Micro Bacterial Pathogenesis

14 Questions

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Micro Bacterial Pathogenesis

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Questions and Answers
  • 1. 
    • A. 

      Gram-negative, oxidase-positive, motile bacillus

    • B. 

      Gram-positive, catalase-positive, coagulase-negative coccus

    • C. 

      Budding yeast

    • D. 

      Gram-positive, catalase-positive, coagulase-positive coccus

    • E. 

      Gram-negative, oxidase-positive diplococcus

  • 2. 
    A patient in the ICU develops diarrhea after several days of treatment with broad- spectrum antibiotics for a severe infection. The causative agent is found to be a Gram- positive, strictly anaerobic rod that produces an enterotoxin (called toxin A) that affects a target host cell's ability to polymerize actin. The C-terminus of this protein binds specific glycosidic structures on the host surface, and after endocytosis the N- terminal glucosyltransferase domain is autoproteolytically cleaved and enters the cytoplasm. What term best classifies the C-terminal part of this protein?
    • A. 

      Type III secretion domain

    • B. 

      ‘B’ domain

    • C. 

      Type V secretion domain

    • D. 

      'C’ domain

    • E. 

      'A" domain

  • 3. 
    A 45-year-old man presents with a cough and fever. His cough is productive of yellowish sputum with rusty streaks. Chest x-ray shows consolidation in the left lower lobe. Gram stain of a sputum smear shows scant epithelial cells, numerous white blood cells, and numerous Gram-positive diplococcii. What are two important virulence factors associated with the most likely causative agent?
    • A. 

      Lipooligosaccharide and capsule

    • B. 

      Elastase and exotoxin A

    • C. 

      Alpha-toxin and Panton-Valentine leukocidin

    • D. 

      Capsule and a cytolysin

    • E. 

      Intimin and bundle-forming pili

  • 4. 
    • A. 

      Alpha-toxin

    • B. 

      Delta-toxin

    • C. 

      Rhamnolipid

    • D. 

      Exotoxin A

    • E. 

      Collagenase

  • 5. 
    A 7-year-old girl is brought to the emergency department with a high temperature and low blood pressure She is in septic shock. Her history reveals that she had been complaining of an earache for the last few days, and her mother had scheduled an appointment with her primary physician for the next day. She wanted her daughter to see her primary physician since she has sickle-cell anemia and has been under that doctor's care for several years. Blood cultures are positive for a Gram-positive diplococcus which binds fluorescently-labeled anti-19A capsular antibody, as assessed by fluorescent microscopy. What set of characteristics would you expect to be displayed by the causative agent?
    • A. 

      Positive for catalase and coagulase, produces protein A

    • B. 

      Positive for oxidase, produces outer membrane blebs

    • C. 

      Negative for catalase and coagulase, is beta-hemolytic

    • D. 

      Negative for catalase and coagulase, is resistant to bile

    • E. 

      Negative for catalase and coagulase, is alpha-hemolytic Correct

  • 6. 
    A 19-year-old man presents with a large abscess on his left thigh. It is painful upon palpation, erythematous, and has pus draining from several openings. He is otherwise healthy. After incision and drainage, a sample of the pus is sent to the laboratory for identification and antibiotic susceptibility testing. A Gram-positive, catalase-positive, coagulase-positive coccus is isolated. What virulence factor, produced by this organ ism, could most likely lead to a severe complication of this patient's infection?
    • A. 

      Pneumolysin

    • B. 

      Exoenzyme

    • C. 

      Delta-toxin

    • D. 

      Toxic shock syndrome toxin-1

    • E. 

      Exfoliating toxin

  • 7. 
    A 14-year-old boy presents to an urgent care clinic with his adoptive mother. He had been complaining of fatigue and a severe sore throat for several days, and had developed a fever and difficulty breathing. His neck was visibly enlarged. His mother states that he had recently moved to the U.S. from Tajikstan, and she was unaware of his prior medical history. Physical examination revealed an adherent membrane over his tonsils and pharynx. The signs and symptoms of this disease are caused by an AB toxin that ADP-ribosylates elongation factor 2. What is the genus of the causative agent?
    • A. 

      Pseudornonas

    • B. 

      Corynebacterium

    • C. 

      Clostridium

    • D. 

      Streptococcus

    • E. 

      Bordetella

  • 8. 
    How would, a bacterial structure that is visualized by the quellung technique most aid in pathogenesis?
    • A. 

      Provide motility

    • B. 

      Reduce ROS damage

    • C. 

      Provide antibiotic resistance

    • D. 

      Prevent phagosome-lysosome fusion

    • E. 

      Reduce phagocytosis

  • 9. 
    A 23-year-old army recruit complained of headaches and neck stiffness soon after moving into the barracks. The next day, she exhibited confusion, a high fever, and low blood pressure. Blood and CSF cultures both grew Gram-negative, oxidase-positive, kidney-shaped diplococci. Soon after, her kidney function became impaired and platelet counts dropped dramatically. What event most directly led to the severe manifestations of her illness?
    • A. 

      Recognition of lipoteichoic adds by TLR 2/11R-6

    • B. 

      Deformation of cells in the meninges due to a T3SS effector protein

    • C. 

      Abrogation of protein synthesis in kidney cells by an A-513 toxin

    • D. 

      Non-specific activation of T cells by a bacterial protein

    • E. 

      Recognition of LIP-bound LOS by TLR-4

  • 10. 
    Given that army recruits are fully immunized, what is the most likely serological classification of the causative agent that caused her infection. A 23-year-old army recruit complained of headaches and neck stiffness soon after moving into the barracks. The next day, she exhibited confusion, a high fever, and low blood pressure. Blood and CSF cultures both grew Gram-negative, oxidase-positive, kidney-shaped diplococci. Soon after, her kidney function became impaired and platelet counts dropped dramatically. What event most directly led to the severe manifestations of her illness?
    • A. 

      0157

    • B. 

      B

    • C. 

      D-K

    • D. 

      K30

    • E. 

      19A

  • 11. 
    • A. 

      Binding to host cell receptors

    • B. 

      Protection from complement deposition

    • C. 

      General adhesion

    • D. 

      Increased antibiotic resistance Correct

  • 12. 
    Considering the case in  question  11 , what is the mechanism of action of an AB exotoxin (described in your exotoxin tables) produced by the causative agent? A 17-year-old patient with cystic fibrosis has recently experienced an acute exacerbation of his pulmonary symptoms. Sputum culture reveals a charge in the colony morphology of the Gram-negative, oxidase-positive, motile bacilli isolated
    • A. 

      Adenylate cyclase activity causes unregulated cAMP production

    • B. 

      ADP-ribosylation of a G protein

    • C. 

      Protcolysis

    • D. 

      Activation of T cells

    • E. 

      ADP-ribosylation of elongation factor-2

  • 13. 
    What are the characteristics of the bacterial species that produces a bacterial exotoxin that degrades proteins involved in the release of a mammalian inhibitory neurotransmitter?
    • A. 

      Gram-positive, aerobic streptobacilli

    • B. 

      Gram negative, aerobic cocci in pairs

    • C. 

      Gram negative, anaerobic co-ccobacillus

    • D. 

      Gram-positive, anaerobic bacillus

    • E. 

      Gram-negative, anaerobic, branching bacilli

    • F. 

      Gram-positive, aerobic cocci in clusters

  • 14. 
    A 53-year-old woman presents to her physician complaining of warmth and pain in her right knee. The joint had been replaced 5 months before, but she had recovered well from the surgery and had no apparent post-operative complications. Inflammation is seen around the joint, and culture of a tissue sample taken from an inflamed area grew a Gram-positive, catalase-positive coccus. There did not appear to be extensive damage to the surrounding tissue. What is the most likely causative agent?
    • A. 

      Streptococcus pyogenes

    • B. 

      Staphylococcus aureus

    • C. 

      Pasteurella multocida

    • D. 

      Neisseria gonorrhoeae

    • E. 

      Staphylococcus epidermidis