Staphylococcus aureus Increases Rhinovirus Replication and Synergistically Enhances Cytotoxicity During Co-infection of the Airway Epithelium

E. Dissanayake1, R. A. Brockman-Schneider1, R. M. Stubbendieck2, C. R. Currie2 and J. E. Gern1;
1Department of Pediatrics, School of Medicine and Public Health; 2Department of Bacteriology, University of Wisconsin-Madison, Madison, WI

Rationale: Early-life colonization patterns of the airway epithelium by bacteria and the co-detection of specific bacterial species with rhinovirus (RV) has been shown to increase the risk of childhood asthma. Staphylococcus aureus is a common nasal symbiont that is implicated in the development of childhood asthma and chronic sinusitis. In this study, we tested the effects of S. aureus and RV co-infection on the bronchial epithelium.

Methods: We developed a co-culture system by differentiating bronchial epithelial cells from a healthy donor at air-liquid interface. We then incubated the apical surface of the mature epithelium for 24 hours with 3×105 colony-forming units of three different S. aureus isolates obtained from the nasal secretions of children. Subsequently, we introduced of 105 plaque-forming units (PFUs) of RV-A16 for 48 hours. We analyzed cell lysates for RV replication by quantitative PCR and assessed cell viability by testing culture medium for lactate dehydrogenase.

Results: The three isolates of S. aureus significantly increased RV replication compared to controls without bacteria (7.21 vs 6.41 log PFU equivalents/sample; P=0.03, Mann-Whitney test). The mean cellular cytotoxicity increased from 6.3% for the no-treatment control, 10% for RV or S. aureus cultured alone to 74% when both pathogens were cultured together with epithelial cells (P=0.003; Kruskal-Wallis test).

Conclusions: Staphylococcus aureus promotes RV replication, which leads to increased cell death in differentiated airway epithelial cells. These in vitro findings suggest that S. aureus colonization of the upper airways could increase susceptibility to RV infection and associated damage to the airway epithelium.

Eishika Dissanayake PhD

University of Wisconsin - Madison

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