Evaluation of Media and Reagents for Indole-spot Tests in Anaerobic Bacteriology

Abstract

Indole-spot tests for use in anaerobic bacteriology were evaluated. Spot test results obtained with four reagents and 143 anaerobic organisms grown on blood agars prepared with three commonly-used bases were compared with those obtained with a tube test utilizing indole-nitrate medium and Kovacs’ test. Correlation of spot test with tube test results was best when organisms were grown on trypticase soy blood agar and tested with 1% p-dimethylaminocinnamaldehyde in 10% (v/v) concentrated hydrochloric acid. This indole-spot test offers a simple, reliable, economical, and rapid method for detection of indole production with anaerobic bacteria.