Impact of Staphylococcus aureus on Pathogenesis in Polymicrobial Infections

Polymicrobial infections involving Staphylococcus aureus exhibit enhanced disease severity and morbidity. We reviewed the nature of polymicrobial interactions between S. aureus and other bacterial, fungal, and viral cocolonizers. Microbes that were frequently recovered from the infection site with S. aureus are Haemophilus influenzae, Enterococcus faecalis, Pseudomonas aeruginosa, Streptococcus pneumoniae, Corynebacterium sp., Lactobacillus sp., Candida albicans, and influenza virus. Detailed analyses of several in vitro and in vivo observations demonstrate that S. aureus exhibits cooperative relations with C. albicans, E. faecalis, H. influenzae, and influenza virus and competitive relations with P. aeruginosa, Streptococcus pneumoniae, Lactoba-cillus sp., and Corynebacterium sp. Interactions of both types influence changes in S. aureus that alter its characteristics in terms of colony formation, protein expression, pathogenicity, and antibiotic susceptibility. Staphylococcus aureus is an opportunistic and resilient humanpathogen that colonizes the mucosal surfaces. It is the caus-ative agent of many serious acute and chronic infections. The an-terior nares are the primary reservoirs of S. aureus. Asymptomatic colonization occurs in approximately 20 % of the normal popula-tion, and 60 % are transiently colonized, while 20 % appear to be rarely or never colonized (1). Extranasal colonization of S. aureus also takes place in several locations, including the skin, rectum