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Inactivation of Mycobacterium avium ssp. paratuberculosis in milk by UV treatment

J Donaghy1, M Keyser, J Johnston

  • 1Agriculture, Food and Environmental Science Division (Food Microbiology Branch), Agri-Food and Biosciences Institute, Belfast, Northern Ireland.

Letters in Applied Microbiology
|June 3, 2009
PubMed
Abstract

Insights

UV radiation alone shows limited effectiveness in reducing Mycobacterium avium ssp. paratuberculosis (Map) in milk. Further research is needed to explore combined treatments for effective inactivation of this pathogen.

Area of Science:

  • Food Microbiology
  • Public Health
  • Dairy Science

Background:

  • Mycobacterium avium ssp. paratuberculosis (Map) is a pathogen of concern in milk.
  • Current pasteurization methods are effective but alternative inactivation strategies are being explored.

Purpose of the Study:

  • To evaluate the efficacy of UV-C radiation in inactivating two strains of Map inoculated into ultra-heat-treated milk.
  • To compare the UV sensitivity of different Map strains and assess inactivation using various enumeration methods.

Main Methods:

  • Pilot-scale UV reactor (20 L) used to treat Map in milk with doses up to 1836 mJ/ml.
  • Map survival monitored via culture (Herrold's egg yolk, Middlebrook 7H10) and phage assay (FASTPlaqueTB).

Main Results:

  • UV-C radiation achieved a Map kill rate of 0.1-0.6 log(10) at 1000 mJ/ml, irrespective of strain or enumeration method.
  • Observed differences in UV sensitivity between Map strains, but overall inactivation was limited.
  • Culture-based methods consistently yielded higher viable counts than the phage assay.

Conclusions:

  • UV radiation alone is insufficient as a sole alternative to current pasteurization for significant Map reduction in milk.
  • The study highlights challenges in UV treatment of opaque liquids and Map's resistance to inactivation.
  • This pilot-scale study provides insights into UV efficacy for Map inactivation in milk, comparable to lab-scale findings.

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