Microbiology Quiz: Enterobacterales Characteristics
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Questions and Answers

Which of the following best describes the Gram staining characteristic of Enterobacterales?

  • Gram-negative coccobacilli (correct)
  • Gram-positive bacilli
  • Gram-positive cocci
  • Gram-negative bacilli

    • Which of the following is NOT a typical method for laboratory diagnosis of Enterobacterales?

  • Culture on XLD agar
  • Culture on MacConkey agar
  • Direct ELISA assay targeted against bacterial proteins (correct)
  • Microscopic examination of stained specimens

    • Which of the following is considered a major challenge related to Enterobacterales infections?

  • Limited options for treatment due to antimicrobial resistance (correct)
  • Decreased incidence of foodborne outbreaks
  • Ease of eradication with readily available pharmaceuticals
  • Poor surveillance strategies hindering outbreak containment

    • What is identified as a significant concern regarding Salmonella infections based on this content?

    <p>The occurrence of typhoid and non-typhoid infections (B)</p> Signup and view all the answers

    Which of the following agar types is NOT specifically mentioned as a common solid culture medium for the growth of Enterobacterales?

    <p>Luria-Bertani (LB) agar (B)</p> Signup and view all the answers

    Which characteristic is NOT associated with Enterobacterales?

    <p>Spore forming (D)</p> Signup and view all the answers

    Which of the following is considered a strict human pathogen within the Enterobacterales group?

    <p>Salmonella typhi (A)</p> Signup and view all the answers

    An Escherichia coli infection leading to bloody diarrhea, abdominal cramps, and potential fever is most likely caused by what?

    <p>A highly virulent serotype such as serotype O157 (A)</p> Signup and view all the answers

    Which of the following is NOT a common site of infection associated with Escherichia coli?

    <p>Respiratory tract (D)</p> Signup and view all the answers

    What is a key characteristic of Enterobacterales with respect to glucose metabolism?

    <p>They ferment glucose, producing acid, with or without gas (C)</p> Signup and view all the answers

    Based on the provided information, which bacterial species is LEAST likely to be associated with causing meningitis?

    <p>Salmonella enterica (C)</p> Signup and view all the answers

    Which enzyme activity is characteristic of Enterobacterales?

    <p>Catalase positive, oxidase negative (A)</p> Signup and view all the answers

    What is the role of the bacteria Escherichia coli within the human body?

    <p>Both a commensal organism and opportunistic pathogen (C)</p> Signup and view all the answers

    What is a primary reason some infections caused by Enterobacterales may not require antibiotic therapy?

    <p>Infections can resolve without treatment in immunocompetent hosts. (D)</p> Signup and view all the answers

    Which of the following methods is highlighted for monitoring food-borne illnesses in Canada?

    <p>PulseNet Canada (A)</p> Signup and view all the answers

    Which preventive measure is NOT mentioned as part of enteric infection prevention?

    <p>Routine antibiotic treatment (B)</p> Signup and view all the answers

    What is a significant concern regarding antibiotic resistance among Enterobacterales?

    <p>Emergence of Extended-spectrum β-lactamases (ESBL) and Carbapenem-resistant Enterobacteriaceae (CRE). (B)</p> Signup and view all the answers

    Which of the following is identified as a culture method for diagnosing infections?

    <p>Blood agar and MacConkey media. (B)</p> Signup and view all the answers

    What is the primary mechanism of illness for Enterotoxigenic E. coli (ETEC)?

    <p>Water secretion (D)</p> Signup and view all the answers

    Which serotype of Shiga toxin-producing E. coli (STEC) is most commonly associated with human disease?

    <p>O157:H7 (A)</p> Signup and view all the answers

    What severe complication can occur in 10-15% of children under 10 years old with STEC infections?

    <p>Hemolytic uremic syndrome (HUS) (B)</p> Signup and view all the answers

    What method has shown to potentially increase the risk of HUS when administered to STEC infection patients?

    <p>Antibiotics (D)</p> Signup and view all the answers

    Which type of E. coli is associated primarily with bloody diarrhea and cell invasion?

    <p>Enteroinvasive E. coli (EIEC) (C)</p> Signup and view all the answers

    Which of the following food items is less likely to be a source of STEC infections?

    <p>Cooked ground beef (B)</p> Signup and view all the answers

    What is the main clinical presentation of infection caused by Enteropathogenic E. coli (EPEC)?

    <p>Infant diarrhea (D)</p> Signup and view all the answers

    What is the main pathogenic mechanism utilized by Enteroaggregative E. coli (EAEC)?

    <p>Bacterial adherence (C)</p> Signup and view all the answers

    What is the primary reason antibiotics are not recommended for suspected STEC infections?

    <p>They may interfere with diagnostic testing. (A), Antibiotics can cause an increase in toxin release. (B)</p> Signup and view all the answers

    Which of the following is a characteristic of uropathogen strains of E. coli (UPEC)?

    <p>They can produce adhesins to bind to urinary tract cells. (B)</p> Signup and view all the answers

    Which species of Salmonella accounts for nearly all human infections?

    <p>Salmonella enterica (C)</p> Signup and view all the answers

    From which source do most nontyphoidal human salmonellosis infections originate?

    <p>Animal excreta through fecal-oral spread (A)</p> Signup and view all the answers

    What enzyme is produced by S. dysenteriae strains that can lead to renal failure?

    <p>Shiga toxin (A)</p> Signup and view all the answers

    What is the predominant mode of transmission for Shigella species?

    <p>Fecal-oral route, primarily via contaminated hands (A)</p> Signup and view all the answers

    Which of the following statements about Salmonella Typhi is accurate?

    <p>It is the only known Salmonella reservoir in humans. (A)</p> Signup and view all the answers

    What type of infections are commonly associated with Shigella species?

    <p>Gastrointestinal infections (D)</p> Signup and view all the answers

    What is a common clinical manifestation of Y.pestis infection?

    <p>Bubonic plague (A)</p> Signup and view all the answers

    Which of the following is NOT a pathogen of the genus Yersinia?

    <p>K.pneumoniae (A)</p> Signup and view all the answers

    What symptom is commonly associated with shigellosis?

    <p>Bloody stools (B)</p> Signup and view all the answers

    What is the typical incubation period for Y.enterocolitica infection?

    <p>4 to 6 days (A)</p> Signup and view all the answers

    What type of infection is K.granulomatis associated with?

    <p>Granuloma inguinale (D)</p> Signup and view all the answers

    Which of the following organisms can grow at 4° C?

    <p>Y.enterocolitica (B)</p> Signup and view all the answers

    What common laboratory method is used for the timely diagnosis of STEC?

    <p>Sorbitol MacConkey culture (A)</p> Signup and view all the answers

    What is a potential complication associated with Y.enterocolitica infection in adults?

    <p>Endotoxic shock (D)</p> Signup and view all the answers

    Flashcards

    Enterobacterales

    A group of bacteria that are rod-shaped (bacilli) and do not retain the stain used in the Gram staining technique, hence they are Gram-negative.

    Coccobacilli

    Enterobacterales are bacteria that can be both rod-shaped (bacilli) and round-shaped (cocci), depending on the species.

    Culturing Enterobacterales

    Enterobacterales are a diverse group that can be identified using specialized tests like MacConkey Agar, XLD Agar, Salmonella-Shigella (SS), and Hektoen Enteric Agar.

    Infections caused by Enterobacterales

    Enterobacterales are commonly found in the intestines of humans and animals, and they can cause infections like pneumonia and urinary tract infections.

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    STEC Infections

    A prominent example of the Enterobacterales family, STEC (Shiga toxin-producing Escherichia coli) can lead to severe intestinal illness, like diarrhea, abdominal cramps, and even kidney failure.

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    Opportunistic pathogen

    A type of bacteria that can cause a variety of infections, including urinary tract infections, pneumonia, and sepsis.

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    Escherichia coli (E. coli)

    A member of the Enterobacterales family that typically lives in the intestines of humans and animals, but can cause infections like urinary tract infections, pneumonia, and gastroenteritis.

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    Gastroenteritis

    An infection of the digestive system that can cause diarrhea, vomiting, abdominal cramps, and fever.

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    Shiga toxin-producing Escherichia coli (STEC)

    A strain of E. coli that produces toxins that can cause severe diarrhea and complications like kidney failure.

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    Meningitis

    An inflammation of the membranes surrounding the brain and spinal cord, which can be caused by various bacteria, including E. coli.

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    Hospital-acquired infection (HAI)

    A type of infection that occurs in a hospital setting, often related to medical procedures or weakened immune systems.

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    Pneumonia

    An infection that affects the lungs, often caused by bacteria like E. coli.

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    Shiga toxin-producing E.coli (STEC)

    A type of Escherichia coli that produces Shiga toxin, causing serious intestinal illness.

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    O157:H7

    The most common serotype of STEC associated with human disease, often linked to contaminated food.

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    Hemolytic Uremic Syndrome (HUS)

    A severe complication of STEC infection characterized by kidney failure, low platelet count, and red blood cell destruction.

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    Contaminated Food

    A common source of STEC infection, often found in undercooked meat and unpasteurized dairy products.

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    Shiga toxin (Stx)

    The toxin produced by STEC that causes damage to the intestinal lining and can lead to HUS.

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    Food-borne and water-borne transmission

    The way STEC is transmitted, commonly through contaminated food or water.

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    Hemorrhagic colitis

    A type of STEC infection that affects the large intestine, causing bloody diarrhea and severe abdominal pain.

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    Antibiotics and STEC infection

    Administering antibiotics to STEC infected patients might increase their risk of developing HUS.

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    What is STEC?

    A type of E. coli that produces Shiga toxin, which causes severe illness like bloody diarrhea, abdominal cramps, and kidney failure.

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    Why shouldn't antibiotics be given to patients with suspected STEC infection?

    Antibiotics are not usually prescribed for patients suspected of having STEC infections until testing confirms the diagnosis.

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    What is a UTI caused by E. coli?

    A type of E. coli infection that affects the urinary tract. It starts in the colon, travels to the urethra, bladder, and potentially kidneys or prostate.

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    How do E. coli strains cause UTIs?

    Bacteria that cause UTIs can attach to the bladder and upper urinary tract (reducing their elimination), and release toxins that damage cells (causing inflammation).

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    What is neonatal meningitis caused by E. coli?

    A serious E. coli infection affecting newborns. About 75% of the strains have a specific K1 capsular antigen.

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    How are humans infected with Salmonella?

    Salmonella species are primary pathogens for many animals, and humans get infected through contaminated food, water, or milk.

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    What are the main species of Salmonella?

    The genus Salmonella includes two species: Salmonella enterica and Salmonella bongori, with Salmonella enterica being responsible for most human infections.

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    What are the different types of Salmonella infections?

    Salmonella infections can present as gastroenteritis, septicemia, typhoid fever, chronic carriage, and localized infections like osteomyelitis, meningitis, brain abscess, and endocarditis.

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    Culture on MacConkey Agar

    A culture-based method for identifying Enterobacterales using selective media, allowing only certain bacteria to grow.

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    Culture-independent diagnostic methods for Enterobacterales

    Laboratory methods used to identify Enterobacterales without having to grow them in a lab. These methods can quickly and accurately detect the bacteria.

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    Antibiotic resistance in Enterobacterales

    The ability of Enterobacterales to resist the effects of antibiotics, making infections harder to treat.

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    Shigellosis

    A bacterial infection characterized by abdominal cramps, diarrhea, fever, and bloody stools.

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    Yersinia (Y. enterocolitica and Y. pseudotuberculosis)

    A group of bacteria that cause gastroenteritis, especially in children. They can mimic appendicitis due to enlarged mesenteric lymph nodes.

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    Yersinia pestis (Y. pestis)

    The causative agent of bubonic and pneumonic plague, spread by infected fleas.

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    Klebsiella pneumoniae

    A type of pneumonia commonly associated with hospital settings and characterized by a thick, mucoid capsule.

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    Granuloma inguinale (donovanosis)

    A sexually transmitted disease causing granulomatous lesions in the genital and inguinal regions.

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    Sorbitol MacConkey Agar (SMAC)

    A specialized culture medium used to identify STEC bacteria.

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    Enzyme-linked immunosorbent assay (EIA) for Shiga toxins

    Tests used to detect the presence of Shiga toxins produced by STEC.

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    Study Notes

    Enterobacterales Overview

    • Enterobacterales is a large and important order of Gram-negative bacilli bacteria.
    • Thousands of species exist within the order.
    • Predominantly found in soil, water, and vegetation, and in the gut flora of animals and humans.
    • Some are strict human pathogens.
    • Others are opportunistic pathogens.
    • Some bacteria can acquire pathogenic genes.

    Enterobacterales Characteristics

    • Gram-negative bacilli
    • Over 50 genera, hundreds of species
    • Aerobic and facultative anaerobic growth
    • Non-spore forming
    • Ferment glucose (acid ± gas)
    • Reduce nitrate (NO3) to nitrite (NO2)
    • Catalase-positive
    • Oxidase-negative

    Clinically Important Gram-Negative Bacteria

    • Enterobacterales (glucose fermenters)
    • Non-glucose fermenters
      • Pseudomonas
      • Acinetobacter (etc)
    • Gram-negative cocci
      • Haemophilus (H. influenzae)
      • Neisseria (N. meningitidis, N. gonorrhoeae)
    • Gram-negative coccobacilli

    Medically Important Species

    • Escherichia coli
    • Klebsiella pneumoniae, Klebsiella oxytoca
    • Proteus mirabilis
    • Salmonella enterica
    • Shigella sonnei, Shigella flexneri
    • Yersinia pestis, Yersinia enterocolitica
    • Citrobacter freundii, Citrobacter koseri
    • Enterobacter aerogenes, Enterobacter cloacae
    • Morganella morganii
    • Serratia marcescens

    Escherichia coli

    • Part of the human and animal gut flora
    • Opportunistic pathogen
    • Associated with various diseases, including
      • Gastroenteritis (watery diarrhea, vomiting, dehydration, low-grade fever; bloody diarrhea and abdominal cramps)
      • Hemorrhagic colitis (bloody diarrhea, HUS)
      • Extraintestinal infections
        • Urinary tract infections (UTIs)
        • Neonatal sepsis/meningitis
        • Bacteremia
        • Hospital-acquired infections (HAIs) (e.g., ventilator-associated pneumonia)

    Shiga Toxin-Producing E. coli (STEC)

    • Nomenclature:
      • Shiga toxin-producing E. coli (STEC)
      • Verocytotoxin-producing E. coli (VTEC)
      • Enterohemorrhagic E. coli (EHEC)
    • All STEC produce Shiga toxin 1 (Stx1) or 2 (Stx2).
    • Common serotype: O157:H7.
    • Non-O157 strains also cause severe gastroenteritis, HUS, and outbreaks.
    • Associated with foodborne illnesses (undercooked ground beef, unpasteurized milk, fruit juices, contaminated water, vegetables).
    • Antibiotics may increase the risk of HUS.

    Salmonella species

    • Genus Salmonella has two species: Salmonella enterica and S. bongari.
    • Salmonella enterica is the primary pathogen in human infections.
    • Over 2,500 serotypes (serovars) of Salmonella enterica.
    • E.g., Salmonella Typhi (Typhoid fever) is a serovar of Salmonella enterica.
    • Animals are the primary source of nontyphoidal salmonellosis via fecal-oral transmission.
    • Humans are the reservoir for Salmonella Typhi.
    • Clinical types
      • Gastroenteritis
      • Septicemia
      • Typhoid fever
      • Chronic carriage
      • Focal infections (e.g., osteomyelitis, meningitis, brain abscess, endocarditis)

    K. pneumoniae and Klebsiella oxytoca

    • Commonly cause Community- or hospital-acquired primary lobar pneumonia.
    • Have capsules, leading to mucoid colonies and enhanced virulence.
    • Also involved in wound infections, UTIs, and sepsis.

    Shigella species

    • Four species: S. dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei.
    • These species are actually biogroups within E. coli
    • Shiga toxins mediate damage to glomerular endothelial cells, potentially leading to HUS.
    • Humans are the only known reservoir.
    • Transmitted via fecal-oral route.
    • Common in children under age 10 or male homosexual adults.
    • Characterized by abdominal cramps, diarrhea, fever, and bloody stools.

    Yersinia species

    • Three human pathogens: Y. pestis, Y. enterocolitica, and Y. pseudotuberculosis.
    • Y. pestis causes plague (endemic and pandemics).
    • Spread by infected fleas.
    • Two clinical manifestations: bubonic plague and pneumonic plague.
    • Y. enterocolitica and Y. pseudotuberculosis cause gastroenteritis.
    • Often linked to contaminated food or water.

    Diagnosis of Enterobacteriaceae

    • Specimens: stool, blood, urine, bone marrow for typhoid fever.
    • Culture: blood agar, MacConkey, other selective media
    • Culture-independent methods

    Treatment of Enterobacteriaceae

    • Some infections do not require antibiotics (e.g., STEC, Salmonella gastroenteritis in immunocompetent host).
    • Antibiotic resistance is increasing in Enterobacteriaceae (e.g., ESBL, CRE).

    Prevention and Control of Enterobacteriaceae

    • Education: safe food handling, appropriate infection control procedures.
    • Vaccine (e.g., Salmonella).
    • Water treatment.
    • Food safety.

    Surveillance Programs for Enterobacteriaceae

    • Nationally notifiable in all Canadian provinces and territories.
    • FoodNet Canada, Canadian Enteric Surveillance Program (NESP), Canadian Notifiable Disease Surveillance System, PulseNet Canada.
    • Pathogen Laboratory Surveillance Programs for outbreak detection & resolution.

    Diagnostic Tools

    • Culture Sorbitol MacConkey agar (SMAC) or CHROMagar
    • Enzyme-linked immunosorbent assay (ELISA) to detect Shiga toxins
    • Molecular assays (PCR) to detect stx genes.

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    Enterobacterales - Jan 9 PDF

    Description

    Test your knowledge on the Gram staining characteristics, common laboratory diagnosis methods, and significant challenges associated with Enterobacterales infections. This quiz covers important aspects of Enterobacterales, including pathogenicity and glucose metabolism. Gain a deeper understanding of this critical group of bacteria.

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