The entero-hemorrhagic Escherichia coli O157:H7( EHEC O157:H7) was identified as the causing agent of the mysterious disease outbreak occurred in China in 1999, based on the clinical, epidemiological, serological and bacterial ev idences. The studies for understanding the unusual phenomena observed in field have resulted in the new methods, idea, technical procedures and strategies for prevention and control of the infection caused be EHEC O157:H7 in China and on the world as well.

Because of the unique epidemiological features observed, we assumed that the domestic animals harboring EHEC O157:H7 was the source of infection by shedding the pathogen in feces into environmental; the contaminated food, meat, vegetables and house-fly transmitted pathogen to human; the appropriate personal and house-hold hygiene played critical rules in the outcome.

In an attempt to investigate the source and routes of the infection, strains isolated from China in the period from 1986 to 2002 from various sources were investigated using pulsed-field gel electrophoresis (PFGE). The PFGE analysis is the bases of so-called PulseNet which is a national network of pubic health and food regulatory laboratories initially established in the US to detect clusters of foodborne disease and respond quickly to foodborne outbreak investigations. The results indicated that the outbreak was caused by same strains with three genotypes, which were isolated from goats, pigs, cattle, hens, as well as from mutton, pork, salted vegetables and flies. The EHEC O157:H7 were also isolated from dung beetles Catharsius molossus,captured below ground at Tongshan County, Jiangsu Province of China, where outbreak was observed. Therefore, the dung beetle might acquire pathogenic E. coli O157:H7 through contact with feces of domestic animals and has potential to transmitted pathogen to environmental and human by its social activities. 

In the 4 years surveillance carried out in provinces of Jiangsu, Anhui and Henan from 1999 to 2002, where clusters of patients with hemolytic uremic syndrome ( HUS) were diagnosed, the prevalence of EHEC O157:H7 in cattle, goat, hens and pigs were investigated. It was observed the high prevalence in domestic animals in the three provinces was statistically correlated with number of HUS patients. Our observation indicated that in the rural areas of China, the prevalence of E.coli O157:H7 should be monitored to predict possible outbreak or epidemic.

The Shiga toxin 2 (Stx2) subtyping of  EHEC O157:H7  isolates revealing that the Stx2vha were the subtypes mostly detected in China (71.4% of the total isolates) since 1999, and three genotypes in signal PFGE group were involved the outbreak of 1999, such as stx2-vha, stx1-stx2 and Stx2. Furthermore, the goat was the first time to be identified as the primary reservoir, followed by cattle, pig and hens respectively.

The supportive treatment for diarrhea caused by EHEC O157:H7 has been recommended. The using of antibiotic is controversial because most antibiotics may cause Shiga toxin-encoding bacteriophage induction and enhanced Shiga toxin (Stx) production, resulting in the higher risk of development of HUS. We isolated a strain of Lactobacillus acidophilus LAI, which could inhibiter the growth of E.coli O157:H7 without enhancing Stx-gene expression in vitro. Using streptomycin-treated mice as model, we demonstrated that oral administration of L. acidophilus LAI dramatically decreased the severity of diarrhea and lowered STEC colonization levels in the gastrointestinal tract and Vero cell cyto-toxicity of fecal samples and. The histological damage to the intestinal mucus induced by E.coli O157:H7 were also decreased. This observation indicated that L.acidophilus has potential to be developed as the safe and effective anti-bacterial medicine for treatment of infection caused by EHEC O157:H7.

The predictive factor for diarrhea patients caused by EHEC O157:H7  to develop HUS are proposed to include urinal protein and/or occult blood, abrupt increase of white blood cell count, urinal NAG, alpha 1 microglobulin, beta 2 microglobulin, low osmolar urine, high thrombomodulin level and others as well.  We observed that the kidney damage could be observed as early as second day of in 30% of bacteriological-confirmed diarrhea patients, such as urine protein. The elevated concentration of serum ？？2-microglubin was observed in all of the diarrhea patients infected by EHEC O157:H7, 31 of 31 patients of hemolytic uremic syndrome (HUS) caused by EHEC O157:H7, 27 of 36 non-O157 diarrhea patients and 4 of 30 age-matched healthy people, with the mean concentration of 3.32？？0.8111.27？？4.14, 2.75？？0.86 and 1.79？？0.29 mg/l respectively.  It seems that serum beta 2-microglobulin has potential to be used as one of predictive parameters for development of HUS in diarrhea patients infected by E.coli O157:H7.