Plasmid-mediated, transferable resistance to clindamycin and erythromycin in Bacteroides fragilis

A clindamycin- and erythromycin-resistant strain of Bacteroides fragilis, TMP10, that had been isolated from a blood culture transferred its drug resistance in a Millipore mating procedure to another strain of B. fragilis, TM2000, and to a strain of Bacteroides thetaiotaomicron. Donor strain TMP10 contained numerous species of extrachromosomal DNA ranging from approximately 2 x 10(6) to 20 x 10(6) daltons in molecular weight, as revealed by agarose gel electrophoresis. Clindamycin- and erythromycin-resistant transcipient cells of B. fragilis strain TM2000 always contained at least two plasmid species with molecular weights of 2 x 10(6) and 20 x 10(6) daltons, respectively, although other plasmid species were also transferred.