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Questions and Answers
How does Yersinia enterocolitica evade the host's inflammatory response?
How does Yersinia enterocolitica evade the host's inflammatory response?
- Through the action of Yersinia outer proteins (Yops) that block pro-inflammatory cytokine secretion and inhibit macrophage activation. (correct)
- By producing a thick capsule that inhibits phagocytosis and complement activation.
- Via the secretion of proteases that degrade complement components and antibodies.
- By altering its LPS structure to prevent recognition by TLR4 receptors on immune cells.
Why does Yersinia enterocolitica form colorless colonies on MacConkey agar?
Why does Yersinia enterocolitica form colorless colonies on MacConkey agar?
- It produces a dark pigment that masks the color change.
- It is a non-lactose fermenter and thus does not produce acid to change the pH indicator. (correct)
- It rapidly consumes any lactose present, reverting the agar to its original color.
- It inhibits the pH indicator in the agar.
What is the clinical significance of Yersinia enterocolitica's ability to grow within Peyer's patches?
What is the clinical significance of Yersinia enterocolitica's ability to grow within Peyer's patches?
- It prevents the bacteria from disseminating to other tissues.
- It facilitates access to the bloodstream, leading to bacteremia.
- It allows the bacteria to establish a latent infection within immune cells.
- It enables the bacteria to replicate and spread to mesenteric lymph nodes, potentially causing mesenteric lymphadenitis and pseudoappendicitis. (correct)
How do siderophores contribute to the virulence of Yersinia enterocolitica?
How do siderophores contribute to the virulence of Yersinia enterocolitica?
What immunological factor is associated with post-infectious sequelae, such as reactive arthritis, following Yersinia enterocolitica infection?
What immunological factor is associated with post-infectious sequelae, such as reactive arthritis, following Yersinia enterocolitica infection?
What is the likely mechanism behind erythema nodosum development following Yersinia enterocolitica infection?
What is the likely mechanism behind erythema nodosum development following Yersinia enterocolitica infection?
Why is serological testing (e.g., ELISA) for Yersinia enterocolitica less commonly used than stool culture for diagnosis?
Why is serological testing (e.g., ELISA) for Yersinia enterocolitica less commonly used than stool culture for diagnosis?
In the context of Yersinia enterocolitica, what is meant by the term 'pseudoappendicitis'?
In the context of Yersinia enterocolitica, what is meant by the term 'pseudoappendicitis'?
During a triple sugar iron (TSI) test, why does Yersinia enterocolitica not produce a black precipitate?
During a triple sugar iron (TSI) test, why does Yersinia enterocolitica not produce a black precipitate?
Which population is at higher risk of developing septicemia from a Yersinia enterocolitica infection?
Which population is at higher risk of developing septicemia from a Yersinia enterocolitica infection?
Flashcards
Yersinia enterocolitica
Yersinia enterocolitica
Gram-negative bacillus causing diarrheal illness (yersiniosis).
Y. enterocolitica Virulence Factors
Y. enterocolitica Virulence Factors
Adhesins (YadA, AilA), Type 3 Secretion System (T3SS), Yersinia outer proteins (Yops), siderophores, and enterotoxin (Yst).
Y. enterocolitica Infections
Y. enterocolitica Infections
Terminal ileitis, enterocolitis, mesenteric lymphadenitis (pseudoappendicitis).
Yersiniosis Symptoms
Yersiniosis Symptoms
Fever, diarrhea (with blood/mucus), abdominal pain; pseudoappendicitis mimics appendicitis.
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Yersiniosis Diagnosis
Yersiniosis Diagnosis
Identifying bacteria in stool cultures; serological tests (less common).
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Y. enterocolitica Treatment
Y. enterocolitica Treatment
Third-generation cephalosporins, trimethoprim-sulfamethoxazole, aminoglycosides, fluoroquinolones, and tetracyclines.
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Erythema Nodosum
Erythema Nodosum
Inflammation of fat cells under the skin due to delayed hypersensitivity to bacterial antigens.
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Reactive Arthritis
Reactive Arthritis
Joint pain/swelling due to bacterial antigens deposited in joints, causing a delayed inflammatory response.
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- Yersinia enterocolitica is a gram-negative bacillus belonging to the Enterobacteriaceae family.
- The Yersinia genus is named after Alexander Yersin, who discovered it.
- Enterocolitica refers to the intestine and colon.
- Yersinia enterocolitica causes a diarrheal illness called yersiniosis.
Morphology and Physiology
- It has a thin peptidoglycan layer, staining pink with Safranin dye during Gram stain.
- It appears as a small pink rod under the microscope.
- Motility varies with temperature: motile at 25 degrees Celsius, non-motile at 37 degrees Celsius.
- It is a facultative anaerobe.
- It is non-spore forming.
- It is oxidase negative.
Culture
- Grows well on MacConkey agar, forming colorless colonies due to being a non-lactose fermenter.
- On cefsulodin-irgasan-novobiocin (CIN) agar, it forms white colonies with a deep red center, resembling bull's-eye colonies, after 24 hours.
- In the triple sugar iron (TSI) test, it does not produce hydrogen sulfide, so no black precipitate forms.
Virulence Factors
- Adhesins like YadA and Ail help attach to gut epithelial cells.
- Type three secretion system (T3SS) delivers Yersinia outer proteins (Yops).
- Yops block secretion of pro-inflammatory cytokines and inhibit macrophage activation, suppressing the host's inflammatory response and helping avoid phagocytosis.
- It can replicate inside Peyer's patches and spread to mesenteric lymph nodes.
- It uses siderophores to acquire iron from host cells.
- Produces an enterotoxin called Yst, potentially involved in diarrheal disease.
Transmission and Diseases
- Transmitted through the fecal-oral route, often from contaminated milk or pork.
- Causes yersiniosis, a gastrointestinal infection.
- Can cause terminal ileitis in the ileum, enterocolitis in the right colon, or mesenteric lymphadenitis in the abdominal mesenteric lymph nodes, potentially leading to pseudoappendicitis.
- In immunocompromised individuals or those with iron overload, it can cause septicemia.
- Post-infection sequelae include reactive arthritis and erythema nodosum, especially in individuals with the HLA-B27 antigen.
Symptoms
- Enterocolitis: fever, diarrhea with blood and mucus, and abdominal pain.
- Pseudoappendicitis: fever, abdominal pain, and right lower quadrant tenderness.
- Septicemia: fever, chills, hypotension, and tachycardia.
- Reactive arthritis: joint pain and swelling.
- Erythema nodosum: red or purple painful lesions, mainly on the legs.
Diagnosis
- Identification of bacteria in stool cultures.
- Reactive arthritis diagnosed by identifying inflammatory cells or bacteria in synovial fluid.
- Serological tests like tube agglutination or ELISA can confirm infection by demonstrating increased antibody titers in the serum.
- Ultrasound or CT scan to exclude appendicitis in cases of pseudoappendicitis.
Treatment
- Yersinia enterocolitica infections are usually treated with third-generation cephalosporins.
- Also susceptible to trimethoprim-sulfamethoxazole, aminoglycosides, fluoroquinolones, and tetracyclines.
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