Rapid assessment of the viability of Mycobacterium avium subsp. paratuberculosis cells after heat treatment, using an optimized phage amplification assay.

Applied and Environmental Microbiology
Antonio FoddaiIrene R Grant

Abstract

Thermal inactivation experiments were carried out to assess the utility of a recently optimized phage amplification assay to accurately enumerate viable Mycobacterium avium subsp. paratuberculosis cells in milk. Ultra-heat-treated (UHT) whole milk was spiked with large numbers of M. avium subsp. paratuberculosis organisms (10(6) to 10(7) CFU/ml) and dispensed in 100-microl aliquots in thin-walled 200-microl PCR tubes. A Primus 96 advanced thermal cycler (Peqlab, Erlangen, Germany) was used to achieve the following time and temperature treatments: (i) 63 degrees C for 3, 6, and 9 min; (ii) 68 degrees C for 20, 40, and 60 s; and (iii) 72 degrees C for 5, 10, 15, and 25 s. After thermal stress, the number of surviving M. avium subsp. paratuberculosis cells was assessed by both phage amplification assay and culture on Herrold's egg yolk medium (HEYM). A high correlation between PFU/ml and CFU/ml counts was observed for both unheated (r(2) = 0.943) and heated (r(2) = 0.971) M. avium subsp. paratuberculosis cells. D and z values obtained using the two types of counts were not significantly different (P > 0.05). The D(68 degrees C), mean D(63 degrees C), and D(72 degrees C) for four M. avium subsp. paratuberculosis strains were 81.8, ...Continue Reading

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Citations

Nov 22, 2011·Analytical and Bioanalytical Chemistry·Abby E SmarttSteven Ripp
May 4, 2010·Antonie van Leeuwenhoek·Bhupender SinghLeif A Kirsebom
Mar 19, 2013·Applied and Environmental Microbiology·Victoria L TkachukKim H Ominski
Feb 26, 2014·Critical Reviews in Food Science and Nutrition·J P P M Smelt, S Brul
Mar 8, 2011·Journal of Food Protection·C O GillW J Meadus
Jan 28, 2021·Microorganisms·Monika Beinhauerova, Iva Slana

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