Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary medicine, Iowa State University, Ames, Iowa 50011, USA.
BMC Microbiol. 2012 Apr 3;12:51. doi: 10.1186/1471-2180-12-51.
Extraintestinal pathogenic Escherichia coli are important pathogens of human and animal hosts. Some human and avian extraintestinal pathogenic E. coli are indistinguishable on the basis of diseases caused, multilocus sequence and phylogenetic typing, carriage of large virulence plasmids and traits known to be associated with extraintestinal pathogenic E. coli virulence.
The gene tkt1 identified by a previous signature-tagged transposon mutagenesis study, was found on a 16-kb genomic island of avian pathogenic Escherichia coli (APEC) O1, the first pathogenic Escherichia coli strain whose genome has been completely sequenced. tkt1 was present in 39.6% (38/96) of pathogenic Escherichia coli strains, while only 6.25% (3/48) of E. coli from the feces of apparently healthy chickens was positive. Further, tkt1 was predominantly present in extraintestinal pathogenic E. coli belonging to the B2 phylogenetic group, as compared to extraintestinal pathogenic E. coli of other phylogenetic groups. The tkt1-containing genomic island is inserted between the metE and ysgA genes of the E. coli K12 genome. Among different extraintestinal pathogenic E. coli of the B2 phylogenetic group, 61.7% of pathogenic Escherichia coli, 80.6% of human uropathogenic E.coli and 94.1% of human neonatal meningitis-causing E. coli, respectively, harbor a complete copy of this island; whereas, only a few avian fecal E. coli strains contained the complete island. Functional analysis showed that Tkt1 confers very little transketolase activity but is involved in peptide nitrogen metabolism.
These results suggest tkt1 and its corresponding genomic island are frequently associated with avian and human ExPEC and are involved in bipeptide metabolism.
肠外致病性大肠杆菌是人和动物宿主的重要病原体。一些人和禽肠外致病性大肠杆菌在引起的疾病、多位点序列和系统发育分型、大毒力质粒的携带以及与肠外致病性大肠杆菌毒力相关的已知特征方面无法区分。
先前的标记基因转座子突变体研究鉴定的 tkt1 基因位于禽致病性大肠杆菌（APEC）O1 的 16kb 基因组岛上，这是第一个完全测序的致病性大肠杆菌株。tkt1 存在于 39.6%（38/96）的致病性大肠杆菌株中，而在无明显临床症状的鸡粪便中分离到的大肠杆菌中仅 6.25%（3/48）为阳性。此外，与其他系统发育群的肠外致病性大肠杆菌相比，tkt1 主要存在于 B2 系统发育群的肠外致病性大肠杆菌中。含有 tkt1 的基因组岛插入大肠杆菌 K12 基因组的 metE 和 ysgA 基因之间。在不同的 B2 系统发育群的肠外致病性大肠杆菌中，分别有 61.7%的致病性大肠杆菌、80.6%的人泌尿道致病性大肠杆菌和 94.1%的人新生儿脑膜炎致病大肠杆菌携带完整的该岛；而只有少数禽粪便大肠杆菌菌株含有完整的岛。功能分析表明，Tkt1 赋予很少的转酮醇酶活性，但参与肽氮代谢。
这些结果表明 tkt1 及其相应的基因组岛经常与禽和人肠外致病性大肠杆菌相关，并参与双肽代谢。
