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Information about Food Poisoing caused by E.coli(O157)
病原性大腸菌(O-157)による食中毒の情報

This month(July), epidemic spread of food poisoning caused by E.coli(O157) was reported from all around Japan. Four have reported to be died for this food poisoing. As this type of E.coli(O157) occasionally cause hemolytic uremic sysndrome, this could be a case for Trauma and Critical Care service. There is few information about this serisous food poisoing on Japanese Internet resource. However, some informations were available around the world.

今月に入り病原性大腸菌(O157)による食中毒が多発し、4名の死亡者が報道されている.この菌種は、hemolytic uremic sysndrome(溶血性尿毒症症候群)をきたす可能性があり救命救急センターへの搬入も配慮される.残念ながら、日本のInternetの検索ではこの中毒に関する情報は乏しいが、海外ではいくつかの情報源を見いだすことができる.

<日本語版はこちら>


How to search information about "E. coli O157"

Unfortunately, not many information was available in the resource of internet in Japan. However, Nikkei Business Publications,Inc. has announced therapeutic manual of E. coli (O157) food poisoning written by Dr. K.Terada, Dept. Pediatrics, Kawasaki Medical College. For pediatric case, symptoms, clinical courses, therapeutic strategies are well documented practically in this paper, with some references.

It is not easy to find useful information for specific subject from innumerable resources in internet. Usual strategy to do this is to use some of the "search engine", which is powerful to find interested web site by keywords. You can search information about "E. coli O157" from one of the excellent search engine "ALTA VISTA" from here.

  • I found four excellent pages focused on pathogenic E. coli O157:H7. One from IFIC(International Food Information Council) which answering common questions about food poisoning by E. coli., mostly for public.
  • Another pages are from Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention. This also announced source of infection and prevention from disease.
  • Excellent medical summery of the pathogenic E. coli is presented by Dr. Glen Armstrong, Department of Medical Microbiology and Immunology, University of Alberta. This article describes more detail including classification of pathogenic E. coli, clinical symptoms and therapeutic strategies. This mainly for general practitioner.
  • The fourth one describes more detail about basic science of E. coli written by Dr. Karl Bettelheim at the University of Birmingham(UK).


Summarizing these information,

Human pathogenic E. coli can classified as;

  1. Enterohaemorrhagic E. coli (EHEC) [Hamburger disease]
  2. Enteropathogenic E. coli (EPEC) [Neonatal diarrhea]
  3. Enterotoxigenic E. coli (ETEC) [Cholera-like]
  4. Enteroinvasive E. coli (EIEC) [Shigella-like]
  5. Enteroaggregative E. coli (EAggEC)
  6. Uropathogenic E. coli (UPEC)
  7. Neonatal menigitis E. coli (NMEC)
E. coli O157:H7 is a serotype which is a dominant(95%) pathogen found in EHEC(Enterohaemorrhagic E. coli) infection.
EHEC is well known as "hamburger disease" or "Barbecue syndrome" in USA.


ABOUT EHEC (O157:H7) INFECTION

Source of Infection:
  • Undercooked hamburger meat and unpasteurized milk products are most common in US. However, the source of infection in Japanese case is not identified. Any kind of food could be a source with careless handling. E. coli does not die under refrigeration. Any unheated food could be a source.
Spreading and Prevention:
  • As E. coli is a most common bacteria found in the intestinal tracts of mammals and man, it could transferred from animal to animal, animal to man, from animal to man on food and from person to person through close contact or food. Only way to avoid spreading of the infection is to heat (up to 160F= 71C) and cook foods, hygiene technique. Any meat (beef, pork or fish) should be heated completely. Keep proper hand washing. Special care should be taken to the young children under 5 years old and elderly.
Incidence and Outbreak:
  • E. coli O157:H7 was first recognized as a cause of food poisoning with severe bloody diarrhea at 1982 in US, and its source was contaminated hamburgers. CDC estimates 20,000 cases a year in US, but not such report was found in Japanese resource. On outbreak of this month in Japan, more than 1500 were suffered and four had reported to be died.
Diagnosis and Testing:
  • It is diagnosed by detecting E. coli O157:H7 from the stool. Sorbitol-MacConkey (SMAC) agar should be used to identify this bacterium, which appears as pink to white colonies on this agar. However, there is not on-site quick test to detect specific type O157:H7 at present time.
Virulence:
  • This type of E. coli is know as highly virulent, because of its toxin. It is suspected that very small number of bacteria could cause illness, after the incubation period of 4 to 9 days.
    Toxin:
    • Major toxins produced by O157:H7 is shiga-like toxins (SLT), also known as "Verotoxins" or "Verocytotoxins" (VT), which causes hemolytic-uremic syndrome(HUS). Prototype of shiga-like toxins is shiga toxin and it consist with an enzymatic A subunit and 5 identical protein subunits B. B subunits bind to glycolipids receptor on the cells and A subunit penetrate cell membrane to destroy cells (cytotoxic).
High Risk Group:
  • Young children under 5 years old and the elderly has high risk to develop complications described below.
Clinical Course:
  • Initial symptoms:
    Children only complaint dullness and unwellness followed by severe abdominal pain(cramp) and frequent watery diarrhea within 2 or 3 days.

    Bloody diarrhea(Hemorrhagic colitis):
    Appears on less than 10% of pathogenic E. coli enteritis. Nonbloody diarrhea or no symptoms is common.

    Fever:
    Usually little or no fever is present (may have low grad fever), and the illness resolves in 5 to 10 days.

Specific Complication:
  • HUS(hemolytic uremic syndrome):
    Children may develop HUS which can cause kidney failure, brain damage, strokes and seizures. Pathophysiology seems to be microvascular (epitherial) injury, thus may cause intravascular hemolysis, renal failure, thrombocytpenia. Unconsciousness and seizures could be due to brain damage(encephalopathy) by same pathogenesis, which is a major cause of death. The cause of death in OKU-town (Chugoku area: OKAYAMA prefecture) was also this encephalopathy.

  • TTP (thrombotic thrombocytopenic purpura):
    TTP can cause strokes, a side-effect often seen in the elderly.
  • About 2%-7% of infections lead to this complication
Treatment:
  • It is important to recognize that most patients recover without antibiotics or other specific treatment in 5-10 days.

  • Antibiotics:
    There is no evidence that antibiotics improve the course of disease. Treatment with some antibiotics may increase chances of HUS(kidney complications) because of releasing amount of toxins(SLT) from dying bacteria. So that antibiotics are not recommended.

  • Antidiarrheal agents:
    Should be avoided. Do not stop diarrea.

  • Hydration:
    Fluid therapy to prevent dehydration by massive watery diarrhea may be the major therapeutic strategy in most of the cases.

  • Treatment of HUS:
    ICU is recommended. Blood transfusions and kidney dialysis are often required until symptoms resolve.(1 - 2 weeks). With intensive care, the death rate for hemolytic uremic syndrome is 3%-5% in US. Anticoagulant therapy may be reasonable from its pathophyisiology. However, plasma exchange or pheresis may have little effect for preventing disease, because the amount of the toxin could be removed is limited.

  • Prognosis of HUS:
    About one-third of persons with hemolytic uremic syndrome have abnormal kidney function many years later, and a few require long-term dialysis. Another 8% of persons with hemolytic uremic syndrome have other lifelong complications, such as high blood pressure, seizures, blindness, paralysis, and the effects of having part of their bowel removed. (from here)
  • Antitoxin therapy:
    Perhaps antitoxin therapy effective in preventing HUS but this still in experimental stages of development. The reference paper could be found at here.
    A phase I study of chemically synthesized vero-toxin(shiga-like toxin) Pk-trisaccharide receptors attached to Chromosorb for preventing hemolytic uremic syndrome, Armstromg GD et al., J Infect Dis 171,1042-1045,1995.


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帝京大学救命救急センター
Trauma and Critical Care Center,
Teikyo University, School of Medicine

鈴木 宏昌 (dangan@ppp.bekkoame.or.jp)
Hiromasa Suzuki, MD

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