Abstract
Background
This study was conducted to describe the geographical and seasonal distributions of reported human SalmonellaTyphimurium (ST) definitive type 104 (DT104) cases, to compare these characteristics to those of non-DT104 cases, and to investigate specific antimicrobial resistance (AMR) patterns in four Canadian provinces.
Methods
All laboratory-confirmed ST cases originating from passive reporting in Alberta, British Columbia, and Saskatchewan, and every second case in Ontario identified from December 1999 through November 2000 were investigated.
Results
A total of 470 human Salmonella Typhimurium cases were identified during the study period. DT104 was the most common phage type, although its incidence varied by province. The proportion of DT104 cases living in urban Ontario, British Columbia and Saskatchewan did not differ from the general population, but in Alberta, the DT104 cases were more likely to live in rural areas. Overall, DT104 isolates were more often R-type ACSSuT compared to non-DT104 cases, and R-type AKSSuT was often associated with DT208. DT104 cases displayed no seasonality whereas non-DT104 cases were more frequent in the summer than in the winter.
Interpretation
Our results suggest that DT104 and non-DT104 cases vary by province, urban vs. rural residential status and by resistance patterns. Lack of seasonality in the DT104 cases may indicate a lesser influence of the agro-environmental route (i.e., farm–manure–water and direct contact) compared to the agro-food route (i.e., farm–animals–food) for these infections. Strain characterization and integration of surveillance information related to ST from animal, food and humans is warranted.
MeSHterms: Salmonella typhimurium, spatial distribution, drug resistance, microbial
Résumé
Contexte
Notre étude vise à décrire la répartition géographique et saisonnière des cas humains déclarés d’infections par Salmonella typhimurium type définitif (DT) 104, à comparer ces caractéristiques à celles des autres salmonelloses à S. typhimurium et à examiner les patrons de résistance aux antimicrobiens dans quatre provinces canadiennes.
Méthode
Nous avons examiné tous les cas de S. typhimurium confirmés en laboratoire déclarés dans les rapports de surveillance passive de l’Alberta, de la Colombie-Britannique et de la Saskatchewan, et un cas sur deux déclaré en Ontario entre décembre 1999 et novembre 2000.
Résultats
En tout, il y a eu 470 notifications d’infections humaines à S. typhimurium pendant la période de l’étude. Le lysotype DT104 était le plus commun, bien que sa fréquence ait varié d’une province à l’autre. La proportion des personnes infectées par DT104 vivant en milieu urbain en Ontario, en Colombie-Britannique et en Saskatchewan était la même que dans la population générale, mais en Alberta, les personnes infectées par DT104 étaient plus susceptibles de vivre en milieu rural. Dans l’ensemble, les isolats de DT104 présentaient plus souvent le phénotype de résistance ACSSuT que les autres lysotypes de S. typhimurium, et le phénotype de résistance AKSSuT était souvent associé au lysotype DT208. Les cas d’infections par S. typhimurium DT104 ne présentaient aucun cycle saisonnier, tandis que les autres lysotypes étaient plus fréquents l’été que l’hiver.
Interprétation
Nos résultats donnent à penser que les cas d’infections par DT104 et par les autres lysotypes de S. typhimurium varient selon la province, la résidence (en milieu urbain ou rural) et les patrons de résistance. L’absence de cycles saisonniers dans les cas d’infections par DT104 pourrait être le signe d’une moindre influence de la voie de transmission agroenvironnementale (ferme - lisier - eau et contact direct) par rapport à la voie agroalimentaire (ferme - animaux -aliments) pour ces infections. Cela confirme l’utilité de la caractérisation des souches et de l’intégration des données de surveillance de S. typhimurium chez les animaux, dans les aliments et chez les humains.
Footnotes
Acknowledgements: The authors thank Richard Reid-Smith, Dave Leger, Andrijana Rajic and Cornelius Poppe for discussions that improved an earlier draft of the manuscript.
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