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Applied and Environmental Microbiology, February 2000, p. 614-619, Vol. 66, No. 2
Molecular Diagnostics Unit, Cork Institute of
Technology, Bishopstown,1 Veterinary
Department, County Hall,2 Regional
Veterinary Laboratory, Department of Agriculture and
Food,3 and Department of Medical
Microbiology, Cork University Hospital,
Wilton,5 Cork, Department of
Bacteriology, National University of Ireland,
Galway,4 and Food Safety Authority of
Ireland, Dublin 1,6 Ireland
Received 24 May 1999/Accepted 5 November 1999
Salmonella enterica is among the principal etiological
agents of food-borne illness in humans. Increasing antimicrobial
resistance in S. enterica is a cause for worldwide concern.
There is concern at present in relation to the increasing incidence of
human infection with antimicrobial agent-resistant strains of S. enterica serotype Typhimurium, in particular of phage type DT104.
Integrons appear to play an important role in the dissemination of
antimicrobial resistance genes in many Enterobacteriaceae
including S. enterica. In this study the antimicrobial
susceptibilities and phage types of 74 randomly collected strains of
S. enterica serotype Typhimurium from the Cork region of
southern Ireland, obtained from human, animal (clinical), and food
sources, were determined. Each strain was examined for integrons and
typed by DNA amplification fingerprinting (DAF). Phage type DT104
predominated (n = 48). Phage types DT104b (n = 3), -193 (n = 9), -195 (n = 6), -208 (n = 3), -204a
(n = 2), PT U302 (n = 1), and two
nontypeable strains accounted for the remainder. All S. enterica serotype Typhimurium DT104 strains were resistant to
ampicillin, chloramphenicol, streptomycin, Sulfonamide Duplex, and
tetracycline, and one strain was additionally resistant to
trimethoprim. All DT104 strains but one were of a uniform DAF type
(designated DAF-I) and showed a uniform pattern of integrons (designated IP-I). The DT104b and PT U302 strains also exhibited the
same resistance phenotype, and both had the DAF-I and IP-I patterns.
The DAF-I pattern was also observed in a single DT193 strain in which
no integrons were detectable. Greater diversity of antibiograms and DAF
and IP patterns among non-DT104 phage types was observed. These data
indicate a remarkable degree of homogeneity at a molecular level among
contemporary isolates of S. enterica serotype Typhimurium
DT104 from animal, human, and food sources in this region.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Molecular Characterization of Irish
Salmonella enterica Serotype Typhimurium: Detection of Class
I Integrons and Assessment of Genetic Relationships by DNA
Amplification Fingerprinting
*
Corresponding author. Mailing address: Molecular
Diagnostics Unit, Cork Institute of Technology, Bishopstown, Cork,
Ireland. Phone: (353-21) 326 235. Fax: (353-21) 545 343. E-mail:
sfanning{at}cit.ie.
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