Enterobacteriaceae Overview and Classification
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Enterobacteriaceae Overview and Classification

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What is the primary characteristic of Enterobacterales?

  • They are anaerobic bacteria.
  • They are gram-negative bacilli. (correct)
  • They are spore-forming bacteria.
  • They are gram-positive cocci.

    • Which of the following infections is commonly associated with Enterobacterales?

  • Respiratory tract infections (correct)
  • Skin infections
  • Intravenous line infections
  • Viral infections

    • Which biomolecule's resistance is noted in Enterobacterales?

  • Beta-lactams (correct)
  • Nucleic acids
  • Carbohydrates
  • Lipids

    • What does the term 'enteric' imply about the habitat of Enterobacterales?

    <p>They are found in the intestines.</p> Signup and view all the answers

    What is a common mechanism of drug resistance found in Enterobacterales?

    <p>Extended-spectrum beta-lactamases</p> Signup and view all the answers

    Which of the following is NOT considered a clinically important organism of Enterobacterales?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What laboratory feature is commonly used to identify Enterobacterales?

    <p>Gram stain appearance</p> Signup and view all the answers

    Which of the following species is an example of Pseudomonas?

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

    Which group of pathogens includes species that are not considered normal flora?

    <p>Citrobacter spp.</p> Signup and view all the answers

    What characteristic is common among most members of the Enterobacterales family?

    <p>They are motile with flagellae.</p> Signup and view all the answers

    What is a significant consequence of Lipopolysaccharide (LPS) in the pathogenesis of Gram-negative bacteria?

    <p>It induces an immune response via endotoxin release.</p> Signup and view all the answers

    Which of the following is a potential effect of endotoxin release due to Lipopolysaccharide in the body?

    <p>Hypotension.</p> Signup and view all the answers

    Which virulence factor aids bacteria in binding to host cells?

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

    Which Enterobacterales species is specifically known for producing toxins like haemolysins?

    <p>Escherichia coli</p> Signup and view all the answers

    What type of metabolic capacity do most Enterobacterales exhibit in relation to carbohydrates?

    <p>They ferment glucose and other carbohydrates.</p> Signup and view all the answers

    What feature of the Gram-negative cell wall contributes to its pathogenicity?

    <p>The presence of O-side chains.</p> Signup and view all the answers

    What is the most appropriate empiric treatment for a urinary tract infection caused by E.coli that is susceptible to nitrofurantoin?

    <p>NITROFURANTOIN PO for 3 days</p> Signup and view all the answers

    In the case of a 36-year-old female presenting with vomiting and left flank pain, which condition is most likely related to the symptoms described?

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

    Which microbiology investigation is most important initially for the patient with suspected pyelonephritis?

    <p>MSU &amp; Blood cultures</p> Signup and view all the answers

    For the infant suspected of meningitis, which of the following pathogens is most likely to be the causative agent?

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

    What is the likely causative pathogen for a 2-day-old baby presenting with tachypnoea and irritability?

    <p>Escherichia coli</p> Signup and view all the answers

    Which treatment regimen is appropriate for an infant with suspected meningitis from the cases described?

    <p>IV AMOXICILLIN / CEFOTAXIME / GENTAMICIN</p> Signup and view all the answers

    What is the significance of E.coli being resistant to trimethoprim in the second case scenario?

    <p>It requires a change in antibiotic therapy.</p> Signup and view all the answers

    Why is nitrofurantoin not suitable in the second case for the treatment of pyelonephritis?

    <p>It is not effective against resistant E.coli.</p> Signup and view all the answers

    Which virulence factor of Enterobacterales is primarily responsible for helping bacteria avoid phagocytosis?

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

    What is the role of Lipopolysaccharide (LPS) in the pathogenicity of Enterobacterales?

    <p>Induces host immune response via endotoxin release</p> Signup and view all the answers

    In the context of Enterobacterales, what does the term 'facultative anaerobes' indicate?

    <p>They can survive in both aerobic and anaerobic conditions.</p> Signup and view all the answers

    What is a significant consequence of the endotoxin release from Lipopolysaccharide during an infection?

    <p>Activation of complement and cytokine release</p> Signup and view all the answers

    Which characteristic of the Enterobacterales' cell wall significantly contributes to its overall structural integrity?

    <p>Presence of an outer membrane</p> Signup and view all the answers

    Which group of bacteria within Enterobacterales is primarily considered important for enteric infections?

    <p>Salmonella spp.</p> Signup and view all the answers

    What does the term 'motile with flagellae' imply about Enterobacterales?

    <p>They exhibit the ability to move.</p> Signup and view all the answers

    What type of response does the activation of cytokines due to endotoxin release typically result in?

    <p>Systemic inflammatory response</p> Signup and view all the answers

    Which of the following statements accurately describes the Enterobacterales family?

    <p>They are rod-shaped and part of the intestinal flora.</p> Signup and view all the answers

    What plays a significant role in the pathogenesis of infections caused by Pseudomonas species?

    <p>Ability to form biofilms on surfaces.</p> Signup and view all the answers

    Which approach is most effective in preventing the spread of infections caused by clinically important Enterobacterales?

    <p>Strict adherence to sanitation and hygiene measures.</p> Signup and view all the answers

    Which characteristic distinguishes Enterobacterales in a laboratory diagnosis?

    <p>They display a Gram stain appearance as pink bacilli.</p> Signup and view all the answers

    In terms of clinical significance, which complication is often associated with infections caused by Enterobacterales?

    <p>Intra-abdominal abscess formation.</p> Signup and view all the answers

    Which of the following best explains the increasing antibiotic resistance observed in Enterobacterales?

    <p>Production of extended-spectrum beta-lactamases (ESBLs).</p> Signup and view all the answers

    Which key factor is crucial for effectively treating infections caused by clinically important Enterobacterales?

    <p>Assessing the antimicrobial susceptibility of the pathogens.</p> Signup and view all the answers

    What is the primary function of coliforms among the Enterobacterales?

    <p>They serve as indicators of fecal contamination.</p> Signup and view all the answers

    What laboratory result is significant in diagnosing the second case scenario?

    <p>Urine culture shows Escherichia coli resistant to trimethoprim</p> Signup and view all the answers

    Which empiric treatment is recommended for a patient with pyelonephritis and E.coli susceptible to cefuroxime?

    <p>Intravenous cefuroxime +/- gentamicin</p> Signup and view all the answers

    Which symptom would most likely indicate a progression of infection in the first case scenario?

    <p>Decreased urine output</p> Signup and view all the answers

    What is the most critical initial microbiology investigation for a patient with suspected pyelonephritis in the second case scenario?

    <p>MSU &amp; blood cultures</p> Signup and view all the answers

    In the third case scenario, which pathogens are the most common causative organisms for meningitis in a 2-day-old baby?

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

    What is a key concern regarding the management of the patient in the second case scenario?

    <p>Potential for renal scarring if untreated</p> Signup and view all the answers

    In the context of antibiotic susceptibility, what would the resistance of E.coli to trimethoprim indicate for treatment choices?

    <p>Need to choose alternative antibiotics for effective therapy</p> Signup and view all the answers

    Which aspect of the CSF laboratory report is integral for diagnosing meningitis in the third case scenario?

    <p>Presence of bacteria on Gram stain</p> Signup and view all the answers

    Study Notes

    Enterobacteriaceae

    • A family of gram-negative rod-shaped bacteria
    • Commonly found in the intestines (GIT)
    • Often responsible for intra-abdominal, respiratory tract, and bloodstream infections
    • A common cause of antibiotic resistance
      • Beta-lactamase production
        • Includes extended-spectrum beta-lactamases (ESBLs)

    Enterobacteriaceae: Classification

    • Escherichia coli & Klebsiella spp. are important pathogens.
    • Proteus spp., Serratia​ spp., Enterobacter spp., and Citrobacter spp. are less important pathogens.
    • Salmonella spp., Shigella spp. and Yersinia spp. are covered in future lectures.
    • Toxin-producing E.coli is important and is covered in Enteric infections.

    Enterobacteriaceae: Microbiology

    • Most are motile with flagellae.
    • Facultative anaerobes (can survive with or without oxygen).
    • Ferment glucose and other carbohydrates.
    • Can be lactose fermenters or non-lactose fermenters.

    Enterobacteriaceae: Structure

    • The cell wall contains lipopolysaccharide (LPS) O-antigen.
    • The capsule contains K-antigen.
    • Fimbriae and flagella are present (H-antigen).
    • LPS is composed of O-side-chains and lipid A.

    Enterobacteriaceae: Pathogenesis

    • Enterobacteriaceae can infect via contact, environment, and AMR.
    • They use adhesins and pili to attach to cells.
    • LPS and toxins damage host cells.
    • Capsular structures help evade the immune system.
    • Enterobacteriaceae can spread further after gaining access to the host.

    Enterobacteriaceae: Virulence Factors

    • Adhesins: Aid in binding to host cells, e.g., fimbriae.
    • Capsules: Help avoid phagocytosis but are poor immunogens.
    • Lipopolysaccharide: A potent inducer of the host immune response via endotoxin release (lipid A).
      • Endotoxin activates complement, cytokines, and WBCs.
      • Can lead to decreased platelet count, disseminated intravascular coagulation (DIC), fever, hypotension, and death.
    • Toxins: e.g., haemolysins of E.coli.
    • Antimicrobial resistance: e.g., via plasmid exchange.

    Case Scenario 1: Urinary Tract Infection (UTI)

    • Presenting symptoms: Urinary frequency, dysuria, otherwise systemically well.
    • Diagnosis: Cystitis (most likely).
    • Empiric treatment: Nitrofurantoin, Trimethoprim, or Fosfomycin.
    • Laboratory findings: Urine white cell count >100/µl.
    • Outcome: E.coli isolated from urine, susceptible to Nitrofurantoin and Trimethoprim. Symptoms resolved with a 3-day course of nitrofurantoin.

    Case Scenario 2: Pyelonephritis

    • Presenting symptoms: Vomiting, left flank pain, temperature of 38.8 °C.
    • Diagnosis: Pyelonephritis (most likely).
    • Important microbiology investigations: MSU and blood cultures.
    • Empiric treatment: IV Cefuroxime +/- Gentamicin.
    • Laboratory findings: Urine white cell count >100/µl.
    • Outcome: Escherichia coli isolated from urine, resistant to Trimethoprim/Co-amoxiclav but susceptible to Nitrofurantoin, Cefuroxime, and Gentamicin.

    Case Scenario 3: Neonatal Meningitis

    • Presenting symptoms: Tachypnoea, feeding poorly, irritable when handled.
    • Diagnosis: Meningitis suspected.
    • Most likely causative pathogen: E.coli.
    • Empiric treatment: IV Cefotaxime/Amoxicillin/Gentamicin.
    • Laboratory findings: CSF white cell count 600/µl.

    Pseudomonas spp. & Related Genera

    • Pseudomonas spp. are covered in a separate lecture.

    Enterobacterales

    • A family of gram-negative bacilli (rod-shaped)
    • Found in the intestines
    • Common causes of intra-abdominal, respiratory tract & bloodstream infections
    • Increasing antibiotic resistance:
      • Beta-lactamase production including extended-spectrum beta-lactamases (ESBLs)

    Enterobacterales: Classification

    • Important organisms: Escherichia coli, Klebsiella spp., Proteus spp.
    • Less important pathogens (not normal flora): Serratia spp., Enterobacter spp., Citrobacter spp.
    • Important, covered in next lecture: Salmonella spp., Shigella spp., Yersinia spp., Toxin-producing E.coli

    Enterobacterales: Microbiology

    • Most are motile with flagellae
    • Facultative anaerobes
    • Ferment glucose and other carbohydrates
    • May be lactose fermenters or non-lactose fermenters

    Enterobacterales: Structure

    • Cell wall: Contains lipopolysaccharide O-antigen
    • Capsule: Contains K-antigen
    • Fimbriae: Small hair-like structures
    • Flagella: Tail-like structures (H-antigen)

    Enterobacterales: Pathogenesis

    • Gets in: Portal of entry is often contact, environment, or AMR
    • Gets out & spreads further: Adhesins, pili, LPS, toxins
    • Attaches to cells: Adhesins, pili
    • Causes damage to host cells: LPS, toxins
    • Defeats/evades the immune system: Capsule

    Virulence Factors

    • Adhesins: Help bacteria bind to host cells e.g. fimbriae
    • Capsules: Help bacteria avoid phagocytosis, but are poor immunogens
    • Lipopolysaccharide (LPS): Potent inducer of the host immune response via endotoxins release (lipid A)
      • Endotoxin: Activates complement, cytokines & WBCs, decreases in platelets, results in DIC (Disseminated Intravascular Coagulation), fever, hypotension, and death
    • Toxins: e.g. haemolysins of E.coli
    • Antimicrobial resistance: Through plasmid exchange

    Case Scenario 1

    • Presenting symptoms: Urinary frequency & dysuria
    • Most likely diagnosis: Cystitis
    • Empiric treatment: Nitrofurantoin PO for 3 days, Trimethoprim PO for 3 days, Fosfomycin single dose
    • Laboratory Report: Urine white cell count >100/µl, E.coli isolated from urine

    Case Scenario 2

    • Presenting symptoms: Vomiting, left flank pain, temperature of 38.8oC
    • Most likely diagnosis: Pyelonephritis
    • Most important microbiology investigations: MSU & Blood cultures
    • Empiric treatment: IV Cefuroxime +/- Gentamicin
    • Laboratory Report: Urine white cell count >100/µl, Escherichia coli isolated from urine

    Case Scenario 3

    • Presenting symptoms: Tachypnoea, feeding poorly, irritable when handled
    • Most likely cause: E.coli
    • Empiric treatment: IV Ceotaxime/Amoxicillin/Gentamicin
    • Laboratory Report: CSF white cell count 600/µl (normally 0-5/µl)

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    Description

    This quiz covers key concepts related to the Enterobacteriaceae family of bacteria, including their classification, microbiological characteristics, and significance in infections. It highlights important pathogens, their antibiotic resistance mechanisms, and unique features such as motility and fermentation abilities.

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