DEVELOPMENT OF DRUG RESISTANCE OF MUTABILE-TYPE VARIANT (MURASE) AND ITS HEREDITY TO THE OFFSPRING

Abstract

Development of drug resistance in Mutabile-type variant and its heredity to further variants mutated from Mutable-type variant were investigated to elucidate if there could be any relations between drug resistance and galactose sensitivity in the same strains of Bact. coli.
Results obtained were as follows:
1. Six strains of Mutabile-type variant were obtained by mutation from the old broth cultures of 2 hundred strains of Bact. coli isolated at the time of admission.
2. From the variant MT (galactose resistant variant mutated from Mutabile-type variant) and RT (so-called back mutant of Mutabile-type variant to original) were obtained by mutation. Furthermore, M' (galactose sensitive variant, just the same one as the starting Mutabile-type variant) was obtained from the RT by mutation.
3. In the so-called O (original) →M→RT (MT) →M' mutation process it was investigated how the pattern of the drug resistance to various antibiotics can be transmitted to the next generation of mutation.
4. Drug resistance of Bact. coli against streptomycin, chloramphenicol, tetracyclin and sulphathiazol were well transmitted to Mutabile-type variant and to the offspring mutated from it, whether it was the one possessed at the admission or the one developed by conjugation with the multiple drug resistant Shigella.
5. Drug resistance of Mutabile-type variant developed also by repeated exposure to antibiotics in serial passages in broth.
6. Inheritance of drug resistance was also demonstrated in S-R mutation of Bact, coll.
From the above experiments it seemed that development of drug (SM, CM, TC and SA) resistance in bact, coli and its inheritance were of no relation to Mutabile-type variation of the same organism.