(M) Lesson 7.3: Gram Positive and Gram Negative Cocci Flashcards
Streptococcus
- Gram-positive cocci in chains
- Non-motile and non-sporeforming
- Negative for catalase
- Facultative anaerobe
- Pinpoint colony
Streptococcus
Laboratory diagnosis basis for suspected Streptococcus?
Hemolytic pattern in the BAP
- Also called Taxo A
- Uses 0.04 units of Bacitracin
- Done for beta-hemolytic Streptococcus
- Confirms Streptococcus pyogenes
- More important than PYR
Bacitracin Susceptibility Test (Taxo A)
Bacitracin Susceptibility Test (Taxo A)
This species results in a susceptible result for Streptococcus pyogenes.
Note: Means highly susceptible to bacitracin and there is no ZOI requirement.
Streptococcus pyogenes
Bacitracin Susceptibility Test (Taxo A)
These species results in resistance.
Note: Positive for PYR test
Enterococcus faecalis and other Streptococci
- Identifies Streptococcus pyogenes
- Follow-up confirmatory test for Bacitracin test
PYR Test (L-pyrrolidonyl B-napthylamide)
What is the principle of the PYR Test?
Streptococcus pyogenes reacts with PYR because of the added D-dimethylaminocinnamaldehyde
PYR Test
These species test positive (red) for this test.
- Streptococcus pyogenes
- Enterococcus faecalis
Other Streptococci test negative.
- Principle: Streptococcus agalactiae reacts with CAMP factor that it releases an arrowhead zone of hemolysis upon interaction with the hemolysin of another
CAMP Test
CAMP Test
Streptococcus agalactiae releases what type of zone of hemolysis?
Arrowhead
CAMP Test
This bacteria is the only one that tests positive for CAMP test denoted by a unique arrowhead zone of hemolysis.
Streptococcus agalactiae
Other beta-hemolytic Streptococci test negative.
- Differentiates Streptococcus agalactiae from other beta-hemolytic cocci
Hippurate Hydrolysis Test
Hippurate Hydrolysis Test
Streptococcus agalactiae releases ____ that hydrolyzes hippurate, resulting in a purple-colored cotton upon reaction with ninhydrin.
Hippurase
Hippurate Hydrolysis Test
This is the only bacteria that tests positive for this test denoted by a purple complex.
Streptococcus agalactiae
Other beta-hemolytic Streptococci test negative.
- For alpha-hemolysis, green growth in BAP
- Utilizes optochin
Optochin Test
- An antimicrobial agent
- Specifically Taxo P
Optochin
Optochin Test
P on antibiotic disk indicates?
Optochin
Optochin Test
P10 on antibiotic disk indicates?
Penicillin
Principle of Optochin Test?
Ethyldrocuprein hydrochloride (optochin) inhibits the growth of Streptococcus pneumoniae
Optochin test
Zone of Inhibition must measure ____ or ____ depending on which Taxo P is used by the laboratory for it to be called susceptible.
greater than 16 mm or 14 mm
Other alpha-hemolytic Streptococci tests negative.
- Principle: Under the influence of bile salt (sodium deoxycholate) or detergent, the organism’s cell wall lyses during cell division
- Streptococcus pneumoniae is bile-soluble
Bile Solubility Test
Positive indicator for Bile Solubility Test?
A suspension of Streptococcus pneumoniae in a solution of sodium deoxycholate (lyses and the solution becomes clear)
Other alpha-hemolytic Streptococci test negative.
- For Group D Streptococci
- Uses bile esculin agar
- Principle: Group D streptococci and Enterococcus
Bile Esculin Hydrolysis Test
These species can grow in the presence of bile and hydrolyzes esculin to esculetin and glucose.
Group D Strep and Enterococcus