Streptococci

Question 1

describe damage by immune response seen in streptococci infection

Answer 1

• cross-reacting antibodies get deposited on normal tissue antigens
  
  • e.g. Rheumatic fever
• immune complex deposition in organs
  
  • e.g. glomerulonephritis

Question 2

describe the cross-reacting antibodies seen in Rheumatic fever

Answer 2

• initial infection with specific strains of Streptococci causing sore throat or rarely skin infections
• lag period of 2-3 weeks after the initial infection
• antibodies generated to M protein of the bacteria cross-react with tissue glycoprotein in joints, heart, skin, etc.
• get deposited in the tissues and elicit inflammatory reaction at the site of deposition
• carditis: Aschoff bodes in the heart

Question 3

acute rheumatic fever is a type ____ hypersensitivity

Answer 3

acute rheumatic fever is a type II hypersensitivity

Question 4

in rheumatic fever, antibodies generated to ____ cross-react with tissue glycoprotein in joints, heart, skin, etc.

Answer 4

in rheumatic fever, antibodies generated to M protein of the bacteria cross-react with tissue glycoprotein in joints, heart, skin, etc.

they get deposited in the tissues and elicit inflammatory reaction at the site of deposition

Question 5

in acute rheumatic fever, ____ are found in the heart

Answer 5

in acute rheumatic fever, Aschoff bodies are found in the heart

Question 6

patients with rheumatic fever then develop fever, ________ (5 other symptoms)

Answer 6

patients with rheumatic fever then develop fever, polyarthritis, carditis, chorea, skin nodules, erythema (ACCNE)

Question 7

in rheumatic fever ____ and ___ would be elevated

Answer 7

in rheumatic fever ASO titer and ESR would be elevated

Question 8

rheumatic carditis can become chronic and lead to _____

Answer 8

rheumatic carditis can become chronic and lead to mitral stenosis

Question 9

describe what is seen in the image

Answer 9

acute vegetation of the mitral valve with fibrosis of the chordae tendineae

Question 10

describe what is seen in the image

Answer 10

Question 11

describe what is seen in the image

Answer 11

Question 12

describe post-streptococcal glomerulonephritis

Answer 12

immune complex mediated

• initial infection with specific strains of Streptococci causing skin infections or rarely sore throat
• lag period of 1-4 weeks after the initial infxn
• then develop acute malaise, fever, oliguria, hematuria, azotemia (increased BUN, creatinine and decreased GFR), hypertension

Question 13

in post streptococcal glomerulonephritis, immune complexes get deposited in the _____ of the _____

Answer 13

in post streptococcal glomerulonephritis, immune complexes get deposited in the basement membrane of the glomeruli

Question 14

describe what is seen in the image

Answer 14

Question 15

describe the etiology of diphtheria

Answer 15

• etiology:
  
  • corynebacterium diphtheria: G+ve rod
  • commonly affect children

Question 16

describe the pathogenesis of diphtheria

Answer 16

• pathogenesis:
  
  • toxin inhibits protein synthesis by ADA-ribosylation of protein synthesis
  • affects the pharynx and tonsils and leads to necrosis of the mucosa
    
    • the necrotic cells, bacteria, PMN and exudate form pseudomembrane (can block the airway)

Question 17

describe the clinical features of diphtheria

Answer 17

• clinical features:
  
  • fever, dysphagia
  • lymph nodes enlargement in the neck (Bull neck)
  • laryngeal edema (may need tracheotomy)
  • adherent thick gray material covering the tonsils and pharynx

Question 18

describe complications of diphtheria

Answer 18

• C. diphtheriae can produce powerful exotoxins
  
  • this can cause myocarditis which can lead to heart failure (3 weeks) and spinal nerve paralysis

Question 19

_______ is an antibiotic-associated colitis

Answer 19

pseudomembranous colitis is an antibiotic-associated colitis

Question 20

describe the etiology of pseudomembranous colitis

Answer 20

• etiology:
  
  • Clostridium difficile (G+ve bacillus)

Question 21

describe the pathogenesis of pseudomembranous colitis

Answer 21

• pathogenesis:
  
  • broad spectrum antibiotics eliminate normal flora of the gut that normally afford protection
    
    • classically seen with the use of Clindamycin, cephalosporin, amoxicillin, ampicillin
  • severe mucosal suppurative inflammation (multiple ulcers) which leads to necrotic mucosa that forms a pseudomembrane (seen on colonoscopy)
  • colitis and pseudomembrane result from bacterial production of large amount of enterotoxins

Question 22

an investigation for pseudomembranous colitis is ____ in the stool

Answer 22

an investigation for pseudomembranous colitis is C. difficile in the stool

Question 23

describe the clinical features of pseudomembranous colitis

Answer 23

• clinical features:
  
  • fever, abdominal cramps and diarrhea (watery, with/without blood)

Question 24

Answer 24

Question 25

describe clostridia perfringens

Answer 25

• G+ve bacilli, anaerobic, produce spores found in soil
• invade traumatic and surgical wounds

Question 26

clostridia perfringens secretes 14 toxins, with the most important being _____

Answer 26

clostridia perfringens secretes 14 toxins, with the most important being Alpha toxin (Lecinthinase)

Question 27

clostridia perfringens degrades ____ and destroys _____

Answer 27

clostridia perfringens degrades lecithin (major component of cell membrane) and destroys RBCs, platelets and muscle fibers (myonecrosis)

Question 28

describe what is seen in the image

Answer 28