Plasmid-Mediated, Transferable Resistance to Clindamycin and Erythromycin in Bacteroides fragilis

Abstract

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 ∼2 × 10⁶ to 20 × 10⁶ 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 × 10⁶ and 20 × 10⁶ daltons, respectively, although other plasmid species were also transferred.