Weagant Stephen D
Food and Drug Administration, Pacific Regional Laboratory Northwest, 22201 23rd Drive SE, Bothell, WA 98021-4421, USA.
J Microbiol Methods. 2008 Feb;72(2):185-90. doi: 10.1016/j.mimet.2007.11.019. Epub 2007 Dec 4.
Several outbreaks of foodborne yersiniosis have been documented and this disease continues to be source of infections transmitted through foods. The selective agars most commonly used to isolate Yersinia enterocolitica in clinical, food and environmental samples, cefsulodin-irgasan-novobiocin (CIN) and MacConkey (MAC) agars, lack the ability to differentiate potentially virulent Y. enterocolitica from other Yersinia that may be present as well as some other bacterial spp. This study proposes the use of an agar medium, Y. enterocolitica chromogenic medium (YeCM), for isolation of potentially virulent Y. enterocolitica. This agar contains cellobiose as the fermentable sugar, a chromogenic substrate and selective inhibitors for suppression of colony formation by many competing bacteria. All strains of potentially virulent Yersinia of biotypes 1B, and biotypes 2-5 formed convex, red bulls-eye colonies on YeCM that were very similar to those described for CIN agar. However, Y. enterocolitica biotype 1A and other related Yersinia formed colonies that were purple/blue on YeCM while they formed typical red bulls-eye colonies on CIN agar. When a mixture of potentially virulent Y. enterocolitica biotype 1B, Y. enterocolitica biotype 1A and 5 other bacterial species was used to artificially contaminate tofu and then spread-plated on three selective agars, Y. enterocolitica biotype 1B colonies were easily distinguished from other strains on YeCM. However, Y. enterocolitica biotype 1B colonies were indistinguishable from many other colonies on CIN and only distinguishable from those of C. freundii on MAC. When colonies were picked and identified from these agars, typical colonies from YeCM were confirmed only as Y. enterocolitica biotype 1B. Typical colonies on CIN and MAC were found to belong to several competing species and biotypes.
已有多起食源性耶尔森菌病暴发的记录，这种疾病仍是通过食物传播感染的源头。在临床、食品和环境样本中，最常用于分离小肠结肠炎耶尔森菌的选择性琼脂培养基，即头孢磺啶-伊红-新生霉素（CIN）琼脂和麦康凯（MAC）琼脂，无法区分潜在致病的小肠结肠炎耶尔森菌与可能同时存在的其他耶尔森菌以及一些其他细菌种类。本研究提出使用一种琼脂培养基，即小肠结肠炎耶尔森菌显色培养基（YeCM），来分离潜在致病的小肠结肠炎耶尔森菌。这种琼脂含有纤维二糖作为可发酵糖、一种显色底物以及用于抑制许多竞争性细菌菌落形成的选择性抑制剂。生物型1B以及生物型2 - 5的所有潜在致病耶尔森菌菌株在YeCM上形成凸起的红色靶心菌落，与CIN琼脂上描述的菌落非常相似。然而，小肠结肠炎耶尔森菌生物型1A和其他相关耶尔森菌在YeCM上形成的菌落为紫色/蓝色，而它们在CIN琼脂上形成典型的红色靶心菌落。当使用潜在致病的小肠结肠炎耶尔森菌生物型1B、小肠结肠炎耶尔森菌生物型1A和其他5种细菌的混合物人工污染豆腐，然后涂布接种在三种选择性琼脂上时，在YeCM上小肠结肠炎耶尔森菌生物型1B菌落很容易与其他菌株区分开来。然而，小肠结肠炎耶尔森菌生物型1B菌落在CIN上与许多其他菌落无法区分，在MAC上仅能与弗氏柠檬酸杆菌的菌落区分开来。当从这些琼脂上挑取菌落并进行鉴定时，YeCM上的典型菌落仅被确认为小肠结肠炎耶尔森菌生物型1B。CIN和MAC上的典型菌落被发现属于几种竞争性的菌种和生物型。
