An Excision-Competent and Exogenous Mosaic Transposon Harbors the tetM Gene in Multiple Mycoplasma hominis Lineages.

The presence of the tetracycline resistance determinant tetM has been reported for Mycoplasma hominis (1, 2) and association with Tn916 genes established (3). To identify the mobile genetic element harboring this gene, genome analysis of M. hominis Sprott (isolated from a nongonococcal urethritis patient before 1978 [4]) and targeted PCR/amplicon sequencing of M. hominis 1630 (1984, arthritis isolate [5]) were undertaken. These analyses revealed that in both isolates, truncated Tn916 resides within an uncharacterized transposon, closely related to several from streptococci that site-specifically integrate into rumA (6, 7). Although Tn916 truncation precludes mobility of that conjugative transposon (CTn), the larger mosaic element retains competency for excision and circularization in M. hominis. While this letter was in preparation, this element was also noted in the M. hominis placental strain PL5 (isolated between 1991 and 1996 [8]). Comparison of the Sprott genome sequence (GenBank accession number CP011538 [9]) to those from M. hominis LBD-4 (10) and PG21 (11) disclosed a 25,257-nucleotide (nt) insertion, which included a truncated tetM-harboring Tn916 unit (13.3 kb). The