Gram Positive Cocci Flashcards
S. aureus express ________, conferring resistance to penicillin, ampiciilin, and early generation cephalosporins.
Beta-lactamase
MRSA:
- Mutation/Gene
- Express what?
mecA gene
-Express PBP2A*
*penicillin target with little affinity for the drug
MRSA Tests. (3)
- Cefoxitin Disk Diffusion testing
- DNA hybridization probes for mecA
- PBP2a with latex agglutination
S. epidermidis characteristics. (2)
Coagulase Negative Staph.
-Hardware infections
S. saphrophyticus characteristics. (3)
Coagulase Negative Staph.
- Uropathogen
- Novobiocin Resistant
S. lugdunensis (SLUG) characteristics. (6)
Coagulase Negative Staph.
- Skin commensal
- Infections similar to S. aureus
- Slide Coag Test (Pos.); Tube Coag Test (Neg.)
- PYR positive
- Ornithine Decarboxyase Positive
Blood agar - Beta hemolysis.
COMPLETE Hemolysis
-Clear Zone
Blood agar - Alpha hemolysis.
Incomplete Hemolysis
-GREEN zone
Blood agar - Gamma hemolysis.
NO hemolysis
Group A Streptococci.
- AKA
- Gram stain
- Blood agar
- Bacitracin (A disk)
- PYR Hydrolysis
- Express what antigens?
Strep Pyogenes
- Gram+ cocci singly, in pairs, short chains
- Beta-hemolysis (wide), large colonies
- Bacitracin (A disk) - Susceptible
- PYR Hydrolysis - Positive
- Express Lancefield group A antigens
Organism that causes toxin-mediated illnesses (ie Toxic shock, Scarlet fever) and Immune-mediated illnesses (ie Rheumatic Fever, Poststrep GN).
Group A strep (S. pyogenes)
Group B strep:
- AKA
- Gram stain
- Blood agar
- CAMP Test
- Hippurate Hydrolysis
S. agalactiae (Group B)
- Gram+ cocci in pairs/short chains
- Beta-hemolysis (narrow), gray/white colonies
- CAMP Test - Positive
- Hippurate Hydrolysis - Positive
When should pregnant females be screened for GBS colonization?
-Methods?
35-37 wks
-Enrichment broth then Culture or Molecular methods
S. pneumoniae:
- Gram stain
- Hemolysis
- Colony morphology
- Optochin Test (P disk)
- Lancet shaped, Gram+ diplococci
- Alpha-hemolytic
- Smooth colonies (polysaccharide capsule)
- Optochin Test - Susceptible
What organism is the leading cause of community acquired pneumonia (may lead to bacteremia and meningitis?
*Otitis Media and Sinusitis
S. pneumoniae
Viridian Streptococci
- Gram stain
- Hemolysis
- Optochin test (P disk)
- 4 groups
- Long chains of Gram+ cocci
- Alpha-hemolysis
- Optochin Resistant
- S. mitis, S. mutans, S. salivarius, S. anginosus
Viridian Streptococci - Group:
-Frequent cause of native valve endocarditis and Late-onset presthetic valve endocarditis.
S. mitis
Viridian Streptococci - Group:
-Principal agent of dental caries and can cause endocarditis.
S. mutans
Viridian Streptococci - Group:
-Occasional cause of bacteremia and endocarditis
S. salivarius group
Viridian Streptococci - Group:
-Abscesses at various sites
S. anginosus group (S. intermedius)
Enterococcus spp.:
- Gram stain
- Hemolysis
- Colony morphology
- Bile test
- PYR test
- 6.5% NaCl
- Express what antigens?
Enterococcus spp.:
- Gram+ Diplococci/short chains
- Nonhemolytic
- Small, gray colonies
- Bile test - Hydrolyze esculin
- Hydrolyze PYR
- Growth in 6.5% NaCl
- Lancefield group D antigens
What are the two most common Enterococcus species in clinical isolates?
- E. faecalis
- E. faecium
E. faecium - Antibiotic resistance.
Express altered Penicillin Binding proteins
- Resistent to:
- -Penicillin
- -Ampicillin
- -Cabapenems
T/F: some strains of E. faecium are resistent to Vancomycin.
True
*Acquisition of the VanA, VanB, or VanD clusters
