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Questions and Answers
What characteristic of Enterobacterales primarily aids in their motility?
What characteristic of Enterobacterales primarily aids in their motility?
Which component of the Enterobacterales cell wall is primarily responsible for its immune response induction?
Which component of the Enterobacterales cell wall is primarily responsible for its immune response induction?
What role do adhesins play in the pathogenesis of Enterobacterales?
What role do adhesins play in the pathogenesis of Enterobacterales?
Which of the following is a common trait of Enterobacterales?
Which of the following is a common trait of Enterobacterales?
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How does the capsule of Enterobacterales contribute to their virulence?
How does the capsule of Enterobacterales contribute to their virulence?
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Which of the following is NOT a known virulence factor of Enterobacterales?
Which of the following is NOT a known virulence factor of Enterobacterales?
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In the case scenario, which diagnosis is most likely given the symptoms of urinary frequency and dysuria?
In the case scenario, which diagnosis is most likely given the symptoms of urinary frequency and dysuria?
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What is the consequence of lipopolysaccharide-induced endotoxin release in the host?
What is the consequence of lipopolysaccharide-induced endotoxin release in the host?
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Which of the following best describes the Enterobacterales family?
Which of the following best describes the Enterobacterales family?
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What is a significant characteristic of Pseudomonas species in clinical infections?
What is a significant characteristic of Pseudomonas species in clinical infections?
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Which of the following infections is most commonly associated with Enterobacterales?
Which of the following infections is most commonly associated with Enterobacterales?
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What role does extended-spectrum beta-lactamases (ESBLs) play in Enterobacterales?
What role does extended-spectrum beta-lactamases (ESBLs) play in Enterobacterales?
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Which of the following species is NOT classified under Enterobacterales?
Which of the following species is NOT classified under Enterobacterales?
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In terms of laboratory diagnosis, which feature is characteristic of Enterobacterales and Pseudomonas species?
In terms of laboratory diagnosis, which feature is characteristic of Enterobacterales and Pseudomonas species?
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What is a common clinical feature of infections caused by Enterobacterales?
What is a common clinical feature of infections caused by Enterobacterales?
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Which of the following measures is NOT recommended for preventing infections caused by Enterobacterales?
Which of the following measures is NOT recommended for preventing infections caused by Enterobacterales?
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What is the recommended empiric treatment for uncomplicated cystitis in the first case scenario?
What is the recommended empiric treatment for uncomplicated cystitis in the first case scenario?
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In case scenario 2, which of the following is the most likely source of symptoms in the 36-year-old female?
In case scenario 2, which of the following is the most likely source of symptoms in the 36-year-old female?
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Which microbiology investigation should be prioritized initially for the patient in case scenario 2?
Which microbiology investigation should be prioritized initially for the patient in case scenario 2?
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In case scenario 3, which pathogen is the most likely cause of meningitis in a 2-day-old baby?
In case scenario 3, which pathogen is the most likely cause of meningitis in a 2-day-old baby?
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Why is nitrofurantoin not suitable for the patient in case scenario 2?
Why is nitrofurantoin not suitable for the patient in case scenario 2?
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What is the common treatment regimen for meningitis suspected in a newborn as per the guideline?
What is the common treatment regimen for meningitis suspected in a newborn as per the guideline?
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What microbiological finding was reported from the CSF sample in case scenario 3?
What microbiological finding was reported from the CSF sample in case scenario 3?
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Which empiric treatment is appropriate for a case of pyelonephritis as per the guidelines?
Which empiric treatment is appropriate for a case of pyelonephritis as per the guidelines?
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Study Notes
Enterobacterales
- A family of Gram-negative bacilli (rod-shaped)
- Commonly found in the intestines (GIT) Leading cause of intra-abdominal, respiratory tract & bloodstream infections
- increasing antibiotic resistance
- Beta-lactamase production including extended-spectrum beta-lactamases (ESBLs)
Enterobacterales: Classification
- Normal intestinal flora
- Escherichia coli
- Klebsiella spp.
- Proteus spp.
- Others
- Serratia spp.
- Enterobacter spp.
- Citrobacter spp.
- 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
- Capsule (contains K-antigen)
- Cell wall (contains lipopolysaccharide O-antigen)
- Fimbriae
- Flagella (H-antigen)
Enterobacterales: Structure (The Gram-Negative Cell Wall)
- Composed of:
- O-side-chains
- Lipid A
Pathogenesis
- Contact, environment, AMR
- Adhesins, pili
- LPS, toxins
- Capsule
- Defeats/evades the immune system
Virulence Factors
- Adhesins - aid in binding to host cells, e.g.fimbriae
- Capsules - help avoid phagocytosis but poor immunogens
- Lipopolysaccharide - potent inducer of host immune response via endotoxin release (lipid A)
- Endotoxin activation of complement, cytokines, WBCs decrease in platelets DIC fever, hypotension, death
- Toxins - e.g. haemolysins of E.coli
- Antimicrobial resistance - e.g. via plasmid exchange
Case Scenario 1
- A 22-year-old female presents with urinary frequency & dysuria
- Empiric treatment:
- NITROFURANTOIN PO for 3 days
- TRIMETHOPRIM PO for 3 days
- FOSFOMYCIN single dose
- Laboratory Report:
- Day 1: Urine white cell count >100/ µl
- Day 2: E.coli isolated from urine; susceptibilities pending
- Day 3: E.coli – SUSCEPTIBLE to NITROFURANTOIN / TRIMETHOPRIM
Case Scenario 2
- A 36-year-old female presents with vomiting, left flank pain and a temperature of 38.8oC.
- Most likely source: Pyelonephritis
- Most important microbiology investigations initially: MSU & Blood cultures
- Empiric Treatment:
- IV CEFUROXIME +/- GENTAMICIN
- Laboratory Report:
- Day 1: Urine white cell count >100/ µl
- Day 2: Escherichia coli isolated from urine; susceptibilities pending
- Day 3: Escherichia coli - RESISTANT to TRIMETHOPRIM / CO-AMOXICLAV – SUSCEPTIBLE to NITROFURANTOIN / CEFUROXIME / GENTAMICIN
Case Scenario 3
- A 2-day-old baby presents with tachypnoea, feeding poorly and irritable when handled.
- Meningitis is suspected
- Most likely causative pathogen: E.coli
- Empiric Treatment:
- IV CEFOTAXIME/AMOXICILLIN/GENTAMICIN
- Laboratory Report (CSF Microscopy, Culture and Susceptibilities)
- Day 1: CSF white cell count 600/µl (normally <5/µl)
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Description
Explore the fascinating world of Enterobacterales, a family of Gram-negative bacilli commonly found in the intestines. This quiz covers their classification, structure, and increasing antibiotic resistance, along with the importance of these bacteria in various infections. Test your knowledge on the characteristics and roles of this critical group of microorganisms.
