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Questions and Answers
Which of the following are characteristics of bacteria belonging to the Enterobacteriaceae family?
Which of the following are characteristics of bacteria belonging to the Enterobacteriaceae family?
What antigen is associated with the polysaccharide capsule of some Salmonella species?
What antigen is associated with the polysaccharide capsule of some Salmonella species?
K antigen
Campylobacter species are oxidase positive.
Campylobacter species are oxidase positive.
True
Campylobacter grows optimally at a temperature of ________.
Campylobacter grows optimally at a temperature of ________.
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Match the species with their associated illness: A) Yersinia pseudotuberculosis. B) Yersinia enterocolitica.
Match the species with their associated illness: A) Yersinia pseudotuberculosis. B) Yersinia enterocolitica.
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What is the characteristic appearance of Salmonella typhoidal bacteria on a gram stain?
What is the characteristic appearance of Salmonella typhoidal bacteria on a gram stain?
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Salmonella typhi is a spore-forming bacteria.
Salmonella typhi is a spore-forming bacteria.
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Salmonella can ferment ______ but not lactose.
Salmonella can ferment ______ but not lactose.
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What specific antigen of Salmonella typhoidal aids in immune evasion by protecting against antibody tagging?
What specific antigen of Salmonella typhoidal aids in immune evasion by protecting against antibody tagging?
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Which of the following regions can Salmonella typhoidal reach and induce hypertrophy, necrosis, and potentially ileal perforation?
Which of the following regions can Salmonella typhoidal reach and induce hypertrophy, necrosis, and potentially ileal perforation?
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Salmonella typhoidal can lead to sepsis.
Salmonella typhoidal can lead to sepsis.
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Match the following symptoms with Salmonella typhoidal infection: Abdominal pain
Match the following symptoms with Salmonella typhoidal infection: Abdominal pain
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Which antibiotic is commonly used to treat Salmonella typhoidal infections?
Which antibiotic is commonly used to treat Salmonella typhoidal infections?
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What type of bacteria is Escherichia coli in terms of gram staining?
What type of bacteria is Escherichia coli in terms of gram staining?
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Which enzyme does Escherichia coli produce that cleaves lactose into glucose and galactose?
Which enzyme does Escherichia coli produce that cleaves lactose into glucose and galactose?
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Escherichia coli is a facultative anaerobe.
Escherichia coli is a facultative anaerobe.
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What is the primary mechanism by which Campylobacter attaches to the mucosa?
What is the primary mechanism by which Campylobacter attaches to the mucosa?
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What is a common complication of Campylobacter infection in children?
What is a common complication of Campylobacter infection in children?
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Which of the following is NOT a symptom of Campylobacter infection?
Which of the following is NOT a symptom of Campylobacter infection?
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What is the primary treatment for severe Campylobacter infections?
What is the primary treatment for severe Campylobacter infections?
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How is Campylobacter typically transmitted?
How is Campylobacter typically transmitted?
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What is a common complication of Campylobacter infection that can lead to paralysis?
What is a common complication of Campylobacter infection that can lead to paralysis?
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What is a characteristic of Campylobacter in terms of motility?
What is a characteristic of Campylobacter in terms of motility?
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What is a characteristic of Campylobacter in terms of shape?
What is a characteristic of Campylobacter in terms of shape?
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What is the mechanism of Shiga-like toxins in causing intestinal injury in STEC?
What is the mechanism of Shiga-like toxins in causing intestinal injury in STEC?
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What is the characteristic symptom of ETEC infection?
What is the characteristic symptom of ETEC infection?
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What is the outcome of STEC toxin release into the bloodstream?
What is the outcome of STEC toxin release into the bloodstream?
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How does ETEC attach to the intestinal mucosa?
How does ETEC attach to the intestinal mucosa?
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What is the mechanism of heat-stable enterotoxin (ST) in ETEC?
What is the mechanism of heat-stable enterotoxin (ST) in ETEC?
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What is the complication of HUS in STEC infection?
What is the complication of HUS in STEC infection?
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How does EIEC attach to and invade the intestinal epithelial cells?
How does EIEC attach to and invade the intestinal epithelial cells?
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What is the outcome of ETEC infection in the intestine?
What is the outcome of ETEC infection in the intestine?
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What is the primary mechanism by which Enteropathogenic E. coli (EPEC) causes diarrhea?
What is the primary mechanism by which Enteropathogenic E. coli (EPEC) causes diarrhea?
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What is the primary symptom of a urinary tract infection (UTI) caused by Uropathogenic E. coli (UPEC)?
What is the primary symptom of a urinary tract infection (UTI) caused by Uropathogenic E. coli (UPEC)?
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What is the primary complication of a Shiga toxin-producing E. coli (STEC) infection?
What is the primary complication of a Shiga toxin-producing E. coli (STEC) infection?
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What is the primary mechanism by which Uropathogenic E. coli (UPEC) adheres to uroepithelial cells?
What is the primary mechanism by which Uropathogenic E. coli (UPEC) adheres to uroepithelial cells?
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What is the primary characteristic of diarrhea caused by Enterotoxigenic E. coli (ETEC)?
What is the primary characteristic of diarrhea caused by Enterotoxigenic E. coli (ETEC)?
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What is the primary mechanism by which Enteroinvasive E. coli (EIEC) causes diarrhea?
What is the primary mechanism by which Enteroinvasive E. coli (EIEC) causes diarrhea?
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What is the primary complication of an Enteropathogenic E. coli (EPEC) infection in children?
What is the primary complication of an Enteropathogenic E. coli (EPEC) infection in children?
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What is the primary mechanism by which Shiga toxin-producing E. coli (STEC) causes bloody diarrhea?
What is the primary mechanism by which Shiga toxin-producing E. coli (STEC) causes bloody diarrhea?
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What is the primary mechanism by which Enteropathogenic E. coli (EPEC) causes diarrhea?
What is the primary mechanism by which Enteropathogenic E. coli (EPEC) causes diarrhea?
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Uropathogenic E. coli (UPEC) can only cause cystitis.
Uropathogenic E. coli (UPEC) can only cause cystitis.
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What is the primary symptom of Enterotoxigenic E. coli (ETEC) infection?
What is the primary symptom of Enterotoxigenic E. coli (ETEC) infection?
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Enteroinvasive E. coli (EIEC) causes _______ diarrhea.
Enteroinvasive E. coli (EIEC) causes _______ diarrhea.
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Match the following E. coli types with their primary mechanisms of infection:
Match the following E. coli types with their primary mechanisms of infection:
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Enteropathogenic E. coli (EPEC) primarily affects children under two years of age.
Enteropathogenic E. coli (EPEC) primarily affects children under two years of age.
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What is the primary mechanism by which Uropathogenic E. coli (UPEC) adheres to uroepithelial cells?
What is the primary mechanism by which Uropathogenic E. coli (UPEC) adheres to uroepithelial cells?
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What is the primary complication of an Enteropathogenic E. coli (EPEC) infection in children?
What is the primary complication of an Enteropathogenic E. coli (EPEC) infection in children?
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What is the primary disease caused by Enterotoxigenic E. coli (ETEC)?
What is the primary disease caused by Enterotoxigenic E. coli (ETEC)?
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Enteroinvasive E. coli (EIEC) invades and destroys intestinal epithelial cells, causing bloody diarrhea.
Enteroinvasive E. coli (EIEC) invades and destroys intestinal epithelial cells, causing bloody diarrhea.
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What is the primary mechanism by which Enteropathogenic E. coli (EPEC) causes diarrhea?
What is the primary mechanism by which Enteropathogenic E. coli (EPEC) causes diarrhea?
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Uropathogenic E. coli (UPEC) causes ___________________________ (UTIs), including cystitis and pyelonephritis.
Uropathogenic E. coli (UPEC) causes ___________________________ (UTIs), including cystitis and pyelonephritis.
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Match the following pathotypes with their disease-causing mechanisms:
Match the following pathotypes with their disease-causing mechanisms:
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Enteropathogenic E. coli (EPEC) is primarily associated with bloody diarrhea.
Enteropathogenic E. coli (EPEC) is primarily associated with bloody diarrhea.
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What is the primary mechanism of heat-labile enterotoxin (LT) in ETEC?
What is the primary mechanism of heat-labile enterotoxin (LT) in ETEC?
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EIEC attaches to the intestinal epithelial cells using fimbriae.
EIEC attaches to the intestinal epithelial cells using fimbriae.
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What is the outcome of ETEC infection in the intestine?
What is the outcome of ETEC infection in the intestine?
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ETEC uses ______________ to adhere to the intestinal mucosa.
ETEC uses ______________ to adhere to the intestinal mucosa.
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What is the primary complication of HUS in STEC infection?
What is the primary complication of HUS in STEC infection?
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Match the following E. coli pathotypes with their primary mechanism of diarrhea:
Match the following E. coli pathotypes with their primary mechanism of diarrhea:
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UPEC causes diarrhea in infected individuals.
UPEC causes diarrhea in infected individuals.
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What is the primary mechanism by which EPEC causes diarrhea?
What is the primary mechanism by which EPEC causes diarrhea?
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Study Notes
Human Pathogens Part 3
Types of Bacteria
- Primary pathogens: capable of causing disease in healthy individuals (e.g., Salmonella, Shigella, Klebsiella pneumoniae, Escherichia coli)
- Opportunistic pathogens: cause disease in individuals with compromised immune systems
- Non-pathogenic bacteria: do not cause disease
General Characteristics of Enterobacteriaceae
- Gram-negative rods with no specific arrangement
- Non-spore forming
- Aerobic and facultative anaerobic
- Motile by peritrichous flagella or non-motile
- Capsulated with ill-defined slime layer or non-capsulated
- Fimbriae or pili present in most species
- Lactose fermenter
- Catalase positive
- Reduce nitrate to nitrite
- Grow on peptone or meat extract media without sodium chloride or other supplements
Antigenic Structure
- O antigens: in the polysaccharide of the cell wall (LPS)
- H antigens: flagellar protein
- K antigen: polysaccharide capsule (only for some species)
- Vi antigen: virulence factor (only for Salmonella species)
Escherichia coli
- >150 serotypes
- Typed by O and H antigens
- Example: O157:H7 (EHEC)
Shigella
- 4 different species: S. dysenteriae, S. flexneri, S. boydii, S. sonnei
- Each have different serogroups: A, B, C, D
- No capsules
Epidemiology of Enterobacteriaceae
- Fecal-oral transmission: contaminated food or water, or from an animal
- Through the gastrointestinal tract
- Can cause diarrhea, urinary tract infections, and other diseases
Campylobacter spp.
General Information
- Gram-negative, comma-shaped bacteria
- Motile with a single polar unsheathed flagellum
- Non-spore former
- Microaerophilic and capnophilic
- Require special growth conditions
Transmission
- Intestinal colonization in chickens
- Contaminated food, water, or milk
- Unpasteurized milk and undercooked poultry are high-risk sources
Pathogenesis and Virulence Factors
- Attachment: uses fimbria-like filaments and cell surface proteins
- Invasion: drills into mucosa using spiral shape and flagella
- Releases cytotoxins, causing cell damage and inflammation
- Complications: toxic megacolon, bacteremia, Guillain-Barré syndrome, reactive arthritis
Symptoms
- Incubation period: 1-7 days
- Initial symptoms: fever, muscle pain, malaise, headache
- Gastrointestinal symptoms: crampy abdominal pain, watery diarrhea, bloody diarrhea
Shigella spp.
General Information
- Family: Enterobacteriaceae
- Species: Shigella dysenteriae, Shigella flexneri, Shigella boydii, Shigella sonnei
- Gram-negative, rod-shaped bacteria
- Facultative anaerobe
- Motility: non-motile
- Non-spore former
- Urease and oxidase negative
- H2S negative
Pathogenesis
- Ingestion and initial infection
- Invasion and immune response
- Spread within the host
- Shiga toxin (specific to Shigella dysenteriae serotype 1)
Symptoms
- Incubation period: 1-3 days
- Typical symptoms: severe abdominal cramps, watery diarrhea, fever, vomiting
- Complications: hemolytic uremic syndrome (HUS), seizures, reactive arthritis
Salmonella spp.
General Information
- Family: Enterobacteriaceae
- Species: Salmonella enterica (with 6 subspecies)
- Gram-negative, rod-shaped bacteria
- Facultative intracellular pathogen
- Motile with flagella
- Non-spore former
- Oxidase negative
- H2S positive
Pathogenesis
- Ingestion and targeting
- Immune evasion
- Survival and replication
- Systemic spread
Symptoms
- Onset: 1-2 weeks after infection
- Typical symptoms: high sustained fever, abdominal pain, constipation, diarrhea, rose or salmon-colored spots on chest and abdomen
- Complications: osteomyelitis, chronic infection, and carrier state
Escherichia coli
Characteristics
- Gram-negative, thin peptidoglycan layer
- Rod-shaped bacteria
- Catalase-positive
- Lactose fermenter
- Encapsulated with a polysaccharide layer
- Motile with flagella
- Facultative anaerobe
Pathogenic Strains
-
Attachment: uses fimbriae to attach to host cells
-
Serotype classification: based on antigens (O, K, H)
-
Pathotypes: based on the disease-causing mechanism and virulence factors### Effacement
-
Injects effector proteins via Type III secretion system, causing actin cytoskeleton rearrangement
-
Leads to pedestal formation and microvilli effacement
-
Impairs absorption, causing watery diarrhea, primarily in children under two years of age
Uropathogenic E. coli (UPEC)
- Colonizes periurethral area and ascends urinary tract
- Adheres to uroepithelial cells using type 1 fimbriae and P fimbriae
- Invades and replicates within bladder cells
- Produces alpha and beta hemolysins, causing lysis of urinary tract cells
Infections and Symptoms
- Cystitis: Infection of the bladder, causing dysuria and frequent urination
- Pyelonephritis: Ascends to kidneys, causing flank pain and more severe symptoms
- Diarrhea: Abdominal cramps, vomiting
- STEC: Bloody diarrhea, low-grade fever, potential HUS with symptoms like body swelling, confusion, and jaundice
- ETEC: Watery diarrhea, possible fever, and bloating
- EIEC: Bloody diarrhea and chills
- EPEC: Severe dehydration in children, prolonged diarrhea leading to malnutrition
- UPEC: UTI symptoms like dysuria, urinary frequency, and possible flank pain if kidneys are affected
Diagnosis
- Gram Staining: On stool or urine sample
- Culture: On eosin methylene blue agar
- HUS Diagnosis: Identifying Shiga toxin in the blood
Treatment
- Diarrhea: Hydration and rest, antibiotics in severe cases (e.g., doxycycline, cotrimoxazole)
- Hemolytic Uremic Syndrome (HUS): Supportive care (dialysis, corticosteroids, blood transfusions, plasmapheresis)
- UTIs: Antibiotics (cotrimoxazole, nitrofurantoin, fluoroquinolones, e.g., ciprofloxacin)
Intracellular Multiplication
- Invades and multiplies within epithelial cells, causing cell destruction
- Triggers a strong inflammatory response, leading to widespread epithelial damage and bloody diarrhea
Enteropathogenic E. coli (EPEC)
- Uses bundle-forming pili (BFP) to attach to intestinal epithelial cells
- Injects effector proteins via a Type III secretion system, causing actin cytoskeleton rearrangement
- Leads to pedestal formation and microvilli effacement
- Impairs absorption, causing watery diarrhea, primarily in children under two years of age
Uropathogenic E. coli (UPEC)
- Colonizes the periurethral area and ascends the urinary tract
- Uses type 1 fimbriae and P fimbriae to adhere to uroepithelial cells
- Invades and replicates within bladder cells
- Produces alpha and beta hemolysins, causing lysis of urinary tract cells
- Can cause cystitis, infection of the bladder, leading to dysuria and frequent urination
- Can ascend to the kidneys, causing flank pain and more severe symptoms (pyelonephritis)
Symptoms and Complications
- General symptoms: diarrhea, abdominal cramps, vomiting
- STEC: bloody diarrhea, low-grade fever, potential HUS with symptoms like body swelling, confusion, and jaundice
- ETEC: watery diarrhea, possible fever, and bloating
- EIEC: bloody diarrhea and chills
- EPEC: severe dehydration in children, prolonged diarrhea leading to malnutrition
- UPEC: UTI symptoms like dysuria, urinary frequency, and possible flank pain if kidneys are affected
- Risk of infection from cows (unpasteurized milk) and infected pets (notably puppies)
Pathogenesis and Virulence Factors
- Attachment: uses fimbri-like filaments and cell surface proteins like PEV-1 and CADF to attach to the mucosa of the small intestine and colon
- Invasion: drills into mucosa using its spiral shape and long flagella
- Releases cytotoxins like cytolethal distending toxins (CDT), causing cell damage and inflammation
- Complications: toxic megacolon, bacteremia, Guillain-Barré Syndrome, and reactive arthritis
Pathogenesis of Each Pathotype
Shiga-like Toxin-Producing E. coli (STEC)
- Attaches to host's intestinal cells using fimbriae
- Produces Shiga-like toxins (Stx1 and Stx2)
- Toxins cause damage to intestinal epithelium and blood vessels, resulting in inflammation
- Inflammation and vessel damage lead to fluid and blood leaking into the intestinal lumen, causing bloody diarrhea
- Systemic toxin release affects the kidneys, leading to hemolytic uremic syndrome (HUS)
Enterotoxigenic E. coli (ETEC)
- Uses fimbriae to adhere to intestinal mucosa
- Produces heat-labile enterotoxin (LT) and heat-stable enterotoxin (ST)
- LT activates adenylate cyclase, increasing cAMP, leading to chloride and water secretion
- ST activates guanylate cyclase, increasing cGMP, leading to electrolyte and water secretion
- Causes watery diarrhea without damaging the intestinal wall
Enteroinvasive E. coli (EIEC)
- Attaches to and invades intestinal epithelial cells
- Causes bloody diarrhea and chills
Escherichia coli (E. coli) Characteristics
- Rod-shaped bacteria
- Catalase-positive: Produces catalase enzyme
- Lactose fermenter: Produces beta-galactosidase and cleaves lactose into glucose and galactose
- Encapsulation: Covered by a polysaccharide layer called a capsule
- Motility: Has flagella for movement
- Facultative Anaerobe: Can live with or without oxygen
Tests and Cultivation
- Catalase Test: Adds hydrogen peroxide to a colony; the presence of catalase results in foaming
- Lactose Fermentation Test: Cultivation on lactose-containing media, resulting in acid production and color change from red to yellow
- Eosin Methylene Blue (EMB) Agar: Grows into black colonies with a greenish-black metallic sheen
Pathogenic Strains
- Attachment: Uses fimbriae to attach to host cells
- Serotype Classification: Based on antigens:
- Somatic (O) antigens: On the cell membrane
- Capsular (K) antigens: On the capsule
- Fimbrial (F) antigens: On the fimbriae
- Flagellar (H) antigens: On the flagella
Pathotype Classification
- Shiga-like toxin-producing E. coli (STEC):
- Produces Shiga toxin, causes bloody diarrhea, and can lead to hemolytic uremic syndrome (HUS)
- Enterotoxigenic E. coli (ETEC):
- Produces heat-labile and heat-stable enterotoxins, causing watery diarrhea
- Enteroinvasive E. coli (EIEC):
- Invades and destroys intestinal epithelial cells, causing bloody diarrhea
- Enteropathogenic E. coli (EPEC):
- Causes disease in children under two years old, leading to watery diarrhea
- Uropathogenic E. coli (UPEC):
- Causes urinary tract infections (UTIs), including cystitis and pyelonephritis
Pathogenesis of Each Pathotype
Shiga-like Toxin-Producing E. coli (STEC)
- Attachment: STEC attaches to the host's intestinal cells using fimbriae
- Toxin Production: Produces Shiga-like toxins (Stx1 and Stx2)
- Intestinal Injury: Toxins cause damage to the intestinal epithelium and blood vessels, resulting in inflammation
- Bloody Diarrhea: Inflammation and vessel damage lead to fluid and blood leaking into the intestinal lumen
- Hemolytic Uremic Syndrome (HUS):
- Systemic Toxin Release: Toxins enter the bloodstream, affecting the kidneys
- Kidney Damage: Toxins bind to endothelial cells in the glomeruli, causing apoptosis and gaps in the capillary walls, leading to proteinuria
- Inflammatory Response: Cytokines and chemokines are released, activating platelets and causing clot formation
- Thrombocytopenia: Decreased platelet count due to clot formation
- Hemolytic Anemia: Red blood cells are fragmented (schistocytes) as they pass through obstructed microvessels
- Ischemic Kidney Damage: Clots obstruct arterioles, leading to kidney ischemia, reduced filtration, and uremia
Enterotoxigenic E. coli (ETEC)
- Attachment: ETEC uses fimbriae to adhere to the intestinal mucosa
- Toxin Production:
- Heat-labile Enterotoxin (LT):
- Mechanism: Activates adenylate cyclase, increasing cAMP, leading to chloride and water secretion
- Heat-stable Enterotoxin (ST):
- Mechanism: Activates guanylate cyclase, increasing cGMP, leading to electrolyte and water secretion
- Heat-labile Enterotoxin (LT):
- Outcome: Causes watery diarrhea without damaging the intestinal wall
Enteroinvasive E. coli (EIEC)
- Attachment and Invasion: EIEC attaches to and invades intestinal epithelial cells
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Description
This quiz covers different types of bacteria, including primary pathogens, opportunistic pathogens, and non-pathogenic bacteria, as well as their characteristics.
