Tn5030: a conjugative transposon conferring clindamycin resistance in Bacteroides species

Several examples of conjugal transfer of antibiotic resistance determinants in the absence of plasmid DNA have been described in gram-positive species. Previous work had suggested that transfer of clindamycin resistance among the gram-negative anaerobic Bacteroides species might occur by a similar mechanism. We report here the characterization of Tn5030, a 45-kb +/- 5-kb chromosomal, mobile genetic element devoid of the detectable terminal repeats typically associated with gram-negative transposons. Tn5030 transfers clindamycin resistance (ermFU) and sequences homologous to tetF in the absence of detectable plasmid DNA. This element represents a novel mechanism of genetic exchange among gram-negative organisms.