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Year : 2007
Tome : 158
Volume : 12
Pages : 641-644
Title : Risk of false-negative results when delaying PCR from sampling for Coxiella burnetii detection in dairy cows
Authors : R. GUATTEO, F. BEAUDEAU, D. LEDOUX, E. LE DREAN AND H. SEEGERS
Summary : Reliable detection of Coxiella burnetii shedders is a critical point for the control of the spread of the infection between animals and from animals to humans. PCR is the most suitable tool for the detection of Coxiella burnetii in cattle. In routine diagnosis, the samples are usually sent to laboratories by postal routing. This study aimed at assessing the risk of false-negative results with delaying PCRs from sampling for Coxiella burnetii detection. Thirty six milk and 13 vaginal mucus samples being PCR positive on sampling day were divided in 8 aliquots each: 3 stored at +4C and 5 frozen at 20C. Real-time PCR were performed on days (D) 1, 2, 3 (or 5) for samples stored at +4C and days 3 (or 5), 7, 14, 28, 63 for frozen samples. Regardless of the storage, the proportion of samples which remained positive on the first test day after sampling day decreased by about one third and one half for milk and vaginal mucus respectively. Regardless the storage, samples found to be persistently-positive had a significantly higher estimated titre on D0 than those which became negative after D0. In absence of hypothesis on the expected bacterial burden in a milk or vaginal mucus sample, PCR assay should be performed on sampling day to minimise the risk of obtaining a false-negative result.
Keywords : Dairy Cow, Coxiella burnetii, real-time PCR, detectability, false negative
Correspondence : R. GUATTEO
Adress : UMR Veterinary School of Nantes & INRA 708 Unit of Animal Health Management, BP 40706, 44307 Nantes Cedex 03, France - E-mail: guatteo@vet-nantes.fr
Link : pdf

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