title: Biofilm prevention of gram-negative bacterial pathogens involved in periprosthetic infection by antibiotic-loaded calcium sulfate beads in vitro.
abstract: Biofilm formation represents a key stage in the pathogenesis of prosthetic infections (PIs). More tolerant to antibiotics than their planktonic counterparts, biofilm bacteria are difficult to eradicate using conventional therapeutic regimes. A common approach in PI management is the adjunctive use of localised antibiotics in addition to systemic administration in an attempt to protect the implant from colonisation by infiltrating bacteria. This study evaluates the antibacterial and antibiofilm efficacy of antibiotic-loaded dissolvable calcium sulphate, previously shown to be effective against key gram-positive pathogens, against gram-negative species important in the establishment of chronic infection in PIs. Synthetic calcium sulfate beads loaded with tobramycin, vancomycin and both antibiotics in combination were assessed for their ability to eradicate planktonic Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae strains. The efficacy of the beads in preventing biofilm formation and eliminating established biofilms over multiple days was evaluated using confocal laser scanning microscopy (CSLM) imaging combined with image analysis and viable cell counts. Beads loaded with antibiotics demonstrated effective eluting concentrations for up to 37 d depending on the bacterial strain. In the presence of repeated bacterial challenges, antibiotic-loaded beads prevented bacterial colonisation and significantly reduce biofilm formation for the duration of the assay (7 d). Complete eradication of established biofilms was more difficult with evidence of biofilm regrowth after 1 week of contact with antibiotic-loaded beads, despite data suggesting a complete kill was achieved at earlier timepoints of 24 h and 72 h in the case of K. pneumoniae and P. aeruginosa. This study provides further evidence that calcium sulfate beads loaded with vancomycin and tobramycin may be a useful adjunctive component to the successful management of PIs.
authors.affiliation: Southampton NIHR Respiratory Biomedical Research Unit, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK. Centre for Biological Sciences, Faculty of Natural and Environmental Sciences and Institute for Life Sciences, Building 85, University of Southampton, Highfield, Southampton, SO17 1BJ, UK. Author to whom any correspondence should be addressed. Microbial Ecology Group, Centre for Biological Sciences, University of Southampton, Life Sciences Building 85, Highfield, Southampton, SO17 1BJ, UK.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Howlin
authors.forename: Christopher
authors.initials: C
authors.lastname: Winnard
authors.forename: Connor J
authors.initials: CJ
authors.lastname: Frapwell
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Webb
authors.forename: John J
authors.initials: JJ
authors.lastname: Cooper
authors.forename: Sean S
authors.initials: SS
authors.lastname: Aiken
authors.forename: Paul
authors.initials: P
authors.lastname: Stoodley
mesh_terms: D040981:Acinetobacter baumannii; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms; D002133:Calcium Sulfate / Q000737:chemistry*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D007711:Klebsiella pneumoniae; D008826:Microbial Sensitivity Tests; D018613:Microscopy, Confocal; D016459:Prosthesis-Related Infections / Q000188:drug therapy / Q000517:prevention & control*; D011550:Pseudomonas aeruginosa; D014031:Tobramycin / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin; D014031:Tobramycin; D002133:Calcium Sulfate