial epithelial cell line) infected with respiratory virus (Adenovirus 5) and the bacteria S. pneumoniae, nontypeable H. influenzae (NTHi) and M. catarrhalis were used in this study. Following the infection of both cell lines with either single bacteria or combinations of bacteria in the presence or absence of adenovirus, the bacterial adherence to the cell line was measured. Results- It was observed that the infection of adenovirus with single bacterium enhanced the adherence of M. catarrhalis to BEAS-2B and S. pneumoniae to both BEAS-2B and A549 cell line (p<0.001). The presence of adenovirus significantly increased the bacterial adherence of both, S. pneumoniae and M. catarrhalis to the A549 cell line, when co-infected together (p<0.001). The presence of all three bacteria and virus did not significantly alter their adherence. Conclusion- The presence of adenovirus significantly enhanced bacterial adherence to epithelial cells. S. pneumoniae and M. catarrhalis when infected alone showed greater ability to adhere to the bronchial epithelial cell line and when co-infected together their adherence was higher on a lung epithelial cell line.