Bacterial gangs attack implants

Opportunistic infections, and biomaterial-centered infections in particular, are often poly-microbial. Two of the most important etiologic agents of infections related to artificial organs, implants, and other medical devices, that is Staphylococcus aureus and Pseudomonas aeruginosa are frequently co-isolated from infections associated with the use of catheters, endotracheal tubes, and intraocular lenses. S. aureus and P. aeruginosa often gang up with Enterococcus faecalis. Because many bacterial species in peri-prosthesis tissues are able to adopt effective systems of communication, interaction and exchange of their virulence factors, thus forming true, close consortia. They use these abilities to “gang up” on their hosts. Alone, bacterial species can be more susceptible to antibiotics and more harmless. But once they reach a critical density, especially if they find themselves together with other bacterial species, they begin to produce and release molecules into the micro-environment through which they communicate “frenetically”. Cooperating to boost their virulence and transferring resistance genes to each other, they become able to evade antibiotic treatments. Bacteria involved in implant poly-microbial infections are usually formers of slimy biofilms which, as is well known, protect them and favor their growth. Therefore, biofilms are networks of bacteria that cooperate with each other to resist attacks of antimicrobial drugs and host immunity, and that work together not only to elude but also to defeat host defenses. Within the biofilms, bacteria can more easily achieve the required “quorum”, so that they “sense” when they are a large army. The potential for interspecies transfer of antimicrobial resistance genes, including resistance to vancomycin, may be enhanced simply by the micro-environment of a biofilm.