Development of a complete ELISA using Salmonella lipopolysaccharides of various serogroups allowing to detect all infected pigs

Abstract

-Although poultry is recognized as the major source of food-poisoning caused by Salmonella, pork also contributes to human infections. This study was therefore undertaken in order to develop a reliable serological method for the evaluation of the Salmonella status of piglets. A complete ELISA was performed using lipopolysaccharides of Salmonella Typhimurium, Anatum, Hadar and Infantis because these serovars were representative of the serogroups isolated from 30 contaminated fattening farms. S. Enteritidis was also added because of its importance in human infection and to include the O : 9 antigen. This method potentially detects 100% of infected pigs. A significant correlation was found between this serological method and the bacteriological data from mesenteric lymph nodes (p = 0.01). In addition, both sensitivity and specificity were high (97% and 94% respectively). The ELISA test was therefore used in a cross-sectional study on 4 farms to evaluate when pigs became contaminated: seropositive pigs were only found for the 20 week old finishing pigs. The antibody response to Salmonella in piglets was also investigated: maternal antibodies persisted until 7 weeks of age and post-Salmonella contamination seroconversion was detected from 8 weeks of age onwards.ELISA / Salmonella / pig / epidemiology Résumé -Mise au point d'une méthode ELISA complète basée sur des lipopolysaccharides de plusieurs sérogroupes permettant de détecter tous les porcs infectés par des salmonelles. Bien que la volaille soit la principale source d'intoxication alimentaire par les salmonelles, le porc contribue aussi à la contamination humaine. Cette étude a été menée pour mettre au point une technique sérologique permettant d'évaluer le statut infectieux des porcelets vis-à-vis des salmonelles. Une technique ELISA dite complète a été élaborée avec des lipopolysaccharides de Salmonella Typhimurium, Anatum, Hadar et Infantis, sérovars représentatifs des sérogroupes isolés dans 30 élevages engraisseurs contaminés. S. Enteritidis a été ajoutée en raison de son importance dans les infections humaines et afin d'inclure l'antigène O : 9. Cette méthode permet de dépister potentiellement 100 % Vet. Res. 31 (2000) [481][482][483][484][485][486][487][488][489][490] 481

Experimental airborne transmission ofSalmonellaAgona andSalmonellaTyphimurium in weaned pigs

“…Despite the fact that S. Typhimurium nal+ has been isolated from tissues collected from one sentinel pig (P12) in Trial II, the presence of lactogenic immunity could explain the lack of Salmonella shedding by the sentinel pigs throughout the experimental period. Indeed, the presence of maternal antibodies against Salmonella may protect piglets during the first weeks [32].…”

Impact of the Salmonella status of market-age pigs and the pre-slaughter process on Salmonella caecal contamination at slaughter

“…The serological Salmonella status of the pigs was assessed using an indirect ELISA [26]. Salmonella IgG antibodies were detected in serum using a complete ELISA based on LPS from S. Typhimurium, Enteritidis, Anatum, Hadar and Infantis [26].…”

“…Salmonella IgG antibodies were detected in serum using a complete ELISA based on LPS from S. Typhimurium, Enteritidis, Anatum, Hadar and Infantis [26]. Optical densities were determined by a Dynatech MR5000 plate reader spectrophotometer using 490 and 630 nm filters as the test and reference filters, respectively.…”

“…Samples with COD ≥ 0.4 were considered to be positive according to the previously defined cut-off value [26]. ELISA sensitivity and specificity were estimated at 97% and 94%, respectively by Proux et al [26].…”

“…2.5). The within-batch Salmonella seroprevalence was assessed by the proportion of seropositive pigs among the 30 pigs randomised in each room adjusted according to the sensitivity and specificity of the ELISA [26] with the Rogan-Gladen formula [29]. A three-level ordinal variable was defined from the tertiles of the adjusted prevalence distribution.…”