Table of Contents:

• Taxonomy Information
• Lifecycle Information
• Genome Information
• Biosafety Information
• Culturing Information
• Epidemiology Information
• Diagnostic Tests Information
• Infected Hosts Information
• Phinet: Pathogen-Host Interaction Network
• Lab Animal Pathobiology & Management
• References
• Data Provenance and Curators

1. Species:
   1. Escherichia coli O157:H7. :
      1. Common Name: Shiga-toxin (Stx)-producing E. coli (STEC), Enterohemorrhagic Escherichia coli (EHEC), Vero cytotoxin-producing E. coli (VTEC).
      2. GenBank Taxonomy No.: 83334
      3. Description: The microorganisms which inhabit the intestinal tract as normal flora are named enteric bacteria. E. coli belongs to the Family Enterobacteriaceae (from the Greek word enterikos, which pertains to the intestine). The name Escherichia comes from the name of the person Escherich, who in 1885 first isolated and characterized this bacterium. E. coli is a normal inhabitant of the intestines of all animals, including humans. When aerobic culture methods are used, E. coli is the dominant species found in feces(Karmali et al., 1983). Normally E. coli serves a useful function in the body by suppressing the growth of harmful bacterial species and by synthesizing appreciable amounts of vitamins. A minority of E. coli strains are capable of causing human illness by several different mechanisms. E. coli serotype O157:H7 is a rare variety of E. coli that produces large quantities of one or more related, potent toxins that cause severe damage to the lining of the intestine(Fegan and Desmarchelier, 1999, Fegan and Desmarchelier, 2002). The recognition of EHEC (Enterohemorrhagic Escherichia coli) as a pathogenic E. coli resulted from two key epidemiologic observations. The first was the 1983 report by Riley et al(Riley et al., 1983). who investigated two outbreaks of a distinctive gastrointestinal illness characterized by severe crampy abdominal pain, watery diarrhea followed by grossly bloody diarrhea, and little or no fever. This illness, designated hemorrhagic colitis (HC), was associated with the ingestion of undercooked hamburgers at a fast-food restaurant chain(Riley et al., 1983, Fegan and Desmarchelier, 2002, Rasmussen and Casey, 2001).

1. E. coli Lifecycle Information
   1. Stage Information:
      1. E. coli lifecycle one stage(Bopp et al., 1987, Kim et al., 1994):
         • Shape: E. coli are rod-shaped bacteria.
         • Picture(s):
           • SEM Image of E. coli on the surface of the Small Intestine (Website 68)
             
             
             
             Description: Photocomposite - E. coli on the surface of the small intestine. E. coli - Gram-negative, facultatively anaerobic, rod prokaryote. Part of human and animal microbiota. E. coli can cause urinary tract infections, traveler's diarrhea and nosocomial infections. Magnification: bacteria x 800; intestine x49.
           • TEM Image of E. coli with fimbriae (Website 68)
             
             
             
             Description: Transmission Electron Micrograph of E. coli with fimbriae on the cell surface. Magnification: x6,105.
           • SEM Image of E. coli strain 0157:H7 - rod prokaryote (hemorrhagic bacterium) (Website 68)
             
             
             
             Description: Scanning Electron Micrograph of E. coli strain 0157:H7 hemorrhagic type. Gram-negative, enteric, facultatively anaerobic, rod prokaryote. Potentially fatal to humans, contracted when contaminated meat is cooked inadequately. Magnification: x2,925.

1. Genome of Escherichia coli O157:H7.
   1. Description: E. coli O157:H7 has a `backbone' sequence of about 4.1 Mb that is co-linear. The `backbone' is punctuated by hundreds of islands of apparently introgressed DNA designated `O-islands' for DNA segments. Of the O-islands, only 40% could be assigned a function(Perna et al., 2001, Hayashi et al., 2001).
   2. E. coli O157:H7 EDL933 Chromosome(Website11)
      1. GenBank Accession Number: AE005174
      2. Size: 5.5 Mb(Perna et al., 2001).
      3. Gene Count: 5361 open reading frames(Hayashi et al., 2001).
      4. Description: Escherichia coli O157:H7 EDL933, complete genome(Perna et al., 2001).
   3. Escherichia coli O157:H7 Chromosome(Website12)
      1. GenBank Accession Number: BA000007
      2. Size: 5.5 Mb(Hayashi et al., 2001).
      3. Gene Count: 5361 open reading frames(Hayashi et al., 2001).
      4. Description: Escherichia coli O157:H7, complete genome(Hayashi et al., 2001).
   4. 92 kb F-like plasmid(Website13)
      1. GenBank Accession Number: NC_002128
      2. Size: 92 kb(Boyce et al., 1995).
      3. Gene Count: 100 open reading frames(Burland et al., 1998).
      4. Description: The 92 kb F-like plasmid is composed of segments of putative genes in a framework of replication and maintenance regions, with seven insertion sequence elements. The coding regions account for 87% of the plasmid(Burland et al., 1998).
   5. A cryptic plasmid pOSAK1(Website14)
      1. GenBank Accession Number: NC_002127
      2. Size: 3.3 kb(Makino et al., 1998).
      3. Gene Count: 3 open reading frames(Makino et al., 1998).
      4. Description: A cryptic plasmid pOSAK1(Makino et al., 1998).

1. General biosafety information
   1. Level: Biosafety Level 2.
   2. Precautions: Hemolytic uremic syndrome occurs in a small proportion of patients and is responsible for most deaths associated with infections with these organisms. Domestic farm animals (particularly bovines) are significant reservoirs of the organisms. However, experimentally infected small animals are also sources of infection in the laboratory. Laboratory Hazards: Enterohemorrhagic E. coli O157:H7 is usually isolated from feces. A variety of foods contaminated with the organisms may serve as vehicles of spread, and include uncooked ground beef and unpasteurized dairy products. It may rarely be found in blood of infected humans or animals. Ingestion is the primary laboratory hazard. The importance of aerosol exposure is not known. Recommended Precautions: Biosafety Level 2 practices, containment equipment, and facilities are recommended for all activities utilizing known or potentially infectious clinical materials or cultures. Animal Biosafety Level 2 facilities and practices are recommended for activities with experimentally or naturally infected animals. Vaccines are currently not available for use in humans. There have been at least three cases of laboratory-acquired infection with E. coli O157:H7 with serious consequences including renal failure and hemorrhagic colitis. No laboratory accident or obvious breach in technique was evident in any of these cases. This level of biohazard is due to the extremely low dose required for infection and the potent effects of shiga toxin (Stx), which are not limited to the intestine(Booth and Rowe, 1993, Rao et al., 1996, Website4).

1. E. coli Culturing Method :
   1. Description: The agar medium most commonly used for the isolation of E. coli O157:H7 is MacConkey agar containing sorbitol (SMAC agar), which is available from multiple commercial sources. This medium contains 1% sorbitol in place of lactose in the standard MacConkey medium. Sorbitol-MacConkey agar plates are inoculated with the fecal specimen and examined after 18 to 24 h of incubation at 37 degrees celcius for the presence of colorless, sorbitol-negative colonies. Multiple sorbitol-nonfermenting colonies (at least 3 and up to 10) should be selected for testing as potential E. coli O157:H7(March and Ratnam., 1986, Gunzer et al., 1992).
   2. Medium: MacConkey agar containing sorbitol (SMAC agar). This medium contains 1% sorbitol in place of lactose in the standard MacConkey medium(March and Ratnam., 1986).
   3. Optimal Temperature: 37 degrees celcius(March and Ratnam., 1986).

1. Outbreak Locations:
   1. Both outbreaks and sporadic cases of E. coli O157:H7 infection have occurred in the United States, Canada, Western Europe, Australia, Japan, Central and South America, the Middle and Far East, as well as Africa(Besser et al., 1999, Peacock et al., 2001).
2. Transmission Information:
   1. From: Cattle(Kudva et al., 1998). , To: Humans(Kudva et al., 1998).
      Mechanism: E. coli O157:H7 can be transmitted by food and water. Most cases are caused by ingestion of contaminated foods, particularly foods of bovine origin. In the United States, ingestion of undercooked hamburgers, prepared in a restaurant or in the home, has been a particularly important cause of outbreaks.The largest outbreak so far reported in North America involved hamburgers from a fast-food restaurant. Contamination of the hamburgers implicated in these outbreaks was the result in part of modern food-processing technology. Beef from thousands of cattle raised on hundreds of farms is ground together in a single hamburger plant, which then distributes frozen patties to thousands of restaurants in several states(Kudva et al., 1998).
3. Environmental Reservoir:
   1. Environmental Reservoir:
      1. Description: Many E. coli O157:H7 outbreaks have been traced to contaminated beef and dairy products(Boyce et al., 1995).
      2. Survival: E. coli O157:H7 may persist for long periods of time in manure (56-130 days) or even for 21 months. Survival by this microbe in soil was greatest (130 days) on soil cores containing rooted grass(Cornick et al., 2000, Pell, 1997, Gagliardi and Karns, 2000). The prevalence of E. coli O157:H7 increases during the summer and early fall months. Conversely, at other times of the year this microbe is present at very low levels, and in many cases its prevalence in cattle declines to zero during the winter months. Human outbreaks of E. coli O157:H7 have also shown seasonality. It was found that 88% of infections occurred in the months of summer and early autumn(Maule, 2000).
4. Intentional Releases:
   1. Intentional Release Information:
      1. Description: E. coli infection.
      2. Emergency Contact: If you believe that you have been exposed to a biological or chemical agent, or if you believe an intentional biological threat will occur or is occurring, contact your local health department and/or your local police or other law enforcement agency. The Centers for Disease Control and Prevention (CDC) Emergency Response Hotline (24 hours) 770-488-7100(Website5, Website6).

1. Organism Detection Test:
   1. Gram Staining :
      1. Time to Perform: minutes-to-1-hour
      2. Description: Gram-staining is a four part procedure which uses certain dyes to make a bacterial cell stand out against its background. The specimen should be mounted and heat fixed on a slide before you procede to stain it(Website7, Website8).
      3. False Positive: Not using enough decolorizer may yield a false Gram (+) results(Website7).
      4. False Negative: Using too much decolorizer could result in a false Gram (-) result(Website7).
2. Immunoassay Test:
   1. Commercial Latex Agglutination Kits :
      1. Time to Perform: 1-to-2-days
      2. Description: The Centers for Disease Control and Prevention (CDC) has evaluated three commercial latex reagent kits for detecting the O157 antigen (Oxoid Diagnostic Reagents, Hampshire, England: http://www.oxoid.com; Pro-Lab Inc., Richmond Hill, Ontario, Canada: http://www.prolabinc.com/; and Remel Microbiology Products, Lenexa, Kansas: http://www.remelinc.com) and one latex reagent kit for detecting the H7 antigen (Remel). The results of this study showed 100% correlation of the commercial O157 kits with the CDC reference antisera. Many strains that gave initial negative reactions with the H7 reagent became positive when passed through motility medium to enhance motility. The CDC study concluded that the commercial latex reagents are good alternatives to standard serologic methods for identifying the E. coli O157 and H7 antigens when the manufacturer directions are closely followed(Fields et al., 1997, Sowers et al., 1996).
      3. False Positive: Some false-positive reactions with both the commercial and CDC sera were seen with a strain of Citrobacter freundii and strains of Salmonella O group N. The O157 antigen was previously shown to be identical to the Salmonella O301 antigen(Sowers et al., 1996).
      4. False Negative: For 106 strains of E. coli and related organisms that were not enhanced for motility through semisolid medium, the Remel H7 latex reagent had a sensitivity of 96%(Sowers et al., 1996).
   2. Assurance EHEC EIA :
      1. Time to Perform: 1-to-2-days
      2. Description: Some kits are available for accuracy detection of O157:H7 in food and environmental samples. Minimal labor for preparation.Assurance EIAs (Assurance EHEC EIA, BioControl Systems, Inc.) are used extensively in industry, independent and government laboratories. E. coli 0157 Immunocapture - a rapid and convenient method which can be used to facilitate and enhance the isolation of E. coli 0157:H7 from enrichment cultures (TECRA, Inc.). Additional information: http://www.rapidmethods.com/products/assehec.html, http://www.tecra.net(Website2, Website3).
3. Nucleic Acid Detection Test: