CME ACTIVITY: Microbial Interactions during Upper Respiratory Tract Infections

Moraxella catarrhalis, and Staphylococcus aureus often colonize the nasopharynx. Children are susceptible to bacterial infections during or soon after upper respiratory tract infection (URI). We describe colonization with these 4 bacteria species alone or in combination during URI. Data were from a prospective cohort of healthy children 6 to 36 months of age followed up for 1 year. Analyses of 968 swabs from 212 children indicated that S. pneumoniae colonization is negatively associated with colonization by H. infl uenzae. Competitive interactions shifted when H. infl uenzae and M. catarrhalis colonized together. In this situation, the likelihood of colonization with all 3 species is higher. Negative associations were identifi ed between S. pneumoniae and S. aureus and between H. infl uenzae and S. aureus. Polymicrobial interactions differed by number and species of bacteria present. Antimicrobial therapy and vaccination strategies targeting specifi c bacterial species may alter the fl ora in unforeseen ways. S pneumoniae, Haemophilus infl uenzae, Moraxella catarrhalis, and Staphylococcus aureus often asymptomatically colonize the nasopharynx of young children and are also associated with disease. S. pneumoniae, H. infl uenzae, and M. catarrhalis are the 3 most common otitis media pathogens (1,2). S. pneumoniae are also common causes of pneumonia, sepsis, and meningitis in young children (3). The proportion of young children colonized with any of these 3 bacteria species can be >50% in certain populations (4–6). S. aureus strains colonize up to 35% of young children and are associated with a wide range of diseases including soft tissue infections, sepsis, and pneumonia (7,8). Increases in the incidence of disease caused by community-acquired methicillin-resistant S. aureus are of great concern (9). Host factors have been shown to in? uence colonization with S. pneumoniae, H. infl uenzae, M. catarrhalis, and S. aureus. These include host immunity, age, gender, race, out-of-home daycare, breastfeeding, and environmental exposure to tobacco smoke (10). The magnitude of host effects may differ by bacteria species. Interactions between bacteria in? uence which species persist in the nasopharynx (11–13). Bacteria species may Microbial Interactions during Upper Respiratory Tract Infections