Sensitivity of Mycobacterium avium subsp paratuberculosis, Escherichia coli and Salmonella enterica serotype Typhimurium to low pH, high organic acids and ensiling
Article first published online: 28 MAY 2013
Published 2013. This is article is a U. S. Goverment work and is in the public domain in the USA.
Journal of Applied Microbiology
Volume 115, Issue 2, pages 334–345, August 2013
How to Cite
Cook, K.L., Flis, S.A. and Ballard, C.S. (2013), Sensitivity of Mycobacterium avium subsp paratuberculosis, Escherichia coli and Salmonella enterica serotype Typhimurium to low pH, high organic acids and ensiling. Journal of Applied Microbiology, 115: 334–345. doi: 10.1111/jam.12243
- Issue published online: 17 JUL 2013
- Article first published online: 28 MAY 2013
- Accepted manuscript online: 6 MAY 2013 12:31AM EST
- Manuscript Accepted: 1 MAY 2013
- Manuscript Revised: 10 APR 2013
- Manuscript Received: 4 DEC 2012
- Escherichia coli ;
- organic acids;
- Salm. Typhimurium;
- Salmonella ;
To evaluate the persistence of Mycobacterium avium subsp paratuberculosis (Myco. paratuberculosis), Salmonella enterica serotype Typhimurium (Salm.Typhimurium) and a commensal Escherichia coli (E. coli) isolate under the low pH and high organic acid (OA) conditions of ensiling of forages.
Methods and Results
Decay rates and the time required to obtain a 90% reduction in cell concentration were calculated following (i) exposure to buffered OA (pH 4·0, 5·0, 6·0 or 7·0) (ii) exposure to silage exudates and (iii) survival through ensiling of forage materials. Salm. Typhimurium had higher decay rates in silage exudates (−0·5601 day−1) than did E. coli (−0·1265 day−1), but both exhibited lower decay rates in silage than in OA or silage exudates. Myco. paratuberculosis showed no decrease in silage and decay rates in silage exudates were significantly lower (2–12 times) than for the other two organisms.
Escherichia coli, Salm. Typhimurium and Myco. paratuberculosis exhibit marked differences in response to acidity. All three organisms show acid resistance, but Myco. paratuberculosis in particular, if present in manure and applied to forage grasses, may survive the low pH and high OA of the ensilaging process; silage may therefore be a potential route of infection if ingested by a susceptible animal.
Significance and Impact of Study
This information contributes to the understanding of potential risks associated with silage preservation and contamination of livestock feed with manure-borne pathogens.