ABSTRACTWhile considerable research has focused on the properties of individual bacteria, relatively little is known about how microbial interspecies interactions alter bacterial behaviors and pathogenesis.Staphylococcus aureusfrequently coinfects with other pathogens in a range of different infectious diseases. For example, coinfection byS. aureuswithPseudomonas aeruginosaoccurs commonly in people with cystic fibrosis and is associated with higher lung disease morbidity and mortality.S. aureussecretes numerous exoproducts that are known to interact with host tissues, influencing inflammatory responses. The abundantly secretedS. aureusstaphylococcal protein A (SpA) binds a range of human glycoproteins, immunoglobulins, and other molecules, with diverse effects on the host, including inhibition of phagocytosis ofS. aureuscells. However, the potential effects of SpA and otherS. aureusexoproducts on coinfecting bacteria have not been explored. Here, we show thatS. aureus-secreted products, including SpA, significantly alter two behaviors associated with persistent infection. We found that SpA inhibited biofilm formation by specificP. aeruginosaclinical isolates, and it also inhibited phagocytosis by neutrophils of all isolates tested. Our results indicate that these effects were mediated by binding to at least twoP. aeruginosacell surface structures—type IV pili and the exopolysaccharide Psl—that confer attachment to surfaces and to other bacterial cells. Thus, we found that the role of a well-studiedS. aureusexoproduct, SpA, extends well beyond interactions with the host immune system. Secreted SpA alters multiple persistence-associated behaviors of another common microbial community member, likely influencing cocolonization and coinfection with other microbes.IMPORTANCEBacteria rarely exist in isolation, whether on human tissues or in the environment, and they frequently coinfect with other microbes. However, relatively little is known about how microbial interspecies interactions alter bacterial behaviors and pathogenesis. We identified a novel interaction between two bacterial species that frequently infect together—Staphylococcus aureusandPseudomonas aeruginosa. We show that theS. aureus-secreted protein staphylococcal protein A (SpA), which is well-known for interacting with host targets, also binds to specificP. aeruginosacell surface molecules and alters two persistence-associatedP. aeruginosabehaviors: biofilm formation and uptake by host immune cells. BecauseS. aureusfrequently precedesP. aeruginosain chronic infections, these findings reveal how microbial community interactions can impact persistence and host interactions during coinfections.
Molecular typing of community-acquired methicillin-resistant Staphylococcus aureus isolated from 2- to 6-year old children by staphylococcal protein A and agr typing in Isfahan, Iran
