Gram Positive Cocci
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- Name the three gram positive cocci
- Staphylococcus, Streptococcus, enterococcus
- What laboratory test is used to identify gram positive cocci?
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Catalase test
Gram Positive will break down H2O2 to water and hydrogen - Name catalase positive cocci.
- Staphylococcus
- Name catalase negative cocci.
- Streptococcus and entercoccus
- What gram positive cocci give positive test in coagulase test aka coagulate-positive staphylococci?
- Staphylococcus aureus
- What test negative in coagulase test aka coagulate-negative staphylococci?
- Staphylococcus epidermitis, staphylococcus saphrophyticus
- What is the effect of novobiocin antibiotic on S. aureus, S. epidermitis, and S. saphrophyticus?
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S.Aureus and S.Epidermitis - sensitive to the drug
S.saphrophyticus - resistant - Where are the sources of S.Aureus?
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- Found in human like the external nares, skin, perineum, oropharynx, feces
- Ppl to ppl contact: hand contact, aerosol
- fomites - What are some of the associated infection caused by S.Aureus?
- - Impetigo, furuncles/boils, carbuncles, folliculitis, bacteremia and endocarditis, osteomyelitis, septic arthritis, pneumonia and empyema
- What are some of the toxin-mediated disease caused by S.Aureus?
- - Bullous impetigo, scalded skin syndrome, TSS, Food poisoning
- What cause staphylococal food poisoning?
- Enterotoxins - will not be inactivated even when food is heated
- Name the virulence factors for S.Aureus?
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Capsules: inhibit phagocytosis, facilitate adherence
Peptidoglycan: Endotoxin like activity and attract leukocytes
Teichoic acid: involved in complement activation, facilitate adherence
Protein A: bind to Fc on IgG reducing phagocytes binding. inhibit complement activation
Catalase:break down H2O2 so neutrophil can't attack due to O2 radical
Coagulase: clots plasma, bacterias hide in there and WBC can't penetrate clot
Enzymes that help spread of bacteria. and Cytotoxinx - What are some of the enzymes that promote bacterial spread?
- Fibrinolysin, Hyaluronidase, Lipase, Nucleases
- What are the virulence factors for S.epidermis?
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- ability to bind to foreign materials
- biofilm production - What are the clinical manifestations of s.epidermis?
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- Endocarditis
- Infections of shunts and catheters
- Infections of prosthetic joints - Name 3 medically important streptococci?
- s.pyogenes, s.agalactiae, s.pneumonia
- How is streptococci classified?
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1. Serologic properties using Lancefield grouping
2. Hemolytic patterns: complete (beta), incomplete (alpha), no (gamma) hemolysis
3. biochemical properties - What group of Serologic grouping do Streptococcus pyogenes and agalactiae belong to respectively?
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Pyogene - Lancefield Group A
Agalactiae - Lancefield Group B
(note: pneumonia is not in any group) - Main disease caused by strep.pyogenese
- Scarlet fever, pharyngitis, necrotizing fasciitis, rheumatic fever, acute glomerulonephritis
- Main disease caused by strep.agalactiae
- - neonatal meningitis, neonatal sepsis, leading cause of infectious death in newborn
- What antibiotic is Strep.pneumonia sensitive to?
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Optochin
(Note: Lyses when put in bile) - Strep. pneumonia causes what disease>
- - pneumonia, otitis media, sinusitis, meningitis
- Enterococci example
- E. Faecium, E. Faecalis
- Characteristis of enterococci
- - low virulence, normally commensal, caused serious disease in hospitalized patients, can become resistant to antibiotic