Bacteriology Primer - IDBR Flashcards
What are the gram positive catalase positive organisms? [3]
Coag + and negative staph
Micrococcus
Kocuria
What are the gram positive catalase negative organisms? [2]
Enterococcus and strep
Which gram positive organisms are beta hemolytic on blood agar? [3]
Staphylococcus aureus
Streptococcus pyogenes
Groups B, C, F, G Streptococci
What gram positive organisms are PYR positive? [2]
Enterococcus species
Streptococcus pyogenes
Is staph aureus hemolytic?
Yes - Beta hemolytic
What gram positive organisms are alpha/gamma hemolytic? [3]
Enterococcus species
Viridans Streptococcus species
Streptococcus pneumoniae [alpha alone]
What gram positive organisms are beta hemolytic? [3]
Staphylococcus aureus
Streptococcus pyogenes
Groups B, C, F, G Streptococci
Gram stain shows gram positive cocci in clusters which is coagulase positive and beta hemolytic. Diagnosis
Staph aureus
Gram stain shows gram positive cocci in clusters which is coagulase negative. Diagnosis? [3]
Coag negative staph
Micrococcus species
Kocuria species
Gram stain shows gram + cocci in pairs and short chains. Ddx? [3]
Enterococcus species
Streptococcus pyogenes
Strep pneumo
Gram stain shows gram + cocci in pairs and long chains. Ddx? [2]
Groups B, C, F, G Streptococci
Viridans Streptococcus species
What is lancefield group A strep?
S. pyogenes
What is lancefield group B strep?
S. agalactiae
What is lancefield group C strep?
S. dysgalactiae subsp. dysgalactiae
What is lancfield group C, G, (A, L) strep?
S. dysgalactiae subsp. equisimilis
What is lance field group A, C, G, F strep?
S. anginosus group
What is lance field group E, P, U, V strep?
S. porcinus
Gram stain shows gram + cocci in pairs and short chains. PYR +, α‐ or ɣhemolytic. Dx?
Enterococcus
Gram stain shows gram + cocci in pairs and short chains. PYR +, Beta hemolytic. Dx?
Streptococcus pyogenes
Gram stain shows gram + cocci in pairs and short chains. PYR -, alpha hemolytic. Dx?
Streptococcus pneumoniae
Gram stain shows gram + cocci in long chains, Catalase (‐), α‐ or ɣ‐ hemolytic. Dx?
Viridans Streptococcus
Gram stain shows gram + cocci in long chains, Catalase (‐), beta hemolytic. Dx?
Groups B, C, F, G Streptococci
What determines lance field groups?
Teichoic acid antigen.
What do gram positive cocci in tetrads indicate on gram stain?
coagulase negative staphylococci or Micrococcus species
What is the only PYR positive strep species?
Strep pyogenes
Abiotrophia/Granulicatella require what to grow?
pyridoxal or cysteine
What agar do Abiotrophia/Granulicatella grow on?
Chocolate agar
What group is strep pneumonia a member of?
Streptococcus mitis
What type of colonies do strep pneumonia form?
Donut shaped, raised edges, indented center
What is the difference between Beta, alpha, and gamma hemolysis?
Beta - completely lyse RBCs leaving a clear zone of hemolysis around the colony
Alpha - incompletely lyse RBCs leaving greenish discoloration of the culture medium surrounding the colony
Gamma hemolytic - Do NOT hemolyze, AKA non-hemolytic
What is the significance of optochin sensitivity?
Both Strep pneumonia and Strep viridian’s is alpha hemolytic. To differentiate this a disc inoculated with optochin is placed on the plate.
Strep pneumonia is inhibited
Strep viridans will grow
What 5 groups of strep make up the virdans group?
mutans, anginosus (milleri), mitis, salivarius, bovis
–> Each group has multiple species in it.
