Detection of Mycobacterium avium subsp. paratuberculosis IgG by a conductometric biosensor: An aid in diagnosis of Johne's disease

The development of a non-laboratory based Johne's disease (JD) diagnostic assay, which is rapid, user-friendly, and supports routine herd testing, would help control the spread of this costly disease of cattle, caused by Mycobacterium avium subsp. paratuberculosis (MAP). The objective of this study was to develop a conductometric biosensor as an on-site, user-friendly, rapid, and inexpensive JD diagnostic assay. First, an immunomigration conductometric biosensor that could detect MAP IgG in bovine serum was designed and fabricated. The MAP IgG detection was measured as electrical resistance. Next, the biosensor elements were optimized to improve accuracy. Finally, the biosensor was tested with field samples and results were compared to a MAP antibody detection ELISA, which is commonly used for JD diagnosis. In the proof of concept study, there was significant difference (P <0.05) between resistance values of the JD positive and JD negative serum samples. Results from the biosensor were obtained in 2 minutes. The assay was simple to run and could be easily transported to and used in a field setting. The assay's precision was improved after optimization. The biosensor had a moderate agreement with ELISA in JD diagnosis (Kappa = 0.41), as well as good sensitivity (71.43%) and specificity (70%). Based on this study, a conductometric biosensor has promise as a diagnostic assay for JD.