Enterobacteriaceae Overview
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Questions and Answers

What life-threatening complication may arise from E.coli infections due to verotoxin?

  • Haemolytic Uraemic Syndrome (correct)
  • Meningitis
  • Respiratory failure
  • Septicemia

    • Why are antibiotics not recommended for treating E.coli infections caused by strain O157:H7?

  • They increase the risk of haemolytic uremic syndrome (correct)
  • They can worsen diarrhea symptoms
  • They promote the growth of E.coli
  • They have no effect on the bacteria

    • What color do E.coli colonies turn on MacConkey’s agar due to lactose fermentation?

  • Blue
  • Green
  • Yellow
  • Rose pink (correct)

    • What is a characteristic of Klebsiella pneumoniae?

    <p>Non-motile with a large polysaccharide capsule</p> Signup and view all the answers

    Which test is used for serology of Klebsiella pneumoniae?

    <p>Slide agglutination test</p> Signup and view all the answers

    What is the result of the IMVC test for Klebsiella pneumoniae?

    <ul> <li> <ul> <li> <ul> <li> <ul> <li></li> </ul> </li> </ul> </li> </ul> </li> </ul> Signup and view all the answers

    What is a common feature of Salmonella compared to other bacteria?

    <p>Motile with peritrichous flagella</p> Signup and view all the answers

    What diagnostic result is expected for E.coli on TSI medium?

    <p>Yellow slant and yellow butt</p> Signup and view all the answers

    What is the primary mode of transmission for Enterohaemorrhagic E. coli (EHEC)?

    <p>Faeco-oral route</p> Signup and view all the answers

    Which toxin produced by Enterotoxigenic E. coli (ETEC) stimulates the secretion of fluids to the gut lumen?

    <p>Heat-stable toxin (ST)</p> Signup and view all the answers

    What is the characteristic effect of Enteropathogenic E. coli (EPEC) infection on intestinal cells?

    <p>Destruction of intestinal microvilli</p> Signup and view all the answers

    What type of diarrhea is associated with Enteroinvasive E. coli (EIEC)?

    <p>Dysentery-like diarrhea</p> Signup and view all the answers

    What is the primary virulence factor for Enteroaggregative E. coli (EAggEC)?

    <p>Pili for adherence</p> Signup and view all the answers

    Which E. coli strain is specifically known for causing hemorrhagic colitis?

    <p>Enterohaemorrhagic (EHEC)</p> Signup and view all the answers

    What is the role of the heat-labile toxin (LT) produced by Enterotoxigenic E. coli (ETEC)?

    <p>Cause watery diarrhea by increasing cAMP</p> Signup and view all the answers

    Which of the following groups is most likely to suffer persistent diarrhea from Enteroaggregative E. coli (EAggEC)?

    <p>Children and HIV patients</p> Signup and view all the answers

    What is a common characteristic of Enterobacteriaceae?

    <p>They ferment glucose but have varying fermentation of other sugars.</p> Signup and view all the answers

    Which of the following genera in Enterobacteriaceae are known to be pathogenic?

    <p>Salmonella and Shigella</p> Signup and view all the answers

    What is the significance of LPS in Enterobacteriaceae?

    <p>It acts as an endotoxin released after bacterial cell death.</p> Signup and view all the answers

    E. coli is primarily known for its role in which disease?

    <p>Urinary Tract Infection</p> Signup and view all the answers

    Which type of E. coli is known for producing enterotoxins?

    <p>Enterotoxigenic E. coli</p> Signup and view all the answers

    Which of the following is NOT a characteristic of non-lactose fermenters in Enterobacteriaceae?

    <p>Ferment lactose abundantly.</p> Signup and view all the answers

    What virulence factor is primarily responsible for E. coli adherence to mucosal surfaces?

    <p>Pili</p> Signup and view all the answers

    How is E. coli primarily transmitted to cause urinary tract infections?

    <p>From its own fecal flora to the urethra.</p> Signup and view all the answers

    What is the primary mode of transmission for typhoid fever?

    <p>Fecal-oral route</p> Signup and view all the answers

    Which group is more commonly affected by typhoid fever?

    <p>Children and young adults</p> Signup and view all the answers

    Which of the following is a nontyphoidal serotype of Salmonella commonly associated with foodborne gastroenteritis?

    <p>S.enteritidis</p> Signup and view all the answers

    What is the incubation period for typhoid fever?

    <p>5-21 days</p> Signup and view all the answers

    What characterizes the systemic disease of typhoid fever?

    <p>Life-threatening systemic disease with multiple organ involvement</p> Signup and view all the answers

    Which symptom is commonly associated with typhoid fever?

    <p>Abdominal symptoms</p> Signup and view all the answers

    What type of carriers are primarily responsible for the transmission of Salmonella after recovery?

    <p>Gall bladder and urinary carriers</p> Signup and view all the answers

    Which of the following is NOT a complication of typhoid fever?

    <p>Chronic fatigue syndrome</p> Signup and view all the answers

    What type of colonies are observed on Bismuth sulphite agar for Enteric Fever diagnosis?

    <p>Brown to black colonies</p> Signup and view all the answers

    Which organism demonstrates H2S production in sugar fermentation tests?

    <p>S. Paratyphi B</p> Signup and view all the answers

    In which week does the Widal test become significant for detecting antibodies in the serum?

    <p>Second week</p> Signup and view all the answers

    What does a high titre of O and H antibodies (>1/160) indicate?

    <p>Recent active infection</p> Signup and view all the answers

    What is one reason the Widal test may yield false negative results during the first week?

    <p>Antibodies are not present yet</p> Signup and view all the answers

    Which of the following vaccines contains live attenuated bacteria?

    <p>Oral living attenuated typhoid vaccine (Vivotif)</p> Signup and view all the answers

    What type of agar shows pale yellow non-lactose fermenting colonies for Enteric Fever culture?

    <p>MacConkey's agar</p> Signup and view all the answers

    What should be expected when using tetrathionate broth for Enteric Fever diagnosis?

    <p>Inhibition of E. coli growth</p> Signup and view all the answers

    Study Notes

    General Characteristics of Enterobacteriaceae

    • Gram-negative bacilli, primarily normal commensals in the colon.
    • Includes pathogenic genera (e.g., Salmonella, Shigella) and commensals (e.g., E. coli, Klebsiella).
    • Facultative anaerobes capable of fermenting glucose; other sugar fermentations vary.
    • Oxidase negative and reduce nitrates to nitrites.
    • Features lipopolysaccharides (LPS) in cell walls; LPS can cause septic shock upon bacterial death.
    • Can cause intestinal and extraintestinal diseases, depending on the genus.
    • Antigenic composition: somatic (O) antigen, flagellar (H) antigen, and capsular (K) antigen present in varying degrees.

    Classification of Enterobacteriaceae

    • Divided into lactose fermenters (e.g., E. coli, Klebsiella) and non-lactose fermenters (e.g., Salmonella, Shigella).
    • Lactose fermenters create rose-pink colonies on MacConkey agar; non-lactose fermenters display pale yellow colonies.

    E. coli

    • Normal intestinal inhabitants; some strains are pathogenic.
    • Morphology: Gram-negative bacilli, motile, some encapsulated.
    • Virulence factors include:
      • Pili for mucosal adherence.
      • K antigen, which is antiphagocytic.
      • LPS as an endotoxin causing fever and shock.
      • Two enterotoxins (heat labile LT and heat stable ST) from enterotoxigenic strains.
      • Verotoxin from enterohaemorrhagic strains.

    Diseases Associated with E. coli

    • Extraintestinal Diseases:

      • Most common cause of urinary tract infections (UTIs); colonizes vaginal and periurethral areas.
      • Nosocomial infections are frequently associated with urinary catheterization.
      • Neonatal septicemia and meningitis.

    • Intestinal Diseases (Gastroenteritis):

      • Diarrhea types include watery (ETEC, EPEC) and bloody (EIEC, EHEC).
      • Transmission primarily through the fecal-oral route.

    Specific E. coli Pathotypes

    • Enterotoxigenic E. coli (ETEC):

      • Causes traveler's diarrhea; produces profuse watery diarrhea through LT and ST toxins.

    • Enteropathogenic E. coli (EPEC):

      • Causes infantile diarrhea; adheres to intestinal mucosa and affects absorption.

    • Enteroinvasive E. coli (EIEC):

      • Causes dysentery-like diarrhea; invades the colonic mucosa leading to bloody diarrhea.

    • Enteroaggregative E. coli (EAggEC):

      • Causes persistent diarrhea in children and HIV patients with patchy adherence to the intestinal mucosa.

    • Enterohaemorrhagic E. coli (EHEC O157:H7):

      • Causes hemorrhagic colitis; linked to undercooked hamburgers; complications can include hemolytic uremic syndrome.

    Diagnosis of E. coli Infections

    • Sample type depends on infection site (e.g., stool, urine).
    • Gram stain shows motile, Gram-negative bacilli.
    • Culture on MacConkey agar yields rose-pink colonies; E. coli also ferments multiple sugars.
    • IMVC testing typically results in positive Indole, Methyl Red, and negative Voges-Proskauer and Citrate Utilization.

    Treatment for E. coli Infections

    • Rehydration is critical for traveler's diarrhea; trimethoprim-sulfamethoxazole may be beneficial.
    • Antibiotics given for diarrhea with fever, blood, or pus; careful consideration for O157:H7, where antibiotics may worsen the condition.

    Klebsiella pneumoniae

    • Causes lobar pneumonia, UTIs (often nosocomial), and septicemia in immunocompromised patients.
    • Morphological traits include Gram-negative bacilli, non-motile, and a large polysaccharide capsule.
    • Culture characteristics show rose-pink colonies on MacConkey agar; mucoid colonies on EMB agar due to extracellular slime.

    Salmonella

    • Morphology: Gram-negative bacilli with peritrichous flagella, non-capsulated.
    • Common species include Salmonella enterica, which has numerous serotypes, notably those causing typhoid (e.g. S. Typhi) and nontyphoidal gastroenteritis (e.g. S. enteritidis, S. typhimurium).

    Typhoid Fever (Enteric Fever)

    • Characterized by severe systemic illness due to bacteria in the bloodstream.
    • Symptoms include chills, fever, headache, and abdominal pain; can lead to complications like intestinal hemorrhage.
    • Mode of transmission is fecal-oral; primarily from human carriers.
    • Chronic carriers can excrete the pathogen intermittently.

    Diagnosis of Enteric Fever

    • Blood culture in the first week identifies the organism.
    • Subsequent analysis includes stool and urine samples, revealing specific culture characteristics and H2S production.
    • Serological tests (e.g., Widal test) assess antibody levels in response to infection.

    Vaccines for Typhoid Fever

    • TAB vaccine: heat-killed vaccine targeting S. Typhi and S. Paratyphi.
    • Oral typhoid vaccine (Vivotif) is a live attenuated option.
    • Inactivated single-dose Vi polysaccharide vaccine available as well.

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    Enterobacteriaceae PDF

    Description

    This quiz covers the general characteristics of the Enterobacteriaceae family, which includes important genera like Salmonella, Shigella, E. coli, and Klebsiella. You will learn about their gram-negative properties, metabolic functions, and ecological roles as either pathogens or commensals.

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