Antibiotic susceptibilities and characteristics of Bacillus licheniformis isolates from traditional Korean fermented soybean foods

The antibiotic susceptibilities and characteristics of 94 Bacillus licheniformis strains isolated from traditional Korean fermented soybean foods were assessed. The minimum inhibitory concentration tests revealed that all strains were susceptible to gentamicin, kanamycin, tetracycline, and vancomycin, and that antibiotic resistances were expressed in a strain-specific manner. The resistances of B. licheniformis to chloramphenicol and streptomycin were established as intrinsic characteristics. The advent of erythromycin-resistant strains was attributed to the acquisition of a plasmid-mediated erythromycin resistance determinant. All strains sustained growth on tryptic soy agar (TSA) containing 14% NaCl (w/v), but 51.1% of strains did not grow at 15% NaCl. All strains exhibited protease and lipase activities on TSA but both activities decreased as the NaCl concentration increased. The function of both enzymes in high-salt soybean fermentation is therefore uncertain.