Abstract
Transmission of multiple drug-resistance (tetracycline: TC, chloramphenicol: CP, streptomycin: SM, sulfisoxazole: SA or TC, SM, SA) through conjugation from Escherichia coil to some strains of Yersinia enterocolitica and vice versa were confirmed. The findings demonstrate that Y. enterocoliticais capable of serving as a host to carry the R-factor of enterobacterial origin.
In primary transmission, the transfer of R-factor was notably low in frequency and patterns of resistance displayed by the recipient were almost analogous to those shown by the donors with a few exceptions of segregation of TC-resistance.
Retransmission was more frequent than in the case of primary transmission and the recipient exhibited the patterns of resistance almost similar to the one of the donor.
In serial subcultures of drug-resistant exconjugants of Y. enterocolitica in drug-free media, no segregation of multiple drug-resistance was noticed after the 10th transfer. After storage at -20° C for 10 months, segregation of TC-resistance alone and of simultaneous multiple resistance were observed in some strains. No experimental evidence was obtained for the involvement of R-factor in the drug-resistance of Y. enterocolitica to ampicillin or cephaloridine.
So far, attempts have not been successful to demonstrate the transmission of drug-resistance through conjugation in any of three Y. enterocolitica strains resistant to SM, to SM and SA or to SM, SA and TC, respectively, that were isolated from intestinal contents of slaughtered swines.
