UV Light Inactivation of Mycobacterium avium subsp. paratuberculosis in Milk as Assessed by FASTPlaque TB Phage Assay and Culture

• Published in: Applied and environmental microbiology Vol. 73; no. 11; pp. 3728 - 3733
• Main Authors: Altic, Leslie C., Rowe, Michael T., Grant, Irene R.
• Format: Journal Article
• Language: English
• Published: 01-06-2007
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.00057-07

ABSTRACT
UV light inactivation of
Mycobacterium avium
subsp.
paratuberculosis
in Middlebrook 7H9 broth and whole and semiskim milk was investigated using a laboratory-scale UV machine that incorporated static mixers within UV-penetrable pipes. UV treatment proved to be less effective in killing
M. avium
subsp.
paratuberculosis
suspended in milk (0.5- to 1.0-log
10
reduction per 1,000 mJ/ml) than that suspended in Middlebrook 7H9 broth (2.5- to 3.3-log
10
reduction per 1,000 mJ/ml). The
FASTPlaque
TB phage assay provided more rapid enumeration of surviving
M. avium
subsp.
paratuberculosis
(within 24 h) than culture on Herrold's egg yolk medium (6 to 8 weeks). Despite the fact that plaque counts were consistently 1 to 2 log
10
lower than colony counts throughout the study, UV inactivation rates for
M. avium
subsp.
paratuberculosis
derived using the phage assay and culture results were not significantly different (
P
= 0.077).