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SIM Media

Sulfur-indole-motility test (SIM media) results for:
(A) Escherichia coli: Motile***, hydrogen sulfide (-), indole (+)*
(B) Staphylococcus aureus: Non-motile, hydrogen sulfide (-), indole (-)
(C) Salmonella arizonae: Motile, hydrogen sulfide (+)**, indole (-)
(D) Enterobacter aerogenes: Motile, hydrogen sulfide (-), indole (-)
(E) Proteus vulgaris: Motile, hydrogen sulfide(+), indole (+)
*After addition of 5-10 drops Kovács reagent, a pink ring at the top of the tube indicates a positive indole result, indole is present,(A and E) meaning that the organism uses tryptophanase to degrade tryptophan and produce indole. A clear yellow ring at the top of the tube after addition of Kovács reagent indicates a negative indole reaction (B, C, and D)
**Blackening of the media indicates hydrogen sulfide production due to the reduction of sodium thiosulfate, using the enzyme cystine desulfanase, causing ferrous sulfide to precipitate out of the media (C and E).
***Growth feathering away from the stab line creating a cloudy appearance in the media indicates motility (A, C, D and E). Growth strictly along the stab line indicates a nonmotile organism (B).

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