title: Spot indole test: evaluation of four reagents.
abstract: Kovacs indole reagent, p-dimethylaminobenzaldehyde, Ehrlich indole reagent and p-dimethylaminocinnamaldehyde were used as spot indole reagents to test 359 strains of gram-negative rods growing on 5% sheep blood agar, Trypticase soy agar (BBL Microbiology Systems), and MacConkey agar. The p-dimethylaminocinnamaldehyde reagent was the most sensitive of those tested and provided results that were easiest to interpret. The p-dimethylaminocinnamaldehyde reagent was able to detect providencia alcalifaciens indole production because of the red-violet color unique to that organism. All reagents tested were accurate in detecting indole produced by members of the Enterobacteriaceae family, with the exception of P. alcalifaciens.
mesh_terms: D001431:Bacteriological Techniques; D001547:Benzaldehydes; D002934:Cinnamates; D004755:Enterobacteriaceae / Q000032:analysis; D005069:Evaluation Studies as Topic; D007202:Indicators and Reagents; D007211:Indoles / Q000032:analysis*; D011532:Providencia / Q000032:analysis
chemical_list: D001547:Benzaldehydes; D002934:Cinnamates; D007202:Indicators and Reagents; D007211:Indoles; C030374:indole; C018523:4-dimethylaminocinnamaldehyde; C510241:p-dimethylaminobenzaldehyde