Bacte - Strep Flashcards
are streptococci typically gram (+) or gram (-)? what is their shape and how are they arranged?
gram positive; cocci, arranged in pairs or chains
True or false
1. motile
2. nonsporeforming
3. facultative anaerobes
4. some species show enhanced growth under increased (10% - 15%) CO2
5. require supportive or enriched media, such as blood agar, Todd-Hewitt broth, or chocolate agar, for growth
6. catalase negative
- false
- true
- false
- true
- true
what are the four classification schemes?
Hemolytic pattern (brown’s classification)
Serologic grouping (lancefield’s classification)
Susceptibility patterns
Biochemical characteristics
the partial or incomplete lysis of red blood cell immediately surrounding the colony
Alpha hemolysis
alpha hemolysis is characterized by what color of the medium
green
in alpha hemolysis, what does the RBC look like under microscope
RBC membrane is still clearly outlined
complete lysis of the RBC around the colony which results from the actions of 2 hemolysins
beta hemolysis
what are the two hemolysins that induce complete RBC lysis around the colony
Streptolysin O and Streptolysin S
angle of stabs into the medium with an inoculating loop where anaerobic conditions fail, thus enhancing Steptolysin O which is oxygen labile
45 degree angle
hemolysin useful for documenting recent infections
Streptolysin O
a small zone of alpha hemolysis around the colony is surrounded by a complete zone of beta hemolysis extending beyond the zone into the medium
alpha prime hemolysis
medium recommended for gamma hemolysis
trypticase soy agar base (TSA)
with 5% defibrinated sheep’s blood free from reducing sugars
what pH is hemolysis best demonstrated at?
7.3 - 7.4
lack of hemolysis; no apparent change in color of area surrounding the colony; nonhemolytic
gamma hemolysis
what is the basis for lancefield’s classification?
C carbohydrate substance
Carbohydrate substance for serologic grouping is possessed by all streptococci except
Viridan’s group
