Quantitative determination of oxytetracycline in honey by cylinder plate microbioassay

Abstract

A cyclinder plate microbioassay is described for the presumptive detection of oxytetracycline (OTC) in honey, using Bacillus cereus var. mycoidesas the test organism. The inhibition of this organism due to naturally occurring inhibitory substances (NOIS) in honey has been reduced to <0.09 8g/g OTC equivalents. In honey with low NOIS level, this procedure detected 0.04 8g OTC/g honey. Most of the NOIS effect in honey was due to its acidic pH. Confirmation of OTC was made using the OTC resistant organism, Staphylococcus epidermidis. The use of the Difco B. cereus spore suspension method proved to be more reproducible and more sensitive than the B. cereus var. mycoicles vegetative cell suspension method. The microbioassay detects OTC in honey with greater sensitivity than other methods presently used.