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Comparative evaluation of four decontamination protocols for the isolation of Mycobacterium avium subsp.
L Dundee1, I R Grant, H J Ball
1Department of Food Science (Food Microbiology), Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK.
Aims:
Four chemical decontamination protocols for milk were compared with respect to mean percentage recovery of spiked Mycobacterium avium subsp. paratuberculosis, minimum detection limit and ease of application.
Methods And Results:
Raw milk spiked with 106 cfu M.a. paratuberculosis was decontaminated prior to culture by: (1) treatment with 0.75% (w/v) hexadecylpyridinium chloride (HPC) for 5 h; (2) and (3) Cornell methods employing brain heart infusion broth containing 0.75% (w/v) and 0.9% (w/v) HPC, respectively; and (4) a C18-carboxypropylbetaine (CB-18)
Method:
The 0.75% HPC method yielded the highest mean percentage recovery of M.a. paratuberculosis (28.7%) and was capable of detecting the lowest number of cells (30 cfu/40 ml).
Conclusion:
Treatment of milk with 0.75% HPC for 5 h was shown to be superior to the other methods for decontaminating milk prior to culture for M.a. paratuberculosis.
Significance And Impact Of Study:
Certain chemical decontamination protocols are too harsh for application to milk. The "best" decontamination protocol only recovered a fraction of the M.a. paratuberculosis cells present in a milk sample.