Streptococcus and Enterococcus Flashcards
Catalase (-), gram positive cocci, non-motile, and non-spore-forming, that are usually arranged in pairs or chains,
facultative anaerobes, some are capnophilic, glucose fermenters, and classified by their hemolysis
Streptococcus
what medias are used in strep?
BAP, Todd-Hewit Broth, or CAP
what classification is based on the hemolysis?
brown’s classification
incomplete or partial hemolysis, green or brown color surrounding the colony
a-hemolysis
what kind of hemolysis does s. pneumoniae and viridans streptococci produce?
a-hemolysis
complete hemolysis of rbc and colorless zone around the colony?
b-hemolysis
what kind of hemolysis does s.pyogenes and s. agalactiae produce?
b-hemolysis
based on the temperature limits of growth, supplemented by other basic characteristics; and the temperature
requirements
sherman’s/academic/bergey’s classification
classify the following using sherman’s classification:
With hemolysis
Not tolerant to
methylene blue, salt,
or alkali
pyogenes
classify the following using sherman’s classification:
No hemolysis
Less tolerant to salt and
alkali
Weak reducing action
viridans
With/without
hemolysis
Tolerance to salt and
alkali
Resistant to
methylene blue
Strong reducing
action
Enterococci
appear smooth, glossy or round and
mucoid, typically pinpoint (0.5-1.0 um in diameter), translucent, opalescent, or clear in appearance & white to gray
in color with beta-hemolysis.
s. pyogenes
– major virulence factor; prevents phagocytosis
m protein
what virulence factor adhesion molecules; adheres to host epithelial cells
protein f
present in capsule; mucoid strains; antiphagocytic; solubilizes connective
tissues; spreading facto
hyaluronic acid
– responsible for the red rashes in Scarlet fever; streptococcal pyogenic exotoxins;
superantigen; ability to stimulate T-lymphocyte proliferation by interactions with MHCII molecules on APC &
specific variable β-chain of the T-cell receptor.
erythrogenic toxins
repeated episodes of pharyngitis; believed to result from a cross-reacting antibody that attacks
cardiac or renal tissue while attempting to destroy streptococcal antigens
post sequelae
aka galloping gangrene; characteristic of “flesh-eating bacteria
necrotizing fascitis
what is the sample collection of s. pyogenes?
throat swab
what is the susceptibility test for scarlet fever?
dick’s test
- Isolated on Blood Agar Plate; colonies can be medium in size, flat, translucent, opaque, show narrow β-hemolysis,
some are gamma hemolytic, yellow to brick-red pigment
Streptococcus agalactiae
what is the identification for s. agalactiae?
CAMP
what is the media for s. agalactiae?
BAP
prevents phagocytosis but is ineffective after opsonization; sialic acid is the
composition of its capsule
capsular polysacchiride
