In vitro evaluation of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans polymicrobial biofilm growth on synthetic surgical implant materials

Abstract

Biofilms are a known important contributor to the infectious complications associated with prosthetic mesh implantation. Previous studies have demonstrated the formation of monomicrobial biofilms on surgical mesh materials by different bacterial species in vitro, but a paucity of data exists examining polymicrobial biofilm formation by antibiotic-resistant organisms, which may be more clinically relevant. Therefore, the aim of this study was to evaluate the ability of three clinical bacterial and fungal isolates to form mixed-species and single-species biofilms on five synthetic implant materials in vitro, including monofilament polypropylene, monofilament polyester, multifilament polyester, monofilament polytetrafluoroethylene (PTFE), and silicone. Methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Pseudomonas aeruginosa, and Candida albicans (alone or in combination) were inoculated into culture medium containing meshes and allowed to attach and propagate into mature biofilms for 48 hours at 37 o C. Additional samples were inoculated with Staphylococcus epidermidis for comparison. Biofilm biomass and the number of viable cells were quantified by crystal violet staining and colony forming units (CFU) counting, respectively. Images of polymicrobial biofilms were obtained using fluorescence microscopy of FM ® 1-43-stained meshes. All materials investigated were capable of harboring biofilms, but the relative abundance was dependent upon both material and organism type. Overall, PTFE meshes exhibited the highest levels of polymicrobial biofilm formation. When comparing monomicrobial biofilms, Pseudomonas aeruginosa demonstrated greater biomass than MRSA and Staphylococcus epidermidis on PTFE, polypropylene, and monofilament polyester, while MRSA and Staphylococcus epidermidis biomass did not differ significantly among mesh types. Thus MRSA, Pseudomonas aeruginosa, and Candida albicans can cooperatively form mature biofilms on surgical implant materials, but different mesh constructs vary in their susceptibility to biofilm formation depending upon the organism(s) present. This suggests that the type of implant material chosen for surgical procedures may affect the patient's wound healing response and clinical outcome, particularly when used in a contaminated environment.