Maluta Renato Pariz, Gatti Maria Silvia Viccari, Joazeiro Paulo Pinto, de Paiva Jacqueline Boldrin, Rojas Thaís Cabrera Galvão, Silveira Flávio, Houle Sébastien, Kobayashi Renata Katsuko Takayama, Dozois Charles M, Dias da Silveira Wanderley
1 Bacterial Molecular Biology Laboratory, Department of Genetics, Evolution, and Bioagents, Biology Institute, State University of Campinas (UNICAMP) , Campinas, São Paulo, Brazil .
Foodborne Pathog Dis. 2014 Jun;11(6):484-9. doi: 10.1089/fpd.2013.1719. Epub 2014 Mar 27.
Avian pathogenic Escherichia coli (APEC) strains harbor a number of virulence genes and cause extraintestinal diseases, such as septicemia, swollen-head syndrome, salpingitis, and omphalitis in poultry. APEC strains are not known to cause intestinal diseases. Herein, for the first time, it is reported that APEC strains were able to induce an enterotoxigenic-like effect in rabbit ligated ileal loops. Strain SEPT362 caused cell detachment of the intestinal villi, which also showed a flattened and wilted appearance, but the integrity of the tight junctions was maintained. Additionally, this strain did not adhere to enterocytes in vivo, although adhesin encoding genes ( fimH, csgA, lpfA2-3, and ECP) were present while other lpfA types, sfa, afa, papC, and ral genes were not. This enterotoxigenic-like activity was conserved after thermal treatment of the supernatant at 65°C but not at 100°C. Moreover, experiments based on filtering with different molecular weight cut-off (MWCO) pore sizes demonstrated that the component associated with the observed biological effect has a molecular weight >100 kDa. Blast search and polymerase chain reaction assays for known E. coli virulence factors showed that strain SEPT362 harbors the gene encoding for the toxin EAST-1 and the serine protease autotransporter (SPATE) Tsh, but is negative for genes encoding for the toxins LT-I, STh, STp, Stx1, Stx2, CNF-1, CNF-2, CDT and the SPATEs Sat, Pic, Vat, SigA, SepA, EatA, EspP, or EspC. A cloned copy of the tsh gene in E. coli K-12 was also tested and was shown to have an enterotoxic effect. These results suggest that APEC might induce fluid accumulation in the rabbit gut. The Tsh autotransporter seems to be one of the factors associated with this phenotype.
禽致病性大肠杆菌（APEC）菌株携带多种毒力基因，可引起家禽的败血症、肿头综合征、输卵管炎和脐炎等肠外疾病。APEC菌株不会引起肠道疾病。在此首次报道，APEC菌株能够在兔结扎回肠袢中诱导类似产肠毒素的效应。菌株SEPT362导致肠绒毛细胞脱落，肠绒毛也呈现扁平枯萎的外观，但紧密连接的完整性得以维持。此外，该菌株在体内不粘附肠上皮细胞，尽管存在粘附素编码基因（fimH、csgA、lpfA2 - 3和ECP），而其他lpfA类型、sfa、afa、papC和ral基因不存在。这种类似产肠毒素活性在65°C热处理上清液后得以保留，但在100°C时则不然。此外，基于不同截留分子量（MWCO）孔径过滤的实验表明，与观察到的生物学效应相关的成分分子量>100 kDa。对已知大肠杆菌毒力因子的Blast搜索和聚合酶链反应分析表明，菌株SEPT362携带毒素EAST - 1和丝氨酸蛋白酶自转运体（SPATE）Tsh的编码基因，但毒素LT - I、STh、STp、Stx1、Stx2、CNF - 1、CNF - 2、CDT以及SPATEs Sat、Pic、Vat、SigA、SepA、EatA、EspP或EspC的编码基因呈阴性。还对大肠杆菌K - 12中tsh基因的克隆拷贝进行了测试，结果显示其具有肠毒素效应。这些结果表明，APEC可能会在兔肠道中诱导液体蓄积。Tsh自转运体似乎是与该表型相关的因素之一。
