Salmonella Contamination in Chicken Skin

Chicken skins were randomly collected from Koch Food Company (USA) and sliced into 10 cm × 10 cm samples. To minimize contamination, chicken skin was washed with 200 ppm chlorine solution (Sigma-Aldrich Co.) and sterilized DW. Then, 200 ml of the Salmonella cocktail was inoculated onto the chicken at concentrations ranging from 10¹ to 10³ CFU/100 cm². An equal amount of PBS was added onto other chicken skins as negative controls. The inoculated chicken skins were dried under a biosafety cabinet for bacterial attachment and placed in an Erlenmeyer flask prior to further incubation in a refrigerator (4°C) for 48 h. Next, 100 ml of brain heart infusion (BHI, EMD Science, Germany) or brilliant green (BG, Difco Laboratories Inc.) broth was added to each flask and incubated at 37°C in an orbital shaker at 250 rpm. Then, 100 μl of sample was collected from BHI and BG broths at 0, 2, 4, and 6 h, and the resuscitated bacterial population was measured using xylose lysine deoxycholate agar (Difco Laboratories Inc.) and recorded as log CFU/chicken for comparison. Subsequently, 20 ml of samples were obtained from both broths and washed 3 times by centrifugation at 4,000 ×g for 20 min. After resuspending with 1 ml of PBS, 100 μl of Salmonella suspension was used for ELISA and GB-LMIS, as described in the previous section. The results are expressed as log CFU/chicken for the comparison.