Transmission of Multiple Drug-Resistance from Shigella to Aeromonas and Non-Agglutinable Vibrio Through Conjugation

Abstract

In 1963, it was reported by Kuwabara and his coworkers that the multiple drug-resistance (R-factor) of Shigella was transferred to freshly isolated strains of V. cholerae and V. eltor through conjugation, and the transmitted resistance was quickly lost after a few subcultures on drug-free nutrient media.
In this report, further experiments were carried out to ascertain the possibility of transmission of R-factor through conjugation from Shigella to Aeromonas and NAG vibrio. Shigella flexneri 2a, strain 103-R₄ was chosen as the donor, and strains of V. cholerae, V. eltor, NAG vibrio and Aeromonas hydrophila were tested for their competences to serve as the recipients of the R-factor. Experimental results revealed that many of the used strains were competent recipients of the R-factor through conjugation, and the transmission frequencies varied according to the used strain and selective drug used.
Drug-resistances of the resistantized recipient strains were relatively low as compared with those of the donor, and some of the selected clones were found only resistant to tetracycline. Transmitted resistances were quickly lost after several successive transfers on drug-free nutrient agar.
Retransmissions of R-factor from resistantized Aeromonas to sensitive V. cholerae, and from resistantized vibrio to Shigella or Salmonella were also accomplished. Resistantized Salmonella and Shigella strains were as highly resistant to SM, CM, TC and SA as the original donor, and their transmitted resistances were maintained at least after 10 subcultures on drug-free nutrient media.