Flashcards in BACTE LEC - Strep pdf Deck (80)
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1
– they grow in the
presence of oxygen but cannot use oxygen for
respiration
Aerotolerant anaerobe
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types of strep based on respiration (???)
Facultative anaerobe
• Aerotolerant anaerobe
• capnophilic
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taxo A positive /
bacitracin(S)
group A strep
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complications of group A [2]
Complications:
- rheumatic fever
- AGN
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Infections of group A [3, PPT]
Infections:
- pharyngitis / strep throat
- pyodermal infections
- toxic shock syndrome
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Test: detects activity
of L-pyrrolidonyl arylamidase or
pyrrolidonyl aminopeptidase
PYR
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Meaning of PYR
(Pyrrolidonyl-anaphthylamide
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group A strep antigenic structure
attached to the peptidoglycan of the cell wall and
extends to the cell surface
– essential for virulence
M protein
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– Best defined virulence factor of group A strep
– Resists phagocytosis
– Adherence of bacterial cell to mucosal cells
M protein
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Both are adhesion molecules that mediate
adherence to host epithelial cells. [group A[
Fibronectin-binding protein (protein F)
• Lipoteichoic acid
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– Group A VF weakly
immunogenic; prevents opsonized
phagocytosis by neutrophils or macrophages;
allows bacterium to mask its antigens and
remain unrecognized by its host
Hyaluronic acid capsule
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– hemolysis incubated anerobically;
oxygen labile; lyzes blood cells; highly
immunogenic, ASO test
SLO
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– hemolysis incubated aerobically; oxygen
stable; lyzes WBC, nonimmunogenic
• SLS
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Most common DNase [grp A]
DNase A,B
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Pyodermal Infections of gp A[CISE]
–
Impetigo, Erysipelas, Cellulitis, scarlet fever
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• Activates plasmin, turning itself into a tissue
degrader
Impetigo Caused by Streptococcus
pyogenes
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- beta hemolytic (small zone)
- taxo A (-)
- CAMP test (+) / Hippurate hydrolysis(+)
Group B
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Group B Virulence Factor
– prevents phagocytosis; ineffective
after opsonization; with sialic acid w/c inhibits
activation of the alternative pathway
• Capsule
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Group B Virulence Factor
– most significant component of the
capsule; critical virulence determinant
• Sialic acid
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Group B - No role in virulence [5]
• Hemolysin
• CAMP factor
• Dnase
• Hyaluronidase
• protease
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Group B – Clinical Infections [2]
- pneumonia or meningitis with bacetermia
• Mastitis in cattle
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Small-colony-forming-
S. anginosus (Viridans)
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Large-colony-forming (w/ Group A) –
pyogenic
streptococci
– S. dysgalactiae subsp. equisimilis – upper
respiratory tract, vagina, skin, spectrum of
infections – like Group A
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nonenterococcus
• Opportunistic infections
Group D Streptococcus
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Species of Group D Streptococcus
– S. equinus
– S. bovis
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Lab ID:
- Alpha or nonhemolytic
- PYR (-)
- psuedocatalase
- Bile esculin(+)
- 6.5% NaCl (-)
Group D Streptococcus
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• Group D antigen
• Same infections as group D Strep
Enterococcus spp.
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Lab ID
Varied hemolysis
- produce acid in CHO broth
- Arginine hydrolysis
- Tolerate 0.04 % tellurite (E. faecalis)
- Utilize pyruvate
- Produce acid from methyl-a-D-glucopyranoside (MGP)
- Growth around 100 ug efrotomycin disk
- motile
- PYR (+)
- Bile esculin(+)
- 6.5% NaCl(+), 45 degrees C, alkaline pH
Enterococcus spp.
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#1 cause of bacterial pneumonia - lobar
(especially in the elderly and in those with
underlying disease) sinusitis, otitis media (most
common isolate in
s. pneumoniae
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