Evaluation of the ResistancePlus MG FleXible Assay for Detection of Wild-Type and 23S rRNA-Mutated Mycoplasma genitalium Strains

Abstract

Antibiotic resistance in Mycoplasma genitalium is rising globally, and resistance-guided diagnostics can facilitate targeted and timely treatment. The ResistancePlus MG FleXible (RPMG Flex) assay for the detection of M. genitalium and macrolide resistance-mediating mutations (MRMM) was evaluated for analytical sensitivity, specificity, reproducibility, and inhibition in the presence of interfering substances by simulating M. genitalium-negative pooled urine and swab matrices with M. genitalium cultures. Furthermore, the clinical sensitivity of the assay was evaluated and compared with a reference real-time PCR assay. The analytical sensitivity of the RPMG Flex assay was 157 genomes/ml for wild-type (WT) and 387 genomes/ml for MRMM strains in both matrices. For clinical specimens, the RPMG assay had an overall sensitivity of 96.1% (95% urine: 10/10 WT, 9/10 MRMM; 96.5% swab: 25/26 WT, 26/29 MRMM) compared to 85.7% for the MgPa/MagNAPure24 assay (95% urine: 19/20; 87% swab: 48/57). Clinical specificity was 100% for urine and 98.5% for swab specimens, respectively. No inhibition due to the presence of any of the tested interfering substances was observed. The RPMG Flex assay was more sensitive than the reference MgPa assay, in particular, for swab specimens. The implementation of this assay may increase ease of use and considerably decrease hands-on time for sample preparation compared to a standard block-based assay. The RPMG Flex assay for the GeneXpert Dx system provides a much-needed platform for the simultaneous detection of MG and MRMM and may thereby facilitate resistance-guided therapy for M. genitalium infections.

Evaluation of ResistancePlus MG FleXible, a ‘near-patient’ test for the detection of Mycoplasma genitalium and macrolide resistance mutations, using freshly collected clinical samples

“…These findings are consistent with a previous report that ResistancePlus MG FleXible has higher analytical sensitivity when testing serial dilutions of samples [7]. Additionally, when compared to extracted DNA tested by MgPa quantitative PCR, the ResistancePlus MG FleXible demonstrated higher sensitivity (86% detection compared to 96% detection, respectively) [8].…”

“…Performance was similar across a variety of sample types. There was also strong concordance for mutation detection (97 %), as found in previous reports using stored samples (93-100%) [7,8].…”

“…A high degree of concordance with the ResistancePlus MG reference assay was identified for M. genitalium detection (94 %), similar to the sensitivity identified in previous reports that analysed collections of stored samples (96–97%) [7, 8]. Performance was similar across a variety of sample types.…”

“…This test reports detection of M. genitalium via detection of the MgPa gene, and MRMs in the 23S rRNA gene (mutations A2058G, A2059G, A2058T, A2058C; Escherichia coli numbering), and has an exogenous internal control. This test has been evaluated for detection limits and evaluated on stored clinical samples [7,8], but has yet to be tested on freshly collected samples. In this study, the ResistancePlus MG FleXible test was validated using freshly collected clinical samples.…”

The Impact of Selected Bacterial Sexually Transmitted Diseases on Pregnancy and Female Fertility

“…An interesting solution is the Resistance Plus MG FleXible (RPMG Flex) assay (SpeeDx). This is a multiplex qPCR test detecting the gene encoding the MgPa adhesion protein and simultaneously detects five 23S rRNA mutations (A2058G, T, or C, and A2059G or C) [ 68 ].…”