Total of 11 strains of Ldctobacillus isolated from lactobacillus-fermented milk and-beverage in March 1980 were examined for susceptibility to 8 drugs, and transferability and transfer frequency of R plasmids by conjugation.
Of 11 isolates each 2 strains were classified as L. cellbiosus and L. helveticus, each 1 strain as L. plantarum, L, lactis, L. acidophilus, L. delbrueckii, L. casei subsp. casei, L. casei subsp, tolerans and L. salivarius subsp. salivarius by Bergey’s manual.
Resistance was the most active to na lidixic acid(NA), followed in decreasing order by chloramphenicol(CP), ampicillin(AP), kanamycin(KM) and streptomycin(SM).
All of isolates were resistant to NA, each 10 strains to CP and AP, 7strains to KM and 6 strains to SM, indicating all of the isolates were resistant to two or more drugs in combination. No strain was resistant to erythromycin(EM), penicillin(PC) and tetracycline(TC). The most frequently encountered resistant patterns were CP NA AP SM KM, followed by CP NA AP KM, NA AP, CP NA, CP NA AP and CP NA AP SM in order.
Transfer experiment of drug resistance showed that of 11 resistant strains, 9 strains transferred parts of their resistance to AP or AP CP or SM AP, indicating 9 strains carried R plasmids determining R (AP), R(AP CP) and R(SM AP).
The conjuga1 frequency of R(AP) from Lactobacillus to E. coli ranged from 2.5×10^(-1)to 5.6×10⁴%, that of R(CP) ranged from 5.0×10^(-1)to 5.0×10^(-3)% and that of R(SM) ranged from 6.0×10^(-5) to 1.4×10^(-5)%, at 37℃ for 18 hours of incubation.
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