Veterinary Research Communications, 27 Suppl. 1 (2003) 281–283 © 2003 Kluwer Academic Publishers. Printed in the Netherlands
Isolation of Salmonella enterica from Slaughtered Pigs S. Bonardi1*, G. Pizzin1, L. Lucidi1, F. Brindani1, F. Paterlini2 and S. Tagliabue2 1Dipartimento di Salute Animale, Sezione di Ispezione degli Alimenti di origine animale, Facolta` di Medicina Veterinaria, Universita` di Parma, Parma; 2Istituto Zooprofilattico Sperimentale della L ombardia e dell’Emilia Romagna ‘B. Ubertini ’, Brescia, Italy *Correspondence: Dipartimento di Salute Animale, Sezione di Ispezione degli Alimenti di origine animale, Facolta` di Medicina Veterinaria, Universita` di Parma, V ia del T aglio 8, 43100 Parma, Italy E-mail:
[email protected] Keywords: pig, Salmonella enterica subsp. enterica, slaughterhouse
INTRODUCTION Pigs at slaughter may be intestinal or pharyngeal carriers of zoonotic bacteria such as Salmonella enterica subsp. enterica. Pork carcase contamination is possible, as contamination hazards cannot be completely eliminated at any stage of the swine slaughtering process. MATERIALS AND METHODS Between December 1999 and December 2000, 150 pigs (150–180 kg weight) were randomly selected in two large slaughterhouses located in Parma province, northern Italy. A total of 450 specimens were examined: 150 caecal material samples, 150 tonsil portions and 150 carcase swabs (sternal and throat regions) were collected. The sample size was defined to give 95% probability of detecting one positive animal/carcase if the carriage/contamination rate was ≥2%. The pigs came from 27 specialized slaughter production herds. The ISO 6579 (1993) method was followed for the detection of S. enterica. Biochemical properties of the isolates were detected using the API 20 E system (bioMe´rieux). Somatic antigens were identified using the slide agglutination test with somatic group and single factor antisera (Difco Laboratories, Detroit, MI, USA), while flagellar antigens were identified using tube agglutination with flagellar antisera (Difco). RESULTS S. enterica was isolated from the caecal content of 55 out of 150 slaughtered pigs (36.7%; CI 95% 29.0–44.4%), from eight tonsils out of 150 (5.3%; CI 95% 1.7–8.9%), 281
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and from nine carcases out of 150 (6.0%; CI 95% 2.2–9.8%). A total of 57 S. enterica carriers were identified; in particular, 51 pigs were intestinal carriers, 6 animals were both intestinal and pharyngeal carriers, and 2 pigs were only pharyngeal carriers. Positive pigs came from 19 herds out of 27 (70.4%). A total of 10 S. enterica serotypes were identified (Table I). S. Derby, S. Bredeney and S. Typhimurium were the more common serotypes. Two isolates showed unusual biochemical features: one S. Give strain was urease-positive, while one S. Bredeney strain was ONPG-positive.
DISCUSSION This study indicated that, in the two abattoirs investigated, the prevalence of S. enterica in the caecal material of finishing pigs was very high. A high prevalence of intestinal carriers of S. enterica is strongly correlated with the hazard of pork carcase contamination at the end of the slaughterline (Berends et al., 1997). Carcase contamination could also be due to the spreading of microorganisms during tonsil removal, which is considered a critical operation in swine slaughter.
ACKNOWLEDGEMENTS The authors gratefully acknowledge the technical assistance of Mrs Ida Poli, Mrs Giuseppina Trentadue and Mrs Rosaria Gallelli. This study was supported by a grant from the Italian MURST 40%, 1999. TABLE I S. enterica serotypes isolated from pigs at slaughter Isolation sources
Serotype S. Derby S. Bredeney S. Typhimurium S. London S. Coeln S. Anatum S. Seftenberg S. Agona S. Give S. India
No. of strains (%) 28 16 11 6 5 3 2 1 1 1
(37.8%) (19.2%) (15.1%) (8.1%) (6.7%) (4.1%) (2.7%) (1.4%) (1.4%) (1.4%)
Tonsils
Caecal material
Carcasses
3 5 – – – – – – – –
20 9 11 4 5 3 2 1 1 1
5 2 – 2 – – – – – –
No. of positive herds (%) 9 5 6 2 2 2 1 1 1 1
(33.3%) (18.5%) (22.2%) (7.4%) (7.4%) (7.4%) (3.7%) (3.7%) (3.7%) (3.7%)
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REFERENCE Berends, B.R., Van Knapen, F., Snijders, J.M. and Mossel, D.A., 1997. Identification and quantification of risks factors regarding Salmonella spp. on pork carcasses. International Journal of Food Microbiology, 36, 199–206
