Conjugational plasmid transfer from A, B and H streptococci to N streptococci

Abstract

Plasmid-mediated resistance to erythromycin and chloramphenicol was successfully transferred from group A, B and H streptococci to group N streptococci by a process akin to conjugation. The results showed that plasmids from streptococcal groups other than N were able to replicate in lactic streptococci as well. The transfer experiments were carried out by using a membrane filter mating technique. Four of the five plasmids used (pSM15346, pSM10419, pIP501, and pEL1) were transferred at frequencies ranging from 10(-1) to 10(-8) transconjugants per donor colony-forming unit. The highest transfer frequencies were obtained when S. pyogenes strain 15346 (pSM15346) served as the donor strain. The identy of transconjugants was verified by testing for the presence of unselected markers of the recipient strains, and both transduction and transformation were ruled out as the mechanisms of transfer.