Plasmid analysis of NDM metallo-β-lactamase-producing Enterobacterales isolated in Vietnam

IncX3 plasmid-mediated spread of blaNDM gene in Enterobacteriaceae among children in China

OBJECTIVES

The blaNDM gene was prevalent among children and became the predominant cause of severe infection in infants and children. This study aimed to investigate the epidemiology and molecular characteristics of blaNDM in Enterobacteriaceae among children in China.

METHODS

Carbapenem-resistant Enterobacteriaceae (CRE) were collected in the Children's Hospital of Fudan University from January 2016 to December 2022. Five carbapenemase genes (blaKPC, blaNDM, blaVIM, blaIMP, blaOXA-48) were screened by PCR method. Multilocus sequence typing (MLST) was conducted for phylogenetic analyses. blaNDM-carrying plasmids were typed by PCR-based Incompatibility (Inc) typing method. Moreover, plasmid comparison was performed with 213 publicly available IncX3 plasmids.

RESULTS

A total of 330 CRE strains were enrolled, 96.4% of which carried carbapenemase genes. blaNDM gene accounted for 64.8% (214 strains) and included four variants, including blaNDM-1 (59.8%), blaNDM-5 (39.3%), blaNDM-7 (0.5%), and blaNDM-9 (0.5%). There were no predominant MLST lineages of blaNDM carrying strains. IncX3 was the major plasmid carrying blaNDM-1 (68.0%) and blaNDM-5 (72.6%) and was dominant in blaNDM-Klebsiella penumoniae (79.8%), blaNDM-Escherichia coli (58.2%), and blaNDM-Enterobacter cloacae (61.0%), respectively. Most (79.0%) clinical IncX3 plasmids in the world carried blaNDM, and the prevalence of blaNDM in IncX3 plasmids was more common in China (95.8%) than other countries (58.1%, P <0.01).

CONCLUSION

blaNDM is highly prevalent in CRE among children in China. The spread of blaNDM was mainly mediated by IncX3 plasmids. Surveillance and infection control on the spread of blaNDM among children are important.

Genomic investigation of multispecies and multivariant blaNDM outbreak reveals key role of horizontal plasmid transmission

OBJECTIVES

New Delhi metallo-β-lactamases (NDMs) are major contributors to the spread of carbapenem resistance globally. In Australia, NDMs were previously associated with international travel, but from 2019 we noted increasing incidence of NDM-positive clinical isolates. We investigated the clinical and genomic epidemiology of NDM carriage at a tertiary-care Australian hospital from 2016 to 2021.

METHODS

We identified 49 patients with 84 NDM-carrying isolates in an institutional database, and we collected clinical data from electronic medical record. Short- and long-read whole genome sequencing was performed on all isolates. Completed genome assemblies were used to assess the genetic setting of blaNDM genes and to compare NDM plasmids.

RESULTS

Of 49 patients, 38 (78%) were identified in 2019-2021 and only 11 (29%) of 38 reported prior travel, compared with 9 (82%) of 11 in 2016-2018 (P = .037). In patients with NDM infection, the crude 7-day mortality rate was 0% and the 30-day mortality rate was 14% (2 of 14 patients). NDMs were noted in 41 bacterial strains (ie, species and sequence type combinations). Across 13 plasmid groups, 4 NDM variants were detected: blaNDM-1, blaNDM-4, blaNDM-5, and blaNDM-7. We noted a change from a diverse NDM plasmid repertoire in 2016-2018 to the emergence of conserved blaNDM-1 IncN and blaNDM-7 IncX3 epidemic plasmids, with interstrain spread in 2019-2021. These plasmids were noted in 19 (50%) of 38 patients and 35 (51%) of 68 genomes in 2019-2021.

CONCLUSIONS

Increased NDM case numbers were due to local circulation of 2 epidemic plasmids with extensive interstrain transfer. Our findings underscore the challenges of outbreak detection when horizontal transmission of plasmids is the primary mode of spread.

Large-scale analysis of putative plasmids in clinical multidrug-resistant Escherichia coli isolates from Vietnamese patients

Introduction

In the past decades, extended-spectrum beta-lactamase (ESBL)-producing and carbapenem-resistant (CR) Escherichia coli isolates have been detected in Vietnamese hospitals. The transfer of antimicrobial resistance (AMR) genes carried on plasmids is mainly responsible for the emergence of multidrug-resistant E. coli strains and the spread of AMR genes through horizontal gene transfer. Therefore, it is important to thoroughly study the characteristics of AMR gene-harboring plasmids in clinical multidrug-resistant bacterial isolates.

Methods

The profiles of plasmid assemblies were determined by analyzing previously published whole-genome sequencing data of 751 multidrug-resistant E. coli isolates from Vietnamese hospitals in order to identify the risk of AMR gene horizontal transfer and dissemination.

Results

The number of putative plasmids in isolates was independent of the sequencing coverage. These putative plasmids originated from various bacterial species, but mostly from the Escherichia genus, particularly E. coli species. Many different AMR genes were detected in plasmid contigs of the studied isolates, and their number was higher in CR isolates than in ESBL-producing isolates. Similarly, the bla_KPC-2, bla_NDM-5, bla_OXA-1, bla_OXA-48, and bla_OXA-181 β-lactamase genes, associated with resistance to carbapenems, were more frequent in CR strains. Sequence similarity network and genome annotation analyses revealed high conservation of the β-lactamase gene clusters in plasmid contigs that carried the same AMR genes.

Discussion

Our study provides evidence of horizontal gene transfer in multidrug-resistant E. coli isolates via conjugative plasmids, thus rapidly accelerating the emergence of resistant bacteria. Besides reducing antibiotic misuse, prevention of plasmid transmission also is essential to limit antibiotic resistance.

Genomic Epidemiological Analysis of Antimicrobial-Resistant Bacteria with Nanopore Sequencing

Antimicrobial-resistant (AMR) bacterial infections caused by clinically important bacteria, including ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) and mycobacteria (Mycobacterium tuberculosis and nontuberculous mycobacteria), have become a global public health threat. Their epidemic and pandemic clones often accumulate useful accessory genes in their genomes, such as AMR genes (ARGs) and virulence factor genes (VFGs). This process is facilitated by horizontal gene transfer among microbial communities via mobile genetic elements (MGEs), such as plasmids and phages. Nanopore long-read sequencing allows easy and inexpensive analysis of complex bacterial genome structures, although some aspects of sequencing data calculation and genome analysis methods are not systematically understood. Here we describe the latest and most recommended experimental and bioinformatics methods available for the construction of complete bacterial genomes from nanopore sequencing data and the detection and classification of genotypes of bacterial chromosomes, ARGs, VFGs, plasmids, and other MGEs based on their genomic sequences for genomic epidemiological analysis of AMR bacteria.

Trends in carbapenem resistance in Pre-COVID and COVID times in a tertiary care hospital in North India

BACKGROUND

Carbapenem resistance is endemic in the Indian sub-continent. In this study, carbapenem resistance rates and the prevalence of different carbapenemases were determined in Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa during two periods; Pre-COVID (August to October 2019) and COVID (January to February 2021) in a north-Indian tertiary care hospital.

METHODS

Details of patient demographics and clinical condition was collated from the Hospital Information System and detection of carbapenemases NDM, OXA-48, VIM, IMP and KPC was done by Polymerase chain reaction (PCR) in 152 and 138 non-consecutive carbapenem resistant isolates during the two study periods respectively. Conjugation assay and sequencing of NDM and OXA-48 gene was done on a few selected isolates.

RESULTS

As compared to Pre-COVID period, co-morbidities and the mortality rates were higher in patients harbouring carbapenem resistant organisms during the COVID period. The overall carbapenem resistance rate for all the four organisms increased from 23 to 41% between the two periods of study; with Pseudomonas aeruginosa and Klebsiella pneumoniae showing significant increase (p < 0.05). OXA-48, NDM and co-expression of NDM and OXA-48 were the most common genotypes detected. NDM-5 and OXA-232 were most common variants of NDM and OXA-48 family respectively during both the study periods.

CONCLUSION

Higher rate of carbapenem resistance in COVID times could be attributed to increase in number of patients with co-morbidities. However, genetic elements of carbapenem resistance largely remained the same in the two time periods.

Study of the molecular characteristics and homology of carbapenem-resistant Proteus mirabilis by whole genome sequencing

Introduction. Proteus mirabilis is part of the family Enterobacteriaceae, and is naturally resistant to various antimicrobial drugs. In recent years, outbreaks of severe nosocomial infections caused by carbapenem-resistant P. mirabilis (CR-PMI) have been frequently reported. Few studies exist on the whole-genome molecular characteristics of this bacterium in China and elsewhere, which stimulated the implementation of this study.Hypothesis. CR-PMI strains contained the multiple drug resistance genes and exhibited a high resistance rate to commonly used antimicrobial drugs.Aim. Our goals here were to identify resistance mechanisms and homology of CR-PMI strains and provide a theoretical basis for clinical treatment and controlling nosocomial infections.Methodology. Bacterial species identification was carried out using matrix-assisted laser desorption/ionization time of flight MS (MALDI-TOF-MS). Antimicrobial susceptibility was determined using the VITEK 2 system and Kirby-Bauer (K-B) disc-diffusion method. Whole-genome sequencing (WGS) was conducted by the Illumina platform NovaSeq sequencer. Antibiotic resistance genes (ARGs) were identified using the NCBI database with Abricate. Plasmid replicon types were identified using PlasmidFinder, available at the Center for Genomic Epidemiology.Results. Five CR-PMI strains collected in our hospital from July 2019 to September 2021 were resistant to almost all antimicrobial agents except aztreonam (ATM), amikacin (AMK) and cefotetan (CTT). All CR-PMI strains contained the carbapenem resistance gene New Delhi metallo-β-lactamase 1 (bla _NDM-1), and two strains harboured extended-spectrum β-lactamase (ESBL) genes bla _PER-4 and bla _CTX-M-65. The five CR-PMI strains contained 27, 18, 30, 25 and 24 drug-resistance genes, respectively. Most antimicrobial resistance genes were detected for aminoglycosides (n=14), followed by cephalosporins (n=7). The phylogenetic tree was divided into five evolutionary groups, and the five CR-PMI strains were in the four evolutionary groups B-E.Conclusion Overall, CR-PMI strains exhibited a high resistance rate to commonly used antimicrobial drugs, and contained the carbapenem resistance gene bla _NDM-1. The CR-PMI strains showed a polyclonal trend in different wards at different times. Most importantly, all strains identified contained important antimicrobial resistance genes, which may lead to severe drug resistance transmission and fatal multiple resistant bacterial infections.

Detection of IMP-4 and SFO-1 co-producing ST51 Enterobacter hormaechei clinical isolates

Purpose

To explore the genetic characteristics of the IMP-4 and SFO-1 co-producing multidrug-resistant (MDR) clinical isolates, Enterobacter hormaechei YQ13422hy and YQ13530hy.

Methods

MALDI-TOF MS was used for species identification. Antibiotic resistance genes (ARGs) were tested by PCR and Sanger sequencing analysis. In addition to agar dilution, broth microdilution was used for antimicrobial susceptibility testing (AST). Whole-genome sequencing (WGS) analysis was conducted using the Illumina NovaSeq 6000 and Oxford Nanopore platforms. Annotation was performed by RAST on the genome. The phylogenetic tree was achieved using kSNP3.0. Plasmid characterization was conducted using S1-pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, conjugation experiments, and whole genome sequencing (WGS). An in-depth study of the conjugation module was conducted using the OriTFinder website. The genetic context of bla _IMP-4 and bla _SFO-1 was analyzed using BLAST Ring Image Generator (BRIG) and Easyfig 2.3.

Results

YQ13422hy and YQ13530hy, two MDR strains of ST51 E. hormaechei harboring bla _IMP-4 and bla _SFO-1, were identified. They were only sensitive to meropenem, amikacin and polymyxin B, and were resistant to cephalosporins, aztreonam, piperacillin/tazobactam and aminoglycosides, intermediate to imipenem. The genetic context surrounding bla _IMP-4 was 5'CS-hin-1-IS26-IntI1-bla _IMP-4-IS6100-ecoRII. The integron of bla _IMP-4 is In823, which is the array of gene cassettes of 5'CS-bla _IMP-4. Phylogenetic analysis demonstrated that E. hormaechei YQ13422hy and YQ13530hy belonged to the same small clusters with a high degree of homology.

Conclusion

This observation revealed the dissemination of the bla _IMP-4 gene in E. hormaechei in China. We found that bla _IMP-4 and bla _SFO-1 co-exist in MDR clinical E. hormaechei isolates. This work showed a transferable IncN-type plasmid carrying the bla _IMP-4 resistance gene in E. hormaechei. We examined the potential resistance mechanisms of pYQ13422-IMP-4 and pYQ13422-SFO-1, along with their detailed genetic contexts.

Ecological dynamics of plasmid transfer and persistence in microbial communities

Plasmids are a major driver of horizontal gene transfer in prokaryotes, allowing the sharing of ecologically important accessory traits between distantly related bacterial taxa. Within microbial communities, interspecies transfer of conjugative plasmids can rapidly drive the generation genomic innovation and diversification. Recent studies are starting to shed light on how the microbial community context, that is, the bacterial diversity together with interspecies interactions that occur within a community, can alter the dynamics of conjugative plasmid transfer and persistence. Here, I summarise the latest research exploring how community ecology can both facilitate and impose barriers to the spread of conjugative plasmids within complex microbial communities. Ultimately, the fate of plasmids within communities is unlikely to be determined by any one individual host, rather it will depend on the interacting factors imposed by the community in which it is embedded.

Potential spread of mcr-9-carrying IncHI2 plasmids in Enterobacter hormaechei in Vietnam

OBJECTIVES

Mobile colistin resistance (mcr) genes are widely distributed around the world. To date, ten major variants of mcr genes are known (mcr-1 to mcr-10). However, only a few instances of Enterobacterales isolates harbouring mcr genes other than mcr-1 have been reported in Vietnam. The aim of this study was to investigate mcr-harbouring antimicrobial-resistant Enterobacterales isolates in Vietnam.

METHODS

Two mcr-9-harbouring Enterobacter hormaechei clinical isolates (NIHE14-1904 and MH17-539M) were obtained from medical institutions in Hanoi, Vietnam, in 2014 and 2017, respectively. Their genomes and plasmid sequences were analysed by short-read and long-read sequencing. Subsequently, comparative sequence analysis of their mcr-9-carrying plasmids was performed.

RESULTS

Strains NIHE14-1904 and MH17-539M belonged to sequence types ST916 and ST66, respectively, according to the Enterobacter cloacae multilocus sequence typing (MLST) scheme. NIHE14-1904 and MH17-539M harboured the mcr-9 gene on similar IncHI2 plasmids, namely pNIHE14-1904-mcr9 (373.1 kb) and pMH17-539M-mcr9 (289.3 kb), respectively. These plasmids were also highly identical to widespread IncHI2 plasmids that are often associated with mcr genes.

CONCLUSION

For the first time, mcr-9-harbouring Enterobacterales isolates were detected in Vietnam, which carried mcr-9 on IncHI2 plasmids. The prevalence of such plasmids needs to be monitored in the future owing to their high dissemination.