Antimicrobial susceptibility of Bifidobacterium breve strains and genetic analysis of streptomycin resistance of probiotic B. breve strain Yakult.
The minimum inhibitory concentrations (MICs) of 17 antimicrobials for 26 Bifidobacterium breve strains of various origins were determined by broth microdilution. MIC distributions for 17 antimicrobials except streptomycin and tetracycline were unimodal for all strains tested, whereas bimodal distributions were observed for streptomycin and tetracycline. The probiotic strain B. breve strain Yakult showed intrinsic susceptibility to all antimicrobials except streptomycin to which the strain showed an atypically higher MIC of >256 microg/ml. Because this strain is a commercial strain, which is often ingested by many consumers on a daily basis, it is very important to determine the genetic basis for streptomycin resistance of this strain. Molecular analysis revealed that a mutation of the rpsL gene for ribosomal protein S12 was responsible for this streptomycin resistance. The resistance of B. breve strain Yakult to streptomycin, therefore, is caused by a chromosomal mutation and very unlikely to be transferred to other microorganisms.
Kiwaki
Mayumi
M
Yakult Central Institute for Microbiological Research, 1796 Yaho, Kunitachi, Tokyo 186-8650, Japan. mayumi-kiwaki@yakult.co.jp
Sato
Takashi
T
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001644:Bifidobacterium / Q000187:drug effects*; D003257:Consumer Product Safety; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D019936:Probiotics; D012269:Ribosomal Proteins / Q000235:genetics*; D013307:Streptomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D012269:Ribosomal Proteins; D013307:Streptomycin