OXA-830, a Novel Chromosomally Encoded Extended-Spectrum Class D β-Lactamase in Aeromonas simiae

Abstract

The diversity of class D β-lactamases mediating resistance to β-lactams has been increasingly reported recently. In this study, a novel class D oxacillinase named OXA-830 was identified in a fully sequenced Aeromonas simiae strain, which was isolated from sewage discharged from a farm in southern China. OXA-830 shares the highest amino acid identity of 79.3% with an OXA-12-like variant named OXA-725. When expressed in E. coli DH5α, OXA-830 conferred resistance to penicillins and selected β-lactamase inhibitors but not to cephalosporins and carbapenems. Kinetic analysis of OXA-830 revealed a broad substrate profile including penicillins, cefazolin, cefoxitin, and ceftazidime but not carbapenems. The hydrolytic activity was significantly inhibited by sulbactam, followed by tazobactam, but was less effectively inhibited by clavulanic acid. The blaOXA–830 gene was located on the A. simiae A6 chromosome and the blaOXA–830-related region was bracketed by a pair of perfect inverted repeats.

Distribution of β-Lactamase Genes and Genetic Context of blaKPC-2 in Clinical Carbapenemase-Producing Klebsiella pneumoniae Isolates

“…Annotation of resistance genes was performed using ISfinder, INTEGRALL and ResFinder with default parameters. 23 …”

“… 24 A map of the plasmid with GC content and GC skew was drawn using the online CGView Server and local GView 1.7 with a visual interface. 23 For the linear comparison of the bla KPC-2 gene-related fragments, wild-type KPC- Kp isolates were mixed, and the plasmids were extracted using a Qiagen Plasmid Mega Kit (Qiagen, Valencia, CA, USA). Sequences containing the bla KPC-2 gene were also obtained from the NCBI nucleotide database using bla KPC-2 , Tn 1721 , IS Kpn6 , and IS Kpn 8 as the key words.…”

Characterization of a Novel Chromosomal Class C β-Lactamase, YOC-1, and Comparative Genomics Analysis of a Multidrug Resistance Plasmid in Yokenella regensburgei W13

“…Kinetic parameters for hydrolysis of β-lactams by the purified β-lactamase YOC-1 were examined using a UV-VIS spectrophotometer (U-3900, HITACHI, Japan) at 37°C in 10 mM phosphate buffer (pH 7.0) in a final reaction volume of 200 μL. The steady-state kinetic parameters ( k cat and K m ) were determined by nonlinear regression of the initial reaction rates with the Michaelis-Menten equation in Prism (version 7) software (GraphPad Software, CA, United States) ( Chen et al, 2019 ).…”

“…The β-lactamase inhibitors avibactam, GMP (disodium 5′-guanosine monophosphate) and clavulanic acid at various concentrations were preincubated with purified YOC-1 at 37°C for 5 min before the addition of substrate. The inhibitor concentration required to reduce the hydrolysis of 100 μM nitrocefin by 50% was determined by nonlinear regression with the log (inhibitor) vs. response – Variable slope equation in Prism (version 7) software (GraphPad Software, CA, United States) ( Chen et al, 2019 ).…”

Distribution of β-lactamase Gene and Genetic Context of blaKPC-2 in Clinical Carbapenemase-producing Klebsiella Pneumoniae Isolates

“…with a visual interface [22] . For the linear comparison of the bla KPC−2 gene-related fragments, wild-type KPC-Kp isolates were mixed, and the plasmids were extracted using a Qiagen Plasmid Mega Kit (Qiagen, Valencia, CA, USA).…”