Trend of Salmonella enterica occurrence and serotypes in Sardinian pig slaughterhouses

Giuliana Siddi; Francesca Piras; Vincenzo Spanu; Mariella Demontis; Maria Pina Meloni; Rita Sanna; Veronica Cibin; Enrico Pietro Luigi De Santis; Christian Scarano

doi:10.4081/ijfs.2021.9362

Trend of Salmonella enterica occurrence and serotypes in Sardinian pig slaughterhouses

Ital J Food Saf. 2021 Aug 25;10(2):9362. doi: 10.4081/ijfs.2021.9362. eCollection 2021 Jun 25.

Authors

Giuliana Siddi¹, Francesca Piras¹, Vincenzo Spanu¹, Mariella Demontis¹, Maria Pina Meloni¹, Rita Sanna¹, Veronica Cibin², Enrico Pietro Luigi De Santis¹, Christian Scarano¹

Affiliations

¹ Department of Veterinary Medicine, University of Sassari.
² OIE and National Reference Laboratory for Salmonellosis, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro (PD), Italy.

Abstract

The aim of this study was to evaluate Salmonella prevalence and serotypes in four Sardinian pig slaughterhouses. Moreover, a population study was conducted with pulsed field gel electrophoresis (PFGE). The results were compared with previous investigations carried out during years 2008 and 2014. A total of 147 samples were collected, 117 from slaughtered pigs (lymph nodes, colon content and carcass surface) and 30 from the slaughterhouse environment (surfaces in contact and not in contact with meat). Salmonella was isolated from 3.4% pig samples and was not detected from environmental samples. Comparing the results with those of previous investigations, occurrence showed a sharp decrease through the years in both animals (18.8% in 2008, 10% in 2014 and 3.4% in 2020) and environmental samples (34.1% in 2008, 3.7 in 2014, and 0% in 2020). At the same time, prevalence of carriers (pigs positive at lymph nodes and/or colon content level) showed a reduction through the years and was always lower in animals coming from local farms rather than those coming from other European Member States, probably indicating the role of stressful factors as transport in increasing Salmonella susceptibility and shedding. Salmonella serotypes were monophasic Typhimurium, Rissen and Muenchen. Overall, 13 different Salmonella serotypes were identified during the three surveys with the most prevalent being serotypes often isolated from slaughtered pigs and during human salmonellosis cases: S. Derby and S. Typhimurium in 2008, S. Anatum and S. Rissen in 2014, monophasic S. Typhimurium in 2020. Population study with pulsed field gel electrophoresis showed a high similarity between Salmonella strains belonging to the same serotype. The results of the investigations showed a decrease of Salmonella occurrence during twelve years in Sardinia, probably due to the improvement in the application of correct GMPs and GHPs at slaughterhouse and also to a reduction of the rate of carrier pigs at farm level.

Keywords: PFGE; Prevalence; Salmonella; Serotyping.

Grants and funding

Funding: this work was funded by the research grant “Rina Mazzette” (D.R. Rep. 2163/2019) and Sassari University (fondo di Ateneo per la ricerca 2019).