Yao Lang, Cooper Ashley L, Gill Alex, Koziol Adam, Wong Alex, Blais Burton W, Carrillo Catherine D
Ottawa Laboratory Carling, Canadian Food Inspection Agency, Ottawa, Ontario, Canada K1A 0C6; Department of Biology, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
Ottawa Laboratory Carling, Canadian Food Inspection Agency, Ottawa, Ontario, Canada K1A 0C6.
J Food Prot. 2024 Jul;87(7):100302. doi: 10.1016/j.jfp.2024.100302. Epub 2024 May 15.
Linking outbreaks of Shigella spp. to specific foods is challenging due to poor selectivity of current enrichment media. We have previously shown that enrichment media, tailored to the genomically-predicted antimicrobial resistance (AMR) of Shiga toxigenic E. coli strains, enhances their isolation from foods. This study investigates the application of this approach for Shigella isolation. The AMR gene profiles of 21,908 published S. sonnei genomes indicated a high prevalence of genes conferring resistance to streptomycin (aadA, aph(3″)-Ib, aph(6)-Id, 92.8%), sulfonamides (sul1, sul2, 74.8%), and/or trimethoprim (dfrA, 96.2%). Genomic analysis and antibiotic susceptibility testing conducted with a panel of 17 outbreak-associated S. sonnei strains confirmed the correlation of AMR gene detection with resistance phenotypes. Supplementation of Shigella Broth (SB) with up to 400 µg/mL of trimethoprim or sulfadiazine did not suppress the growth of sensitive strains, whereas 100 µg/mL of streptomycin increased the selectivity of this broth. All three antibiotics increased the selectivity of modified Tryptone Soya Broth (mTSB). Based on these results, supplemented media formulations were developed and assessed by measuring the relative growth of S. sonnei in cultures coinoculated with a strain of bacteriocin-producing E. coli that is inhibitory to Shigella growth. S. sonnei was not recovered from cocultures grown in SB or mTSB without antibiotics. In contrast, media supplemented with streptomycin at 50 and 100 µg/mL, trimethoprim at 25 and 50 µg/mL, and sulfadiazine at 100 µg/mL increased the relative proportion of S. sonnei in postenrichment cultures. The enhanced recovery of resistant S. sonnei strains achieved in this study indicates that, in cases where genomic data are available for clinical S. sonnei isolates, customization of selective enrichment media based on AMR gene detection could be a valuable tool for supporting the investigation of foodborne shigellosis outbreaks.
由于当前增菌培养基的选择性较差，将志贺氏菌属的暴发与特定食物联系起来具有挑战性。我们之前已经表明，针对产志贺毒素大肠杆菌菌株的基因组预测抗菌耐药性（AMR）量身定制的增菌培养基，能提高从食物中分离出这些菌株的效率。本研究调查了这种方法在志贺氏菌分离中的应用。21908个已发表的宋内志贺氏菌基因组的AMR基因谱表明，赋予对链霉素（aadA、aph(3″)-Ib、aph(6)-Id，92.8%）、磺胺类药物（sul1、sul2，74.8%）和/或甲氧苄啶（dfrA，96.2%）耐药性的基因普遍存在。对一组17株与暴发相关的宋内志贺氏菌菌株进行的基因组分析和抗生素敏感性测试证实了AMR基因检测与耐药表型之间的相关性。在志贺氏菌肉汤（SB）中添加高达400μg/mL的甲氧苄啶或磺胺嘧啶不会抑制敏感菌株的生长，而100μg/mL的链霉素提高了该肉汤的选择性。所有三种抗生素都提高了改良胰蛋白胨大豆肉汤（mTSB）的选择性。基于这些结果，开发了补充培养基配方，并通过测量与一株对志贺氏菌生长有抑制作用的产细菌素大肠杆菌共接种的培养物中宋内志贺氏菌的相对生长情况进行评估。在没有抗生素的SB或mTSB中培养的共培养物中未回收宋内志贺氏菌。相比之下，添加50和100μg/mL链霉素、25和50μg/mL甲氧苄啶以及100μg/mL磺胺嘧啶的培养基增加了增菌后培养物中宋内志贺氏菌的相对比例。本研究中耐药宋内志贺氏菌菌株回收率的提高表明，在可获得临床宋内志贺氏菌分离株基因组数据的情况下，基于AMR基因检测定制选择性增菌培养基可能是支持食源性志贺氏菌病暴发调查的一个有价值的工具。
