MIDTERMS: L3 - STREPTOCOCCUS Flashcards
MOTF
- Streptococcus - catalase positive
- Nutritionally fastidious
1 false, 2 true
1 - catalase neg
T OR F
Streptococcus - Requires an enriched medium with decreased Carbon
dioxide and high oxygen concentration
False
Streptococcus - Requires an enriched medium with increased Carbon
dioxide and low oxygen concentration
3 Classification of Streptococcus:
- Bergey’s/Academic Classification - Based on physiologic classifications of Streptococcus such as their thermal requirement
- Lancefield Classification - Classifies Streptococcus on its cell wall polysaccharide
- Smith and Brown Classification - Based on the hemolytic pattern of bacteria on
the Blood Agar
Contains a C polysaccharide unrelated to
Lancefield grouping
Streptococcus pneumoniae
Viridans group of Streptococci (enumerate its groups)
mutans, salivarius, bovis, anginosus,
and mitis
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
1 true, 2 false
2 - alpha hemolytic (partial hemolysis)
Gamma hemolytic (no hemolysis) - some viridans
Gram-Positive Selective Media (examples)
- Columbia Agar with Colistin
2. Nalidixic acid and Phenylethyl Alcohol Agar
Identify Group B streptococcus in
vaginal or rectal swab in pregnant
agen
Too-Hewitt Broth with Gentamicin, Nalidixic
Acid , or Colistin and Nalidixic Acid or LIM broth
Isolate Group A streptococcus (selective media)
BAP with SXT
Pinpoint, Large Zone of B-Hemolysis
Group A
Larger, narrow zone of B hemolysis
Group B
Small,gray, glistening, dome-shaped, mucoid, umbilicated, a-hemolysis
S. pneumoniae
Presumptive identification of beta hemolytic Streptococcus pyogenes from other beta hemolytic strep
Bacitracin (Taxo A) Susceptibility test
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
Both True
Positive: ZOI = Susceptible: Group A
ZOI greater than 10mm
Negative: No ZOI = Resistant: non- Group A (ex. Group B, C, F & G)
MOTF
SXT (Trimethoprim-sulfamethoxazole)
1. Positive: Susceptible (ZOI) = Not Group A & B (Viridans streptococci)
2. Negative: Resistant = Group A & B
Both true
A and B - NO ZOI (resistant)
- Identifies Group B Streptococcus (Streptococcus agalactiae)
- Distinguishes Group B from oher B-hemolytic streptococci
CAMP test (Christie, Atkins, and Munch-Peterson)
Extracellular thermostable antigenic protein produced by Group B
CAMP
In CAMP test, there is a synergistic hemolysis between S. agalactiae and _______ causing an enhanced hemolysis
S. aureus
Results of CAMP test:
Positive: Enhanced hemolysis in arrowhead pattern = Group B Strep
Negative: No enhanced hemolysis = Not Group B
Test for the ability to hydrolyze hippuric acid to benzoic acid and glycine (Distinguish group B)
Hippurate hydrolysis
Positive: Deep blue (purple) = Group B Streptococci
Negative: Colorless = Group A / Not Group B
Streptococci
- Presumptively identifies Group D Streptococcus and Enterococcus
- Test for the ability to grow in 40% bile and hydrolyse esculin to esculetin
Bile Esculin Hydrolysis
Positive: Blackening of the agar slant = Group D Negative: No blackening = Viridans Streptococci
- Differentiates Group D Non-enterococcus and Enterococcus
2. Test the organism’s ability to grow in 6.5% NaCl
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
- Presumptively identifies Streptococcus pneumonia
- Differentiates S. pneumonia from a-hemolytic
streptococcus
Optochin (Taxo P)
- contains ethyhydrocupreine hcl
Positive: ≥ 14mm: S. pneumoniae
Negative: No ZOI: other a-hemolytic Streptococcus
- Test for the solubility to Bile salt
2. Differentiates S. pneumonaie from other a-hemolytic streptococci
Bile Solubility Test
Positive: Colony disintegrates = S. pneumoniae
Negative: Intact colonies = other a-hemolytic
streptococcus