猪源大肠杆菌(ETEC、STEC、AEEC)毒力基因及其与O抗原型的关系

Virulence genes of pathogenic Escherichia coli from ill pigs in China and their relationship with O-serogroups

【目的】揭示从我国部分地区仔猪腹泻或水肿病病猪体内分离到的300个大肠杆菌分离株所属病原型(pathotype)、毒力基因及其与O血清型的关系。【方法】O血清型采用常规的凝集试验进行测定,毒力基因采用PCR方法检测。【结果】通过对这300个分离株的O血清型及其毒素、紧密素和黏附素基因进行鉴定,结果显示除50株未定型、17株自凝外,测定出233个分离株的血清型,这些分离株覆盖了45个血清型,其中以O149、O107、O139、O93和O91为主,共133株,占定型菌株的57.1%;拥有estⅠ、estⅡ、elt、stx2e和eaeA基因的菌株分别为102(34.0%)、190(63.3%)、81(27.0%)、57(19.0%)和54(18.0%)株;分离株中有51株K88基因阳性(其中菌毛表达率为100%),75株F18基因阳性(其中菌毛表达率为50.7%),在K88菌株中,O149血清型与estⅠ或estⅡ+elt密切相关,在F18菌株中,O107血清型与estⅠ或estⅡ、O139血清型与stx2e紧密相关。依其毒力特征可将这些分离株分为以下6种类型:ETEC、STEC、AEEC、ETEC/STEC、AEEC/ETEC和AEEC/ETEC/STEC,分别拥有190、24、36、32、17和1个菌株,占分离株的63.3%、8.0%、12.0%、10.7%、5.7%和0.3%。通过分析这些分离株的O血清型、毒素类型和黏附素型之间的相关性:猪源ETEC以O149、O107、O93和O98等血清型为主,O149:K88菌株主要与estⅡ或estⅡ+elt肠毒素相关,O107:F18菌株主要与estⅡ相关,O93和O98血清型菌株主要与estⅡ肠毒素相关;STEC菌株以O139:F18血清型为主,拥有stx2e;AEEC菌株拥有紧密素,无明显优势血清型;ETEC/STEC菌株以O107:F18和O116:F18血清型为主,主要与estⅠ+stx2e或estⅡ+stx2e密切相关,ETEC/AEEC菌株以O91和O107血清型为主,全部拥有肠毒素estⅠ和紧密素基因。【结论】我国至少存在6种病原型的猪肠道致病性大肠杆菌,其中ETEC为我国部分地区猪大肠杆菌病的主要病原,同时其病原型日益复杂。

[Objective] We determined the distribution of serogroups and virulence factors among Escherichia coli isolates from pigs with diarrhea and/or edema disease from 10 provinces in China between 1998 and 2007. [Methods] Three hundred E. coli isolates were serogrouped with O-antisera and detected for genes of enterotoxins, shiga-toxin-two-variant （Stx2e）, intimin, K88, K99, 987P, F18 and F41 fimbrial antigens by PCR. [Results] Among 300 isolates, 233 were determined to be placed in serogroups, 50 were unable to be serogrouped, and the rest 17 auto-agglutinated. These isolates distributed in 45 serogroups and 57.1% （133/233） belonged to 50 serogroups： O149, O107, O139,O93 and O91. Several uncommon O serogroups were discovered. PCR analysis confirmed the genes of est Ⅰ （STa）, est Ⅱ （STb）, elt （LT）, stx2e （Stx2e） and eaeA （Intimin） within the isolates. There were six pathotypes of porcine E. coli by their pathogenic factors, namely enterotoxigenic E. coli （ETEC）, shiga toxin-producing E. coli （STEC）, attaching-effacing E. coli （AEEC）, ETEC/ STEC, AEEC/ETEC and AEEC/ETEC/STEC. The correlation between pathotypes and serogroups showed that the combinations of O1491K88/estⅡ, O149/K88/estⅡ＋ elt. O107/F18/estⅡ, O93/estⅡand O98/estⅡ were common types in ETEC strains, O139/ F18/stx2e for STEC strains, eaeA gene for AEEC strains, O107/F18/estI＋stx2e, O107/F18/estⅡ ＋ stx2e and O1l6/F18/est I ＋elt＋stx2e for ETEC/STEC strains, O91/est Ⅰ/eaeA and O107/est Ⅰ/eaeA for AEEC/ETEC/STEC strains.＂[Conclusion] ETEC was commonly associated with swine colibacillosis, whereas the kinds of enteric E. coli pathogens become more complex in China.