Phagomagnetic separation-quantitative PCR: A rapid, sensitive and specific surveillance tool for viable Mycobacterium avium ssp. paratuberculosis in bulk tank and individual cow milk samples

Bulk tank milk samples from 392 Northern Ireland dairy farms and individual animals (n = 293) on 4 of these were tested by a novel phagomagnetic separation (PhMS)-quantitative (q)PCR assay able to detect quantify viable Mycobacterium avium ssp. paratuberculosis (MAP), demonstrate its potential utility as surveillance tool. Viable MAP detected in 26.5% the bulk milks, with contamination levels ranging 1 8,432 MAP/50 mL milk; less than 2% had >100 their milk. Follow-up PhMS-qPCR testing that highest numbers milks indicated 17 24% each herd shedding Mean ranged between 6.7 42.1 No significant correlation was observed detection or parallel ELISA results, results any other recording (somatic cell count, total bacterial % butterfat, protein). IS900 qPCR 52 (85.2%) Pozzato broth cultures 61 PhMS-qPCR-positive after 12 wk incubation, suggesting few false positives. The mean sensitivities applied estimated Bayesian latent class analysis be 0.7096 0.2665, respectively, specificities similar (0.9626 0.9509). Our findings clearly could useful tool for processors, monitoring Johne's disease control quality assurance programs.