Bayesian Estimation of qPCR and Bacterial Culture Accuracy for Detection of Bovine Coagulase-Negative Staphylococci from Milk and Teat Apex at Different Test Cut-off Points

Y. S. Mahmmod*, L. Svennesen, J. Katholm, Karl Pedersen, I. C. Klaas

*Corresponding author for this work

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Aim
    primarily to estimate the sensitivity (Se) and specificity (Sp) of the commercially available Mastit4 qPCR assay and bacterial culture (BC) for diagnosis of intramammary infections (IMI) and teat apex colonization (TAC) with coagulase‐negative staphylococci (CNS) at different cut‐offs for qPCR cycle threshold (Ct) values using Bayesian latent class analysis (LCA). A secondary objective was to evaluate two cut‐offs of BC for diagnosis of IMI and TAC with CNS.

    Methods and Results
    we randomly selected 13 to 20 cows with subclinical mastitis from 8 dairy herds. Teat skin samples and aseptically collected foremilk samples were collected from the right hindquarters (n = 149) for BC and qPCR analysis. The Se of qPCR was always higher than BCSe in diagnosis of IMI, however; the Sp of BC was higher than qPCRSp. BCSe and BCSp showed no substantial difference between the tested BC cut‐offs. In contrast to IMI, estimates of BC and qPCR in diagnosing TAC were different. BCSe was higher than qPCRSe at all tested cut‐offs, however; qPCRSp was higher than BCSp.

    Conclusion
    the overall performance of qPCR is higher than BC in the diagnosis of IMI however; the performance of BC is better than qPCR in diagnosis of TAC. The qPCR and BC are valid diagnostics for bovine IMI with CNS. Whereas for TAC, both techniques require further investigation to reduce the uncertainty of the true status of the quarter and teat skin.

    Significance and Impact of the Study
    we reported, for the first time, the diagnostic performance of new mastitis technology (Mastit4 PCR) and culture for detection of CNS in milk and non‐milk samples in dairy herds with automatic milking systems. Our findings will improve the interpretation of the test results of culture and qPCR assay and subsequently, will strengthen the control of IMI with CNS in dairy cows.
    Original languageEnglish
    JournalJournal of Applied Microbiology
    Volume127
    Issue number2
    Pages (from-to)406-417
    ISSN1364-5072
    DOIs
    Publication statusPublished - 2019

    Keywords

    • bovine mastitis
    • diagnostic test evaluation
    • latent class analysis
    • non-aureus staphylococci
    • sensitivity and specificity
    • teat skin colonization

    Cite this

    @article{d654a3ee0ced436495560ae7b2e52471,
    title = "Bayesian Estimation of qPCR and Bacterial Culture Accuracy for Detection of Bovine Coagulase-Negative Staphylococci from Milk and Teat Apex at Different Test Cut-off Points",
    abstract = "Aimprimarily to estimate the sensitivity (Se) and specificity (Sp) of the commercially available Mastit4 qPCR assay and bacterial culture (BC) for diagnosis of intramammary infections (IMI) and teat apex colonization (TAC) with coagulase‐negative staphylococci (CNS) at different cut‐offs for qPCR cycle threshold (Ct) values using Bayesian latent class analysis (LCA). A secondary objective was to evaluate two cut‐offs of BC for diagnosis of IMI and TAC with CNS.Methods and Resultswe randomly selected 13 to 20 cows with subclinical mastitis from 8 dairy herds. Teat skin samples and aseptically collected foremilk samples were collected from the right hindquarters (n = 149) for BC and qPCR analysis. The Se of qPCR was always higher than BCSe in diagnosis of IMI, however; the Sp of BC was higher than qPCRSp. BCSe and BCSp showed no substantial difference between the tested BC cut‐offs. In contrast to IMI, estimates of BC and qPCR in diagnosing TAC were different. BCSe was higher than qPCRSe at all tested cut‐offs, however; qPCRSp was higher than BCSp.Conclusionthe overall performance of qPCR is higher than BC in the diagnosis of IMI however; the performance of BC is better than qPCR in diagnosis of TAC. The qPCR and BC are valid diagnostics for bovine IMI with CNS. Whereas for TAC, both techniques require further investigation to reduce the uncertainty of the true status of the quarter and teat skin.Significance and Impact of the Studywe reported, for the first time, the diagnostic performance of new mastitis technology (Mastit4 PCR) and culture for detection of CNS in milk and non‐milk samples in dairy herds with automatic milking systems. Our findings will improve the interpretation of the test results of culture and qPCR assay and subsequently, will strengthen the control of IMI with CNS in dairy cows.",
    keywords = "bovine mastitis, diagnostic test evaluation, latent class analysis, non-aureus staphylococci, sensitivity and specificity, teat skin colonization",
    author = "Mahmmod, {Y. S.} and L. Svennesen and J. Katholm and Karl Pedersen and Klaas, {I. C.}",
    year = "2019",
    doi = "10.1111/jam.14309",
    language = "English",
    volume = "127",
    pages = "406--417",
    journal = "Journal of Applied Microbiology",
    issn = "1364-5072",
    publisher = "Wiley-Blackwell",
    number = "2",

    }

    Bayesian Estimation of qPCR and Bacterial Culture Accuracy for Detection of Bovine Coagulase-Negative Staphylococci from Milk and Teat Apex at Different Test Cut-off Points. / Mahmmod, Y. S.; Svennesen, L.; Katholm, J.; Pedersen, Karl; Klaas, I. C.

    In: Journal of Applied Microbiology, Vol. 127, No. 2, 2019, p. 406-417.

    Research output: Contribution to journalJournal articleResearchpeer-review

    TY - JOUR

    T1 - Bayesian Estimation of qPCR and Bacterial Culture Accuracy for Detection of Bovine Coagulase-Negative Staphylococci from Milk and Teat Apex at Different Test Cut-off Points

    AU - Mahmmod, Y. S.

    AU - Svennesen, L.

    AU - Katholm, J.

    AU - Pedersen, Karl

    AU - Klaas, I. C.

    PY - 2019

    Y1 - 2019

    N2 - Aimprimarily to estimate the sensitivity (Se) and specificity (Sp) of the commercially available Mastit4 qPCR assay and bacterial culture (BC) for diagnosis of intramammary infections (IMI) and teat apex colonization (TAC) with coagulase‐negative staphylococci (CNS) at different cut‐offs for qPCR cycle threshold (Ct) values using Bayesian latent class analysis (LCA). A secondary objective was to evaluate two cut‐offs of BC for diagnosis of IMI and TAC with CNS.Methods and Resultswe randomly selected 13 to 20 cows with subclinical mastitis from 8 dairy herds. Teat skin samples and aseptically collected foremilk samples were collected from the right hindquarters (n = 149) for BC and qPCR analysis. The Se of qPCR was always higher than BCSe in diagnosis of IMI, however; the Sp of BC was higher than qPCRSp. BCSe and BCSp showed no substantial difference between the tested BC cut‐offs. In contrast to IMI, estimates of BC and qPCR in diagnosing TAC were different. BCSe was higher than qPCRSe at all tested cut‐offs, however; qPCRSp was higher than BCSp.Conclusionthe overall performance of qPCR is higher than BC in the diagnosis of IMI however; the performance of BC is better than qPCR in diagnosis of TAC. The qPCR and BC are valid diagnostics for bovine IMI with CNS. Whereas for TAC, both techniques require further investigation to reduce the uncertainty of the true status of the quarter and teat skin.Significance and Impact of the Studywe reported, for the first time, the diagnostic performance of new mastitis technology (Mastit4 PCR) and culture for detection of CNS in milk and non‐milk samples in dairy herds with automatic milking systems. Our findings will improve the interpretation of the test results of culture and qPCR assay and subsequently, will strengthen the control of IMI with CNS in dairy cows.

    AB - Aimprimarily to estimate the sensitivity (Se) and specificity (Sp) of the commercially available Mastit4 qPCR assay and bacterial culture (BC) for diagnosis of intramammary infections (IMI) and teat apex colonization (TAC) with coagulase‐negative staphylococci (CNS) at different cut‐offs for qPCR cycle threshold (Ct) values using Bayesian latent class analysis (LCA). A secondary objective was to evaluate two cut‐offs of BC for diagnosis of IMI and TAC with CNS.Methods and Resultswe randomly selected 13 to 20 cows with subclinical mastitis from 8 dairy herds. Teat skin samples and aseptically collected foremilk samples were collected from the right hindquarters (n = 149) for BC and qPCR analysis. The Se of qPCR was always higher than BCSe in diagnosis of IMI, however; the Sp of BC was higher than qPCRSp. BCSe and BCSp showed no substantial difference between the tested BC cut‐offs. In contrast to IMI, estimates of BC and qPCR in diagnosing TAC were different. BCSe was higher than qPCRSe at all tested cut‐offs, however; qPCRSp was higher than BCSp.Conclusionthe overall performance of qPCR is higher than BC in the diagnosis of IMI however; the performance of BC is better than qPCR in diagnosis of TAC. The qPCR and BC are valid diagnostics for bovine IMI with CNS. Whereas for TAC, both techniques require further investigation to reduce the uncertainty of the true status of the quarter and teat skin.Significance and Impact of the Studywe reported, for the first time, the diagnostic performance of new mastitis technology (Mastit4 PCR) and culture for detection of CNS in milk and non‐milk samples in dairy herds with automatic milking systems. Our findings will improve the interpretation of the test results of culture and qPCR assay and subsequently, will strengthen the control of IMI with CNS in dairy cows.

    KW - bovine mastitis

    KW - diagnostic test evaluation

    KW - latent class analysis

    KW - non-aureus staphylococci

    KW - sensitivity and specificity

    KW - teat skin colonization

    U2 - 10.1111/jam.14309

    DO - 10.1111/jam.14309

    M3 - Journal article

    C2 - 31077513

    VL - 127

    SP - 406

    EP - 417

    JO - Journal of Applied Microbiology

    JF - Journal of Applied Microbiology

    SN - 1364-5072

    IS - 2

    ER -