Streptococcus and Related Genera Objectives

Question 1

Obj.1 Identify the major macroscopic, microscopic and structural characteristics of the Streptococcaceae.

Answer 1

*Gram positive cocci
*Usually arranged in pairs or chains (divide
in one plane)
*Catalase negative
*Aerobic or facultative anaerobes

Question 2

Obj.2 **Differentiate using colonial, microscopic or biochemical properties between the Staphylococci and Streptococci.

**quiz question

Answer 2

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

Question 3

Obj.3 Describe the difference between the types of hemolysis: alpha, beta and gamma.

Answer 3

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

Question 4

Obj.4 Correlate alpha and beta hemolysis with possible Streptococcus species (or groups) and Enterococcus.

Answer 4

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)

Question 5

Obj.5 Differentiate between Streptolysin O and Streptolysin S, including the significance of culture setup and/or incubation.

Answer 5

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

Question 6

Obj. 6 Recognize the principle of Lancefield grouping.

Answer 6

“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

Question 7

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

CATALASE

Answer 7

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

Question 8

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

LAP Test

Answer 8

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

Question 9

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)

Answer 9

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

Question 10

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

6.5% NaCl

Answer 10

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

Question 11

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

PYR Test

Answer 11

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

Question 12

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

Optochin Susceptibility Test

Answer 12

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

Question 13

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

Bile Solubility Test

Answer 13

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

Question 14

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

Quellung Test

Answer 14

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

Question 15

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

Bacitracin Test

Answer 15

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

Question 16

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

CAMP Test

Answer 16

BETA HEMOLYTIC
CAMP Test: CAMP factor, of Strep, enhances beta lysin when in contact w/ S. aureus
-Reagent: streak S. aureus in the center of plate; stagger controls and unknowns on each side (arrowhead of hemolysis = positive)
*Beta Strep (Group B) – positive

+ control: Beta Strep (Group B)
- control: non-group B beta hemolytic strep

Question 17

Obj.7 Describe the principles and procedures of each test used in the identification of Streptococcus (groups or species) or Enterococcus.

Sodium Hippurate Hydrolysis (NaHippurate)

Answer 17

BETA HEMOLYTIC
Sodium Hippurate Hydrolysis: detection of hippuric acid hydrolyzed
-Reagent: details not required for examination (purple = positive)
*Beta Strep (Group B) – positive

Question 18

Obj.8**List the tests which are used for identification of Streptococci (include whether the tests are used for all Streptococci, alpha Streptococci, or beta Streptococci).

**quiz question

Answer 18

ALL Streptococci
*Catalase
*LAP Test
*Esculin hydrolysis (Bile Esculin Agar)
*6.5% NaCl
*PYR
Alpha Steptococci
*Optochin Susceptibility
*Bile Solubility Test
*Quellung Test
Beta Steptococci
*Bacitracin Test
*CAMP Test
*Sodium Hippurate Hydrolysis

Question 19

Obj.11 Recognize which of the identification tests are rapid vs. overnight tests.

Answer 19

Rapid
*Catalase
*LAP Test
*PYR
*Bile Solubility Test
*Quellung Test
Overnight
*Esculin hydrolysis (Bile Esculin Agar)
*6.5% NaCl
*Optochin Susceptibility
*Bacitracin Test
*CAMP Test
*Sodium Hippurate Hydrolysis

Question 20

Obj.12 **Propose alternative biochemical tests which could be used for organism identification if a biochemical test is unavailable for use.

**quiz question

Answer 20

1. Antigen testing (direct/indirect)
2. Fluorescent AB (esp. Group A)
3. Kit systems

Question 21

Obj.14 Define “pyogenic” and list the streptococcal groups that more commonly cause pyogenic infections.

Answer 21

“Pus forming”
1. S. pyogenes (Group A)
2. S. agalactiae (Group B)
3. S. dysgalactiae (Groups C,G)

Question 22

Obj.15 Discuss the symptoms, pathogenicity and complications of post streptococcal diseases that occur with Group A Strep infections.

Answer 22

Damage resulting from Ag/Ab complexes – NOT an infection
1. Acute Glomerulonephritis
*Ag/Ab complexes causes inflammation of glomeruli
2. Acute Rheumatic Fever
*Fever, inflammation of heart, joints, blood vessels and subcutaneous tissues
*Results in damage to heart valves

Question 23

Obj.16 Recognize the major virulence factor of Group A Streptococci.

Answer 23

M protein (only Group A)

Question 24

Obj.17 Explain the actions of various bacterial metabolites which are responsible for the virulence of Group A Streptococci (erythrogenic toxin causes scarlet fever rash, etc.).

Answer 24

1. Erythrogenic toxin causes scarlet fever rash
2. Streptokinase/fibrolysin and hyaluronidase causes spreading of the infection
3. Other exotoxins that cause fever, shock, tissue damage, etc.

Question 25

Obj.18 Recognize the symptoms of Scarlet fever.

Answer 25

Can result from strep throat -- associated with the erythrogenic toxin -- rash that begins on chest/truck and spreads, strawberry tongue

Question 26

Obj.19 Discuss the various methods for performing “Strep screens” and the rationale for these methods.

Answer 26

1. Throat cultures *ONLY looking for Group A Strep 2. SBA incubated anaerobically *To detect strains that are producing ONLY Steptolysin O 3. SXT (trimethoprim-sulfa) plate *Inhibits normal flora, Group A will grow

Question 27

Obj. 20 Compare and contrast Strep cultures with rapid Strep screens (ease of use, final report time, sensitivity, specificity, etc.)

Answer 27

*Throat swab *Direct Ag detection of Group A Strep *TAT is minutes relative to 24-48 hrs. for culture results *High specificity, lower sensitivity -- conclusive for positive results, MUST reflex to culture if negative

Question 28

Obj. 21 Recognize that Group A Strep infections are universally susceptible to...

Answer 28

Penicillin

Question 29

Obj. 22 Discuss the rationale for screening pregnant women for Group B Streptococcus and the recommendations for screening, including when to screen and recommended broth for culture.

Answer 29

Because some women may have Group B Strep colonized that can be transmitted to the newborn upon birth leading to meningitis/septicemia -- ALL pregnant women must be screen at 35-37 weeks LIM broth or "carrot" broth

Question 30

Obj. 23 Identify patient populations at risk for infections with Group B Streptococcus.

Answer 30

Newborns, post-partum women, females

Question 31

Obj. 25 List the species of Streptococcus which is/are capnophilic.

Answer 31

S. pneumoniae

Question 32

Obj. 26 Recognize the two groups of Streptococci that make up “viridans” Streptococci.

Answer 32

Alpha or Gamma hemolytic

Question 33

Obj. 27 List the areas of the body where “viridans” Streptococci are found as normal flora.

Answer 33

Oral, GI, and skin flora

Question 34

Obj. 28 Recognize the Streptococcal group (and species name) that is frequently isolated from the blood of patients with colon cancer.

Answer 34

Streptococcus bovis group (Group D)