Evaluation of Agar Disc Diffusion Method for Determining Antibiotic Susceptibility of Lactic Acid Bacteria Strains by a Selected Culture Medium

Abstract:

The evaluation of antibiotic susceptibility of lactic acid bacteria (LAB) is a major part of the safety of probiotic foods. However, there is no international standard method of the susceptibility testing of LAB till now. We investigated 6 culture media and selected a proper commercial one from them. We optimized the agar disc diffusion method and assayed 9 strains of LAB encompassing the genera Lactobacillus, Bifidobacterium, Streptococcus and Lactococcus for susceptibility to 51 antibiotics on RCA agar. The optimized method proved to be an applicable technique for antibiotic susceptibility testing of LAB. This contributes to the establishment of a standardized procedure for antibiotic susceptibility testing of LAB.

Key words:Probiotic, Lactic acid bacteria, Antibiotic susceptibility, RCA culture medium, Agar disc diffusion