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.

This study demonstrates that antibiotic-loaded CaSO beads may represent an effective antibacterial and antibiofilm strategy to combat prosthetic infections in which P acnes is involved.

Preoperative joint aspiration and culture is a sensitive and specific test for the confirmation of diagnosis in patients at a moderate to high risk of prosthetic joint infection. Culture of saline injection-reaspiration also provides accurate diagnostic information in the event of a 'dry tap'. Both methods allow susceptibility testing of relevant organisms and are therefore able to guide perioperative antibiotic therapy. Cite this article: Bone Joint J 2018;100-B:749-54.

Despite current low rates, the incidence of arthroplastyassociated infections (AAI) is likely to increase over the next few years as the number of joint replacement operations continues to rise worldwide. AAI pose a challenge for both patients and surgeons. They have become a major economic burden on healthcare systems. Debridement and implant retention is not a widely considered option for chronic AAI probably due to low success rates. Negative Pressure Wound Therapy and intra-articular antibiotics instillation using VAC ULTA/VeraFlo system is an alternative strategy in the management of chronic AAI where implant retention is sought. Further evaluations and studies are needed to address the efficacy of this strategy and its cost effectiveness.

Uncovering microbial populations in the lumen of neonatal enteral feeding tubes utilising 16s 1 rRNA sequencing. 2 3 4 Christopher J Winnard1,2. Sue Green3. Alison Baylay4. Mark J Johnson5,6. Mandy Fader3. 5