Investigation article published in PLoS ONE

November 14^th, 2011

Advances in the diagnosis of Mycobacterium bovis infection in wildlife hosts may benefit the development of sustainable approaches to the management of bovine tuberculosis in cattle. In the present study, three laboratories from two different countries participated in a validation trial to evaluate the reliability and reproducibility of a real time PCR assay in the detection and quantification of M. bovis from environmental samples. The sample panels consisted of negative badger faeces spiked with a dilution series of M. bovis BCG Pasteur and of field samples of faeces from badgers of unknown infection status taken from badger latrines in areas with high and low incidence of bovine TB (bTB) in cattle. Samples were tested with a previously optimised methodology. The experimental design involved rigorous testing which highlighted a number of potential pitfalls in the analysis of environmental samples using real time PCR. Despite minor variation between operators and laboratories, the validation study demonstrated good concordance between the three laboratories: on the spiked panels, the test showed high levels of agreement in terms of positive/negative detection, with high specificity (100%) and high sensitivity (97%) at levels of 105 cells g−1 and above. Quantitative analysis of the data revealed low variability in recovery of BCG cells between laboratories and operators. On the field samples, the test showed high reproducibility both in terms of positive/negative detection and in the number of cells detected, despite low numbers of samples identified as positive by any laboratory. Use of a parallel PCR inhibition control assay revealed negligible PCR-interfering chemicals co-extracted with the DNA. This is the first example of a multi-laboratory validation of a real time PCR assay for the detection of mycobacteria in environmental samples. Field studies are now required to determine how best to apply the assay for population-level bTB surveillance in wildlife

Travis ER., Gaze WH., Pontiroli A., Sweeney FP., Porter D., Mason S., Keeling MJ., Jones RM., Sawyer J., Aranaz A., Castellanos E., Cork J., Delahay RJ., Wilson GJ., Hewinson RG., Courtenay O. and H Wellington EM.

An inter-laboratory validation of a Real Time PCR assay to measure host excretion of bacterial pathogens, particularly of Mycobacterium bovis

An inter-laboratory validation of a Real Time PCR assay to measure host excretion of bacterial pathogens, particularly of Mycobacterium bovis

	Servicio de Micobacterias (MYC). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).
	University of Warwick.
	Animal Health and Veterinary Laboratories Agency (AHVLA). Department for Environment, Food and Rural Affairs (Defra).
	Food and Environment Research Agency (FERA). Department for Environment, Food and Rural Affairs (Defra).