escherichia coli

    • Escherichia coli
      • part of the normal flora of the colon in humans
      • has fimbriae or pili that are important for adherence to host mucosal surfaces
      • Most strains can ferment lactose (that is, they are Lac+) in contrast to the major intestinal pathogens, (MCQ)
        • Salmonella and Shigella cannot ferment lactose (that is, they are Lac–) (MCQ)
      • E. coli produces both acid and gas during fermentation of carbohydrates.
      • E. coli shares many properties with the other Enterobacteriaceae. (MCQ)
        • all are facultative anaerobes
        • all ferment glucose
        • all can generate energy by aerobic or anaerobic respiration (using nitrate, nitrite, or fumarate as terminal electron acceptors).
        • all lack cytochrome c oxidase (that is, they are oxidase negative).
      • Typing strains is based on differences in three structural antigens: O, H, and K
      • O antigens (somatic or cell wall antigens)
        • found on the polysaccharide portion of the LPS(MCQ)
        • heat stable
        • shared among different Enterobacteriaceae genera
        • commonly used to serologically type many of the enteric gram-negative rods. (MCQ)
      • H antigens
        • are associated with flagella
        • only flagellated (motile) Enterobacteriaceae such as E. coli have H antigen. (MCQ)
      • K antigens
        • Located within the polysaccharide capsules. (MCQ)
      • A serotype of E. coli possessing O157 and H7 (designated O157:H7) causes a severe form of hemorrhagic colitis (MCQ)
    • Clinical significance: intestinal disease
      • Transmission of intestinal disease is commonly by the fecal–oral route
      • contaminated food and water serving as vehicles for transmission.
      • five types of intestinal infections
        • entero- toxigenic (ETEC)
        • entero pathogenic (EPEC)
        • entero hemorrhagic (EHEC)
        • entero invasive (EIEC),
        • entero aggregative (EAEC)
      • EHEC E. coli infection should be suspected in all patients with acute bloody diarrhea, particularly if associated with abdominal tenderness and absence of fever. (A Very important MCQ)
      • Enterotoxigenic E. coli:
        • a common cause of traveler’s diarrhea. (MCQ)
        • Transmission occurs through
          • food and water contaminated with human waste
          • by person-to-person contact.
        • colonize the small intestine
        • pili facilitate the binding of the organism to the intestinal mucosa
        • enterotoxins
          • cause prolonged hypersecretion of chloride ions and water by the intestinal mucosal cells
          • inhibit the reabsorption of sodium. (MCQ)
          • result in significant watery diarrhea
          • heat-stable toxin (ST) (MCQ)
            • works by causing an elevation in cellular cGMP  levels
          • heat-labile toxin (LT) (MCQ)
            • causes elevated cAMP
            • LT is essentially identical to cholera toxin
      • Enteropathogenic E. coli:
        • an important cause of diarrhea in infants(MCQ)
        • newborn becomes infected perinatally
        • occurs especially in locations with poor sanitation
        • attach to mucosal cells in the small intestine by use of bundle-forming pili (BfpA).
        • Characteristic lesions in the small intestine
          • attaching and effacing lesions (A/E) (MCQ)
          • destruction of the microvilli
          • caused by injection of effector proteins into the host cell by way of a type III secretion system (T3SS).
        • EPEC are not invasive and, thus, do not cause bloody diarrhea. (MCQ)
        • Toxins are not elaborated by EPEC strains.
        • Watery diarrhea results
      • Enterohemorrhagic E. coli:
        • produce one of two exotoxins (Shiga-like toxins 1 or 2),
        • result in a severe form of copious, bloody diarrhea (MCQ) (hemorrhagic colitis) in the absence of mucosal invasion or inflammation.
        • Serotype O157:H7 is the most common strain of E. coli that produce Shiga-like toxins.
        • This strain is also associated with outbreaks of a potentially life-threatening, acute renal failure (hemolytic uremic syndrome, or HUS) (MCQ)
          • characterized by fever, acute renal failure, microangiopathic hemolytic anemia and throm- bocytopenia
          • occur in children younger than ages 5 to 10 years
        • The primary reservoir of EHEC is cattle
          • possibility of infection can be greatly decreased by thoroughly cooking ground beef and pasteurizing milk. (MCQ)
      • Enteroinvasive E. coli
        • cause a dysentery-like syndrome with fever and bloody stools (MCQ)
        • Plasmid-encoded virulence factors are nearly identical to those of Shigella species(MCQ)
        • These virulence factors allow the
          • invasion of epithelial cells (Ipa) (MCQ)
          • intercellular spread by use of actin-based motility
        • In addition, EIEC strains produce a hemolysin (HlyA) (MCQ)
      • Enteroaggregative E. coli:
      • EAEC also cause traveler’s diarrhea and persistent diarrhea in young children.
      • Adherence to the small intestine is mediated by aggregative adherence fimbriae(MCQ)
      • The adherent rods resemble stacked bricks (MCQ)
      • result in shortening of microvilli
      • EAEC strains produce a heat-stable toxin that is plasmid encoded.
    • Clinical significance: extraintestinal disease
      • The source of infection for extraintestinal disease is frequently the patient’s own flora, in which the individual’s own E. coli is non- pathogenic in the intestine
      • it causes disease in that individual when the organism is found, for example, in the bladder or bloodstream (normally sterile sites).
      • Urinary tract infection
        • E. coli is the most common cause of urinary tract infection (UTI), including cystitis and pyelonephritis. (MCQ)
        • Women are particularly at risk for infection.
          • Uncomplicated cystitis
            • It is the most commonly encountered UTI
            • It is caused by uropathogenic strains of E. coli, characterized by (MCQ)
              • P fimbriae (an adherence factor)
              • hemolysin, colicin V
              • resistance to the bactericidal activity of serum complement. (MCQ)
          • Complicated UTI (pyelonephritis)
            • occur in settings of obstructed urinary flow (MCQ)
            • caused by nonuropathogenic strains.
      • Neonatal meningitis:
        • E. coli is a major cause
        • The K1 capsular antigen, which is chemically identical to the polysaccharide capsule of group B Neisseria meningitidis, is particularly associated with such infections. (MCQ)
      • Nosocomial (hospital-acquired) infections:
        • sepsis/bacteremia, endotoxic shock, and pneumonia.
    • Laboratory identification
      • Intestinal disease
        • Because E. coli is normally part of the intestinal flora, detection in stool cultures of disease-causing strains is generally difficult
        • EIEC strains
          • often do not ferment lactose (MCQ)
          • detected on media such as MacConkey agar
        • EHEC
          • unlike most other strains of E. coli, ferment sorbitol slowly, if at all,
          • detected on MacConkey sorbitol agar. (MCQ)
          • polymerase chain reaction is used  to identify E. coli strains producing Shiga-like toxins.
      • Extraintestinal disease:
        • Isolation of E. coli from normally sterile body sites (for example, the bladder or cerebrospinal fluid) is diagnostically significant

    E coli
    E. coli Video
    E. coli are a large and diverse group of bacteria. Although most strains of E. coli are harmless, others can make people sick. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness and pneumonia, and other illnesses. Still other kinds of E. coli are used as markers for water contamination.
    E. coli la bacteria asesina.
    Breve descripción de la Escherichia Coli, cepa 0157
    Tomada del documental “Investigación sobre epidemias, La bacteria asesina”

    Outbreak Investigation. Subido con fines didácticos y sin ánimo de lucro de ningún tipo.
    Escherichia Coli – Microbiologia
    Escherichia coli, grupos patogenos, epidemiologia, patogenia, clinica
    Bacteria of Interest: Escherichia coli
    48 Hour E. coli on a MAC plate.
    48 hour time lapse photography of Gram Negative Rod, Escherichia coli, streaked out and growing on a Macconkey agar Medical Laboratory diagnostic plate in a 37 degree Celsius CO2 incubator at Weber State University, Ogden Utah. This time lapse footage shows the organisms ability to utilize lactose as a food source and revert back to usage of peptones after consuming all of the lactose present. Filmed using a GoPro HD Hero 3 Black Edition Action Sports Camera.
    Infecciones por Escherichia Coli, Diarrea Hemorrágica por E Coli, Causas y Síntomas del E Coli
    All About Escherichia Coli & Escherichia Coli Infection (E. Coli)
    Enterobacteriaceae ( Escherichia coli _ Klebsiella pneumoniae).mp4
    Enterobacteriaceae ( Escherichia coli _ Klebsiella pneumoniae).mp4

Previous articlePseudomonas
Next articleCerebral Circulation