Enterobacterales Quiz
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What is a key microscopic feature of Enterobacterales?

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

    • Which of the following is NOT typically considered a solid culture medium for Enterobacterales?

  • Mannitol Salt Agar (correct)
  • Xylose-lysine-deoxycholate (XLD) agar
  • MacConkey agar
  • Blood agar

    • What is the primary focus regarding Enterobacterales when conducting food-borne illness surveillance?

  • Tracing sources of infection during outbreaks (correct)
  • Analyzing antibiotic resistance of all bacteria
  • Identifying specific species of Enterobacterales
  • Studying the environmental impact of bacterial growth

    • What is a critical aspect of STEC infection mentioned in the context?

    <p>The importance of laboratory diagnosis methods</p> Signup and view all the answers

    Which of these is a major concern regarding Enterobacterales, as mentioned in the learning objectives?

    <p>Antimicrobial resistance and its effects</p> Signup and view all the answers

    Which of the following E. coli strains is MOST associated with bloody diarrhea and hemolytic uremic syndrome (HUS)?

    <p>Shiga toxin-producing <em>E. coli</em> (STEC)</p> Signup and view all the answers

    What is the primary mechanism by which Enteroaggregative E. coli (EAEC) causes diarrhea?

    <p>Plasmid-mediated adherence of bacteria</p> Signup and view all the answers

    Which E. coli strain is MOST commonly associated with infant diarrhea specifically in developing countries?

    <p>Enteropathogenic <em>E. coli</em> (EPEC)</p> Signup and view all the answers

    What are the characteristic symptoms of hemolytic uremic syndrome (HUS), a severe complication of STEC infection?

    <p>Acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia</p> Signup and view all the answers

    Which of the following is NOT a recognized route for transmission of STEC infection?

    <p>Airborne transmission</p> Signup and view all the answers

    Why are antibiotics generally NOT recommended for patients with suspected STEC infections?

    <p>They can sometimes increase the risk of developing HUS</p> Signup and view all the answers

    Which of the following is a characteristic of Enterobacterales?

    <p>Ferments glucose</p> Signup and view all the answers

    Which of the following serotypes of STEC is most commonly associated with human disease?

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

    Which of these Enterobacterales is considered a human pathogen?

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

    What is the primary mechanism by which Enteroinvasive E. coli (EIEC) causes diarrhea?

    <p>Plasmid-mediated cell invasion</p> Signup and view all the answers

    Which of the following is NOT a medically important species of Enterobacterales?

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

    What type of infections is Escherichia coli NOT typically associated with?

    <p>Fungal lung infection</p> Signup and view all the answers

    What is the primary mechanism of pathogenesis for Enterotoxigenic E. coli (ETEC) related diarrhea?

    <p>Plasmid-mediated water secretion</p> Signup and view all the answers

    What is a common location where Enterobacterales are found?

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

    Which characteristic is common to all Enterobacterales?

    <p>Catalase positive</p> Signup and view all the answers

    Which E. coli serotype is associated with bloody diarrhea and hemolytic uremic syndrome?

    <p>O157</p> Signup and view all the answers

    Which of the following best describes the primary method of transmission for Yersinia pestis?

    <p>Transmission through infected flea bites.</p> Signup and view all the answers

    What is a key characteristic of Klebsiella species that contributes to their virulence?

    <p>Possession of a prominent capsule.</p> Signup and view all the answers

    Which of the following clinical presentations is most closely associated with Yersinia enterocolitica and Yersinia pseudotuberculosis?

    <p>Gastroenteritis, potentially mimicking appendicitis.</p> Signup and view all the answers

    What is the significance of Sorbitol MacConkey (SMAC) agar in the context of STEC detection?

    <p>It's used for culturing and differentiating Shiga toxin-producing E.coli.</p> Signup and view all the answers

    Which of the following is a unique characteristic of Yersinia species that contributes to transfusion-related infections?

    <p>Their ability to grow at $4^{\circ}C$.</p> Signup and view all the answers

    What is the primary purpose of using PCR to detect stx genes in the context of enteric infections?

    <p>To identify the presence of specific virulence factors associated with STEC.</p> Signup and view all the answers

    Which of the following is NOT typically a specimen source for diagnosing enteric infections?

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

    What is the primary reason why some Salmonella gastroenteritis cases do not require antibiotic treatment?

    <p>The infection is mild and usually resolves on its own, especially in immunocompetent individuals.</p> Signup and view all the answers

    What is the main purpose of surveillance programs like FoodNet Canada and NESP?

    <p>To monitor and track cases of foodborne illnesses and identify trends at the population level.</p> Signup and view all the answers

    What recent advancement is used in pathogen laboratory surveillance to improve outbreak investigation?

    <p>Whole genome sequencing (WGS)</p> Signup and view all the answers

    Which bacterial structure primarily enables Uropathogenic E. coli (UPEC) to adhere to the cells lining the urinary tract?

    <p>P pili</p> Signup and view all the answers

    What is the primary source of nontyphoidal Salmonella infections in humans?

    <p>Ingestion of contaminated food, water, or milk from animal sources</p> Signup and view all the answers

    Which E. coli virulence factor is most associated with the development of neonatal meningitis?

    <p>K1 capsular antigen</p> Signup and view all the answers

    Which species of Shigella produces Shiga toxin, potentially leading to hemolytic uremic syndrome (HUS)?

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

    What is the primary mode of transmission of Shigella infections?

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

    What is the condition that can originate from a UTI and lead to the spread of bacteria in the blood?

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

    Which of the following best describes the current taxonomic classification of the four Shigella species?

    <p>They are classified as biogroups within the species <em>E. coli</em>.</p> Signup and view all the answers

    Which of these is NOT a recognised clinical type of Salmonella infection?

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

    Study Notes

    Enterobacterales Overview

    • Enterobacterales are a wide taxonomic order of bacteria
    • Dr. Yang Yu MD PhD FRCPC provided the original slide deck

    Agenda

    • Introduction and Overview
    • General Characteristics of Enterobacterales
    • Medically Important Species
    • Diagnosis and Treatment
    • Prevention and Control

    Learning Objectives

    • Describe general characteristics of the order Enterobacterales, including biochemical testing, microscopic Gram staining and macroscopic appearances
    • Describe methods for detecting Enterobacterales in clinical specimens, comparing culture-based vs. culture-independent tests
    • List common solid culture media for Enterobacterales (blood, MacConkey, xylose-lysine-deoxycholate (XLD), Salmonella-Shigella (SS) and Hektoen enteric agar)
    • Describe the importance of STEC infection and available lab diagnosis methods
    • Describe Salmonella infection, including typhoid and non-typhoid, and typhoid prevention
    • Describe antimicrobial resistance features in Enterobacterales and its impact on treatment and infection prevention and control (IPAC)
    • Describe foodborne infection surveillance and outbreak investigation

    General Characteristics of Enterobacterales

    • Gram negative bacilli
    • More than 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
    • Gram-negative cocci
    • Gram-negative coccobacilli
    • Pseudomonas
    • Acinetobacter
    • Haemophilus
    • Neisseria (H. influenzae, N. meningitis, N. gonorrhoeae)

    Enterobacterales - Ubiquitous & Opportunistic Bacteria

    • Ubiquitous in soil, water, vegetation and gut flora across animals and humans
    • Some are strict human pathogens (e.g., Salmonella typhi, Yersinia pestis)
    • Some are opportunistic pathogens (e.g., Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis)

    Enterobacterales - Structure & Virulence Factors

    • Structural components of cells, including:
      • Flagella (H antigen)
      • Capsule (K or Vi antigen)
      • Lipopolysaccharide (LPS) or endotoxin
      • Common antigen
      • Outer membrane
      • Periplasmic space
      • Lipoprotein
      • Peptidoglycan
      • Inner membrane
      • Cytoplasm
      • O polysaccharide
      • Lipid A (endotoxin)
    • Common virulence factors include endotoxins, capsules, and secretion systems

    Traditional Bacterial Identification

    • Methods for identifying bacteria rely on biochemical properties (e.g., PRG acid, PR-L, PR-M, Methyl Red, VP, Indole, Ureases, Citrates, TSI, Gas, H₂S)

    Automated Bacterial Identification System

    • Automated testing systems exist to identify bacteria rapidly and help with diagnosis

    Medically Important Species - Specific examples

    • Escherichia coli (opportunistic)
    • Klebsiella pneumoniae (pneumonia)
    • Proteus mirabilis (infections)
    • Salmonella enterica
    • Shigella spp.
    • Yersinia pestis (plague)
    • Y. enterocolitica
    • Other species (e.g., Citrobacter freundii, Citrobacter koseri, Enterobacter aerogenes, Enterobacter cloacae, Morganella morganii, Serratia marcescens)

    Escherichia coli - Gastroenteritis

    • Common part of the human and animal gut flora
    • Associated with various diseases, including gastroenteritis
    • Some strains cause watery diarrhea, vomiting, and dehydration
    • Some serotypes are associated with more severe illnesses like hemorrhagic colitis, and hemolytic uremic syndrome (HUS), caused by strains such as E. coli O157:H7
    • Extraintestinal infections include urinary tract infections (UTIs) neonatal septicemia, meningitis, bacteremia, and HAI including ventilator-associated pneumonia

    Escherichia coli Associated with Gastroenteritis (Specific types)

    • Enterotoxigenic E. coli (ETEC)
    • Enteropathogenic E. coli (EPEC)
    • Enteroaggregative E. coli (EAEC)
    • Shiga toxin-producing E. coli (STEC)
    • Enteroinvasive E. coli (EIEC)

    Shiga Toxin-Producing E.coli (STEC)

    • Nomenclature: Shiga toxin-producing E. coli (STEC), Verocytotoxin-producing E. coli (VTEC), Enterohemorrhagic E. coli (EHEC)
    • All STEC strains produce Shiga toxin 1 (Stx1) and/or 2 (Stx2)

    Shiga toxin-producing E. coli (STEC) - Human Disease

    • O157:H7 is the most common serotype among human cases, with the 2000 Walkerton water contamination incident as a notable example
    • Non-O157 strains also cause HUS and foodborne outbreaks (e.g., 2011 E. coli 0104:H4, 2007 E. coli 0121)

    STEC Infection

    • Ranges from mild diarrhea to hemorrhagic colitis with severe complications like HUS
    • HUS is characterized by acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia
    • Occurs in children under 10
    • Foodborne outbreaks associated with undercooked meat, unpasteurized milk or juice and contaminated vegetables

    E. coli Associated with Extraintestinal Infections

    • Pathogens originate in the colon and may migrate to the kidney, bladder or prostate
    • Uropathogenic E. coli (UPEC) produce adhesins (P pili, AAF/I, AAF/III) helping them adhere to urinary tract cells
    • Leading to urinary tract infections (UTIs), neonatal meningitis (K1 antigen), septicemia, and other intraabdominal infections

    Salmonella Species

    • Genus Salmonella has two species—Salmonella enterica and S. bongari
    • Salmonella enterica accounts for almost all human infections
    • Common serovars include S. typhi, a cause of typhoid fever
    • Animals are the main reservoir for most non-typhoidal Salmonella

    Salmonella Species - Clinical Presentation

    • Clinical presentation includes gastroenteritis, septicemia and typhoid fever
    • Includes focal infections (osteomyelitis, meningitis, brain abscess, endocarditis)

    Typhoid Fever Pathogenesis

    • Bacteria are ingested
    • Bacteria multiply in small intestine, Peyer's patches
    • Septicemia through lymphatic and mesenteric nodes
    • Multiplication in macrophages of liver, spleen and bone marrow
    • Symptoms include fever, abdominal pain, and potentially complications like cholecystitis

    Shigella Species

    • Four species: S. dysenteriae, Shigella flexneri, Shigella boydii; and Shigella sonnei.
    • DNA analysis shows they are bio-groups in E. coli, not distinct species.
    • S. dysenteriae produces Shiga toxin, causing damage to glomerular endothelial cells, potentially leading to renal failure (HUS)
    • Human reservoir for Shigella

    Shigella Species - Transmission and Symptoms

    • Fecal-oral transmission through contaminated hands or food
    • Common in young children or male homosexual adults
    • Symptoms include abdominal cramps, diarrhea, fever, bloody stools

    Yersinia Species

    • Three human pathogens: Y. pestis, Y. enterocolitica, Y. pseudotuberculosis
    • Y. pestis is associated with the plague (endemic/pandemic)
    • Transmitted animal-to-human usually via infected fleas
    • Two clinical presentations: bubonic plague and pneumonic plague

    Yersinia enterocolitica and Y. pseudotuberculosis

    • Cause gastroenteritis, often with complications such as appendicitis or mimics
    • Ingestion of contaminated food or water
    • Symptoms include fever diarrhea and abdominal pain
    • May lead to other issues like septicemia, arthritis, intra-abdominal abscess, hepatitis, and or osteomyelitis

    Klebsiella Species

    • K. pneumoniae and Klebsiella oxytoca are common causes of community and hospital-acquired pneumonia, characterized by mucoid colonies due prominent capsules
    • Infections include wound and soft tissue infections along with UTIs and septicaemia
    • K. granulomatis is the agent of granuloma inguinale

    Diagnosis

    • Specimens include stool, blood, urine, and bone marrow
    • Culture media used include blood agar, MacConkey, and other selective media
    • Culture-independent methods exist for detection
    • Methods for STEC diagnosis include Sorbitol MacConkey (SMAC) or CHROMagar cultures, Enzyme-linked immunosorbent assays (EIAs), and polymerase chain reaction (PCR)
    • Identification of specific toxins or genes

    Treatment and Antimicrobial Susceptibility

    • Some STEC infections and Salmonella gastroenteritis cases in immunocompetent hosts may not need antibiotics
    • Antibiotic resistance is increasing among Enterobacterales (ESBL, CRE, AmpC).

    Prevention and Control of Enteric Infections

    • Education on food safety and preparation
    • Infection control procedures like handwashing, and proper disposal of contaminated material
    • Vaccines (Salmonella)
    • Water treatment and food safety protocols
    • Surveillance helps to detect and contain outbreaks

    Surveillance Programs

    • Canada uses various programs for monitoring foodborne illnesses, including FoodNet Canada, the National Enteric Surveillance Program, and PulseNet Canada

    Pathogen Laboratory Surveillance Programs

    • PulseNet uses molecular subtyping methods such as pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS) to track and analyze bacteria

    WGS process

    • WGS is a laboratory procedure that determines the precise order of a microorganism's DNA bases
    • Provides a highly detailed fingerprint to investigate links between individual cases, and helps to identify outbreaks much faster.

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    Related Documents

    Enterobacterales - Jan 9 PDF

    Description

    Test your knowledge on Enterobacterales and their implications in food-borne illnesses. This quiz covers key characteristics, strains, and mechanisms of diarrhea related to this important group of bacteria. Assess critical aspects like STEC infections and their symptoms.

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