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Streptococci that are Catalase Negative and Facultative Anaerobic
- Streptococcus agalactiae (group B)
- Group D- Enterococci and Non-enterococci
- Streptococcus viridans
- Streptococcus pneumoniae
- Streptococcus pyogenes (group A) are microaerophilic
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Beta-hemolytic streptococci:
- Streptococcus pyogenes (groupA)
- Streptococcus agalactiae (groupB)
- GroupD subtypes (are alpha, beta and gamma)
Beta-hemolytic completely lyse the RBCs leaving a clear zone of hemolysis around the colony.
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Alpha-hemolytic Streptococci:
- Streptococcus viridans
- Streptococcus pneumoniae
Alpha-hemolytic only partially lyse the RBCs leaving a greenish discoloration of the culture medium.
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Streptococcus pyogenes (groupA) virulence:
- 1. M-protein: Adherence factor, Anti-phagocytic, Antigenic
- 2. Lipoteichoic Acid- Adherence factor
- 3. Streptokinase
- 4. Hyaluronidase
- 5. DNAase
- 6. Anti-C5a peptidase
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Streptococcus agalactiae pathology:
- 1. neonatal meningitis
- 2. neonatal pneumonia
- 3. neonatal sepsis
- 4. sepsis in pregnant women (with secondary infection of fetus)
- 5. increasing incidence of infections in elderly >65 years of age and patients with diabetes or neurological disease: causes sepsis and pneumonia
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Staphylococci (for our purposes) are:
- Catalase positive
- Facultative anaerobic
- S. aureus- Coagulase positive
- S. epidermidis, S. saprophyticus- Coagulase NEGATIVE
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Biofilm
- Staphylococcus epidermidis
- highly resistant to antibiotics
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Purulent meningitis with a rapid onset in young children and adults (not newborns)
- Streptococcus pneumoniae
- NOT S. agalactiae
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Gram-positive diplococci
Streptococcus pneumoniae
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What is the major virulence factor of Streptococcus pneumoniae?
- Capsule!
- The halos visible around many of the cocci may be polysaccharide capusles of S. pneumoniae.
- >80 types of capsules- differ in virulence, prevalence and drug resistance
- Capsule interferes with phagocytosis by preventing complement C3b opsonization fo the bacterial cells.
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Characteristics of typical pneumonia:
- sudden onset, chills, fever, dyspnea, productive cough with purulent sputum, rales
- - Streptococcus pneumoniae (community acquired)
- - others: Staphylococcus aureus (secondary, post viral)
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Characteristics of atypical pneumonia:
gradual onset, nonproductive cough, headache, sore throat
- -viral, uncommon in adults
- - Mycoplasma, Chlamydia, Legionella
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Which bacteria ferment lactose?
- Escherichia coli
- Klebsiella pneumoniae
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What are the characteristics of Pseudomonas aeruginosa?
- Hospital acquired- medical devices, healthcare workers
- sweet, grape-like odor
- produces pigments when cultured- pyocyanin and pyoverdin
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