The activity of plazomicin and clinically relevant aminoglycosides was tested against 346 extended-spectrum-␤-lactamase/AmpC-producing Escherichia coli urinary isolates, and the results were correlated with the presence of aminoglycoside-modifying enzymes (AMEs). Data showed that plazomicin was very active against all ESBL/AmpCproducing E. coli urinary isolates. Its activity was not related to the AME genes studied.KEYWORDS AMEs, ESBL, Escherichia coli, plazomicin, aminoglycosides E scherichia coli strains producing extended-spectrum ␤-lactamases (ESBLs) have emerged as major global pathogens, primarily associated with urinary tract infections (1). These strains possess plasmids that carry genes conferring resistance to multiple antibiotic classes (2). As a result, therapeutic options against these ␤-lactamresistant E. coli infections are extremely limited.Aminoglycoside resistance in Gram-negatives is mainly conferred by production of aminoglycoside-modifying enzymes (AMEs) (3). Genes encoding AMEs are located on mobile genetic elements along with other resistance determinants, resulting in multidrug-resistant (MDR) isolates (3). Plazomicin is a next-generation aminoglycoside modified to evade AMEs. The compound is currently under clinical development for the treatment of complicated urinary tract infections (cUTIs) and acute pyelonephritis as a single agent (4,5).In this study, we evaluated the activity of plazomicin and clinically relevant aminoglycosides against 346 ESBL/AmpC-producing E. coli urinary isolates. The presence of four AME genes was also investigated, and the relationship between the AME genes detected and the resistance phenotype found was determined.The isolates were obtained prospectively during 2013 at the Hospital Clínico San Carlos (Madrid, Spain). Only one isolate per patient was included. PCR characterization (6, 7) showed 302 ESBL producers and 44 AmpC producers.MICs of gentamicin, tobramycin, amikacin, and plazomicin were determined by the agar dilution method. MICs of plazomicin were also determined by the broth microdilution method (8). Antimicrobial agents were obtained from their respective manufacturers. Plazomicin was supplied from Achaogen (South San Francisco, CA). The results were interpreted according the guidelines of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) (9).All isolates resistant to at least one of the aminoglycosides studied were tested by PCR for the presence of AME genes. Sets of primers for the following genes were

Objectives To assess the genetic contexts surrounding blaNDM-1 genes carried on IncM plasmids harboured by six carbapenemase-producing Enterobacterales (CPE) isolates referred to the UK Health Security Agency’s Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit. Methods Between 2014 and 2018, the AMRHAI Reference Unit undertook WGS of CPE isolates using Illumina NGS. Nanopore sequencing was used for selected isolates and publicly available plasmid references were downloaded. Analysis of incRNA, which encodes the antisense RNA regulating plasmidic repA gene expression, was performed and bioinformatics tools were used to analyse whole plasmid sequences. Results Of 894 NDM-positive isolates of Enterobacterales, 44 NDM-1-positive isolates of five different species (Citrobacter spp., Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca) encoded the IncRNA locus of IncM2 plasmids. Long-read sequencing of six diverse isolates revealed related IncM2, NDM-1-encoding plasmids. Plasmid ‘backbone’ areas were conserved and contrasted with highly variable resistance regions. Sub-groupings of IncM2 plasmids encoding blaNDM-1 were detected; one sub-group occurred in five different health regions of England in every year. The diversity of NDM-1-encoding resistance gene integrons and transposons and their insertions sites in the plasmids indicated that NDM-1 has been acquired repeatedly by IncM2 variants. Conclusions The use of sequencing helped inform: (i) a wide geographical distribution of isolates encoding NDM-1 on emergent IncM2 plasmids; (ii) variant plasmids have acquired NDM-1 separately; and (iii) dynamic arrangements and evolution of the resistance elements in this plasmid group. The geographical and temporal distribution of IncM2 plasmids that encode NDM-1 highlights them as a public health threat that requires ongoing monitoring.

No abstract