不同来源致病性大肠杆菌分离株中 CRISPR 基因座和毒力基因的多样性。
Diversity of CRISPR loci and virulence genes in pathogenic Escherichia coli isolates from various sources.
机构信息
Department of Food Science, The Pennsylvania State University, 202 Rodney A. Erickson Food Science Building, University Park, PA 16802, USA; Department of Food Science, Ginling College, Nanjing Normal University, Nanjing 210097, PR China.
Department of Food Science, The Pennsylvania State University, 202 Rodney A. Erickson Food Science Building, University Park, PA 16802, USA.
出版信息
Int J Food Microbiol. 2015 Jul 2;204:41-6. doi: 10.1016/j.ijfoodmicro.2015.03.025. Epub 2015 Mar 27.
Shiga toxin-producing Escherichia coli (STEC) strains, including those of O157:H7 and the "big six" serogroups (i.e., O26, O45, O103, O111, O121, and O145) are food-borne pathogens that pose a serious health threat to humans. Ruminants, especially cattle, are a major reservoir for O157 and non-O157 STEC. In the present study, 115 E. coli strains isolated from small and very small beef processing plants were screened for virulence genes (stx1, stx2, eae) using a multiplex polymerase chain reaction (PCR). Thirteen (11.3%) of the 115 isolates tested positive for stx1, stx2, or eae genes, but only 4 (3.5%) tested positive for either stx1 or stx2. A multiplex PCR reaction targeting eight O-serogroups (O26, O45, O103, O111, O113, O121, O145, O157) identified 12 isolates as O26, O103, O111, or O145, with E. coli O26 being the most predominant serogroup (61.5%). The thirteen isolates were further analyzed using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) subtyping. Consistent with previous studies, CRISPR alleles from strains of the same serogroup were similar in their spacer content and order, regardless of the isolation source. A completely different CRISPR allele was observed in one isolate ("7-J") which exhibited a different O-serogroup (O78). Our results confirmed previous findings that CRISPR loci are conserved among phylogenetically-related strains. In addition, 8 E. coli O26 isolates and a collection of 42 E. coli O26 isolates were screened for 12 enterohemorrhagic E. coli-specific genes. Seven genes (ECs848-Hypothetical Protein, ECs2226-Hypothetical Protein, ECs3857-nleB, ECs3858-Hypothetical Protein, ECs4552-escF, ECs4553-Hypothetical Protein, and ECs4557-sepL) were found in all 50 isolates. An additional 5 genes (ECs1322-ureA urease subunit γ, ECs1323-ureB urease subunit β, ECs1326-ureF, ECs1561-Hypothetical Protein, and ECs1568-Hypothetical Protein) were found to be highly prevalent in isolates from human sources, while lower in isolates from beef processing plants, cattle, and other sources. This finding indicates the possible role of these genes in virulence of human O26 strains.
产志贺毒素大肠杆菌（STEC）菌株，包括 O157：H7 和“六大”血清群（即 O26、O45、O103、O111、O121 和 O145）是食源性病原体，对人类健康构成严重威胁。反刍动物，尤其是牛，是 O157 和非 O157 STEC 的主要储存宿主。在本研究中，使用多重聚合酶链反应（PCR）筛选了来自小型和超小型牛肉加工厂的 115 株大肠杆菌菌株的毒力基因（stx1、stx2、eae）。在 115 株检测的菌株中，有 13 株（11.3%）携带 stx1、stx2 或 eae 基因，但只有 4 株（3.5%）携带 stx1 或 stx2。针对八个 O 血清群（O26、O45、O103、O111、O113、O121、O145、O157）的多重 PCR 反应鉴定出 12 株为 O26、O103、O111 或 O145，其中大肠杆菌 O26 是最主要的血清群（61.5%）。这 13 株分离株进一步通过聚类规则间隔短回文重复（CRISPR）分型进行分析。与先前的研究一致，来自同一血清群的菌株的 CRISPR 等位基因在间隔物的内容和顺序上相似，而与分离源无关。在一株名为“7-J”的分离株中观察到一个完全不同的 CRISPR 等位基因，其表现出不同的 O 血清群（O78）。我们的结果证实了先前的发现，即 CRISPR 基因座在系统发育相关菌株中是保守的。此外，对 8 株大肠杆菌 O26 分离株和 42 株大肠杆菌 O26 分离株进行了 12 种肠出血性大肠杆菌特异性基因的筛选。在所有 50 株分离株中发现了 7 个基因（ECs848-假设蛋白、ECs2226-假设蛋白、ECs3857-nleB、ECs3858-假设蛋白、ECs4552-escF、ECs4553-假设蛋白和 ECs4557-sepL）。另外 5 个基因（ECs1322-ureA 脲酶亚基 γ、ECs1323-ureB 脲酶亚基 β、ECs1326-ureF、ECs1561-假设蛋白和 ECs1568-假设蛋白）在人源分离株中高度流行，而在牛肉加工厂、牛和其他来源的分离株中流行程度较低。这一发现表明这些基因可能在人类 O26 株的毒力中发挥作用。
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