MIDTERMS: L3 - STREPTOCOCCUS

Question 1

MOTF

1. Streptococcus - catalase positive
2. Nutritionally fastidious

Answer 1

1 false, 2 true

1 - catalase neg

Question 2

T OR F
Streptococcus - Requires an enriched medium with decreased Carbon
dioxide and high oxygen concentration

Answer 2

False
Streptococcus - Requires an enriched medium with increased Carbon
dioxide and low oxygen concentration

Question 3

3 Classification of Streptococcus:

Answer 3

1. Bergey’s/Academic Classification - Based on physiologic classifications of Streptococcus such as their thermal requirement
2. Lancefield Classification - Classifies Streptococcus on its cell wall polysaccharide
3. Smith and Brown Classification - Based on the hemolytic pattern of bacteria on
   the Blood Agar

Question 4

Contains a C polysaccharide unrelated to

Lancefield grouping

Answer 4

Streptococcus pneumoniae

Question 5

Viridans group of Streptococci (enumerate its groups)

Answer 5

mutans, salivarius, bovis, anginosus,

and mitis

Question 6

MOTF
1. Pathogenic Group A Strep or Streptococcus
pyogenes and Group B Strep or Streptococcus
agalactiae - Beta hemolytic (complete hemolysis)
2. Alpha hemolytic (No hemolysis)- Streptococcus pneumoniae

Answer 6

1 true, 2 false

2 - alpha hemolytic (partial hemolysis)

Gamma hemolytic (no hemolysis) - some viridans

Question 7

Gram-Positive Selective Media (examples)

Answer 7

1. Columbia Agar with Colistin

2. Nalidixic acid and Phenylethyl Alcohol Agar

Question 8

Identify Group B streptococcus in
vaginal or rectal swab in pregnant
agen

Answer 8

Too-Hewitt Broth with Gentamicin, Nalidixic

Acid , or Colistin and Nalidixic Acid or LIM broth

Question 9

Isolate Group A streptococcus (selective media)

Answer 9

BAP with SXT

Question 10

Pinpoint, Large Zone of B-Hemolysis

Answer 10

Group A

Question 11

Larger, narrow zone of B hemolysis

Answer 11

Group B

Question 12

Small,gray, glistening, dome-shaped, mucoid, umbilicated, a-hemolysis

Answer 12

S. pneumoniae

Question 13

Presumptive identification of beta hemolytic Streptococcus pyogenes from other beta hemolytic strep

Answer 13

Bacitracin (Taxo A) Susceptibility test

Question 14

MOTF
Taxo A
1. Positive result of Taxo A - presence of ZOI meaning susceptible = Group A
2. Use of Taxo A impregnated with 0.04 units of bacitracin on the surface of BAP

Answer 14

Both True

Positive: ZOI = Susceptible: Group A
ZOI greater than 10mm

Negative: No ZOI = Resistant: non- Group A (ex. Group B, C, F & G)

Question 15

MOTF
SXT (Trimethoprim-sulfamethoxazole)
1. Positive: Susceptible (ZOI) = Not Group A & B (Viridans streptococci)
2. Negative: Resistant = Group A & B

Answer 15

Both true

A and B - NO ZOI (resistant)

Question 16

1. Identifies Group B Streptococcus (Streptococcus agalactiae)
2. Distinguishes Group B from oher B-hemolytic streptococci

Answer 16

CAMP test (Christie, Atkins, and Munch-Peterson)

Question 17

Extracellular thermostable antigenic protein produced by Group B

Answer 17

CAMP

Question 18

In CAMP test, there is a synergistic hemolysis between S. agalactiae and _______ causing an enhanced hemolysis

Answer 18

S. aureus

Question 19

Results of CAMP test:

Answer 19

Positive: Enhanced hemolysis in arrowhead pattern = Group B Strep

Negative: No enhanced hemolysis = Not Group B

Question 20

Test for the ability to hydrolyze hippuric acid to benzoic acid and glycine (Distinguish group B)

Answer 20

Hippurate hydrolysis

Positive: Deep blue (purple) = Group B Streptococci

Negative: Colorless = Group A / Not Group B
Streptococci

Question 21

1. Presumptively identifies Group D Streptococcus and Enterococcus
2. Test for the ability to grow in 40% bile and hydrolyse esculin to esculetin

Answer 21

Bile Esculin Hydrolysis

Positive: Blackening of the agar slant = Group D Negative: No blackening = Viridans Streptococci

Question 22

1. Differentiates Group D Non-enterococcus and Enterococcus

2. Test the organism’s ability to grow in 6.5% NaCl

Answer 22

Salt Tolerance Test (6.5%)

Positive: Visible turbidity = enterococcus
○ With or without color change from purple to yellow

Negative: No turbidity = Group D Non-enterococcus

Question 23

1. Presumptively identifies Streptococcus pneumonia
2. Differentiates S. pneumonia from a-hemolytic
   streptococcus

Answer 23

Optochin (Taxo P)
- contains ethyhydrocupreine hcl

Positive: ≥ 14mm: S. pneumoniae

Negative: No ZOI: other a-hemolytic Streptococcus

Question 24

1. Test for the solubility to Bile salt

2. Differentiates S. pneumonaie from other a-hemolytic streptococci

Answer 24

Bile Solubility Test

Positive: Colony disintegrates = S. pneumoniae

Negative: Intact colonies = other a-hemolytic
streptococcus

Question 25

In Bile solubility test one will apply:

1. One to two drops of ________

Answer 25

10% sodium deoxycholate - plate

2%sodium deoxycholate - tube

Question 26

Presumptively identifies Group A streptococci (Streptococcus pyogenes) and Enterococci by the presence of the enzyme L-pyrrolidonyl arlyamidase

( detector reagent
N,N-dimethylaminocinnamaldehyde)

Answer 26

PYR Test

Positive: Bright red color within 5mins = Enterococcus fecalis and S. pyogenes

Negative: No color change or an orange color