Flow chart from colony on SBA

Transcription

1 Flow chart from colony on SBA Transparency Opaque Translucent Gram neg rod Gram + cocci Gram + cocci Gram neg rod See Gram negative rod chart Regular shape Listeria Bacillus Lactobacillus Gram + rod Irregular shape Corynebacterium Catalase + Coagulase + Staph aureus Coagulase neg Coag neg staph Micrococcus Catalase neg Beta strep Alpha Strep S. pneumo See Strep chart Gram + rod See Gram Negative Rod chart

2 Flow chart Aerobic Gram positive organisms Gram stain morphology Rods Cocci Regular rods Irregular, coryneform Catalase + Catalase negative Beta hemolytic on Day 2 Catalase negative Coagulase + Coag Neg Beta hemolytic Listeria Bacillus Lactobacillus Stop here OK Coag negative staphylococcus or Micrococcus Arcanobacterium Corynebacterium Staphylococcus aureus See Strep chart S. pneumoniae.other viridans strep, or Enterococcus

3 Flow chart for streptococci on Blood Agar Plate (BAP) Gram positive cocci pairs & chains Catalase negative Beta hemolytic Alpha or non hemolytic Regular size colony Tiny colony < 0.5 mm Tiny colony < 0.5 mm Regular size colony Soft hemolysis only under colony Group B Strep or rarely Enterococcus (PYR +) and PYR + S. pyogenes Other beta strep Caramel, burnt sugar, or butterscotch smell Can have grp A, C, G, or F antigen S. anginosus ( S. milleri ) group PYR + Enterococcus PYR + Bile soluble S. pneumo Other alpha strep Grp. B = CAMP + & PYR Neg

4 Beta hemolytic Streptococci Major pathogens: Streptococcus pyogenes (group A) & S. agalactiae (group B) In abscesses and body fluids also S. anginosus group ( S. milleri ) Gram + cocci chains Catalase negative PYR negative & CAMP + CAMP + or Tiny colonies <0.5 mm Caramel smell S. milleri group If none of the above: PYR positive Group B positive Group A positive S. agalactiae (group B) B-strep not A or B S. pyogenes (group A) or

5 Alpha streptococci vs Streptococcus pneumoniae on sheep blood agar Alpha hemolytic (green color) and do not grow on MacConkey; catalase negative After bile added Streptococcus pneumoniae: Colonies more mucoid, may have concave centers. Dissolve in 10 min with bile (sodium desoxycholate) Zone of inhibition around optochin (P) disk Viridans streptococci: Pathogens only in blood cultures. Colonies smaller & more dry Will not dissolve with bile zone around P disk Optochin Sensitive

6 Staphylococci Major pathogen: Staphylococcus aureus Others: S. lugdnunensis in abscesses and serious wounds; coagulase-negative staph in multiple blood cultures Gram + cocci clusters Catalase positive Slide coagulase Negative Perform tube coagulase test Positive but clumpy Colony more white; non-hemolytic on Day 1 Positive Typical hemolytic colony Staphylococcus aureus If PYR and coagulase negative: Coagulase negative staphylococci PYR negative Perform tube coagulase test If tube coagulase positive: Staphylococcus aureus PYR positive Staphylococcus lugdunensis

7 Flow diagram for Gram Neg Rods on BAP & MacConkey (NOT for stool isolates) Lactose + (fermenter) on Mac Indole + Oxidase + Oxidase - Colony mucoid Odor of fresh bread Enterobacter, Providencia, Citrobacter, Others Klebsiella Rare Enterobacter n-mucoid E. coli Rare Citrobacter or other Enteric GNR Colony metallic Odor of grapes B. cepacia, B. pseudomallei, Pasteurella, Others P. aerug Serratia, Citrobacter, Enterobacter, S. maltophilia, Acinetobacter, Others Indole + Swarming on BAP E. coli Proteus sp.

8 Flow chart for identification of stool pathogens (enteric fecal pathogens) Major pathogens: Salmonella, Shigella, Vibrio, Campylobacter, Enteropathogenic E.coli Other pathogens: Aeromonas Campy agar after 48 h Lac neg on Mac Lac + on Mac Oxidase +, moist, beige colonies Campylobacter Neg Oxidase Possible Salmonella, Shigella or Yersinia enterocolitica or pathogenic E. coli Need additional tests Swarming on BAP Proteus + Growth on TCBS Green Possible Vibrio parahemolyticus Oxidase Neg Possible pathogenic E. coli Need additional tests Salm on HEK agar Perform serotyping TSI = S. typhi, Shigella, & Salm Yellow Possible Vibrio cholerae Possible V. alginolyticus ne Yellow colonies on HEK Oxidase + Possible Aeromonas

9 Pseudomonas aeruginosa Major pathogen in any site Gram rods (In blood culture) longer & thinner than enteric rods Colonies can be metallic Rough colonies on BAP n-lactose fermenters on MacConkey Usually beta hemolytic Grape-like smell Oxidase positive Pigment usually green but can be purple or blue

10 Haemophilus influenzae Chocolate agar for isolation; does not grow on BAP without V factor added Gram negative rod with coccoid and filamentous forms on Gram stain from plate Grows well on chocolate agar Smells like mice or mild bleach Requires X (hemin) and V (NAD) Grows on BAP next to streak of Staph aureus Grows on Mueller- Hinton with XV factor disk Gram negative coccobacilli in original specimen X disk only V disk only Satellite around various colonies on original BAP culture plates