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