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Eradication of Multidrug-Resistant Pseudomonas Biofilm from Infected Prolene Mesh with Pulsed Electric Fields
Saiqa I. Khan, Daniela Vecchio, Alexander Golberg, Harry M. Salinas, Michael McCormack, Martin Yarmush, Michael R. Hamblin, William G. Austen, Jr.
Massachusetts General Hospital, Boston, MA

Objective: The purpose of this study was to investigate the effect of Pulsed Electric Fields (PEF) on infected mesh. Over one million abdominal wall hernia repairs are performed each year in the United States. Infection is a significant postoperative complication with reported rates ranging from 4% to 16%. Infected mesh is treated with removal, resulting in the morbidity of a subsequent defect that often must be closed under tension, leading to inevitable hernia recurrence.We hypothesize PEF is a novel method to eradicate bacteria from infected mesh, therefore avoiding the increased morbidity associated with reoperation for mesh removal. High voltage, short PEF create non-thermal permanent damage to cell membranes. PEF have been shown to be effective in non-thermal ablation of solid tumors. Intermittent delivery of PEF has been demonstrated to control bacteria in pharmaceuticals and food. Our previous studies have shown complete scarless regeneration of epidermis, hair follicles, and sebaceous glands, two months after non-thermal ablation with PEF in rodents. Additionally, we have previously used PEF to effectively treat antimicrobial-resistant Acinetobacter baumannii burn wound infections in the murine model. PEF have not been investigated in the treatment of synthetic implant infections. This study investigates the effect of PEF on infected mesh.

Design: Prolene mesh, commonly used to repair abdominal wall hernias and other fascial defects, was infected with bioluminescent pathogenic Pseudomonas. PEF were delivered using a cylindrical system, with a centrally located 18-gauge steel needle and an outer brass ring, forming two concentric electrodes. Alligator clips were attached to the brass ring and the 18G needle. The system was placed on the infected mesh with the needle located at the center of the mesh (Figure 1). The clips were hooked up to the BTX 830 pulse generator (Harvard Apparatus Inc, Holliston MA, USA). The following PEF parameters used were: 1500 Volts, 50?s pulse duration, 85 pulses, and 1Hz frequency. A bioluminescent imaging system (Hamamatsu Photonics KK, Bridgewater, NJ) and ARGUS software (Hamamatsu) were utilized to obtain the images. The image-processing software calculates the total pixel valves (in Relative Luminescence Units [RLU]) of the mesh. Imaging was performed before and after treatment. Untreated and treated mesh were processed for Scanning Electron Microscopy.

Results: Prior to treatment, the RLU of the Pseudomonas-infected mesh was 5,684,912 (Figure 1). After one treatment, the RLU decreased to 1,427,144, resulting in a 75% reduction over the entire piece of mesh with central clearing where the needle was in contact with the mesh. Bioluminescent imaging demonstrated eradication of infection at the area of treatment (Figure 1, black arrow). The goal of this experimental design was to obtain central clearing of the mesh since the PEF apparatus delivers a centripetal gradient of disinfection from the center outwards to the periphery. Scanning Electron Microscopy of the mesh samples confirms eradication of the biofilm (Figure 2).

Conclusion: We have demonstrated a novel method for in vitro eradication of infection in contaminated mesh with antiseptic PEF. Pulsed Electric Fields reduced the load of multidrug-resistant pseudomonas without damaging the mesh. We plan to conduct in vivo studies implanting infected mesh in a murine model and demonstrating lack of infection recurrence after treatment with PEF. The PEF treatment will be delivered noninvasively through the external application of contact electrodes measuring 1cm2. We hypothesize that in patients, combining systemic antibacterial therapy with PEF will yield a synergistic effect leading to eradication of mesh infections, therefore avoiding mesh removal and preventing the associated morbidity of recurrent hernias and reoperations.

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