oa Southern African Journal of Epidemiology and Infection - Tetracycline resistance genes of ureaplasmas : original research



In the medical setting, limited information is available on antimicrobial susceptibilities and resistance development in ureaplasmas. This study addresses tetracycline and doxycycline resistance in clinical isolates of and . Culture, with species polymerase chain reaction (PCR) confirmatory techniques, was applied to 191 endocervical specimens, collected during the period January - March 2006. Minimum inhibitory concentration (MIC) determinations were performed by microbroth dilution, with tetracycline resistance (tetM), and int-Tn genes were characterised by PCR and sequencing. Sixty-six ureaplasma cultures (35 , 9 , 22 and ) were obtained. On screening the ureaplasma cultures, tetM gene regions were demonstrated from tetracycline-susceptible and -resistant ureaplasmas. Seven isolates (six and one ) were resistant to tetracycline, with dual doxycycline resistance observed in three strains. Int-Tn gene characterisation of the seven tetracycline-resistant strains revealed that three types were present, indicating that transposons from different origins had integrated into ureaplasma genomes. TetM sequences of five tetracycline-resistant strains were seen to be highly mosaic in structure. The finding of transposon and / or tetM regions in all ureaplasma cultures investigated, with, or without, full expression of tetracycline resistance, in conjunction with tetM and int-Tn gene mosaic or diversity, verifies that ureaplasmas undergo extensive genetic exchange of transposon or resistance genes, with concomitant genomic remodelling.


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