STEP 1 Gram Positive Bacteria 1 Flashcards
Staphylococcus Aureus
- Shape and stain
- Virulence Factor and how it works
Gram positive cocci in clusters
Catalase +
Coagulase +
Protein A Virulence factor–binds Fc-IgG, inhibits complement activation and phagocytosis
Staph aureus causes which types of diseases (3)
Inflammatory disease, toxin-mediated disease, MRSA
Staph aureus inflammatory infections (5)
- Skin infections
- Organ abscesses
- Pneumonia (usually after influenza virus)
- Endocarditis
- Osteomyelitis
Staph aureus toxin-mediated disease (3)
- Toxic shock syndrome (TSST-1)
- Scalded skin syndrome
- Rapid-onset food poisoning (enterotoxins)
How is MRSA resistant to PCN and nafcillin?
Altered penicillin-binding proteins
How does TSST work? Symptoms (5 total but 3 major) Predisposition from (2)
Superantigen that binds MHC II and T-cell receptor, resulting in polyclonal T-cell activation.
Causes: fever, vomiting, desquamination, shock, and end-organ failure
Predisposed by vaginal or nasal tampons
S. aureus food poisoning:
ingestion of?
incubation?
toxin stability?
Ingestion of pre-formed spores
Short incubation (2-6hours)
Toxin is heat stable so NOT destroyed by cooking
Staphylococcus epidermis characteristics
gram, shape, catalase, sensitivity, coagulase
Gram + Cocci in clusters
Catalase +
Novobiocin sensitive
coagulase -
Staph epidermis commonly infects what? It’s something nearly every patient in a hospital has
Infects prosthetic devices and IV catheters by producing adherent biofilms
Staphylococcus saprophyticus
gram, shape, catalase, coagulase, resistance (this is what sets it apart from s. epidermis)
Gram + cocci
Catalase +
Coagulase -
Novobiocin resistant
Staphylococcus saprophyticus:
2nd most common cause of what?
Second most common cause of UTI in young women. First would be E.Coli
Streptpcoccus pneumoniae
gram, shape, catalase, hemolysis, capsule?, sensitivity, GI susceptibility, protease
Gram + cocci in chains (lancet shaped diplococci) Catalase - Alpha hemolysis Capsule present Optochin sensitive Bile soluble (lysed by bile) IgA protease
Streptococcus pneumoniae is most common cause of what? (4)
Meningitis
Otitis Media (in children)
Pneumonia
Sinusitis
Strep pneumoniae:
sputum color
causes what is sickle cell patients?
Associated with what procedure?
No virulence without?
- Rusty Sputum
- Sepsis in sickle cell anemia
- Splenectomy (encapsulated organism)
No virulence without capsule
What is Staphylococcus saprophyticus’s nickname?
Honeymooner’s UTI due to its association with sex
Viridans streptococci (2)
- Streptococci mutans
2. Streptococci sanguinins
Viridans streptococci:
gram, shape, catalase, and hemolysis
normal colonization location
Gram positive cocci
Catalase negative, coagulase negative
Alpha-hemolytic
Colonize the oropharynx
S. mutans causes what?
Dental caries
S. sanguinins causes what? How?
Subacute bacterial endocarditis.
S. Sanguinins makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves
Viridans streptococci are resistant to which chemical? How is this helpful when dealing with S. pneumo?
Optochin resistant.
S. pneumo is optochin sensitive
Streptococcus pyogenes (group A strep) gram, shape, catalase, hemolysis, coagulase
Gram positive cocci
Catalase and coagulase negative
B-hemolysis (clear hemolysis)
S. pyogenes causes three types of infections
- Pyogenic
- Toxigenic
- Immunologic
S. pyogenes pyogenic infections (3)
pharyngitis, cellulitis, and impetigo
S. pyogenes toxigenic infections (3)
scarlet fever, toxic shock-like syndrome, necrotizing fasciitis
S. pyogenes immunologic consequences (2)
rheumatic fever and glomerulonephritis
S. pyogenes (GAS) is sensitive to…
bacitracin
How does rheumatic fever come about?
Antibodies to M protein (of GAS) enhance host defenses against S. pyogenes but can give rise to rheumatic fever via cross reactivity against heart muscle
What is the JONES criteria for rheumatic fever?
J-Joints (polyarthritis) O-that's supposed to be a heart (carditis) N-Nodules (subcutaneous) E-Erythema marginatum S-Sydenham chorea
