A testing scheme for the detection of Mycobacterium avium subsp. paratuberculosis in bovine feces utilizing the ESP para-JEM liquid culture system

Abstract

A testing scheme for the detection of Mycobacterium avium subsp. paratuberculosis (MAP) in broth cultures of bovine fecal samples carried out in ESP para-JEM System was evaluated. The scheme included acid-fast staining (on signal-positive and signal-negative samples), and confirmation by PCR for 2 MAP-specific targets and subculture of all acid-fast positive PCR-negative samples. Two hundred and fifty bovine fecal samples were evaluated for the presence of MAP using this scheme. Thirty-seven (15%) of 250 fecal samples had a positive culture result when the proposed testing scheme was used, compared to 14 (6%) positive results when using the standard ESP para-JEM protocol (requiring samples to have a positive signal from the system, a positive acid-fast stain, and a positive IS900 PCR result), and 20 (8%) positives when conventional culture was performed on Herrold egg yolk (HEY) media. A preliminary comparison of real-time and conventional PCR on DNA extracted from 15 MAP-positive broth cultures by 3 different protocols suggested that conventional PCR may be a better choice for the confirmation of the presence of MAP in the liquid cultures than real-time PCR.