Comparison of Conventional Culture Methods and Two Commercial Enzyme Immunoassays for Detection ofSalmonellain Porcine Fecal Samples and Cecal Contents

Abstract

Abstract. Two commercial enzyme immunoassays, designated EIA-1 and EIA-2, for the detection of salmonella in feces and cecal contents were compared to conventional culture methods. Out of 362 cecal content samples, 35 were positive by EIA-1 and 30 were positive by EIA-2 and conventional methods. Out of 189 fecal samples, 41 were positive by EIA-1, 30 were positive by EIA-2, and 24 were positive by conventional culture methods. The EIA-1 assay method detected more positive samples overall, although only comparison of the fecal samples was statistically significant. The results indicate that the EIA-1 method is rapid, requiring only 24 hours, and may be more sensitive than the EIA-2 assay and conventional culture techniques. Enzyme immunoassays for the detection of salmonella in fecal samples or cecal contents provide a reasonable alternative to conventional culture techniques.Infection of pigs with Salmonella enterica species may lead to clinical disease with fever and profuse watery diarrhea or subclinical infections without clinical signs. Detection of salmonellae in subclinically infected animals is hampered by intermittent shedding and low numbers of bacteria in the feces. 3 Subclinical salmonella infection in swine constitutes a human health risk because fecal material from the animal may contaminate the carcass during slaughter. Meat from the contaminated carcass may subsequently give rise to human disease, directly or indirectly, by cross-contamination of other food products along the manufacturing and distribution line from the slaughterhouse to the consumer. 11 The importance of pork as a source of human salmonellosis has been shown in a number of investigations. Pork was estimated to be the primary source of sporadic human infections with Salmonella typhimurium in Denmark in 1992 and 1993. 2,14 Furthermore, contaminated pork distributed from a single slaughterhouse was found to be the source of a major Danish Salmonella infantis outbreak involving approximately 550 documented cases of disease in 1993. 13 In order to reduce salmonella contamination of Danish pork, a microbiologic screening program was conducted with the objective of detecting swine herds with subclinical salmonella infection. 3 Swine from infected herds could then be slaughtered under increased hyFrom the Danish Veterinary Laboratory, 27 Bülowsvej, DK-1790 Copenhagen V, Denmark.Received for publication July 5, 1996. giene measures in order to reduce carcass contamination. Samples of cecal contents were collected at slaughter, and infected farms were subsequently visited for collection of fecal pen samples in order to detect foci of infection within the herd and to devise a strategy for salmonella reduction.A number of conventional detection methods were previously evaluated for the detection of salmonella in swine cecal samples. 1 Pre-enrichment in buffered peptone water (BPW) followed by selective culture on modified semisolid Rappaport-Vassiliadis medium (MSRV) was found to be more sensitive than pre-enrichment in BPW followed by se...

Importance of pre-enrichment media for isolation of Salmonella spp. from swine and poultry

“…However, a recent report showed that the addition of certain metabolic en- Table 3 Comparison of alternative pre-enrichment methods with bu¡ered peptone water for isolation of Salmonella from poultry neck-skin samples UB (2) Revive ( Table 1 for key. When using the SEB protocol in the present study, the BG agar plates are available 1 day earlier (48 h) than the MSRV method (72 h), and thereby the result of serotyping can be available after 48 h. In addition, the SEB medium has been shown to be highly sensitive in combination with a semi-automated enzyme immunoassay [7]. The SEB method in the porcine samples resulted in a sensitivity (0.71) comparable to the standard method.…”

“…Modi¢ed semisolid Rappaport-Vassiliadis (MSRV) and Swarm agar were prepared as described previously [7]. The Salmonella Enrichment Broth I (SEB) was prepared according to instructions from the producer as described previously [8].…”

Importance of pre-enrichment media for isolation ofSalmonellaspp. from swine and poultry

“…The SEB method in the porcine samples resulted in a sensitivity (0.71) comparable to the standard method. When using the SEB protocol in the present study, the BG agar plates are available 1 day earlier (48 h) than the MSRV method (72 h), and thereby the result of serotyping can be available after 48 h. In addition, the SEB medium has been shown to be highly sensitive in combination with a semi‐automated enzyme immunoassay [7].…”

“…Modified semisolid Rappaport‐Vassiliadis (MSRV) and Swarm agar were prepared as described previously [7]. The Salmonella Enrichment Broth I (SEB) was prepared according to instructions from the producer as described previously [8].…”