抄録
The purpose of these experiments was to elucidate the relation between the behavior of El Tor cholera Vibrio (ETCV) to antibiotics and that of Escherichia coli (E. coli) as one of intestinal bacterial floras.
In the presence of several antibiotics equivalent to a minimum inhibitory concentration (MIC) for ETCV, ETCV was mixed with two strains of E. coli which were different in sensitivity to antibiotics. The change of the viable cells of each bacterium was then observed.
The results obtained were as follows :
1) ETCV on these experiments was not very sensitive to polymyxin B (PL) and colistin (CL).
2) In the mixed cultures with antibiotic-resistant E. coli containing ampicillin (ABPC), cephalothin (CET), amikacin sulfate (AMK) and chloramphenicol (CM), an upward tendency of MIC for ETCV was observed.
3) When the inoculum size of E. coli was as much as, or more than that of ETCV in the mixed cultures containing ABPC, sensitivity of E. coli to ABPC was the factor which influ-enced the behavior of ETCV during a period of six hours.
4) When the inoculum size of E. coli was as much as, or less than that of ETCV in the mixed cultures containing CET, the difference of antibiotic-resistance between the two strains of E. coli influenced the growth of ETCV.
5) In the mixed cultures containing CM, the difference of antibiotic-resistance between the two strains of E. coli influenced the growth of ETCV.
6) In the mixed cultures with the standard strain of E. coli containing tetracycline (TC), the growth of ETCV was inhibited for a long period. But in the mixed cultures with the antibiotic-resistant strain of E. coli, the growth of ETCV had a tendency to be inhibited in an inverse proportion to the inoculum size of E.coli.
7) In the mixed cultures containing PL, ETCV showed almost the same behavior independently of the strain and inoculum size of E. coli.
