Synergistic Interactions of Pseudomonas aeruginosa and Staphylococcus aureus in anIn VitroWound Model

Abstract

ABSTRACTIn individuals with polymicrobial infections, microbes often display synergistic interactions that can enhance their colonization, virulence, or persistence. One of the most prevalent types of polymicrobial infection occurs in chronic wounds, wherePseudomonas aeruginosaandStaphylococcus aureusare the two most common causes. Although they are the most commonly associated microbial species in wound infections, very little is known about their interspecies relationship. Evidence suggests thatP. aeruginosa–S. aureuscoinfections are more virulent than monoculture infection with either species; however, difficulties in growing these two pathogens togetherin vitrohave hampered attempts to uncover the mechanisms involved. Here we describe a simple and clinically relevantin vitrowound model that supported concomitant growth ofP. aeruginosaandS. aureus. We observed that the ability ofP. aeruginosaandS. aureusto survive antibiotic treatment increased when they were grown together in planktonic cocultures and that antibiotic tolerance was further enhanced when they were grown together in the wound model. We attributed this enhanced tolerance to both the “host-derived” and “bacterium-derived” matrix components. Taken together, our data indicate thatP. aeruginosaandS. aureusmay benefit each other by coinfecting wounds and that the host-derived matrix may serve as important a role as the bacterium-derived matrix in protecting bacteria from some antibiotics.