Genetic determinants of antimicrobial resistance in three multi-drug resistant strains of isolated from patients with acne: a predictive study.

Objectives: Using available whole genome data, the objective of this study was to identify genetic mechanisms that could explain the antimicrobial resistance profile of three multi-drug resistant (MDR) strains (CA17, CA51, CA39) of the skin bacterium previously recovered from patients with acne. In particular, we were interested in detecting novel genetic determinants associated with resistance to fluoroquinolone and macrolide antibiotics that could then be confirmed experimentally.

Methods: A range of open source bioinformatics tools were used to 'mine' genetic determinants of antimicrobial resistance and plasmid borne contigs, and to characterise the phylogenetic diversity of the MDR strains.

Results: As probable mechanisms of resistance to fluoroquinolones, we identified a previously described resistance associated allelic variant of the gene with a 'deleterious' S101L mutation in type IA strains CA51 (ST1) and CA39 (ST1), as well as a novel E761R 'deleterious' mutation in the type II strain CA17 (ST153). A distinct genomic sequence of the efflux protein YfmO which is potentially associated with resistance to MLSB antibiotics was also present in CA17; homologues in CA51, CA39, and other strains of , were also found but differed in amino acid content. Strikingly, in CA17 we also identified a circular 2.7 kb non-conjugative plasmid (designated pCA17) that closely resembled a 4.8 kb plasmid (pYU39) from the MDR strain YU39.

Conclusions: This study has provided a detailed explanation of potential genetic determinants for MDR in the strains CA17, CA39 and CA51. Further laboratory investigations will be required to validate these results, especially in relation to pCA17.