Streptococcus and Related Genera Objectives Flashcards
Obj.1 Identify the major macroscopic, microscopic and structural characteristics of the Streptococcaceae.
*Gram positive cocci
*Usually arranged in pairs or chains (divide
in one plane)
*Catalase negative
*Aerobic or facultative anaerobes
Obj.2 **Differentiate using colonial, microscopic or biochemical properties between the Staphylococci and Streptococci.
**quiz question
Staphylococci:
*Colonies are more opaque, and
white/creamy/yellow
*Catalase positive
*Growth occurs in 6.5% NaCl solution
*PYR test: S. aureus negative, other
species (SI, SL, SS) are positive
Streptococci:
*Colonies are more translucent and gray
*Catalase negative
*Growth occurs in 6.5% NaCl solution
*PYR test: Group A Strep is positive
Obj.3 Describe the difference between the types of hemolysis: alpha, beta and gamma.
Alpha: partial lysis of RBCs around colony;
greenish color around colony
Beta: complete lysis of RBCs around
colony; clear area around colony
Gamma: no lysis of RBCs around colony
Obj.4 Correlate alpha and beta hemolysis with possible Streptococcus species (or groups) and Enterococcus.
Alpha (or gamma) hemolytic
*Group D Strep
*Streptococcus pneumoniae
*Enterococcus spp.
*Alpha Strep (not Group D)
Beta hemolytic
*Group A: S. pyogenes
*Group B: S. agalactiae
*Group D (rarely beta hemolytic)
*Enterococcus spp. (rarely beta hemolytic)
*Beta Strep (not Group A, B, D)
Obj.5 Differentiate between Streptolysin O and Streptolysin S, including the significance of culture setup and/or incubation.
Group A: S. pyogenes, can produce two (2) enzymes, Streptolysin O or Streptolysin S – Streptolysin O is oxygen labile (destroyed by the presence of oxygen) and MUST be incubated in anaerobic conditions to demonstrate the beta hemolysis
Obj. 6 Recognize the principle of Lancefield grouping.
“C substance” that was extracted from cell wall and was reacted with a specific antibody – these antigens are denoted by letters and are the basis for strep grouping systems
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
CATALASE
ALL SPECIES
Catalase: detecting the presence of this
enzyme (prevents against oxidative damage)
-Reagent: hydrogen peroxide
*Strep – negative
*Enterococci – mainly negative, some are
weakly positive
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
LAP Test
ALL SPECIES
LAP Test:
-Reagent: inoculate a Disk onto a colony and place a drop of colored reagent onto the Disk and observe for a color change (red = positive)
* Strep and Enterococci – positive
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
Esculin hydrolysis (Bile Esculin Agar)
ALL SPECIES
Esculin hydrolysis (Bile Esculin Agar): selective due to the presence of bile, differential based on the ability to hydrolyze esculin
-Reagent: streaking of the Bile Esculin Agar; incubate and observe for the black precipitate
*Group D Strep and Enterococci – positive
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
6.5% NaCl
ALL SPECIES
6.5% NaCl
-Reagent: inoculate organism into NaCl solution; incubate and observe for growth (turbidity and color change)
*Enterococci – positive
*Group B strep – variable
*Group D strep – negative
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
PYR Test
ALL SPECIES
PYR Test: detecting the hydrolysis of PYR
-Reagent: inoculate a Disk onto a colony and place a drop of colored reagent onto the Disk and observe for a color change (red = positive)
*Group A strep and Enterococci – positive
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
Optochin Susceptibility Test
ALPHA (OR GAMMA) HEMOLYTIC
Optochin Susceptibility Test
-Reagent: create a bacterial lawn, place disk in the middle; incubate and observe for susceptibility/resistance
*S. pneumoniae = Optochin susceptible
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
Bile Solubility Test
ALPHA (OR GAMMA) HEMOLYTIC
Bile Solubility Test: detecting the presence of lysing by the bile salts
-Reagent: tube method - create a turbid suspension, add bile salt, and observe for clearing/turbidity (clearing = positive)
plate method – a drop of bile salt placed onto colony; observe for flattening/disappearance of colony (+ positive)
*S. pneumoniae – positive
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
Quellung Test
ALPHA (OR GAMMA) HEMOLYTIC
Quellung Test
-Reagent: add a known antibody that will
react with the capsule forming a precipitate (swelling or clearing around organism = positive)
*S. pneumoniae – positive
Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.
Bacitracin Test
BETA HEMOLYTIC
Bacitracin Test
-Reagent: create a bacterial lawn, place disk in the middle; incubate and observe for susceptibility/resistance
*Beta Strep (Group A) = susceptible
