SIM Medium

Differentiate enteric gram-negative bacilli based on sulfide production, indole formation, and motility using Thermo Scientific™ Remel™ SIM Medium (Sulfide, Indole, Motility). Sulkin and Willet reported that H₂S detection is an important parameter to differentiate Salmonella and Shigella from other members of the family Enterobacteriaceae¹. Blazevic used motility-indole medium to differentiate Klebsiella from Enterobacter and Serratia². Green et al., using smaller quantities of SIM Medium, demonstrated motility results could be interpreted after incubation periods shorter than 18-24 hours³.

Sulfide, indole and motility have been combined in one tube for easy use. Indole is detected by adding Kovac's Reagent or Ehrlich's Reagent and it combines with para-dimethylaminobenzaldehyde to produce a red complex. Addition of agar forms a semisolid medium which is ideal for the detection of motility.

• Ready to use – Convenience of prepared medium
• Easy to interpret
  1. Hydrogen Sulfide (S)
     • Positive test – Blackening along the line of inoculation
     • Negative test – No blackening of the medium
  2. After addition of Indole (I) reagent
     • Positive test – Red color development in the upper portion of the medium
     • Negative test – No red color development
  3. Motility (M)
     • Positive test – Diffuse growth outward from the stab line or turbidity throughout the medium
     • Negative test – Growth only along the line of inoculation

This medium contains casein and meat peptones that supply nitrogenous compounds and amino acids necessary for growth of enteric gram-negative bacilli. Sodium thiosulfate is a sulfur source. Ferric ammonium citrate is an indicator which reacts with H₂S produced by sulfate-reducing bacteria to form a black precipitate, ferrous sulfide. Organisms that possess the enzyme tryptophanase degrades tryptophan to produce indole which is detected by the addition of Kovac's or Ehrlichs's reagent. The addition of agar results in a semisolid medium suitable for the detection of motility.

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Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.