Growth inhibitory factors in bovine faeces impairs detection of Salmonella Dublin by conventional culture procedure

Abstract

Aims: To analyse the relative importance of different biological and technical factors on the analytical sensitivity of conventional culture methods for detection of Salmonella Dublin in cattle faeces. Methods and Results: Faeces samples collected from six adult bovines from different salmonella‐negative herds were split into subpools and spiked with three strains of S. Dublin at a concentration level of c. 10 CFU g−1 faeces. Each of the 18 strain‐pools was divided into two sets of triplicates of four volumes of faecal matter (1, 5, 10 and 25 g). The two sets were pre‐enriched with and without novobiocin, followed by combinations of culture media (three types) and selective media (two types). The sensitivity of each combination and sources of variation in detection were determined by a generalized linear mixed model using a split‐plot design. Conclusions: Biological factors, such as faecal origin and S. Dublin strain influenced the sensitivity more than technical factors. Overall, the modified semi‐solid Rappaport Vassiliadis (MSRV)‐culture medium had the most reliable detection capability, whereas detection with selenite cystine broth and Mueller Kauffman tetrathionate broth combinations varied more in sensitivity and rarely reached the same level of detection as MSRV in this experiment. Significance and Impact of the Study: The study showed that for MSRV‐culture medium and xylose lysine decarboxylase agar as the indicative medium, the sensitivity of the faecal culture method may be improved by focusing on the strain variations and the ecology of the faecal sample. Detailed investigation of the faecal flora (pathogens and normal flora) and the interaction with chemical factors may result in developing an improved method for detection of S. Dublin.

Factors affecting costs for on-farm control of salmonella in Swedish dairy herds

“…However, this study did not show any signs of higher costs due to longer restriction periods in herds with S. Dublin infections either. An explanation for this might be a lower diagnostic sensitivity for S. Dublin versus other serotypes [23–25] resulting in premature lifting of restrictions in herds with S. Dublin. Serological testing in herds where restrictions have been lifted suggests that this may be the case.…”

A structured approach to control of Salmonella Dublin in 10 Danish dairy herds based on risk scoring and test-and-manage procedures

“…Consequently, infections in some groups of animals or even in the whole herd would go unnoticed, if bacteriology had been used for evaluation of progress in the control of Salmonella Dublin in this study. The sensitivity is poor due to intermittent shedding, low concentrations of bacteria in the samples and other factors related to the origin of the faecal material and the strain of bacteria (Baggesen, Nielsen, Sørensen, Bødker, & Ersbøll, 2007). Thus, the use of bacteriology would not provide sound conclusions, and it was decided to use the more cost-effective and sensitive ELISAs in this study.…”

Detecção De Salmonella SPP Com O Meio Semissólido Rapapport Vassiliadis (Msrv) Em Tubos

“…Segundo a literatura, o enriquecimento seletivo com o meio MSRV é considerado há mais de uma década uma das melhores alternativas para o isolamento de salmonelas de amostras da produção primária, 37 As desvantagens observadas do método proposto são a preparação mais demorada do meio de cultura, exigindo maior manipulação na transferência do meio fluido para os tubos de ensaio e introdução da ponteira e maior manipulação na inoculação da alíquota de cultura em APT, pois exige o desrosqueamento da tampa e rosqueamento posterior para fechá-lo, e, ainda, a possibilidade de menor detecção de amostras positivas em 24 horas de incubação.…”