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Streptococcus pneumoniae gram stain morphology
"Lancet shaped" gram positive diplococci
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Streptococcus pneumoniae colony morphology
- Alpha hemolytic
- "Oily" (capsulated) to dry (non-capsulated) colonies
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Streptococcus pneumoniae identification tools
- Susceptible to Optichin (>14 mm)
- Bile Soluble (+)
- Alpha hemolytic
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Streptococcus pneumoniae common disease conditions
- Pneumonia
- Otitis media (ear infections)
- Meningitis
- Normal flora
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Streptococcus pyogenes (Group A) gram stain
Gram positive cocci (chains)
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Group A Strep colony morphology
Small beta hemolytic colonies
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Group A Strep identification tools
- Bacitracin (S)
- SXT (R)
- PYR (+)
- Beta hemolytic
- Direct antigen tests (common)
- Serological test ("Streptozyme", ASO, Anti-Hyaluronidase) can detect antibodies from recent infections
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Group A Strep infections
- "Strep throat"
- Wounds (cuts, abscesses)
- Pneumonia
- Glomerular nephritis (kidney infections)
- Scarlet fever
- Rheumatic fever
- Necrotizing fascitis ("flesh eating bacteria")
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Group A Strep treatment
susceptible to penicillin and erythromycin
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Streptolysin O
- only works under anaerobic conditions
- -"Stabbing" the agar pushes organisms below the surface and into an anaerobic environment whee Streptolysin O hemolyzes RBCS
- SSA plate
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Streptococcus agalactae (Group B) gram stain
Gram positive cocci (chains)
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Group B Strep colonies
Beta/Gamma hemolytic colonies (may require 48 hours for beta hemolysis)
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Group B Strep infectious conditions
- Neonatal meningitis and sepsis
- Puerperal fever
- Pneumonia
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Group B Strep identification tools
- Hippurate hydrolysis (+)
- CAMP (+)
- Direct antigen tests from female genital sources
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Group B Strep treatment
Susceptible to penicillin and aminoglycosides
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Enterococcus gram stain
(Lancefield Group D)
Gram positive cocci (pairs and chains)
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Enterococcus Identification tools
- Catalase may be weakly positive
- PYR (+)
- Bile esculin (+)
- 6.5% NaCl (+)
- Usually gamma hemolytic
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Enterococcus Infectious conditions
- Normal flora in the GI tract
- Nosocomial Opportunistic UTI and abdominal infections
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Enterococcus treatment
Difficult to treat resistant to many antibiotics, including penicillin and vancomycin
Successful treatment often requires a synergystic relationship between penicillin and vancomycin
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Streptococcus bovis (Group D) gram stain
Gram positive cocci (pairs and chains)
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Streptococcus bovis (Group D) identification tools
- Bile esculin (+)
- 6.5% NaCl (=)
- Gamma/Alpha hemolytic
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Streptococcus bovis (Group D) infectious conditions
- Newborn sepsis
- Endocarditis
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Streptococcus bovis (Group D) treatment
Susceptible to penicillin
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Virdans Streptococci ("Strep viridans") gram stain
Oval, gram positive cocci (chains)
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Strep viridans colony
alpha or gamma hemolytic
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Strep viridans treatment
Susceptible to penicillin
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Strep viridans
Normal flora in the upper respiratory and GI tract
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Nutritionally Variant Streptococci (NVS) gram stain
Pleomorphic, gram positive cocci
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Nutritonally Variant Streptococci (NVS) colonies
- Very small colonies, require Vitamin B6 or cysteine for growth
- Growth may only occur near Staph aureus colonies ("satelitism")
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NVS treatment
Susceptible to penicillin
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Tests used to ID Streptococcus
- Hemolysis
- Catalase (all Strep neg)
- Bile Solubility
- Optichin (P-disk)
- Bacitracin (A-disk)
- SXT (SXT-disk)
- PYR Hydrolysis
- CAMP Test
- 6.5% NaCl Broth
- Bile-Esculin Hydrolysis (BE)
- Hippurate Hydrolysis
- Direct Antigen detection of Strep pneumoniae
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Special Streptococcus media
- LIM Broth/Todd-Hewett Broth
- VRE agar
- SSA
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