Reduction of Salmonella spp. levels in swine carcass at the slaughterhouse, using hot water bath at 80°c

Porcine salmonellosis is of important economic and food safety importance, as it is a cause of food infections in humans, and is present in large scale in finishing pigs due to lymph node latency and rearing conditions. The objective of this study was to evaluate the reduction in Salmonella spp. in slaughter swine carcasses, after slaughtering under a bath with water at 80 ° C. Ninety swine carcasses were evaluated after slaughter at four harvesting points (leg, loin, belly and double chin), before and after bathing with water at 80 °C, in 720 samples, with quantitative analysis by the number method more probable. In slaughtering 43.33% (39/90) of the animals were positive before hot water application represented by 62 positive samples. After the intervention, 88.71% (55/62) of the positive samples zeroed the counts, in seven samples there was no reduction and in 11 samples, there was positivity in previously negative animals. The typifications of all positives were Salmonella Typhimurium. The samples with the greatest reduction in the count were double chin and belly samples with a concentration of 330 NMP / g that subsequently zeroed. Treatment with hot water bath in the carcasses was efficient, with significant difference of positivity before and after the intervention. There were cases of cross contamination after intervention in animals that remained positive and animals negative. Intervention by bathing the carcasses after gutting with 80 ° C water reduces the Salmonella spp. count and is economically viable.


Introduction
Salmonella spp. it is a bacterium of the Enterobacteriaceae family, involved in numerous cases of foodborne infection in humans, especially infections arising from the consumption of swine products (CDC, 2018). In Brazil, salmonellosis until 2017 led the cases of foodborne infections registered, with 38.2% of cases. From 2000 to 2013, over 1500 cases were reported (BRASIL, 2018). In most cases, swine are asymptomatic carriers; however, they can intermittently excrete the bacteria due to cross contamination or animal positivity, and carry the pathogen for fresh meat and or by products (CASTAGNA et al., 2004).
The faecal-oral route is considered the main route of transmission, and the bacterium quickly settles in the host, expressing virulence genes to overcome these barriers (HURD et al., 2001;OCHOA;RODRIGUEZ, 2005;SCHWARTZ et al., 2006) Many animals reach slaughter with high levels of positivity and few studies describe the decontamination effect of swine carcasses. Carcasses from batches with high contamination undergo intervention with hot water in the slaughterhouse as an extra measure for decontamination before carcass Zuffo; Vaz; Soares, Mendonça, Ferraz Reduction of Salmonella spp. levels in swine carcass at the… cooling and associated with the other HACCP and Hazard Analysis interventions, resulting in decontamination efficiency (MUSING et al., 1997;BERENDS et al. 1997;HURD et al, 2002;CHRISTENSEN, 2004). The duration of the hot water bath followed the normal flow of carcasses passage through the nomad until storage, being on average 1.5 minutes.
During this period, all carcasses were bathed in an arc shower over their entire surface with constant pressure and a constant temperature of 80 ° C.
The points were sampled using sterile wipes soaked in physiological solution, in 100 cm² of the carcass, delimited by a sterile plastic mold, totalling 400 cm² of sampled area for the whole carcass. After collection, the tissues were placed back in their original sterile packaging, identified and immediately sent to the laboratory for analysis. Samples from the refrigerator were processed following the Most Probable Number (MPN) quantitation technique, adapted from that described by Blodgett and Garthright (1998). Each of the 720 samples collected were pre-enriched in 1:10 2% buffered peptone water, incubated in a bacterial aerobic greenhouse at 37 °C / 18 to 24 hours. After this period each sample was transferred to six tubes of Rappaport Vassiliardis selective enrichment broth containing 9 mL of broth, and in the first five tubes added 1mL of the sample (10 -2 dilution), and after homogenization of the fifth tube was passed 1mL from this to the sixth tube (10 -3 dilution).
The tube series was incubated at 42 °C / 18 to 24 hours. After incubation, all Rappaport Vassiliardis tubes were seeded on XLT4 selective agar and incubated at 37 °C/18 to 24 hours. Suspected Salmonella colonies were inoculated in biochemical tests, according to Silva (2007), and then submitted to poly O antiserum, in serology, to confirm the presence of Salmonella spp.. When confirmed the Salmonella spp. colonies, they were counted by most probable number (MPN) by the combination of positive tubes, as described by Blodgett and Garthright (1998 are also shown in Figure 1. There were 11 samples (17.74%) that did not present counts at harvest before treatment and were positive after the intervention. Counts and collection locations are shown in Figure 3. This work proves that the use of hot water as a carcass bath was effective to reduce contamination by Salmonella spp. by 89%. The information matches the findings of Goldbach and Alban (2006) who found 72% efficiency in hot water decontamination in Danish slaughterhouses.
These same authors report in their findings that hot water decontamination is effective without compromising the quality of the final product. Also Hamilton et al. (2010) observed that hot water use reduced the surface prevalence of Escherichia coli from 92.9% to 9.8% in a slaughterhouse in Australia. However, for Morild et al. (2011), performing experimental inoculation of Salmonella Typhimurium on muscle and skin of swine, observed increase in pathogen count after application of water at 80 ° C and lactic acid.
The use of hot water, although it promotes an extra expense in the refrigerator due to energy consumption, is already an input present in the production line, and the benefit of its use in decontamination justifies the use and increase of charges against its efficiency.
Intervention becomes a cheap and effective alternative, taking into account contamination reduction efficiency and the risk of having Salmonella in the finished product. Goldbach and Alban (2006) also report the advantages of using hot water when describing the cost-benefit of pathogen reduction interventions in Denmark.
The 11 samples that were not positive before the intervention and developed after the use of hot water show us the existence of cross contamination in the area after slaughter, by contact with positive carcasses or operator handling. These contamination can be conveyed by operator gloves, contact of positive carcasses and decontaminated carcasses, or by the production processes (hooks and structure). Highlight for the double chin that was the place with more than half of the findings in this mode. Berends et al. (1997) state that 70% of the contamination at the end of the slaughter line comes from a carrier animal.
Samples for shipment to the laboratory were packaged in sterile containers sealed in boxes, negative controls between the sample group were used in the process to signal contamination, in addition to ISO 17025 accredited traceability to the laboratory reinforcing the idea of no cross contamination in the diagnosis. This set of information directs us to reinforce the concept of Good Production Practices (BPP), as well as the use of interventions, because it is possible that much of the problem is the subsequent recontamination to decontamination alternatives. For this, care after using the 80 ° C water bath should be directed to operators and facilities. Measures such as changing gloves, washing and disinfecting facilities, biofilm removal, stringent HACCP oversight can help improve the performance of interventions, including hot water decontamination, so that applying the technique is not just a cost increase. Goldbach and Alban (2006) state that the temperature of 80 ° C affects the bacterial structure of Salmonella, as it is well above the ideal temperature for growth of the pathogen (which is 40 ° C to 42 °C). However, Zuffo; Vaz; Soares, Mendonça, Ferraz Reduction of Salmonella spp. levels in swine carcass at the… it can also be hypothesized that part of the success of the technique is due to the mechanical removal of water flow in the finished carcass, a point that did not participate in the variables of this study.
Regardless of whether the reduction synergy is linked to physical removal and water temperature, the study gives us an alternative viability of positive carcasses, and an executable way to reduce the surface contamination pressure of the product. This intervention meets the findings of Hamilton et al. (2010), who attribute success to this intervention and indicate as a good way to improve the conditions of the final product.

Conclusion
Bathing the carcasses after evisceration with water at 80 ° C reduces the Salmonella spp. The intervention is economically viable and is accepted by Brazilian law.