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Questions and Answers
A patient presents with hemolytic anemia, thrombocytopenia, and kidney failure following a bout of bloody diarrhea. Which virulence factor of E. coli is most likely responsible for these symptoms?
A patient presents with hemolytic anemia, thrombocytopenia, and kidney failure following a bout of bloody diarrhea. Which virulence factor of E. coli is most likely responsible for these symptoms?
- Lipopolysaccharide (LPS), triggering a systemic inflammatory response leading to disseminated intravascular coagulation (DIC).
- Bundle-forming pili, disrupting the microvillus structure of intestinal cells and causing malabsorption.
- Shiga-like toxin, removing an adenine base from the 28S ribosomal RNA and inhibiting protein synthesis. (correct)
- Heat-stable enterotoxin, stimulating guanylate cyclase and leading to fluid loss.
A microbiology student is studying a bacterial isolate from a patient with a urinary tract infection (UTI). The isolate is Gram-negative, ferments lactose on MacConkey agar, and is oxidase-negative. Based on this information, which virulence factor is most likely contributing to the bacterium's ability to cause a UTI?
A microbiology student is studying a bacterial isolate from a patient with a urinary tract infection (UTI). The isolate is Gram-negative, ferments lactose on MacConkey agar, and is oxidase-negative. Based on this information, which virulence factor is most likely contributing to the bacterium's ability to cause a UTI?
- Secretion of heat-labile toxin causing increased cAMP.
- Aggregation and adherence to intestinal mucosa via enterotoxins.
- Production of Shiga-like toxin that inhibits protein synthesis.
- Expression of pili and fimbriae facilitating adherence to the urinary tract epithelium. (correct)
A researcher is investigating the mechanism of action of an E. coli toxin that causes watery diarrhea. The researcher discovers that the toxin increases intracellular cAMP levels in intestinal cells, leading to increased chloride secretion and fluid loss. Which type of E. coli is most likely producing this toxin?
A researcher is investigating the mechanism of action of an E. coli toxin that causes watery diarrhea. The researcher discovers that the toxin increases intracellular cAMP levels in intestinal cells, leading to increased chloride secretion and fluid loss. Which type of E. coli is most likely producing this toxin?
- Enteroaggregative E. coli (EAEC).
- Enteropathogenic E. coli (EPEC).
- Enteroinvasive E. coli (EIEC).
- Enterotoxigenic E. coli (ETEC). (correct)
A clinician is treating a patient with sepsis caused by E. coli. Which of the following mechanisms is primarily responsible for the pathophysiological effects observed in sepsis, such as fever, hypotension, and disseminated intravascular coagulation (DIC)?
A clinician is treating a patient with sepsis caused by E. coli. Which of the following mechanisms is primarily responsible for the pathophysiological effects observed in sepsis, such as fever, hypotension, and disseminated intravascular coagulation (DIC)?
A public health investigation is initiated following an outbreak of hemorrhagic colitis associated with the consumption of undercooked beef. Which characteristic of E. coli O157:H7 contributes most significantly to its ability to cause severe illness?
A public health investigation is initiated following an outbreak of hemorrhagic colitis associated with the consumption of undercooked beef. Which characteristic of E. coli O157:H7 contributes most significantly to its ability to cause severe illness?
A newborn infant develops meningitis shortly after birth. The causative agent is identified as E. coli. What is the most likely route of transmission in this case?
A newborn infant develops meningitis shortly after birth. The causative agent is identified as E. coli. What is the most likely route of transmission in this case?
A researcher is evaluating the efficacy of a novel antimicrobial agent against E. coli. The agent inhibits the synthesis of a specific structure that is essential for the bacterium's ability to adhere to host cells. Which of the following structures is most likely being targeted by this new antimicrobial?
A researcher is evaluating the efficacy of a novel antimicrobial agent against E. coli. The agent inhibits the synthesis of a specific structure that is essential for the bacterium's ability to adhere to host cells. Which of the following structures is most likely being targeted by this new antimicrobial?
A patient is diagnosed with pyelonephritis caused by E. coli. The patient is allergic to both trimethoprim-sulfamethoxazole and ciprofloxacin. Which of the following alternative treatment options would be most appropriate?
A patient is diagnosed with pyelonephritis caused by E. coli. The patient is allergic to both trimethoprim-sulfamethoxazole and ciprofloxacin. Which of the following alternative treatment options would be most appropriate?
A microbiologist is analyzing different strains of E. coli isolated from patients with diarrhea. Which characteristic would best differentiate Enteroinvasive E. coli (EIEC) from other diarrheagenic E. coli strains?
A microbiologist is analyzing different strains of E. coli isolated from patients with diarrhea. Which characteristic would best differentiate Enteroinvasive E. coli (EIEC) from other diarrheagenic E. coli strains?
A researcher aims to develop a vaccine against uropathogenic E. coli (UPEC). Which of the following would be the most effective target for such a vaccine?
A researcher aims to develop a vaccine against uropathogenic E. coli (UPEC). Which of the following would be the most effective target for such a vaccine?
Flashcards
E. coli Infections
E. coli Infections
Causes gastroenteritis, UTIs, meningitis, and sepsis. Cystitis is bladder infection; pyelonephritis is kidney infection.
E. coli Characteristics
E. coli Characteristics
Gram-negative rods, facultative anaerobe, encapsulated, and motile.
E. coli Identification
E. coli Identification
Ferments lactose (pink colonies on MacConkey's), oxidase negative, catalase positive, ferments glucose, no hemolysis on blood agar, green sheen on EMB agar
E. coli Transmission
E. coli Transmission
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Enterotoxigenic E. coli (ETEC)
Enterotoxigenic E. coli (ETEC)
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Enteropathogenic E. coli (EPEC)
Enteropathogenic E. coli (EPEC)
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Shiga-like Toxin-Producing E. coli (STEC)
Shiga-like Toxin-Producing E. coli (STEC)
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E. coli: UTIs
E. coli: UTIs
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E. coli UTI Treatment
E. coli UTI Treatment
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E. coli Neonatal Treatment
E. coli Neonatal Treatment
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Study Notes
- Escherichia coli (E. coli) is a bacterium responsible for gastroenteritis (diarrhea), UTIs, meningitis, and sepsis.
- E. coli causes cystitis when the bladder is infected, and pyelonephritis when the kidney is infected.
- E. coli are Gram-negative rods and facultative anaerobes found in the colon and feces.
- They are encapsulated, motile, ferment lactose (producing pink colonies on MacConkey agar), oxidase-negative, and catalase-positive.
- E. coli forms green-sheen colonies on eosin methylene blue agar and ferments glucose, but does not cause hemolysis on blood agar.
- Large numbers of E. coli are present in the GI tract, making it an opportunistic pathogen.
- While most infections are endogenous, neonatal meningitis and gastroenteritis are exceptions.
- Transmission routes include birth canal to neonate, ingestion of contaminated food/water, and undercooked beef.
- Transmission via birth canal can lead to neonatal meningitis, while exogenous E. coli can populate the genitourinary tract.
- Consumption of food and water contaminated with human feces during travel can lead to traveler’s diarrhea.
- Undercooked beef can harbor enterohemorrhagic E. coli O157 due to cattle acting as a reservoir.
E. coli strains and their effects
- Enterotoxigenic E. coli (ETEC) secretes toxins that cause traveler’s diarrhea.
- ETEC enterotoxins act on cells of the jejunum and ileum.
- Heat-labile toxin causes ADP-ribosylation, stimulating adenylate cyclase and increasing cAMP, which leads to watery diarrhea.
- Heat-stable toxin stimulates guanylate cyclase, also causing watery, non-bloody, short duration diarrhea.
- Enteropathogenic E. coli (EPEC) causes infant diarrhea.
- EPEC adheres to host cells using bundle-forming pili, disrupting microvillus structure and causing malabsorption and diarrhea.
- Enteroaggregative E. coli (EAEC) causes persistent diarrhea, especially in children and immunocompromised individuals.
- EAEC aggregates and adheres to the intestinal mucosa and produces enterotoxins and cytotoxins, resulting in diarrhea.
- Shiga-like Toxin-Producing E. coli (STEC) causes hemorrhagic colitis (bloody diarrhea) and hemolytic uremic syndrome (HUS).
- STEC removes an adenine from the 28S ribosomal RNA, halting protein synthesis resulting in bloody diarrhea.
- E. coli O157 has a low ID50 of approximately 100 organisms, leading to kidney failure, hemolytic anemia, and thrombocytopenia.
- Enteroinvasive E. coli (EIEC) causes a dysentery-like illness with bloody diarrhea, mucus, and pus.
- EIEC invades the epithelium of the large intestine and causes bloody diarrhea with neutrophils in the stool.
Uropathogens and treatment
- Uropathogens cause UTIs by colonizing and infecting the urethra, bladder, ureters, or kidneys via structures like pili and fimbriae.
- Cranberry juice contains flavonoids that inhibit the binding of pili to receptors, potentially preventing infection.
- Secreted endotoxin (LPS) can cause sepsis, characterized by fever, hypotension, and DIC.
- E. coli is a frequent cause of nosocomial UTIs due to urinary catheters.
- Cystitis can be treated with oral trimethoprim-sulfamethoxazole or nitrofurantoin.
- Pyelonephritis can be treated with ciprofloxacin or ceftriaxone.
- Sepsis treatment involves cefotaxime, with or without an aminoglycoside like gentamicin.
- Neonatal meningitis is treated with a combination of ampicillin and cefotaxime.
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