Comprehensive Study of Pathogenic Genes Distributed in Escherichia coli Isolated from Cattle

摘要

2012年11月から2013年8月に牛腸内容物から分離された大腸菌が保有する病原遺伝子について，マルチプレックスPCR法を用いた包括的実態調査を行った。ウシ100頭中79頭から病原遺伝子を持つ下痢原性大腸菌延べ180株が検出され，そのうちウシ32頭から検出された45株が腸管出血性大腸菌（STEC)であった。半数以上のウシがastAを保有しており，次いで，cdt, cnf, stx2の順で保有率が高かった（＞30%)。今回の調査ではSTh遺伝子，LT遺伝子，inuE， aggR， afaDは検出されなかった。STEC 45株中6株はstx1とstx2を同時保有し，19株はstx2を単独で保有していた。その他17株はべロ毒素遺伝子に加えて，STp遗伝子，astAあるいはcdtぬを同時保有していた。STEC以外の135株は，STp遺伝子保有の腸管毒素原性大腸菌18株。eae保有の腸管病原性大腸菌25株，およびその他の下痢原性大腸菌92株に分類された。OおよびH血清型が決定できた48株中，3株のO157 :H7は患者由来株と同様にstx2とeaeを保有していた。%Pathogenic genes such as stxl, stx2, STh gene, STp gene, LT gene, invE, eae, aggR, afaD, astA, cdt and cnf were investigated in Escherichia coli isolated from cattle during Nov. 2012 and Aug. 2013. Plural pathogenic genes were concurrently detected by multiplex PCR, and screen-positive genes were confirmed and sub-classified by PCR. Among100 cattle investigated,180 E. coli strains with diarrheic genes (DEC) were.detected in 79 cattle, and 45 of them, isolated from 32 cattle, were Shiga toxin-producing E. coli (STEC). More than 30% of cattle carried astA, cdt, cnf and stx2 in descending order. STh gene, LT gene, invE, aggR and afaD were not detected in this study. Both stxl and stx2 were concurrently detected from 6 of 45 STEC strains and stx2 alone was detected from19. Seventeen STEC strains carried STp gene, astA, or cdt along with stxl or stx2. Additionally,135 remaining DEC were classified into18 enterotoxigenic E. coli with STp gene, 25 enteropathogenic E. coli with eae, and 92 other DEC with astA, cdt and cnf. Both O and H serotypes were identified in 48 strains, including 0157 ： H7, 01H7 and so on. 0157 ： H7 were identified in 3 strains that carried stx2 and eae together, as found in human pathogenic strains isolated from patients with gastroenteritis and hemolytic-uremic syndrome.