Clinical and Experimental studies on the Drug-sensitivity of Dysentery Bacilli.

II. Antibiotics-resistant dysentery bacilli.

Abstract

Biological characteristics of highly drug-resistant dysentery bacilli isolated from 1953 to 1957 were investigated.
The results were as follows;
1) An oxytetracycline-, chlortetracycline- and tetracycline-resistant strain of Sh. fl. 2b was isolated in 1953, a streptomycin-, chloramphenicol-, oxytetracycline-, chlortetracyclineand tetracycline-resistant strain of Sh. fl. 4a in 1955, a chloramphenicol-, oxytetracycline-, chlortetracycline- and tetracycline- and tetracycline-resistant strain of Sh. sonnei in 1956 and a streptomycin-, chloramphenicol-, oxytetracycline-, chlortetracycline- and tetracyclineresistant strain of Sh. fl. 2b in 1957, respectively.
2) No difference in the biological behaviours i. e. fermentation reactions, IMViC reactions, catalase reaction, KNO3 reducing activity, virulence, acid-agglutination, ultraviolet ray resistance and requirement of nutrition was noted between the drug-resistant strains and the drug-sensitive strains.
3) Degree of drug-resistance to antibiotics was constant for a long period of time as, long as 4 years and 8 months.
4) There was a close cross-resistance among oxytetracycline, chlortetracycline and tetracycline and a slight one among tetracycline-drugs and chloramphenicol. When a strain was made streptomycin-resistant artificially, its resistance to chloramphenicol and tetracycline-drugs decreased.
5) All bacilli in one colony were equal in the degree of sensitivity to antibiotics.
6) With the single cell culture technique of a drug-resistant strain, all bacilli from a drug-resistant strain were equal in the degree of sensitivity to the original strain.