Podcast
Questions and Answers
A researcher is studying the pathogenesis of Shigella and observes that the bacteria utilize a specific mechanism to invade adjacent cells. Which virulence factor is most likely responsible for this?
A researcher is studying the pathogenesis of Shigella and observes that the bacteria utilize a specific mechanism to invade adjacent cells. Which virulence factor is most likely responsible for this?
- Secretion of urease, disrupting the local pH and promoting invasion.
- Production of Shiga toxin, leading to direct cellular damage.
- Actin-based motility, facilitating movement within and between cells. (correct)
- Flagella-mediated motility to actively seek out new host cells.
Shigella is transmitted through the fecal-oral route. Which scenario represents the highest risk of a Shigella outbreak, based on common modes of transmission?
Shigella is transmitted through the fecal-oral route. Which scenario represents the highest risk of a Shigella outbreak, based on common modes of transmission?
- Consumption of undercooked poultry from a large commercial farm.
- A community swimming pool with regulated chlorine levels.
- A daycare center with frequent diaper changes and limited handwashing facilities. (correct)
- Contaminated surgical equipment in a major metropolitan hospital.
A public health investigation identifies a foodborne Shigella outbreak linked to a specific agricultural product. Which product is the MOST likely source, given the typical transmission routes of Shigella?
A public health investigation identifies a foodborne Shigella outbreak linked to a specific agricultural product. Which product is the MOST likely source, given the typical transmission routes of Shigella?
- Pasteurized milk from a local dairy farm.
- Imported spices treated with irradiation.
- Canned goods processed in a facility with strict sanitation protocols.
- Fresh produce irrigated with contaminated water. (correct)
Following a Shigella outbreak, a researcher aims to develop a novel therapeutic strategy targeting a key virulence factor. Which of the following would be the MOST promising target, considering Shigella's pathogenic mechanisms?
Following a Shigella outbreak, a researcher aims to develop a novel therapeutic strategy targeting a key virulence factor. Which of the following would be the MOST promising target, considering Shigella's pathogenic mechanisms?
A clinician is treating a patient with severe dysentery and suspects a Shigella infection. What diagnostic test would provide the MOST rapid and specific confirmation of Shigella, guiding appropriate treatment strategies?
A clinician is treating a patient with severe dysentery and suspects a Shigella infection. What diagnostic test would provide the MOST rapid and specific confirmation of Shigella, guiding appropriate treatment strategies?
An 8-year-old child presents with bloody diarrhea, high fever, and abdominal cramps. Stool culture confirms Shigella sonnei infection. Which of the following factors would MOST significantly influence the choice of antibiotic therapy?
An 8-year-old child presents with bloody diarrhea, high fever, and abdominal cramps. Stool culture confirms Shigella sonnei infection. Which of the following factors would MOST significantly influence the choice of antibiotic therapy?
A physician decides to treat a patient with severe shigellosis using ciprofloxacin. What crucial information should the physician convey to the patient regarding additional medications?
A physician decides to treat a patient with severe shigellosis using ciprofloxacin. What crucial information should the physician convey to the patient regarding additional medications?
A clinical study is evaluating the effectiveness of a new vaccine against Shigella. Which immunological marker would provide the MOST direct indication of vaccine-induced protection against Shigella infection?
A clinical study is evaluating the effectiveness of a new vaccine against Shigella. Which immunological marker would provide the MOST direct indication of vaccine-induced protection against Shigella infection?
Which characteristic of Shigella contributes to its high infectivity?
Which characteristic of Shigella contributes to its high infectivity?
A researcher is investigating potential genetic mutations that could increase the virulence of Shigella. Which mutation would MOST likely lead to a significant increase in the severity of shigellosis?
A researcher is investigating potential genetic mutations that could increase the virulence of Shigella. Which mutation would MOST likely lead to a significant increase in the severity of shigellosis?
Flashcards
Enterocolitis/Bacillary Dysentery
Enterocolitis/Bacillary Dysentery
Inflammation of the small intestine and colon, often with bloody diarrhea containing pus and mucus.
Shigella Characteristics
Shigella Characteristics
Gram-negative, facultative anaerobic bacteria that doesn't have flagella. It uses actin-based motility.
Shigella Metabolism
Shigella Metabolism
Negative for oxidase and urease; doesn't ferment lactose or produce H2S or gas when it ferments glucose.
ID50 (Infectious Dose 50)
ID50 (Infectious Dose 50)
Indicates the number of bacterial cells needed to infect 50% of the individuals exposed. Shigella is very effective.
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Shigella Transmission
Shigella Transmission
The main route of transmission for Shigella, often involving fingers, flies, food, and feces.
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Shiga Enterotoxin
Shiga Enterotoxin
Released by Shigella that is similar to shiga-like toxins produced by E. coli. It helps the bacteria invade cells.
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Shigella O Antigen
Shigella O Antigen
Blocks complement activation and phagocytosis, aiding in immune evasion.
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Shigella Incubation Period
Shigella Incubation Period
Ranges from 1 to 4 days; typically resolves in 2 to 3 days.
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Shigella Complications
Shigella Complications
Can include bacteremia, sepsis, reactive arthritis, hemolytic-uremic syndrome, and seizures.
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Shigella Diagnosis
Shigella Diagnosis
Non-lactose fermenting, colorless colonies, methylene blue staining finds neutrophils, agglutination test.
Signup and view all the flashcardsStudy Notes
- Causes enterocolitis and bacillary dysentery (severe bloody diarrhea with pus, blood, and mucus).
- Gram-negative, facultative anaerobe.
- Non-motile due to lack of flagella, but uses actin-based motility via enterotoxin.
- Oxidase-negative, urease-negative, non-lactose fermenting.
- Can grow on MacConkey agar.
- Does not produce gas during glucose fermentation or H2S.
- Highly effective enteric bacteria, with a low ID50.
- Transmitted through the fecal-oral route (4 Fs: fingers, flies, food, and feces).
- Foodborne outbreaks are twice as common as waterborne outbreaks.
- Outbreaks often occur in mental hospitals and daycare nurseries.
- Children under 10 account for over half of positive stool cultures.
- Serogroup D (Shigella sonnei) is most common in the U.S.
- In the U.S. most cases originate from travelers abroad.
Virulence Factors
- Shiga enterotoxin: Is similar to shiga-like toxins 1 and 2 produced by E. coli.
- Type III-secretion system: Invades the colonic epithelium.
- Actin-based motility: Enters adjacent cells.
- O antigen: Evades host immune recognition by hindering complement activation and phagocytosis.
Symptoms and Progression
- Incubation period: 1 - 4 days.
- Resolution: Typically in 2 - 3 days.
- Key symptoms: abdominal cramps, vomiting, high fever, loss of appetite.
- Extreme cases in children: tonic-clonic seizures.
- Sepsis: Possible in neonates, malnourished children, and those with S. dysenteriae serotype I.
Complications
- Bacteremia and sepsis
- Reactive arthritis
- Hemolytic-uremic syndrome
- Seizure
Diagnosis
- MacConkey/EMB agar: Non-lactose fermenting colorless colonies.
- Methylene blue staining: Identifies neutrophils in fecal samples.
- Agglutination test: Confirms the presence of Shigella antigens.
Treatment
- Mild cases: Supportive fluids and electrolyte replacement.
- Severe cases: Fluoroquinolones (e.g., ciprofloxacin).
- Alternative: Trimethoprim sulfamethoxazole, however, antibiotic sensitivity test is recommended.
- Anti-peristaltic drugs are contraindicated in shigellosis.
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