Tetracycline Resistance Mediated by tet (M) Has Variable Integrative Conjugative Element Composition in Mycoplasma hominis Strains Isolated in the United Kingdom from 2005 to 2015

Abstract

A minimal genome and absent bacterial cell wall renders Mycoplasma hominis inherently resistant to most antimicrobials except lincosamides, tetracyclines and fluoroquinionlones. Often dismissed as a commensal (except where linked to preterm birth), it causes septic arthritis in immunodeficient patients and is increasingly associated with transplant failure (particularly lung) accompanying immunosuppression. We examined antimicrobial susceptibility (AST) on strains archived between 2005-2015 submitted to the Public Health England reference laboratory and determined the underlying mechanism of resistance by whole genome sequencing (WGS). Archived M. hominis strains included 32/115 from invasive infection (sepsis, CSF, peritoneal and pleural fluid) over the 10-year period (6.4% of all samples submitted between 2010-2015 were positive). No clindamycin resistance was detected, while two strains were resistant to moxifloxacin and levofloxacin (resistance mutations: S83L or E87G in gyrA and S81I or E84V in parC). One of these strains and 11 additional strains were tetracycline resistant, mediated by tet(M) carried within an integrative conjugative element (ICE) consistently integrated at the somatic rumA gene; however, the ICEs varied widely in 5-19 associated accessory genes. WGS analysis showed tet(M)-carrying strains were not clonal, refuting previous speculation that the ICE was broken and immobile. We found tet(M)-positive and -negative strains (including the multi-resistant 2015 strain) to be equally susceptible to tigecycline and josamycin, however, the British National Formulary does not include guidance for these. Continued M. hominis investigation and AST surveillance (especially immunocompromised patients) is warranted, and expansion of the limited therapeutics needs to be expanded in the UK.

Evaluation of the MYCOPLASMA IST3 urogenital mycoplasma assay in an international multicentre trial

“…All characterized M. hominis and Ureaplasma spp. (predominantly from previously published investigations) 16,17,19 carrying the tet(M) resistance genes were identified correctly, in addition to four clinical M. hominis samples (19% WT prevalence of tetracycline resistance) with endogenous tet(M) and tetracycline resistance. Out of the 108 clinical samples with endogenous Ureaplasma spp., only 1 isolate was found to carry the tet(M) gene (MIC = 16 mg/L), as well as a second isolate with MIC = 2 mg/L (just at the threshold) that did not carry tet(M) resistance (2% WT prevalence of tetracycline resistance).…”

“…moxifloxacin/levofloxacin resistance-mediating mutations in both the gyrA and parC genes. 19 Evaluating fluoroquinolone resistance in Ureaplasma spp. was more complicated, but not due to the MYCOPLASMA IST3 assay.…”

Determination of In Vitro Antimicrobial Susceptibility for Lefamulin (Pleuromutilin) for Ureaplasma Spp. and Mycoplasma hominis

“…All M. hominis strains were inherently resistant to erythromycin and azithromycin (data not shown), mediated by the previously published inherent conserved polymorphism G2057A transition in their 23S rRNA sequences [ 20 ]. This cohort also included multi-drug resistant strains (Urogen006 and MH15-3) that are additionally resistant to all fluoroquinolones (mediated by S83L gyrA and S81I parC mutations) and tetracyclines (mediated by tet M) [ 21 ]. Susceptibility testing against lefamulin found no isolate to have an MIC >0.25 mg/L after 48 h incubation (range of 0.03–0.25 mg/L; MIC 50 of 0.06 and MIC 90 of 0.12 mg/L) ( Table 1 ).…”

“…A panel of 90 isolated strains (25 Ureaplasma parvum , 25 Ureaplasma urealyticum , and 40 M. hominis ), characterised from previously published clinical cohorts [ 21 , 22 , 23 , 24 ] as well as from the UROGEN study (IRAS 251053; Spiller O.B. and Jones L.C.…”

Integrating the Human and Animal Sides of Mycoplasmas Resistance to Antimicrobials

“…The absence of Tn916 conjugation genes precludes mobility, but the larger mosaic element retains competency for excision and circularization. It was subsequently shown that, in several M. hominis strains, this tet(M)-harboring transposon of variable length comprises a 13 kb region homologous to Tn916 and is consistently integrated between the somatic rumA gene and an hypothetical protein [83,84]. The tet(M) carrying Tn916 transposon is a notable exception, as there have been a limited number of mobile genetic elements in mycoplasmas described so far.…”