Pathogenic Escherichia coli
Escherichia coli is a normal flora of the human gastrointestinal tract. Pathogenicity occurs when Escherichia coli strains acquire certain additional genetic material. Escherichia coli is one of the most common bacterial causes of diarrhea.
features
Different pathogenic types of Escherichia coli have different epidemiological, clinical, and pathogenic features:
肠产毒型大肠埃希菌(ETEC)
ETEC survives easily in water and food and is one of the most common bacterial causes of dehydrating diarrhoeal disease in children under 2 years of age in resource-limited settings. ETEC can also cause diarrhoea in travellers to the tropics and is emerging as a pathogen in resource-rich areas. ETEC produces plasmid-encoded toxins that primarily cause watery diarrhea.
肠致病型大肠埃希菌(EPEC)
EPEC can cause sporadic diarrhoeal diseases and outbreaks of diarrhoea, most commonly in infants younger than 6 months of age in resource-limited countries. Identification characteristics of EPEC strains include characteristic "adhesion-smoothing" effects upon contact with intestinal epithelial cells and the absence of Shiga toxin. EPEC proteins can affect cell physiology by adhesion and inducing signal transduction.
Enterohemorrhagic Escherichia coli (EHEC)
EHEC strains are capable of producing Shiga toxin, which, like EPEC strains, can cause "adhesion-smoothing" damage. EHEC strains have caused large outbreaks of bloody diarrhoea, particularly the O157:H7 serotype (and O104:H4 serotype), and some strains have been associated with hemolytic uremic syndrome (HUS).
肠侵袭型大肠埃希菌(EIEC)
EIEC infection appears to be less common. The clinical disease initially presents as watery diarrhea and can progress to bloody diarrhoea and dysentery. EIEC is closely related to Shigella, and the pathogenesis of both infections is driven by the same genes. EIEC invades intestinal cells, multiplies within cells, and spreads to adjacent intestinal cells.
肠集聚型大肠埃希菌(EAEC)
In many populations in both resource-limited and resource-rich settings, EAEC can cause persistent and acute diarrhoeal illness and may cause growth retardation. Tissue culture adhesion assays showed that EAEC exhibited a unique palisade-like adhesion on human epithelial cell type 2 (HEp-2). The pathogenesis of diarrhea due to EAEC has not been fully elucidated.
microbiology
Under aerobic conditions, it is easy to grow Escherichia coli from stool samples. However, the appearance of colonies on culture plates and the results of routine biochemical testing do not distinguish pathogenic and non-pathogenic E. coli strains, nor can they distinguish between pathogenic E. coli strains. Escherichia coli O157:H7 belongs to EHEC and is the only pathogenic strain that can be easily identified without molecular testing. With the increasing availability of commercially available molecular tests for diagnosing diarrhoeal pathogens, other pathogenic types of Escherichia coli are increasingly identified.
Clinical diagnosis
Identification of a pathogenic Escherichia coli isolate by stool molecular testing does not equate to the presence of E. coli infection. It needs to be clinical, and consider whether there are other possible causes. A positive test in an asymptomatic patient does not suggest infection.
treat
Supportive care
Diarrhoeal disease is treated supportively, including fluid and electrolyte replacement and nutritional therapy.
The role of antibiotics
-For patients with diarrhea with pathogenic Escherichia coli on stool testing, we suggest against routine antibiotic therapy.
-Patients with severe, bloody, or persistent diarrhea may be treated with antibiotics (eg, azithromycin or ciprofloxacin), especially in children or immunocompromised individuals.