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Link to thesis (pdf file, 245 pages, ca. 6 MB):
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Title:

Disinfection of Salmonella in poultry houses (ISBN 87-988795-3-7)

Affiliations:

Place of Work:
Danish Institute for Food and Veterinary Research, Department of Poultry, Fish and Fur Animals, Aarhus, Denmark

Matriculation:

University of Bristol, Department of Clinical Veterinary Science, UK

Examination:

April 2, 2004 (Langford, University of Bristol, UK)

Abstract:

Factors related to cleanability of materials, cleaning and disinfection were tested in a questionnaire-based, retrospective field study of 78 broiler houses that received two Salmonella serotypes with day-old chicks. Serotype and combined surface disinfection
and fogging vs. any method used separately were significantly associated with house
status (infected in one or more crop cycles).
In a worst-case scenario laboratory heating study,
Salmonella was spiked into organic
matter (feed or faeces), and various factors (final heating temperatures, drying or not
prior to and during heating) were investigated. A gold standard of 60 oC, 100% RH during
a 24-hour period killed all
Salmonella and naturally occurring E. coli, with high correlation between survival of the two species.
This gold standard was tested in field studies performed in naturally
Salmonella infected
layer houses. After application of steam, usually with 30 ppm formaldehyde, no
Salmonella was detected, there were large reductions in coliforms, and organic samples had no surviving indicator bacteria.
In addition, two identical houses on the same farm were heat treated, one with dry heat, and the other with steam. The bacteriological results were significantly better in the latter.
To determine whether
Salmonella persistence was related to disinfectant resistance, MICs
for 286
Salmonella isolates involving five commonly used disinfectants were determined,
but no association was found with persistence or the use of certain disinfectant types. Adaptation and de-adaptation studies with these disinfectants did not alter MICs. Selected isolates adapted to triclosan showed increased MICs, but no cross-resistance to the other
five disinfectants.
Worst-case scenario surface disinfection tests, using poultry house materials plus feed, egg yolk and oil, were performed at low temperatures. There were significant differences
related to the three disinfectants, bacteria (two
Salmonella and one E. faecalis isolate,
the latter being more resistant) and some types of organic matter.






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