Selection of AmpC β-lactamase variants and metallo-β-lactamases leading to ceftolozane/tazobactam and ceftazidime/avibactam-resistance during treatment of MDR/XDR Pseudomonas aeruginosa infections

Infections caused by ceftolozane/tazobactam and ceftazidime/avibactam-resistant P. aeruginosa infections are an emerging concern. We aimed to analyze the underlying ceftolozane/tazobactam and ceftazidime/avibactam resistance mechanisms in all MDR/XDR P. aeruginosa isolates recovered during one year (2020) from patients with a documented P. aeruginosa infection. Fifteen isolates showing ceftolozane/tazobactam and ceftazidime/avibactam resistance were evaluated. Clinical conditions, previous positive cultures and β-lactams received in the previous month were reviewed for each patient. MICs were determined by broth microdilution. MLSTs and resistance mechanisms were determined using short- and long-read WGS. The impact of PDCs on β-lactam resistance was demonstrated by cloning into an ampC -deficient PAO1 derivative (PAOΔC) and construction of 3D models. Genetic support of acquired β-lactamases was determined in silico from high-quality hybrid assemblies. In most cases, the isolates were recovered after treatment with ceftolozane/tazobactam or ceftazidime/avibactam. Seven isolates from different STs owed their β-lactam resistance to chromosomal mutations and all displayed specific substitutions in PDC: Phe121Leu and Gly222Ser, Pro154Leu, Ala201Thr, Gly214Arg, ΔGly203-Glu219 and Glu219Lys. In the other eight isolates, the ST175 clone was overrepresented (6 isolates) and associated with IMP-28 and IMP-13, whereas two ST1284 isolates produced VIM-2. The cloned PDCs conferred enhanced cephalosporin resistance. 3D PDC models revealed rearrangements affecting residues involved in cephalosporin hydrolysis. Carbapenemases were chromosomal (VIM-2) or plasmid-borne (IMP-28, IMP-13), and associated with class-1 integrons located in Tn402-like transposition modules. Our findings highlight that cephalosporin/ß-lactamase inhibitors are potential selectors of MDR/XDR P. aeruginosa strains producing PDC variants or metallo-ß-lactamases. Judicious use of these agents is encouraged.

Complete Genome Sequences of 12 Quinolone-Resistant Escherichia coli Strains Containing qnrS1 Based on Hybrid Assemblies

ABSTRACT In total, 12 quinolone-resistant Escherichia coli (QREC) strains containing qnrS1 were submitted to long-read sequencing using a FLO-MIN106 flow cell on a MinION device. The long reads were assembled with short reads (Illumina) and analyzed using the MOB-suite pipeline. Six of these QREC genome sequences were closed after hybrid assembly.

Role of the mobilome in the global dissemination of the carbapenem resistance gene blaNDM

The mobile resistance gene blaNDM encodes the NDM enzyme capable of hydrolysing carbapenems, a class of antibiotics used to treat some of the most severe bacterial infections. blaNDM is globally distributed across a variety of Gram-negative bacteria and is typically located within a transposon-rich genomic region common to multiple plasmids. We compiled a dataset of over 2000 bacterial genomes harbouring the blaNDM gene including 112 new PacBio hybrid assemblies from China and developed a novel computational approach to track structural variants in bacterial genomes. We were able to correlate specific structural variants with plasmid backbones, bacterial host species and sampling locations, and identified multiple transposition events that occurred during the global dissemination of blaNDM. Our results highlight the importance of transposons in the global spread of antimicrobial resistance genes and suggest that genetic recombination, rather than mutation, was the dominant force driving the evolution of the blaNDM genomic region.

Extending the structural landscape of Mo(VI) hydrazonato inorganic-organic POM-hybrids: an experimental and computational study

Five hexamolybdate and five octamolybdate-based organic-inorganic hybrid assemblies, with dioxomolybdenum(VI) hydrazonato complex cations, were synthesized from the [MoO2(acac)2] and isonicotinoyl hydrazone ligands bearing OH (H2L1,2) and OMe (H2L3,4) electron-donating groups....