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Lab 9 Organisms

Expected Results of gram positive organisms

  • Streptococcus pneumoniae: Taxos P (optochin) sensitive (zone of inhibition)

  • Streptococcus mitis: Taxos P resistant (no zone of inhibition)

  • Streptococcus pyogenes: Taxos A (bacitracin) sensitive (zone of inhibition)

  • Streptococcus agalactiae: Taxos A resistant (no zone of inhibition)

Expected Results of gram negaive organisms

Escherichia coli

  • MacConkey: Ferments lactose (striking pink colony).

  • Glucose tube: Ferments glucose with gas production (yellow with a bubble in the Durham Tube).

  • SIM: Does not produce H 2S gas, indole positive (rose ring), and may or may not be motile.

  • KIA: A yellow slant and a yellow butt indicate that both glucose and lactose are fermented. Bubbles, mostly in the butt of the tube, specify gas production.

Proteus mirabilis

  • MacConkey: Does not ferment lactose (colorless colony).

  • Glucose tube: Ferments glucose with gas production (yellow with a bubble in Durham Tube).

  • SIM: Produces H 2S, does not produce indole (no rose ring), and motile (variable with some species/strains).

  • KIA: A red slant and a yellow butt show that only glucose is fermented. Bubbles and a black precipitate in the butt indicate that gas and H 2S, respectively, are produced.

Shigella dysenteriae

  • MacConkey: Does not ferment lactose (colorless colony).

  • Glucose tube: Ferments glucose without producing gas (yellow broth, no bubble in Durham Tube).

  • SIM: Does not produce H 2S, indole negative, and non-motile.

  • KIA: A red slant and a yellow butt indicate that only glucose is fermented.

Pseudomonas aeruginosa

  • MacConkey: Does not ferment lactose (colorless colony).

  • Glucose tube: Does not ferment glucose (red broth).

  • SIM: Does not produce H 2S, indole negative, and motile.

  • A red slant and a red butt show that no fermentation occurs.

           

Other organisms mentioned

  • Pseudomonas fluorescens

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