Homology Between Clindamycin Resistance Plasmids in Bacteroides

Two different species of clindamycin-resistant Bacteroides were isolated from the same infection. One isolate contained a single 15-kb plasmid (pCP1) which encoded transferable clindamycin resistance. pCP1 appears similar to the Bacteroides clindamycin resistance plasmid pBFTM10 isolated independently by F.P. Tally, D.R. Snydman, M.J. Shimell, and M.H. Malamy (1982, J. Bacteriol. 151, 686-691). The second strain had a 10-kb plasmid (pCP2) but did not transfer resistance. DNA hybridization studies revealed that pCP1 shares a 5-kb region of homology with the B. fragilis R plasmid pBF4 studied by R.A. Welch and F.L. Macrina (1981, J. Bacteriol. 145, 867-872). This region in both plasmids was shown to be bounded by homologous direct repeats and contains the putative clindamycin resistance determinant. pCP1 and pCP2 were found to share extensive homology but sequences homologous to the clindamycin resistance region were missing from pCP2 and found instead in the whole cell DNA of the host strain. These results identify a transposon-like structure on Bacteroides clindamycin resistance plasmids.