Isolation of Salmonella enterica from Slaughtered Pigs

Phentotypic, gentotypic antimicrobial resistance and pathogenicity of Salmonella enterica serovars Typimurium and Enteriditis in poultry and poultry products

For detection and isolation of Salmonella enterica, 650 meat and tissue samples were processed using Rappaport-Vassiliadis Enrichment broth and Salmonella Chromogenic agar followed by confirmation through specific antisera and polymerase chain reaction (PCR) targeting their Specific Serovar Genomic Regions (SSGRS). Isolates were tested for 15 antibiotics (CRO, AMX, GEN, STR, TET, CHL, CLR, LVX, OFX, GAT, CIP, SXT, AMP, LIN and AZM) according to the disc diffusion method and antimicrobial resistant genes (tet(A), tet(B), tet(C), strA/strB, aadA, aac(3)IV), aadB, sul1, sul2 and sul3, blaCMY-2, blaTEM and blaSHV) using PCR. The overall prevalence of Salmonella enterica was 12%, being higher in markets (15%) as compared to poultry farms (37.2%). The MPN of all positive meat and tissue samples was found 3.6 MPN/gram (0.17-18). A total of 234 isolates were obtained, serovar Typimurium (139) and Enteridits (95) were the most prevalent. Antimicrobial resistance patterns were different in different serovars according to origin of Salmonella isolates. The overall isolates were highly resistant for LIN (93.1%, 218/234) followed by AMX (80%, 187/234), AMP (74.3%, 174/234), TET (64.5%, 151/234) and STR (64.5%, 151/234). Overall, the most common ARG was bla_TEM (76%, 178/234), followed by bla_SHV (71.7%, 168/234), tet(A) (64%, 151/234) and tet(B) (64%, 150/234), while the least ARG was aadB (7.2%, 17/234). Both Typimurium and Enteridits were tested in the Balb/C mice for pathogenicity. Both Typimurium and Enteridits were found to cause successful colonization, 100% morbidity but Enteriditis were found to cause 33% mortality.

Role of slaughtering in Salmonella spreading and control in pork production

Salmonella is one of the major foodborne pathogens worldwide. Pork products are among the main sources of Salmonella infection in humans, and several countries have established Salmonella surveillance and control programs. The role of slaughtering in carcass contamination has been indicated by studies focused on the slaughterhouse environment. In this review, we examine and discuss the information available regarding the influence that farm status, pig transport, and lairage have on the carriage of Salmonella by pigs entering the slaughter line. The evolution of carcass contamination throughout the slaughtering process, the main sources of contamination in the dirty and clean zones of the slaughter line, and previously reported prevalence of Salmonella on carcasses and factors affecting this prevalence also are discussed. The importance of implementing interventions at the slaughter level is discussed briefly. Consistent with the information available, pigs from infected farms and newly acquired or recrudescent infections in pigs at the subsequent stages of transport and lairage are important sources of Salmonella at the slaughtering plant. The continuous introduction of Salmonella into the slaughterhouse and the potential for resident flora constitute a risk for carcass contamination. At the slaughterhouse, some dressing activities can reduce carcass contamination, but others are critical control points that jeopardize carcass hygiene. This information indicates the importance of considering slaughter and previous stages in the pork production chain for controlling Salmonella in swine production.

Occurrence of Salmonella in the Ileum, Ileocolic Lymph Nodes, Tonsils, Mandibular Lymph Nodes and Carcasses of Pigs Slaughtered for Consumption

This study evaluates the occurrence of Salmonella in pork carcasses and in some risk tissues (ileum, ileocolic and mandibular lymph nodes and tonsils), that can be involved in Salmonella contamination during slaughter. Salmonella was identified in 27 (26.7%) pigs and in 13 (12.9%) carcasses. From these positive carcasses, 69.2% presented the same serotype as that identified in the corresponding pig, which emphasize the pigs importance as a source of Salmonella during the slaughter, suggesting that measures should be taken at the level of pig production in order to reduce the slaughtering of Salmonella-positive animals. The highest value of Salmonella occurrence was reached in the ileocolic lymph nodes (18.8%) and in the ileum (13.9%), representing Salmonella potential faecal source during pork processing at the abattoir. In these samples, a high level of Salmonella was observed in the ileocolic lymph nodes in comparison with the ileum. The mandibular lymph nodes (12.9%) also presented a higher occurrence in comparison with the tonsils (9.9%). These results indicate that the lymph nodes analysis could be more sensitive in the detection of Salmonella than the closer drainage tissue. Otherwise, the presence of Salmonella in the lymph nodes indicates lymphatic spread of the organism, which reflects an increased risk of pork contamination. These results also indicate that, in order to achieve a better control of Salmonella contamination during the slaughter process, it is important to consider the improvement of the evisceration practices and the tonsils as well the extraction of mandibular lymph nodes after slaughter.