Other Streptococci and Enterococci-Felton

Question 1

What are the basic characteristics of Streptococcus pneumoniae (Pneumococcus)?

Answer 1

1. Grows as pairs of cocci (diplococcic).
2. Major respiratory pathogen.
3. Produces few toxins.
4. Patients present with RUST-colored sputum, fever, and cough.

Question 2

What is the microscopic morphology of Streptococcus pneumoniae (Pneumococcus)? What is the colony morphology of Streptococcus pneumoniae (Pneumococcus)? What are the metabolism and growth requirements for Streptococcus pneumoniae (Pneumococcus)?

Answer 2

1. Microscopic Morphology:
   •Gram+, lancet-shaped diplococcus.
   •Capsulated, non-motile and non-sporulating.
2. Colony Morphology:
   •Alpha hemolytic. (green gooey color on blood agar)
3. Metabolism and Growth Requirements:
   •Ferments (not respirates) w/ lactic acid as end product.
   •Facultative. (can go aerobically or anaerobically)
   •Fastidious.
   •Sensitive to drying out.
   •Has autolysins. (causes it to look Gram-variable)

Question 3

What are the identifying features of Streptococcus pneumoniae (Pneumococcus)?

Answer 3

1. Optochin sensitivity: Optochin disk placed on blood agar plate and inoculated w/ bacteria. Incubated overnight. Pneumococcus is sensitive to Optochin and will show a zone of inhibition.
2. Bile solubility:
   •Based on the presence of autolytic enzyme in the cell wall. Enzyme is activated by bile and bile salts.
   •Grow up saline suspension of bacteria. Then mix 10% solution of deoxycholate.
   •Suspension will become clear if pneumococcus. Bile soluble.

Question 4

What are the virulence factors associated with the capsular polysaccharide for Streptococcus pneumoniae (Pneumococcus)?

Answer 4

1. Surface antigen.
2. Antiphagocytic.
3. Differs in the 83 serotypes of pneumococcus.
4. The most important virulence factor.
5. Anticapsular antibodies are protective against infection but are type-specific.
6. There is a new polyvalent vaccine effective against 23 serotypes.

Question 5

What are the virulence factors associated with the extracellular products for Streptococcus pneumoniae (Pneumococcus)?

Answer 5

1. Pneumolysin: hemolysin that contributes to virulence.
2. Lipoteichoic acid (endotoxin-like activity)
3. Purpura-producing principle: causes purpura and dermal hemorrhage (derived from peptidoglycan).
4. Neuraminidase: enzyme against glycosyl groups on cell surface glycoproteins. Plays a role in spread.
5. IgA Protease: cleaves IgA at the hinge region.
6. Amidase: autolysin (lyses the cell) inducing inflammation

Question 6

What are the virulence factors associated with the epidemiology for Streptococcus pneumoniae (Pneumococcus)?

Answer 6

1. Found in the throat and nasopharynx of healthy people.

2. Infection usually involves a new strain not previously carried by that person.

Question 7

What are the virulence factors associated with antibiotic resistance for Streptococcus pneumoniae (Pneumococcus)?

Answer 7

They have developed resistance to penicillins due to chromosomal mutation, affecting PBPs. (not penicillinase or plasmid mediated)

Question 8

What are the virulence factors associated with common infection for Streptococcus pneumoniae (Pneumococcus)?

Answer 8

1. Lobar Pneumonia-Local Complications (empyema, pericarditis, lung abscesses)
2. Bacteremia
3. Otitis Media
4. Mastoiditis and sinusitis
5. Endocarditis
6. Septic Arthritis
7. Peritonitis
8. Conjunctivitis (pink eye), Corneal Ulcer
9. Meningitis

Question 9

What group of Streptococci does Enterococci belong to? What are the characteristics of Enterococci? What does Enterococci cause?

Answer 9

Group D Strep.
1. Normal flora in the lower GI tract.
2. No hemolysis pattern.
3. Heat resistant.
4. Bile resistant.
5. Salt resistant.
6. Not sensitive (tolerant) to penicillin. (doesn’t kill them but inhibits growth)
7. Resistant to antibiotics (Vancomycin).
Causes: Urinary tract infections, wound infections, peritonitis, bacteremias, and endocarditis

Question 10

What are the characteristics of Non-enterococci in the group D Strep family? What are 2 examples?

Answer 10

• Heat resistant.
• Bile resistant.
• NOT salt resistant.
• Examples: S. equinus and S. bovis (causes endocarditis)

Question 11

What are the characteristics of “Viridans” Streptococci (7)?

Answer 11

1. Alpha hemolytic. (greenish hemolysis)
2. Pleomorphic.
3. Normal resident flora in mouth, oropharynx and upper respiratory tract.
4. Heat and salt sensitive.
5. Usually non-pathogenic.
6. If invasion of blood stream occurs, it may cause: bacteremia and endocarditis.
7. Streptococcus mutans
   •Uses sucrose to produce a glycocalyx which helps in adherence.
   •Primary etiologic agent in dental caries. (forms plaque)