Andrysiak Ashleigh K, Olson Adam B, Tracz Dobryan M, Dore Kathryn, Irwin Rebecca, Ng Lai-King, Gilmour Matthew W
Bacteriology and Enteric Diseases Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada.
BMC Microbiol. 2008 Jun 6;8:89. doi: 10.1186/1471-2180-8-89.
Salmonella enterica serovar Heidelberg ranks amongst the most prevalent causes of human salmonellosis in Canada and an increase in resistance to extended spectrum cephalosporins (ESC) has been observed by the Canadian Integrated Program for Antimicrobial Resistance Surveillance. This study examined the genetic relationship between S. Heidelberg isolates from livestock, abattoir, retail meat, and clinical human specimens to determine whether there was a link between the emergence of MDR S. Heidelberg in chicken agri-food sources and the simultaneous increase of MDR S. Heidelberg in human clinical samples.
Chromosomal genetic homogeneity was observed by pulsed-field gel electrophoresis (PFGE), DNA sequence-based typing (SBT) and DNA microarray-based comparative genomic hybridization (CGH). Sixty one percent of isolates were indistinguishable by PFGE conducted using XbaI and BlnI restriction enzymes. An additional 15% of isolates had PFGE patterns that were closely related to the main cluster. SBT did not identify DNA polymorphisms and CGH revealed only genetic differences between the reference S. Typhimurium strain and S. Heidelberg isolates. Genetic variation observed by CGH between S. Heidelberg isolates could be attributed to experimental variation. Alternatively, plasmid content was responsible for differences in antimicrobial susceptibility, and restriction fragment length polymorphism (RFLP) analyses followed by replicon typing identified two divergent plasmid types responsible for ESC resistance.
Due to the overall limited genetic diversity among the isolates, it was not possible to identify variable traits that would be suitable for source tracking between human and agri-food isolates of S. Heidelberg in Canada.
肠炎沙门氏菌海德堡血清型是加拿大人类沙门氏菌病最常见的病因之一，加拿大抗菌药物耐药性综合监测计划观察到该血清型对超广谱头孢菌素（ESC）的耐药性有所增加。本研究检测了来自家畜、屠宰场、零售肉类和临床人类标本的海德堡沙门氏菌分离株之间的遗传关系，以确定鸡农业食品源中多重耐药海德堡沙门氏菌的出现与人类临床样本中多重耐药海德堡沙门氏菌的同时增加之间是否存在联系。
通过脉冲场凝胶电泳（PFGE）、基于DNA序列的分型（SBT）和基于DNA微阵列的比较基因组杂交（CGH）观察到染色体遗传同质性。使用XbaI和BlnI限制酶进行的PFGE分析显示，61%的分离株无法区分。另外15%的分离株具有与主要聚类密切相关的PFGE模式。SBT未鉴定出DNA多态性，CGH仅揭示了参考鼠伤寒沙门氏菌菌株与海德堡沙门氏菌分离株之间的遗传差异。CGH观察到海德堡沙门氏菌分离株之间的遗传变异可归因于实验变异。或者，质粒含量是抗菌药物敏感性差异的原因，通过复制子分型进行的限制性片段长度多态性（RFLP）分析确定了两种导致ESC耐药的不同质粒类型。
由于分离株之间总体遗传多样性有限，无法确定适合追踪加拿大海德堡沙门氏菌人类和农业食品分离株来源的可变特征。
