Reduction of Escherichia coli O157:H7 and salmonella following application of various sanitizing treatments to harvesting knives

Escherichia coli O157:H7 (E. coli O157:H7) and Salmonella are enteric pathogens that can cause severe illness and possible death if consumed. These pathogens are potential contaminants to meat during animal harvest. If not properly sanitized, knives used during this process can become a vehicle to spread contamination of these pathogens from carcass to carcass during the harvest process. The purpose of this study was to assess the effectiveness of non-thermal sanitation along with changes to treatment application interval, while evaluating E. coli O157:H7 and Salmonella reduction on knives. Chemical dip treatments included, 1.1% sodium metasilicate (SMS), 200 ppm quaternary ammonium compounds (QAC), 200 ppm chlorine (Cl2), 5% lactic acid (LA), 82.2°C water (HW), and 21°C water (RTW). Three replications of 18 knives were processed after inoculation of both E. coli O157:H7 and Salmonella (separately) to show initial and treated pathogen survival on a CFU/cm2 basis. Knife blades were inoculated with a three strain cocktail of either E. coli O157:H7 or Salmonella. A single side of the knife blade was sampled with a sponge, which was pre-hydrated with 10 ml of a neutralizer specific to the sanitizing treatment; in the case of water treatments sponges pre-hydrated with buffered peptone water (BPW) were used for sampling. Thirty second immersion treatments in sanitizing solutions were applied. The other side of the knife blade was sampled just as pre-treated sides to evaluate reduction. Dilutions of E. coli O157:H7 samples were plated onto MacConkey agar, and Salmonella sample dilutions were plated onto Xylose Lysine Desoxycholate media. Arithmetic means of pathogen numbers on untreated knives inoculated with E. coli O157:H7 and Salmonella showed an attachment of 4.51 and 5.09 log CFU/cm2, respectively. Treatment * time interaction of least square (LS) mean log reductions of knives inoculated with E. coli O157:H7 were 1.16, 3.51, 3.38, 1.38, 3.82, and -0.41 CFU/cm2, following treatment in SMS, QAC, Cl2, LA, HW, and RTW, respectively (P ≤ 0.05). Furthermore, treatment * time interactions of knives inoculated with Salmonella resulted in LS mean log reductions of 0.78, 3.42, 3.40, 2.91, 4.12, and 0.36 CFU/cm2, following treatment in SMS, QAC, Cl2, LA, HW, and RTW, respectively (P ≤ 0.05). Results depict that utilization of sanitizing agents in ambient temperature water treatments have potential to provide significant reduction of E. coli O157:H7 and Salmonella on knives used during animal harvest.