www.eJManager.com Balkan Military Medical Review 2014; 17(4):111-114 ISSN: 1107-6275 111 BALKAN Military Medical REVIEW Original Research Tracing the origin of bacterial contamination in close and medium range gunshot wounds in a sheep limb model David C Kieser 1,2 , Michael Harrington 1 , Heather Brooks 1 , Sonya Mros 1 , Sandra CJ Kieser 1 , Glynny A Kieser 1 , Jean-Claude Theis 1 , Jules A Kieser 1 1 Department of Health Sciences, University of Otago, Dunedin, New Zealand, 9016. 2 Medical Corps, New Zealand Defence Force, Wellington, New Zealand, 5045. Received November 13, 2014 Accepted December 16, 2014 Published Online December 24, 2014 DOI 10.5455/bmmr.172847 Corresponding Author David C Kieser, PO Box 6458, Dunedin, New Zealand, 9016 kieserdavid@gmail.com Key Words Ballistic, bullet, gunshot, infection, contamination Abstract Background: Gunshot injuries have a variable rate of infection, the source of remains debatable. This study aimed to determine whether bacteria found on bullets, within the gun barrel or on the victim’s skin and clothing could be deposited into the deep tissues and bone at the time of injury. And to determine the effects of bullet design, soft tissue thickness and victim distance on bacterial deposition. Methods: Fifty-two sheep legs were shot in the tibia or femur at close range (10cm) or medium range (5m) with .22mm rifles, using solid or hollow point bullets. Streptomycin resistant Streptococcus salivarius was inoculated along different points of the bullet path including the bullet, barrel, skin and clothing. Results: Bacteria were isolated in the deep tissues and bone in all samples with varying consistency. Interestingly, the hollow point bullet deposited bacteria more consistently than the solid point, bacteria within the barrel were transmitted to the target even at 5m and no observable difference was seen in the rate of bacterial transmission between tibial and femoral gunshot wounds. Conclusions: We confirm previous research, showing that low velocity bullets do not auto- sterilise on firing. In addition, we show that bacteria can be deposited into the deep tissues in a viable state, irrespective of soft tissue thickness. Importantly, hollow point bullets transmit bacteria more consistently than pointed tip bullets, and finally, bacteria anywhere along the bullet’s path can be collected by the bullet and deposited into the deep tissues in close and medium range experimental gunshot wounds. INTRODUCTION Gunshot wounds continue to cause significant morbidity and mortality worldwide with over 2 million people affected annually [1]. Most gunshot wounds (50-70%) involve the limbs [2]. Infection rates for limb injuries vary from 2% to 11% for treated low velocity civilian gunshot wounds [3-6], but much higher in battlefield casualties, reaching as high as 77% in the pre-antibiotic era [7]. Historically, bullets were thought to auto-sterilise on firing due to the heat and pressure generated by the explosion of gunpowder, the friction on the projectile whilst traversing the barrel and the impact of the bullet upon its target [8-10]. The ensuing infection of the deeper soft tissues and bone was thought to be caused by skin micro-flora being sucked into the depths of the wound by the projectile [11-13]. However, research on bacterial survival on low velocity projectiles suggests that these bullets do not auto-sterilise on firing and thus, an ensuing infection of the deep tissues following a gunshot injury may be due to the inoculum of bacteria delivered by the bullet [11,14,15]. So far, there has been no research into the question of how soft tissue depth; bullet design or shot distance may affect this phenomenon. The aim of this study was to determine whether bacteria contaminating the bullet, gun barrel, skin or clothing could be transmitted into the depths of a gunshot wound. In addition, we assessed the effects of variables of soft tissue thickness, bullet design and