Microbiological method using Bacillus megaterium with fusidic acid for detection of macrolides in milk

Abstract

The microbiological method to attain a sensitive detection of macrolides using Bacillus megaterium in agar medium with fusidic acid was designed. To this aim, Mueller-Hinton medium fortified with glucose at pH 8.0, a combination of redox indicators (brilliant black and toluidine blue) and different concentrations of fusidic acid were tested. The addition of fusidic acid in the culture medium improves the sensitivity of this bacteria test and decreases the detection limits of bioassay. The addition of 200 µg/lof fusidic acid detects 35 µg/lof erythromycin, 58 µg/lof tylosin, and 57 µg/lof tilmicosin in milk. This microbiological bioassay could be used as an alternative method of commercial screening test for detecting macrolides in milk, in order to maintain food safety.