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Questions and Answers
What characteristic is NOT shared by all members of the Enterobacteriaceae family?
What characteristic is NOT shared by all members of the Enterobacteriaceae family?
Which type of fermentation is used to identify Enterobacteriaceae on MacConkey agar?
Which type of fermentation is used to identify Enterobacteriaceae on MacConkey agar?
Which of the following is a lactose fermenter among the Enterobacteriaceae?
Which of the following is a lactose fermenter among the Enterobacteriaceae?
What type of media is used to differentiate between lactose fermenters and non-lactose fermenters?
What type of media is used to differentiate between lactose fermenters and non-lactose fermenters?
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Which pathogen is NOT associated with gastrointestinal diseases caused by Enterobacteriaceae?
Which pathogen is NOT associated with gastrointestinal diseases caused by Enterobacteriaceae?
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What does the 'E' in EHEC stand for regarding pathogenic E. coli strains?
What does the 'E' in EHEC stand for regarding pathogenic E. coli strains?
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Which antigenic structure is commonly associated with most motile Enterobacteriaceae?
Which antigenic structure is commonly associated with most motile Enterobacteriaceae?
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What is indicated by the presence of E. coli in water?
What is indicated by the presence of E. coli in water?
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What type of test is the Widal test?
What type of test is the Widal test?
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Which serotype is primarily responsible for salmonellosis?
Which serotype is primarily responsible for salmonellosis?
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What is a common characteristic of the disease caused by S.choleraesuis?
What is a common characteristic of the disease caused by S.choleraesuis?
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Which statement about typhoid fever is correct?
Which statement about typhoid fever is correct?
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What is the primary method of transmission for Salmonella typhi?
What is the primary method of transmission for Salmonella typhi?
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What role does the Vi antigen play in typhoid pathogenesis?
What role does the Vi antigen play in typhoid pathogenesis?
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In the case of uncomplicated salmonellosis, what is generally recommended?
In the case of uncomplicated salmonellosis, what is generally recommended?
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Which statement about antibiotic therapy for typhoid fever is true?
Which statement about antibiotic therapy for typhoid fever is true?
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What characteristic differentiates Enterotoxigenic E.coli (ETEC) from Enteroinvasive E.coli (EIEC)?
What characteristic differentiates Enterotoxigenic E.coli (ETEC) from Enteroinvasive E.coli (EIEC)?
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Which virulence factor is specifically associated with Enteropathogenic E.coli (EPEC)?
Which virulence factor is specifically associated with Enteropathogenic E.coli (EPEC)?
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What is the primary treatment approach for E.coli infections?
What is the primary treatment approach for E.coli infections?
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What type of toxin is produced by Enterotoxigenic E.coli (ETEC) that causes gastrointestinal symptoms?
What type of toxin is produced by Enterotoxigenic E.coli (ETEC) that causes gastrointestinal symptoms?
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In what way does Enteroinvasive E.coli (EIEC) resemble Shigella?
In what way does Enteroinvasive E.coli (EIEC) resemble Shigella?
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Which group of E.coli is primarily responsible for causing hemolytic-uremic syndrome?
Which group of E.coli is primarily responsible for causing hemolytic-uremic syndrome?
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What is a common symptom of gastroenteritis caused by Enterotoxigenic E.coli (ETEC)?
What is a common symptom of gastroenteritis caused by Enterotoxigenic E.coli (ETEC)?
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What is the optimal growth temperature range for E.coli?
What is the optimal growth temperature range for E.coli?
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What type of bacteria is E.coli in terms of its Gram staining characteristics?
What type of bacteria is E.coli in terms of its Gram staining characteristics?
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Which E.coli serovar is most commonly associated with Enterohemorrhagic E.coli (EHEC)?
Which E.coli serovar is most commonly associated with Enterohemorrhagic E.coli (EHEC)?
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What is the role of fimbriae in the pathogenicity of pathogenic E.coli?
What is the role of fimbriae in the pathogenicity of pathogenic E.coli?
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What is the main factor that increases the risk of urinary tract infections (UTIs) related to E.coli?
What is the main factor that increases the risk of urinary tract infections (UTIs) related to E.coli?
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Which testing medium would be suitable for cultivating E.coli from a urine sample?
Which testing medium would be suitable for cultivating E.coli from a urine sample?
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What is a major clinical significance of Enteroaggregative E.coli (EaggEC)?
What is a major clinical significance of Enteroaggregative E.coli (EaggEC)?
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What is the primary cause of shigellosis?
What is the primary cause of shigellosis?
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Which Shigella species is considered the most pathogenic?
Which Shigella species is considered the most pathogenic?
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What is the main transmission route for Shigella infections?
What is the main transmission route for Shigella infections?
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Which of the following symptoms is NOT commonly associated with shigellosis?
Which of the following symptoms is NOT commonly associated with shigellosis?
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What is the infective dose of Shigella needed to cause infection?
What is the infective dose of Shigella needed to cause infection?
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Which diagnostic method is used for detecting a Shigella infection?
Which diagnostic method is used for detecting a Shigella infection?
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How can Shigella species contribute to antibiotic resistance?
How can Shigella species contribute to antibiotic resistance?
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Which of the following is a common clinical finding in patients with shigellosis?
Which of the following is a common clinical finding in patients with shigellosis?
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What role does Shiga toxin play in the pathogenesis of shigellosis?
What role does Shiga toxin play in the pathogenesis of shigellosis?
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Which measure is NOT recommended for the management of shigellosis?
Which measure is NOT recommended for the management of shigellosis?
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Which organism is NOT a reservoir for Shigella?
Which organism is NOT a reservoir for Shigella?
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What is the incubation period for shigellosis?
What is the incubation period for shigellosis?
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What bacterial structure is primarily responsible for the movement of Salmonella through intestinal mucus?
What bacterial structure is primarily responsible for the movement of Salmonella through intestinal mucus?
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Which Salmonella species is commonly associated with gastroenteritis?
Which Salmonella species is commonly associated with gastroenteritis?
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Study Notes
Enterobacteriaceae Characteristics
- Gram-negative, non-spore-forming rods
- Commonly found in the large intestine as commensals; some are highly pathogenic
- Motile (peritrichous flagella) or non-motile
- Facultative anaerobes
- Not fastidious
- Non-capsulated (except Klebsiella)
- Grow on bile-containing media (MacConkey agar)
Enterobacteriaceae Metabolism
- Ferment glucose
- Reduce nitrates to nitrites
- Oxidase-negative
- Lactose fermentation is key for isolation and identification
Enterobacteriaceae Classification
- Two major groups:
- Lactose fermenters (LF): E. coli, Citrobacter, Klebsiella, Enterobacter
- Non-lactose fermenters (NLF): Salmonella, Shigella, Proteus, Yersinia
- Selective and differential media (e.g., MacConkey agar, Triple Sugar Iron (TSI) agar) differentiate LF and NLF
Enterobacteriaceae Identification
-
MacConkey Agar:
- LF organisms form pink colonies
- NLF organisms form colorless colonies
- Triple Sugar Iron (TSI) Agar: used for further characterization
Enterobacteriaceae Antigenic Structures
- Lipopolysaccharide (endotoxin): O antigen
- Flagella: H antigen
- Capsule: K antigen (e.g., Vi in Salmonella)
- Cell envelope proteins
- Pili (various antigen types, sometimes encoded by plasmids)
Enterobacteriaceae Gastrointestinal Diseases
- Escherichia coli
- Salmonella
- Shigella
- Yersinia enterocolitica
Escherichia coli (E. coli)
- Normal GI flora
- Extraintestinal infections: UTI, septicemia, neonatal meningitis
-
Intestinal infections (pathotypes):
- ETEC (enterotoxigenic)
- EIEC (enteroinvasive)
- EPEC (enteropathogenic)
- EHEC (enterohemorrhagic)/STEC (Shiga toxin-producing)/VTEC (verocytotoxin-producing)
- EAEC (enteroaggregative)
- DAEC (diffuely adherent)
- Diarrheagenic E. coli: 6 pathotypes associated with diarrhea
E. coli Morphology & Characteristics
- Gram-negative rods
- Single or pairs
- Motile (peritrichous flagella), few strains non-motile
- Non-spore-forming, non-acid-fast
- Aerobic/facultative anaerobes
- Growth range: 10-40°C, optimum at 37°C
- Simple medium growth
- Colonies: large, grayish, thick, white, moist, smooth, opaque
- May contain capsule
- MacConkey medium: bright pink colonies (lactose fermenters)
- Numerous O, K, and H antigens
E. coli Virulence Factors
- Surface antigens
- Toxins
- O antigen: endotoxic activity
- K antigen: protects against phagocytosis
- Fimbriae: promote virulence (important in UTIs)
Pathogenesis of Pathogenic E. coli Groups
- ETEC: watery diarrhea, nausea, and cramps; caused by heat-labile and heat-stable enterotoxins
- EIEC: dysentery, resembling shigellosis, caused by invasion of intestinal cells
- EPEC: low-grade fever, diarrhea; causes destruction of intestinal microvilli
- EHEC: bloody diarrhea, possible hemolytic-uremic syndrome (HUS), caused by Shiga toxin
- EAEC: persistent, watery diarrhea, caused by enteroaggregative heat-stable toxin (EAST)
E. coli, Shigella and Salmonella Infections: Diagnostics and Treatment
- Diagnostic specimens: stool, urine, blood, bone marrow (as appropriate)
- Culture/identification, immunological tests
- Treat with antibiotics, primarily in severe systemic infections
- Treatment in uncomplicated cases is primarily fluid and electrolyte replacement
Shigella Bacterium
- Non-lactose fermenters (except S. sonnei)
- Four serogroups (based on O antigens) causing bacillary dysentery or shigellosis (bloody diarrhea with pain)
- Shigella invades the intestine, leading to epithelial damage
- Disease symptoms develop within 2-3 days
- Viriulence factors: Shiga toxin (neurotoxic, enterotoxic, cytotoxic)
- Highly contagious & infective dose is low; primarily infections amongst young children
- Stool specimen collection/culture, immunological tests for diagnosis,
- Antibiotic treatment for severe cases, supportive care for mild disease
Salmonella
- Over 2,000 serotypes
- Transmitted via the fecal-oral route
- Presents as gastroenteritis, typhoid fever, or septicemia
- Antigenic components: O, H, Vi antigens
- Pathogenicity factors: endotoxin, capsule (some strains), adhesions, enterotoxin, outer membrane proteins, flagella
- Common diseases:
- Gastroenteritis: usually caused by S. enteritidis (often from poultry/eggs), non-bloody stools, self-limiting
- Septicemia: S. choleraesuis often involved, high fever, little gastrointestinal involvement
- Typhoid fever (enteric fever): S. typhi, systemic infection; bacteria multiply in cells of reticuloendothelial system, re-enters intestine; longer duration, human reservoir, diagnosed via blood/bone marrow samples
- Diagnosis: stool samples, blood cultures
- Treatment: primarily antibiotics; severe cases require antimicrobials
Sanitary Significance of E. coli
- Total bacterial count, coliform index are measures for water contamination (standards for drinking water).
E. coli and Urinary Tract Infections (UTIs)
- Leading cause of UTIs
- Commonly associated with instrumentation (catheters), prostatic enlargement, urinary calculi, and pregnancy
- Fecal strains often enter urethra leading to cystitis
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Description
Test your knowledge on the Enterobacteriaceae family with this quiz. Explore characteristics, fermentation types, and pathogen associations specific to this important group of bacteria. This quiz is designed for microbiology students and enthusiasts who want to deepen their understanding of lactose and non-lactose fermenters.
