Inhibition and reversal of Salmonella typhimurium attachment to poultry skin using zinc chloride

Abstract

A skin attachment model was used to determine if ZnCl2 would reverse or inhibit Salmonella attachment to broiler skin. In the reversal experiments, skin samples, treated first with 1 ml of Salmonella Typhimurium suspension (108 CFU/ml) for 30 min, were then treated with 25 or 50 mM ZnCl2 for 5 or 15 min. Zinc chloride solutions were applied while the culture was present on the skin. In the inhibition experiments, ZnCl2 solutions were added first; treatment solutions were discarded after 5 or 15 min of application, and then the culture was added. Firmly and loosely attached Salmonella were enumerated on xylose lactose tergitol plates. A duplicate section of skin, subjected concurrently to the above treatments, was observed under a scanning electron microscope to enumerate attached bacteria directly. In the reversal experiments, 25 and 50 mM ZnCl2 reduced (P < 0.01) firmly attached cells by 77 and 89%, respectively, when compared to the control (water). Micrographs indicated that 25 and 50 mM ZnCl2 reduced (P < 0.1) Salmonella attachment by 69 and 99.9%, respectively, in the reversal experiments. In the inhibition experiments, 25 and 50 mM ZnCl2 reduced (P < 0.01) firmly attached cells by 82 and 91%, respectively. Reduction of Salmonella may be attributed, in part, to the bactericidal activity of ZnCl2 in addition to bacterial cell detachment.