Bailey 3

Question 1

Streptococcus sp characteristics

Answer 1

Gram +
Cocci
  -Chains or diplococci
Non-spore forming
Facultative anaerobes
Catalase neg
Infect humans and animals

Question 2

Streptococcus sp classification/identification

Answer 2

-Hemolysis pattern
alpha-partial clearing (green)
beta-clearing
gamma-no clearing
-Lancefield group-cell wall carb antigens
*Agglutinated antigen-latex=positive result
-Metabolic reactions

Question 3

GAS diseases

Answer 3

• Acute pharyngitis
• Pyoderma
  
  • Impetigo (skin)
  • Erysipelas (skin and subQ)
  • Cellulitis
• GAS pneumonia
• Necrotizing fascitis and myositis
• Childbed (peurperal) fever
• Foodborne outbreaks

Question 4

GAS-S. pyogenes causes what?

Answer 4

Strep throat and scarlet fever (strep w/ red skin rash)

Question 5

What is ARF

Answer 5

Acute rheumatic fever

• Nonsuppurative sequelae following GAS infection
  
  • Inflammation of heart and joints
  • polyarthritis, carditis
  • Severe valvular scarring
  • All but carditis resolve over time
• Infection must invoke immune response
  
  • Hypersensitivity rxn caused by cross-reacting antibodies
  • Few people susceptible
  • Can occur after asymptomatic infection

Question 6

How is ARF treated

Answer 6

Can be prevented by treating strep w/ full course of penicillin
-ARF does not respond to drugs but can be prevented
High susceptibility to recurrence-prophylactic antibiotics for life

Question 7

What is APSGN

Answer 7

Acute Post-streptococcal glomerulonephritis

• Active inflammation in the glomeruli of kidney
• Selectively removes uremic waste products
• Urine smoky due to proteins, WBC, RBCs and renal failure->dialysis
• Only caused by a few types of GAS

Question 8

How do ARF and APSGN differ?

Answer 8

ARF:
  -Only follows pharyngitis
  -Few people susceptible
  -Susceptibility of recurrence is high
  -Prevented by penicillin
APSGN:
  -Follows pharyngitis or pyodermal inf.
  -Many people susceptible
  -Susceptibility of recurrence is low
  -Not prevented by penicillin

Question 9

GAS encounter, reservoir, transmission

Answer 9

• Live on skin and mucous membranes (nasopharynx)
• Person to person transmission
  
  • Resp or hand to mouth
  • Food
  • Skin/wound

Question 10

GAS entry and adherence

Answer 10

• Cannot penetrate intact skin
• Bacteria bind to epithelial cells using adhesins
  
  • LTA makes GAS sticky and binds to fibronectin of host
  • Protein F-fibronectin binding protein
  • M protein-keratinocytes (outer skin) adhesin

Question 11

GAS spread in body

Answer 11

Depends on how infection was acquired

• Skin or mucous membrane->localized inf
• Deeper tissue infections->rapid spread due to digestive enzymes

Question 12

GAS virulence factors

Answer 12

DNAses
Hyaluronidase
Chemotaxins
Hemolysins
Streptokinase-clot lysis by breaking down fibrin

Question 13

GAS antiphagocytic factors

Answer 13

M protein
Hyaluronic acid capsule
  -most capsules-made of polysaccharides!
C5a peptidases
  -inactivates phagocyte chemotaxin

Question 14

M protein

Answer 14

• most important antiphagocytic factor
  
  • central to pathogenesis and required for virulence
  • binds to host serum proteins->forms dense coating->complement cant bind so no opsonization and no complement cascade
  • contain antigenic protein tips that antibody can opsonize

Question 15

Hyaluronic acid capsule

Answer 15

• most capsules-made of polysaccharides!
  
  • makes GAS slippery so phagocytes cannot attach
  • ARF isolates heavily encapsulated

Question 16

What are SPEs

Answer 16

Strep Pyrogenic exotoxins

• Intense inflamm response in tissues
• Superantigens activate macrophages and T cells to release cytokines
• Three types: SPEA, B, and C
• Responsible for rash of scarlet fever
• Similar to TSST-1
• Produce Strep TSS

Question 17

GBS characteristics

Answer 17

• More common but less notorious than GAS
• Inhabit lower GI and female genital tract
• Cause neonatal sepsis and meningitis (S. agalactiae)
• Cause cellulitis, arthritis, and meningitis
• Polysaccharide capsule that is antigenic (unlike GAS capsule)

Question 18

B-hemolytic strep groups other than GAS and GBS

Answer 18

C, G, and F

Question 19

GCS, GGS, and GFS characteristics

Answer 19

• M protein, bind fibrinogen and secrete similar extracellular enzymes
• Group C also has hyaluronic acid capsule (like GAS)
• Implicated in AGN but not ARF

Question 20

GDS

Answer 20

• alpha or gamma hemolytic
• enterococci on nonenterococci strains
  
  • S. faecalis=enterococcus faecalis
• normal flora of GI and GU tracts
• Low virulence

Question 21

Enterococci is referred to as _____? why?

Answer 21

Worlds toughest pathogenic bacteria

• Grows in high salt and in detergents
• Inhibited but not killed by penicillin
• Resistant to most antibiotics (synergism required)

Question 22

Vancomycin resistant enterococci (VRE)

Answer 22

• Low virulence but untreatable
• Transfer vancomycin resistance to staph.
• dalfopristin-quinipristin combination

Question 23

Nonenterococcal GDS

Answer 23

S. bovis.=most common for human disease

• Subacute bacterial endocarditis-affects abnormal heart valves
• Bactermia-colonic lesions-colon cancer
• Does not grow in high salt
• Penicillin is effective

Question 24

Viridans strep.

Answer 24

• alpha hemolytic-aka “greening”
• 30-60% of oropharyngeal flora
• Low virulence
• Most common cause of subacute bacterial endocarditis-affects heart valves
• Produce dextrans for adherence

Question 25

What is responsible for caries

Answer 25

Viridans streptococci-mutans group

-includes S. mutans, s. sanguis, s. salivarius, s. mitis, s minitor, and s. milleri

Question 26

How to viridans streptococci mutans group cause caries

Answer 26

• Surface proteins bind salivary glycoprotein on teeth (pellicle)
• Thrive on sucrose
• Ferment sugar to lactic acid that demineralizes enamel