Evaluation of the antimicrobial activity of lysostaphin-coated hernia repair meshes.

Bacterial infections by antibiotic-resistant Staphylococcus aureus strains are among the most common postoperative complications in surgical hernia repair with synthetic mesh. Surface coating of medical devices/implants using antibacterial peptides and enzymes has recently emerged as a potentially effective method for preventing infections. The objective of this study was to evaluate the in vitro antimicrobial activity of hernia repair meshes coated by the antimicrobial enzyme lysostaphin at different initial concentrations. Lysostaphin was adsorbed on pieces of polypropylene (Ultrapro) mesh with binding yields of ∼10 to 40% at different coating concentrations of between 10 and 500 µg/ml. Leaching of enzyme from the surface of all the samples was studied in 2% (wt/vol) bovine serum albumin in phosphate-buffered saline buffer at 37°C, and it was found that less than 3% of adsorbed enzyme desorbed from the surface after 24 h of incubation. Studies of antibacterial activity against a cell suspension of S. aureus were performed using turbidity assay and demonstrated that the small amount of enzyme leaching from the mesh surface contributes to the lytic activity of the lysostaphin-coated samples. Colony counting data from the broth count (model for bacteria in wound fluid) and wash count (model for colonized bacteria) for the enzyme-coated samples showed significantly decreased numbers of CFU compared to uncoated samples (P < 0.05). A pilot in vivo study showed a dose-dependent efficacy of lysostaphin-coated meshes in a rat model of S. aureus infection. The antimicrobial activity of the lysostaphin-coated meshes suggests that such enzyme-leaching surfaces could be efficient at actively resisting initial bacterial adhesion and preventing subsequent colonization of hernia repair meshes.

Incidence and management of inferior vena cava filter thrombus detected at time of filter retrieval.

PURPOSE: To evaluate inferior vena cava (IVC) venograms (ie, cavograms) before filter retrieval to determine the incidence and volume of filter thrombus relative to filter dwell time and evaluate subsequent changes in thrombus volume with additional anticoagulation. MATERIALS AND METHODS: IVC filter retrieval attempts between December 2002 and June 2010 were retrospectively reviewed to determine the incidence of filter thrombus and estimate thrombus volume on a preretrieval cavogram. Correlation between filter dwell times (assessed at 30-d intervals) and incidence and volume of thrombus was assessed. Follow-up images and management of filters with thrombus that were not initially removed were analyzed. RESULTS: A total of 463 retrieval attempts were performed in 440 patients, with a mean filter dwell time of 95 days ± 145 (SD; range, 0-1,762 d). Thirty (6.5%) had filter thrombus on initial cavograms, with a mean thrombus volume of 2.8 cm(3) ± 7.3 (range, 0.04-40.02 cm(3)). Incidence rate and estimated thrombus volume were highest in the 0-30-day dwell interval (8.0% and 6.3 cm(3), respectively) and decreased at subsequent time intervals. On linear regression analysis, incidence of filter thrombus was inversely related to dwell time (P < .05; correlation coefficient, -0.86). Seven patients with thrombus underwent additional anticoagulation for a mean of 48 days ± 25 (range, 14-90 d); thrombus resolved completely in five (71%) and partially in one (14%), and increased in one (14%). CONCLUSIONS: The incidence of filter thrombus at the time of filter retrieval appears to decrease with dwell time. If thrombus is detected, an additional period of anticoagulation is likely to reduce the thrombus burden and facilitate later retrieval.

Lysostaphin-coated mesh prevents staphylococcal infection and significantly improves survival in a contaminated surgical field.

Mesh and wound infections during hernia repair are predominantly caused by Staphylococcus aureus. Human acellular dermis (HAD) is known to lose its integrity in the face of large bacterial loads. The goal of this study was to determine if lysostaphin (LS), a naturally occurring anti-Staphylococcal protein, can protect HAD mesh from S. aureus infection. HAD samples, 3 cm × 3 cm, were implanted in the onlay fashion on the anterior abdominal wall of rats (n = 75). Subjects were grouped based on presence of antimicrobial bound to HAD (none or LS) and presence of S. aureus inoculum (sterile, 106, 108 CFU). At 60 days, meshes were explanted, and bacterial growth, histology, and mesh tensile strength were examined. None of the controls receiving bacterial inoculation without LS survived to 60 days. All LS-HAD sterile and LS-106 animals survived to explantation. The LS-HAD 108 group had a mortality rate of 50 per cent. All surviving LS-treated animals (n = 25) had negative wound and mesh cultures. Blinded gross and histologic evaluation and measured tensile strengths between all LS groups were comparable. Animals implanted with LS-HAD had a dramatically improved rate of survival. All animals surviving to 60 days had completely cleared S. aureus from their wounds with maintenance of mesh integrity and tensile strength. These findings strongly suggest the clinical use of LS-treated mesh in contaminated fields may translate into a more durable hernia repair.