title: Detection of Mycobacterium avium subsp. paratuberculosis in bulk tank milk by combined phage-PCR assay: evidence that plaque number is a good predictor of MAP.
abstract: Conventional culture and a rapid phage-PCR method were used to detect Mycobacterium avium subsp. paratuberculosis (MAP) in bulk tank milk (BTM) samples. Only two of 225 samples (0.9%) were found to contain MAP by culture whereas 50 (22%) MAP-positive samples were identified using the phage-PCR assay, including both samples that were MAP-culture positive. Results using the phage-based method for independently tested duplicate samples indicated that the assay is very reproducible (r(2)=0.897), especially when low levels of mycobacteria are present. A relationship was established between plaque number and the presence of MAP in a sample. A cut-off value was determined allowing identification of MAP-positive samples based on plaque number alone (90% sensitivity, 99% specificity; area under the curve=0.976). These results indicate that the assay is a robust method for screening BTM, providing results within 24 h.
authors.affiliation: Division of Food Sciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leics., LE12 5RD, UK.
authors.forename: George
authors.initials: G
authors.lastname: Botsaris
authors.forename: Maria
authors.initials: M
authors.lastname: Liapi
authors.forename: Charalambos
authors.initials: C
authors.lastname: Kakogiannis
authors.forename: Christine E R
authors.initials: CE
authors.lastname: Dodd
authors.forename: Catherine E D
authors.initials: CE
authors.lastname: Rees
mesh_terms: D000818:Animals; D004269:DNA, Bacterial / Q000032:analysis; D005516:Food Microbiology / Q000379:methods*; D008892:Milk / Q000382:microbiology*; D016927:Mycobacterium avium subsp. paratuberculosis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D010948:Viral Plaque Assay / Q000592:standards
chemical_list: D004269:DNA, Bacterial