Proteomic identification of Axc, a novel beta-lactamase with carbapenemase activity in a meropenem-resistant clinical isolate of Achromobacter xylosoxidans

Abstract

The development of antibiotic resistance during treatment is a threat to patients and their environment. Insight in the mechanisms of resistance development is important for appropriate therapy and infection control. Here, we describe how through the application of mass spectrometry-based proteomics, a novel beta-lactamase Axc was identified as an indicator of acquired carbapenem resistance in a clinical isolate of Achromobacter xylosoxidans. Comparative proteomic analysis of consecutively collected susceptible and resistant isolates from the same patient revealed that high Axc protein levels were only observed in the resistant isolate. Heterologous expression of Axc in Escherichia coli significantly increased the resistance towards carbapenems. Importantly, direct Axc mediated hydrolysis of imipenem was demonstrated using pH shift assays and 1H-NMR, confirming Axc as a legitimate carbapenemase. Whole genome sequencing revealed that the susceptible and resistant isolates were remarkably similar. Together these findings provide a molecular context for the fast development of meropenem resistance in A. xylosoxidans during treatment and demonstrate the use of mass spectrometric techniques in identifying novel resistance determinants.

Achromobacter Infections and Treatment Options

“…Some in vitro studies demonstrated that mutations in transcription regulators of unnamed ␤-lactamases, or increased expression of a putative ␤-lactamase gene (i.e., bla AXC ), may contribute to carbapenem resistance in Achromobacter spp. (43,57,58). Comparative genomic analysis of carbapenem-susceptible and -resistant strains is essential to elucidate the genetic mechanisms behind carbapenem resistance of genus Achromobacter.…”

Motility, Biofilm Formation and Antimicrobial Efflux of Sessile and Planktonic Cells of Achromobacter xylosoxidans

“…A clinical isolate of A. xylosoxidans resistant to meropenem with increased levels of a novel betalactamase with carpabanemase activity, Axc, and an amino acid substitution at position 29 of the axyZ gene (V29G) suggests that axc expression is regulated by AxyZ [44]. The putative TetR family transcriptional regulator, encoded by the axyZ gene, functions as a negative regulator of the AxyXY-OprZ efflux pump.…”

Enigmatic Achromobacter

“…В дополнение к существующим конститутивным бета лактамазам, ахромобактерии могут приобретать гены карбапенемаз bla NDM1 [55], bla VIM1 и bla VIM2 [56,57], bla IMP19 [58], bla IMP1 [59], axc [60]. У A. xylosoxidans были найдены обеспечивающие устойчивость к сульфанила мидам/триметоприму плазмидные гены dfrA1 и dfrA16 (кодируют триметоприморезистентную дигидрофолатре дуктазу) и гены sul1 (кодируют сульфаниламидрезистент ную дигидроптероатсинтазу) [34,61].…”