Detecção de Salmonella enterica e Listeria monocytogenes em carcaças suínas na etapa de pré-resfriamento / Salmonella enterica and Listeria monocytogenes detection on pre-chill pig carcasses

ABSTRACT

Background: Salmonellosis is one of the most prevalent foodborne diseases worldwide. Although listeriosis has been quite less reported, it is considered a major public health hazard due to the severity of symptoms caused in humans. Previous studies demonstrated that the genus Listeria and Salmonella can be found infecting pigs in Brazil, however there are yet few reports about their isolation from carcasses after the slaughtering process. From this, the aims of this study were to investigate the presence of Salmonella enterica and Listeria monocytogenes on pre-chill pig carcasses and to evaluate the presence of fecal carriers at the lairage. Materials, Methods & Results: Two sampling events were conducted in each of three slaughterhouses located in the state of Santa Catarina, Brazil. In each sampling event, pen feces from pigs belonging to three slaughter batches originated from different farms were collected. Thereafter, swabs were taken on the surface (loin, jowls, belly and ham) of 42 carcasses belonging to the same pig batches sampled at the lairage. All samples were submitted to a protocol for isolation of S. enterica and L. monocytogenes. Moreover, coliforms were enumerated in the samples taken from the carcasses. From a total of 18 samples of pen feces, 83.3% (15/18) were positive for S. enterica. The genus Listeria was isolated from 66.7% (12/18) of pen feces samples, but only one isolate was confirmed as L. monocytogenes. Among the 252 pre-chill carcasses sampled, S. enterica was isolated from 27.4% (69/252); and S. Typhimurium was the most frequent serovar identified. On the other hand, L. monocytogenes was detected in 19.8% (50/252) of the carcasses. In slaughterhouse B, a signifi cantly higher frequency (P < 0.001) of L. monocytogenes isolation than in the other slaughterhouses was observed. S. enterica was significantly more (P < 0.001) isolated than L. monocytogenes in the other two sampled slaughterhouses. The coliform mean counts found on carcass samples ranged from 1.25 x 100 to 8.25 x 104. In slaughterhouse A, the coliform mean was significantly lower (P < 0.001) than the mean of coliforms determined in the other slaughterhouses. Discussion: The significantly higher frequency of L. monocytogenes isolation from carcasses sampled at the slaughterhouse B suggests that there were flaws in its slaughter process. Nevertheless, the L. monocytogenes contamination on the carcasses may not have been originated from feces, since this Listeria specie was found in only one sample of pen feces. In spite of the fact that slaughterhouse A presented a significantly lower mean of coliforms on the pre-chill carcasses, indicating that there was a better hygiene in the slaughtering process, the frequency of S. enterica on the carcasses was not different in comparison to those found in the other sampled slaughterhouses. This result may be related to the large number of fecal carriers detected at the lairage, which in turn may have led to an increase on the carcass contamination hazard throughout the slaughter line. In conclusion, S. enterica and L. monocytogenes can be isolated from pre-chill pig carcasses. Whereas the high number of Salmonella fecal carriers may have contributed to the frequency of contaminated carcasses, L. monocytogenes strains found on carcasses were probably not originated from feces.