The Use of 2,3,5-Triphenyltetrazolium Chloride as a Test for Antibiotic Substances in Milk

Abstract

A test based on the conversion of 2,3,5-triphenyltetrazolium chloride to formazane was outlined for the detection of antibiotic substances in milk. The reaction is characterized by a color change from the leucoform to red in the presence of growing bacterial cells. This conversion is inhibited by antibiotics at low levels of concentration. When Streptococcus thermophilus is used as a test culture, penicillin at 0.04 unit, Aureomycin at 0.2 [mu]g, terramycin at 0.25 [mu]g, and streptomycin at 4.0 fig/ml can be detected in raw milk. The total time for the test is 2.5 hours.