产志贺样毒素且具侵袭力的大肠杆菌的研究

我国临床腹泻病人粪便标本中，约有６０％检不出任何已知病原，而能分离出几乎纯培养的大肠杆菌。这些大肠杆菌过去被误认为是肠道正常菌样，我们对在北京西城区三个医院从腹泻病患者粪便本本中分离的１７２株所谓正肠杆菌，进行质粒ＤＮＡ，Ｈｅｐ－２细胞粘附试验，和１０种ＤＮＡ探针分析，结果表发现这些所谓的肠道正常大肠杆菌并不正常，其中４４％可为致泻性大肠杆菌，包括ＥＨＥＣ１６株，占所检查菌株的９．３％；ＥＰＥＣ８

A new diarrhea pathogen: Entero-SLTs-producing and invasive Escherichia coli was over-looked as normal flora E.coli

In clinical laboratories of Beijing, China, no known entero-pathogen but almost pure E. coli strains could be isolated from more than 60% fecal samples of diarrheal patients, which had been recognized as normal flora E. coli and dismissed. We suspected that some of the so-called normal flora E. coli strains might be virulent. To prove our idea, We collected 172 strains of E. coli isolated from diarrheal patients from whom no other enteric bacterial pathogens had been identified, including EPEC, EIEC, ETEC. With plasmid DNA analysis, Hep-2 cell adherence assay and 10 DNA probe hybridization, we found that the so-called normal flora E. coli was abnormal, 44% of them were virulent, of which 16 (9.3) were EHEC, 8 EPEC (4.7%), 11 EAggEC (6.8%). Fifty-four of 172 strains were hybridized with INV and SLT1 or SLT2 probes, which had never been reported. These strains could invade Hep-2 cells, but were lack of ipaB gene, a key gene of invasiveness gene cluster of Shigella species and EIEC. The aggregative adherence to Hep-2 cells was observed, but the strains were not hybridized with EAggEC specific DNA probe. The purified toxin protein and cell filtrate were toxic to vero cells. Based on the data obtained, we believed that this is a new category of diarrhea-genic E. coli, named as entero-SLTs-producing and invasive E. coli (ESIEC). ESIEC occupied 31.4% of the strains tested, the isolation of it was probably higher than those of ETEC, EPEC in P R China.