Optimalization of Salmonella detection in chickens’ caecum using PCR method (short communication)

Abstract. PCR analysis is regarded to be a quick and reliable method of Salmonella detection in food and animal samples. The mode of sampling and sample preparation influence the sensitivity and accuracy of the analysis. The 10 days old, clinically healthy Salmonella-free chickens were experimentally infected with Salmonella enterica subsp. Enteritidis strain. Five randomly selected birds were euthanized at intervals from 2 days to 16 days post-infection (pi). DNA detection with polymerase chain reaction (PCR) as a mean of identifying Salmonella infection in chickens' caecum was used. The caecal sample was diluted into LB medium and incubated to eliminate inhibitory compounds and to allow enrichment of the bacteria. The DNA was extracted from cultures by boiling method. The pair of primers used was those directed at the invA gene. As expected a 243 bp fragment DNA was amplified from extracted DNA by PCR. Salmonella DNA was detected throughout the entire test period. The number of chickens containing salmonellae in caecum varied during the 16 days post-infection between 100% and 60%. The stated sensitivity of PCR reaction was 1 CFU of used strain in pure culture. The faeces and caecum content were simultaneously examined by conventional culture procedure. The microbiological examinations showed the presence of salmonellae in faeces during the entirely experiment. The results of this study confirm that PCR is a useful tool for the detection of Salmonella infection in poultry.