Identification of biofilm-associated proteins in vitro and in the plasma of patients with biofilm-related implant disease

Despite the rapid advancement in implantable medical devices (IMD) and surgical techniques, the problem of IMD-associated infections has increased from 2% to 40%, depending on the type of IMDs. It is estimated that approximately 65 to 85% of all hospital-acquired infections are associated with biofilms, this represents a serious challenge. Staphylococcus aureus and coagulase-negative staphylococci account for about 80% of medical device-related diseases. Infections associated with biofilms are enormously problematic to eliminate due to their elevated tolerance against the host immune defence system and antimicrobials. There is currently no effective technique for early identification of biofilms. In addition, recent findings of biofilms on dry hospital surfaces emphasise the failures in current cleaning practices and disinfection, and the difficulty in removing these dry surface biofilms (DSB). DSB have been shown to be principally composed of protein. Therefore, we compared the proteomes of S. aureus during planktonic, hydrated (wet) biofilms and DSB in vitro. In vivo, we compared the plasma proteome (following depletion of high-abundant proteins) of healthy patients with those of patients with biofilm-related breast implant capsular contracture (CC). The proteomes were determined using high-resolution Tandem Mass Tag (TMT)-based mass spectrometry. In the in vitro proteomics study, we identified 1636 non-redundant total biofilm extractomes from S. aureus. Among the significant upregulated proteins in 3-day wet biofilm (wet) compared to planktonic, we identified proteins associated with ABC transporters, biosynthesis of amino acids, response to stress, a biofilm dispersing extracellular enzyme hysA; whereas virulence factors, energy metabolism and chitinase, an extracellular enzyme responsible for preventing intial attachment of biofilm formation, were significantly downregulated. HysA in conjunction with chitinase may play an important role in the elimination and/or prevention of biofilm development. In comparison with 3-day wet and 12-day wet biofilm, we observed a significant range of quantitative proteomic shifts in different stages of biofilms. Further pathway analysis showed that the major alterations in biofilm formation results from the changes in the level of metabolic activity in different growth mode of biofilms. Therefore, changes in metabolic activity could be a significant factor of S. aureus biofilm maturation and persistence. In the novel DSB proteomics study, proteins significantly upregulated in DSB were involved in energy metabolism and peptidoglycan biosynthesis pathway such as ptaA, murC and murB. These three proteins are all linked with peptidoglycan biosynthesis pathway and are responsible for cell wall formation and may play a role in biofilm formation and persistence of DSB on dry surfaces. In the in vivo plasma proteomics study, we have seen clear differences in plasma proteome of biofilm-related breast implant CC patients in comparison to healthy controls. These novel findings promote further research to verify outcomes in large groups of patients and various clinical backgrounds. In summary, the current pioneering study could potentially prove useful in designing vaccines, anti-biofilm agents, diagnostic biomarker(s), and much needed antimicrobial therapies for biofilm-related diseases, as well as advanced, targeted disinfectants and detergents to remove biofilms from dry environments -- abstract.