A quantitative polymerase chain reaction method for the detection in avian faeces of salmonellas carrying thespvRgene

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Abstract
Summary: A quick, semi-quantitative method of detectingSalmonellaspecies which contain the virulence plasmid has been developed using the polymerase chain reaction (PCR). A pair of primers have been synthesized encompassing a 500 bp fragment of thespvRvirulence gene. Competitor DNA consisting of thespvRgene with a 94 bp deletion situated between the primer recognition sequences, was cloned into a plasmid vector. Co-amplification of the ‘unknown’ target salmonella DNA with known quantities of competitor DNA in the same reaction tube gave PCR products of 500 and 406 bp respectively. Visual assessment of the ratio of the two products on ethidium bromide stained agarose gels provided an estimate of the approximate number of salmonella cells present in avian faeces.The technique could be applied to detect quantifiably any non-host DNA in clinical samples if a suitable DNA sequence for primer construction is available.