Development of a novel immunochromatographic lateral flow assay specific for Mycobacterium bovis cells and its first application in combination with immunomagnetic separation to test badger faeces
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This study reports development of a novel immunochromatographic lateral flow device (LFD) and its application in combination with immunomagnetic separation (IMS) to detect Mycobacterium bovis cells in faeces of European badgers (Meles meles). The prototype LFD developed, which incorporated two different M. bovis-specific IgG antibodies, was shown to have unique specificity for M. bovis, no cross-reactivity against a range of other Mycobacterium spp., and a limit of detection (LOD50%) of 1.7 x 104 M. bovis cells/ml. IMS was employed to selectively capture and concentrate M. bovis from badger faeces prior to detection by the LFD. LOD50% of the IMS-LFD assay was 2.8 x 105 M. bovis cells/ml faecal homogenate. When freshly collected faeces from badgers of unknown infection status were tested, 78 (18%) of 441 samples tested positive by the IMS-LFD assay, whereas 140 (32%) tested positive by IMS-qPCR; there was poor agreement between results of these two tests (Kappa -0.009 ± 0.044, p=0.838). Subsequently, when 130 faeces samples from live captured, or captive, badgers of known infection status (on basis of StatPak, interferon-γ and/or culture results) were tested, the IMS-LFD assay was shown to have higher diagnostic specificity (Sp 0.926), but poorer diagnostic sensitivity (Se 0.081), than IMS-qPCR (Sp 0.706, Se 0.581) and IMS-MGIT culture (Sp 0.794, Se 0.436). It was concluded that the novel IMS-LFD assay would be capable of detecting infectious badgers shedding high numbers of M. bovis (≥104-5 cells/g) in their faeces, and the test would therefore be of limited use as a non-invasive test for badger surveillance purposes. Other potential applications for the novel LFD are being explored.
- Mycobacterium bovis, European badger (Meles meles), lateral flow assay, immunomagnetic separation (IMS), faeces, Diagnostics