Project description:Background: The rapid evolution and dissemination of mobilized colistin resistance gene (mcr) family has revealed as a severe threat to the global public health. Nevertheless, dramatic reduction in the prevalence of mcr-1, the major member of mcr family, was observed after the withdrawal of colistin in animal fodder in China since 2017, demonstrating that colistin acts as a selective stress to promote the dissemination of mcr-1. As the second largest lineage, mcr-3 was firstly discovered in 2017 and has been identified from numerous sources. However, whether the spreading of mcr-3 is driven by colistin remains unknown. Methods: To this end, we investigated the global prevalence of mcr-3 from 2005 to 2022 by an up-to-date systematic review, along with a nation-wide epidemiological study to establish the change of mcr-3 prevalence in China before and after 2017. To investigate the fitness cost imposed by MCR-3 upon bacterial host, in vitro and in vivo competitive assays were employed, along with morphological study and fluorescent observation. Moreover, by replacing non-optimal codons with optimal codons, synonymous mutations were introduced into the 5’-coding region of mcr-3 to study mechanisms accounting for the distinct fitness cost conferred by MCR-1 and MCR-3. Furthermore, by combining AlphaFold and molecular dynamics (MD) simulation, we provided a complete characterization on the putative lipid A binding pocket localized at the linker domain of MCR-3. Crucially, inhibitors targeting at the putative binding pocket of MCR-1 or MCR-3 were identified from small molecules library using the pipeline of virtual screening. Findings: The global prevalence of mcr-3 increased continuously from 2005 to 2022. The average prevalence was 0.18% during 2005-2014 and rapidly increased to 3.41% during 2020-2022. The prevalence of mcr-3 in China increased from 0.79% in 2016 to 5.87% in 2019. We found that the fitness of mcr-3-bearing E. coli and empty plasmid control was comparable but higher than that of mcr-1-positive strain. Although the putative lipid A binding pocket of MCR-3 was similar to that of in MCR-1, mcr-3 occupies remarkable codon bias at the 5’-end of coding region that disrupted the stability of mRNA, further reduced its protein expression in E. coli, resulting in the low fitness burden of bacterial host. Moreover, the 5’-end codon usage frequency appeared as a critical factor related with the evolution of mcr family. Furthermore, based on the similar lipid A binding pocket among MCR family protein, we identified three novel MCR inhibitors targeting at such pocket by screening from small-molecule library, which effectively restored the colistin susceptibility of mcr-bearing E. coli. Interpretation: For the first time, we found that the prevalence of mcr-3 increased continuously during 2016-2019 in China, demonstrating that the withdrawal of colistin in husbandry failed to prevent the dissemination of mcr-3. Our study evidenced that the 5’-end codon bias appeared as a crucial regulator upon the fitness cost conferred by horizontally transferred genes. Most importantly, the putative lipid A binding pocket verified from current study was a promising target site for designing inhibitors against mcr-positive strains.
Project description:Conjugative plasmids, major vehicles for the spread of antibiotic resistance genes, often contain multiple toxin‒antitoxin (TA) systems. However, the physiological functions of TA systems remain obscure. By studying TA families commonly found on colistin-resistant IncI2 mcr-1-bearing plasmids, we discovered that the HicAB TA, acts as a crucial addiction module to increase horizontal plasmid‒plasmid competition.
Project description:BackgroundEscherichia coli carrying clinically important antimicrobial resistances [i.e., against extended-spectrum-beta-lactamases (ESBL)] are of high concern for human health and are increasingly detected worldwide. Worryingly, they are often identified as multidrug-resistant (MDR) isolates, frequently including resistances against quinolones/fluoroquinolones.ResultsHere, the occurrence and genetic basis of the fluoroquinolone resistance enhancing determinant qnrB in ESBL-/non-ESBL-producing E. coli was investigated. Overall, 33 qnrB-carrying isolates out of the annual German antimicrobial resistance (AMR) monitoring on commensal E. coli (incl. ESBL-/AmpC-producing E. coli) recovered from food and livestock between 2013 and 2018 were analysed in detail. Whole-genome sequencing, bioinformatics analyses and transferability evaluation was conducted to characterise the prevailing qnrB-associated plasmids. Furthermore, predominant qnrB-carrying plasmid-types were subjected to in silico genome reconstruction analysis. In general, the qnrB-carrying E. coli were found to be highly heterogenic in their multilocus sequence types (STs) and their phenotypic resistance profiles. Most of them appeared to be MDR and exhibited resistances against up to ten antimicrobials of different classes. With respect to qnrB-carrying plasmids, we found qnrB19 located on small Col440I plasmids to be most widespread among ESBL-producing E. coli from German livestock and food. This Col440I plasmid-type was found to be highly conserved by exhibiting qnrB19, a pspF operon and different genes of unassigned function. Furthermore, we detected plasmids of the incompatibility groups IncN and IncH as carriers of qnrB. All qnrB-carrying plasmids also exhibited virulence factors and various insertion sequences (IS). The majority of the qnrB-carrying plasmids were determined to be self-transmissible, indicating their possible contribution to the spread of resistances against (fluoro)quinolones and other antimicrobials.ConclusionIn this study, a diversity of different plasmid types carrying qnrB alone or in combination with other resistance determinants (i.e., beta-lactamase genes) were found. The spread of these plasmids, especially those carrying antimicrobial resistance genes against highest priority critically important antimicrobial agents, is highly unfavourable and can pose a threat for public health. Therefore, the dissemination pathways and evolution of these plasmids need to be further monitored.
Project description:Background: It remains unclear how high-risk Escherichia coli lineages, like sequence type (ST) 131, initially adapt to carbapenem exposure in its progression to becoming carbapenem resistant. Methods: Carbapenem mutation frequency was measured in multiple subclades of extended-spectrum β-lactamase (ESBL) positive ST131 clinical isolates using a fluctuation assay followed by whole genome sequencing (WGS) characterization. Genomic, transcriptomic, and porin analyses of ST131 C2/H30Rx isolate, MB1860, under prolonged, increasing carbapenem exposure was performed using two distinct experimental evolutionary platforms to measure fast vs. slow adaptation. Results: All thirteen ESBL positive ST131 strains selected from a diverse (n=184) ST131 bacteremia cohort had detectable ertapenem (ETP) mutational frequencies with a statistically positive correlation between initial ESBL gene copy number and mutation frequency (r = 0.87, P<1e-5). WGS analysis of mutants showed initial response to ETP exposure resulted in significant increases in ESBL gene copy numbers or mutations in outer membrane porin (Omp) encoding genes in the absence of ESBL gene amplification with subclade specific adaptations. In both experimental evolutionary platforms, MB1860 responded to initial ETP exposure by increasing blaCTX-M-15 copy numbers via modular, insertion sequence 26 (IS26) mediated pseudocompound transposons (PCTns). Transposase activity driven by PCTn upregulation was a conserved expression signal in both experimental evolutionary platforms. Stable mutations in Omp encoding genes were detected only after prolonged increasing carbapenem exposure consistent with clinical observations. Conclusions: ESBL gene amplification is a conserved response to initial carbapenem exposure, especially within the high-risk ST131 C2 subclade. Targeting such amplification could assist with mitigating carbapenem resistance development.
Project description:The Moutan Cortex Radicis (MCR) has been used as an analgesic, sedative and anti-inflammatory agent. This study investigated the changes in gene expression by MCR treatment when stimulated with lipopolysaccharide (LPS) in cultured human gingival fibroblasts (HGFs) and the gene expression changes by the MCR when challenged with LPS using a microarray chip.
Project description:Genomic Insights into the Epidemiology and Transmission Dynamics of mcr-Carrying, ESBL-Producing Escherichia coli from Thai Pig Abattoirs.
Project description:The rapid dissemination of colistin resistance via mcr-carrying plasmids (pMCRs) poses a significant public health challenge. This study examined the genomic diversity and conjugation mechanisms of pMCRs, with a particular focus on the role of type IV secretion systems (T4SS) in IncI2 plasmids. The 868 complete plasmid sequences revealed various replicon types of pMCRs, with IncI2 as the primary epidemic type, and the co-transfer risk of multidrug resistance genes associated with IncHI2. T4SS was identified in 89.9% of pMCRs, with the T4SS sequence exclusively carried by IncI2 being conserved and typical of the VirB/D4 type, consisting of 12 subunits. Conjugation assays confirmed the essential role of the pilus subunit VirB2 and the significant impact of VirB5P3 on conjugation. This was further validated in the in vivo intra-species competitive conjugation of Escherichia coli. Structural predictions show that a hypervariable region at the C-terminus of the pentameric VirB5 co-evolves in sequence with VirB6, and the conserved N-terminal may act as a potential drug target to inhibit the plasmid transfer channel. This study will deepen the understanding of the pMCR epidemic patterns and provide additional insights for controlling the spread of resistant plasmids.