Transcontinental Dissemination of Enterobacterales Harboring blaNDM-1 in Retail Frozen Shrimp

The global food trade provides a means of disseminating antimicrobial resistant (AMR) bacteria and genes. Using selective media, carbapenem-resistant species of Enterobacterales (Providencia sp. and Citrobacter sp.), were detected in a single package of imported frozen shrimp purchased from a grocery store in Ohio, USA. Polymerase chain reaction confirmed that both isolates harbored blaNDM-1 genes. Following PacBio long read sequencing, the sequences were annotated using the NCBI Prokaryotic Genome Annotation Pipeline. The blaNDM-1 genes were found in IncC plasmids, each with different antimicrobial resistance island configuration. We found that the blaNDM-1 AMR islands had close relationships with previously reported environmental, food, and clinical isolates detected in Asia and the United States, highlighting the importance of the food chain in the global dissemination of antimicrobial resistance.

The impact of armed conflict on the development and global spread of antibiotic resistance: a systematic review

BACKGROUND

Scant data are available on the link between armed conflicts and the development and spread of antimicrobial resistance.

OBJECTIVES

We performed a systematic review with the aim to summarize the available data on the prevalence and features of antibiotic resistance and the causes of antibiotic resistance development during armed conflicts in the 21st century.

METHODS

Data sources: PubMed and SCOPUS databases were searched from 1 January 2000 to 30 November 2023.

STUDY ELIGIBILITY CRITERIA

Original articles reporting data on armed conflicts and antimicrobial resistance were included in this systematic review. No attempt was made to obtain information from unpublished studies. No language restriction was applied. Methods of data synthesis: Both quantitative and qualitative information were summarized by means of textual descriptions.

PARTICIPANTS

Patients or soldiers deployed in armed conflict zones.

TESTS

culture-dependent antibiotic sensitivity testing or molecular detection of the genetic determinants of antibiotic resistance after a confirmed diagnosis of bacterial infection. Assessment of risk of bias: To evaluate the quality of the included studies, we adapted the tool recommended by the Joanna Briggs Institute.

RESULTS

Thirty-four studies were identified, published between November 2004 and November 2023. The quality of included studies was high and medium in 47% and 53% of the studies, respectively. The included studies reported high infection and colonization rates of multidrug-resistant bacteria. Studies performed during the Eastern Ukraine conflict reported high rates of New Delhi metallo-β-lactamase producers.

DISCUSSION

Our findings confirm that wars lead to a large pool of multidrug-resistant infections that could potentially spread. Infection control in healthcare facilities in conflict zones and proper antimicrobial stewardship are crucial.

Sequential Treatment Failure With Aztreonam-Ceftazidime-Avibactam Followed by Cefiderocol Due to Preexisting and Acquired Mechanisms in a New Delhi Metallo-β-lactamase-Producing Escherichia coli Causing Fatal Bloodstream Infection

We report a fatal case of New Delhi metallo-β-lactamase (NDM)-producing Escherichia coli in a bacteremic patient with sequential failure of aztreonam plus ceftazidime-avibactam followed by cefiderocol. Acquired resistance was documented phenotypically and mediated through preexisting and acquired mutations. This case highlights the need to rethink optimal treatment for NDM-producing organisms.

Changing Genotypic Distribution, Antimicrobial Susceptibilities, and Risk Factors of Urinary Tract Infection Caused by Carbapenemase-Producing Pseudomonas aeruginosa

Background

Carbapenem-resistant Pseudomonas aeruginosa (CrPA) is a leading cause of healthcare-associated urinary tract infections (UTIs). Carbapenemase production is an important mechanism that significantly alters the efficacy of frequently used anti-pseudomonal agents. Reporting the current genotypic distribution of carbapenemase-producing P. aeruginosa (CPPA) isolates in relation to antimicrobial susceptibility, UTI risk factors, and mortality is necessary to increase the awareness and control of these strains.

Methods

In total, 1,652 non-duplicated P. aeruginosa strains were isolated from hospitalized patients between 2015 and 2020. Antimicrobial susceptibility, carbapenemase genotypes, risk factors for UTI, and associated mortality were analyzed.

Results

The prevalence of carbapenem-non-susceptible P. aeruginosa isolates showed a decreasing trend from 2015 to 2018 and then increased in the background of the emergence of New Delhi metallo-β-lactamase (NDM)-type isolates since 2019. The CPPA strains showed 100.0% non-susceptibility to all tested antibiotics, except aztreonam (94.5%) and colistin (5.9%). Carbapenems were identified as a risk and common predisposing factor for UTI (odds ratio [OR]=1.943) and mortality (OR=2.766). Intensive care unit (ICU) stay (OR=2.677) and white blood cell (WBC) count (OR=1.070) were independently associated with mortality.

Conclusions

The changing trend and genetic distribution of CPPA isolates emphasize the need for relentless monitoring to control further dissemination. The use of carbapenems, ICU stay, and WBC count should be considered risk factors, and aggressive antibiotic stewardship programs and monitoring may serve to prevent worse outcomes.

Emergence and rapid dissemination of highly resistant NDM-14-producing Klebsiella pneumoniae ST147, France, 2022

BackgroundSince 2021, an emergence of New Delhi metallo-β-lactamase (NDM)-14-producing Klebsiella pneumoniae has been identified in France. This variant with increased carbapenemase activity was not previously detected in Enterobacterales.AimWe investigated the rapid dissemination of NDM-14 producers among patients in hospitals in France.MethodsAll NDM-14-producing non-duplicate clinical isolates identified in France until June 2022 (n = 37) were analysed by whole genome sequencing. The phylogeny of NDM-14-producers among all K. pneumoniae sequence type (ST) 147 reported in France since 2014 (n = 431) was performed. Antimicrobial susceptibility testing, conjugation experiments, clonal relationship and molecular clock analysis were performed.ResultsThe 37 NDM-14 producers recovered in France until 2022 belonged to K. pneumoniae ST147. The dissemination of NDM-14-producing K. pneumoniae was linked to a single clone, likely imported from Morocco and responsible for several outbreaks in France. The gene bla NDM-14 was harboured on a 54 kilobase non-conjugative IncFIB plasmid that shared high homology with a known bla NDM-1-carrying plasmid. Using Bayesian analysis, we estimated that the NDM-14-producing K. pneumoniae ST147 clone appeared in 2020. The evolutionary rate of this clone was estimated to 5.61 single nucleotide polymorphisms per genome per year. The NDM-14 producers were highly resistant to all antimicrobials tested except to colistin, cefiderocol (minimum inhibitory concentration 2 mg/L) and the combination of aztreonam/avibactam.ConclusionHighly resistant NDM-14 producing K. pneumoniae can rapidly spread in healthcare settings. Surveillance and thorough investigations of hospital outbreaks are critical to evaluate and limit the dissemination of this clone.

In Vitro Activity of New β-Lactamase Inhibitor Combinations against blaNDM, blaKPC, and ESBL-Producing Enterobacteriales Uropathogens

Antibiotic resistance in uropathogens has increased substantially and severely affected treatment of urinary tract infections (UTIs). Lately, some new formulations, including meropenem/vaborbactam (MEV), ceftazidime/avibactam (CZA), and ceftolozane/tazobactam (C/T) have been introduced to treat infections caused by drug-resistant pathogens. This study was designed to screen Enterobacteriales isolates from UTI patients and to assess their antimicrobial resistance pattern, particularly against the mentioned (new) antibiotics. Phenotypic screening of extended-spectrum β-lactamase (ESBL) and carbapenem resistance was followed by inhibitor-based assays to detect K. pneumoniae carbapenemase (KPC), metallo-β-lactamase (MBL), and class D oxacillinases (OXA). Among 289 Enterobacteriales, E. coli (66.4%) was the most predominant pathogen, followed by K. pneumoniae (13.8%) and P. mirabilis (8.3%). The isolates showed higher resistance to penicillins and cephalosporins (70-87%) than to non-β-lactam antimicrobials (33.2-41.5%). NDM production was a common feature among carbapenem-resistant (CR) isolates, followed by KPC and OXA. ESBL producers were susceptible to the tested new antibiotics, but NDM-positive isolates appeared resistant to these combinations. KPC-producers showed resistance to only C/T. ESBLs and carbapenemase encoding genes were located on plasmids and most of the genes were successfully transferred to recipient cells. This study revealed that MEV and CZA had significant activity against ESBL and KPC producers.

Infection Prevention Control Strategies of New Delhi Metallo-β-lactamase Producing Klebsiella pneumoniae

The spread of multi-drug resistant organisms (MDROs) is increasing at an alarming rate worldwide. Among these, Carbapenemase-producing New Delhi Metallo-β-lactamase (NDM) poses a significant clinical threat, and appropriate measures must be taken to prevent or limit its penetration into still-free territories. The present report describes two independent cases of patients from Ukraine colonized by NDM-producing Klebsiella pneumoniae and admitted to two separate wards of an acute university hospital in a territory not yet affected by Carbapenemase producers of this class. Moreover, this report illustrates the infection prevention control (IPC) strategies promptly implemented by the IPC operational team to verify the possible spread of the microorganism in the ward and avoid any possible further contamination. The identification of genes coding for Carbapenemases, performed using real-time PCR, revealed no other cases within the wards involved. These cases emphasize the importance of early case recognition of multidrug-resistant bacteria, the necessity of effective inter-hospital communication, the need for effective antimicrobial stewardship protocol, and the importance of adequate IPC policies. Additionally, we highlight the need to improve screening procedures in the case of patients from countries with a high prevalence of MDRO, as essential measures to prevent potential nosocomial outbreaks and/or endemization.

Betaxolol as a Potent Inhibitor of NDM-1-Positive E. coli That Synergistically Enhances the Anti-Inflammatory Effect in Combination with Meropenem

With significant human and economic losses, increasing bacterial resistance is a serious global threat to human life. Due to their high efficacy, broad spectrum, and cost-effectiveness, beta-lactams are widely used in the clinical management of bacterial infection. The emergence and wide spread of New Delhi metallo-β-lactamase (NDM-1), which can effectively inactivate β-lactams, has posed a challenge in the design of effective new antimicrobial treatments. Medicine repurposing is now an important tool in the development of new alternative medicines. We present a known glaucoma therapeutic, betaxolol (BET), which with a 50% inhibitory concentration (IC50) of 19.3 ± 0.9 μM significantly inhibits the hydrolytic activity of the NDM-1 enzyme and may represent a potential NDM-1 enzyme inhibitor. BET combined with meropenem (MEM) showed bactericidal synergism in vitro. The efficacy of BET was further evaluated against systemic bacterial infections in BALB/c mice. The results showed that BET+MEM decreased the numbers of leukocytes and inflammatory factors in peripheral blood, as well as the organ bacterial load and pathological damage. Molecular docking and kinetic simulations showed that BET can form hydrogen bonds and hydrophobic interactions directly with key amino acid residues in the NDM-1 active site. Thus, we demonstrated that BET inhibited NDM-1 by competitively binding to it and that it can be developed in combination with MEM as a new therapy for the management of infections caused by medicine-resistant bacteria.

High prevalence of Escherichia coli co-harboring conjugative plasmids with colistin- and carbapenem resistance genes in a wastewater treatment plant in China

Emergence and dissemination of resistance to last-resort antibiotics such as carbapenem and colistin is a growing, global health concern. Wastewater treatment plants (WWTPs) link human activities and the environment, can act as reservoirs and sources for emerging antibiotic resistance, and likely play a large role in antibiotic resistance transmission. The aim of this study was to investigate occurrence and characteristics of colistin- and carbapenem-resistant Escherichia coli (CCREC) in wastewater and sludge samples collected over a one-year period from different functional areas of an urban WWTP in Jinan city, Shandong, China. A total of 8 CCREC were isolated from 168 samples with selective agar and PCR, corresponding to high prevalence of 4.8%, co-harboring carbapenem resistance genes (bla_NDM) and colistin resistance gene (mcr-1) and subsequently whole-genome sequenced. Additionally, all isolates were multidrug-resistant by antimicrobial susceptibility testing and carried a variety of antibiotic resistance genes. Two isolates carrying virulence genes associated with avian pathogenic E. coli were identified, one belonging to the high-risk clone O101:H9-ST167. Southern blotting was used to characterize CCREC isolates and plasmids carrying bla_NDM-genes or mcr-1 could be transferred to a recipient strain E. coli J53 by in vitro conjugation assays. Resistance to other antibiotic classes were sporadically co-transferred to the transconjugant. Transposition of and mcr-1-carrying element from a transferable IncHI2-plasmid was observed among two CCREC clones isolated within 4 days of each other. The occurrence of multidrug-resistant CCREC capable of transferring their antibiotic resistance genotypes via conjugative plasmids is alarming. WWTPs bring bacteria from different sources together, providing opportunities for horizontal exchange of DNA among compatible hosts. Further dissemination of the colistin-, carbapenem-, or both colistin- and carbapenem resistant E. coli could lead to a serious threat to public health.

Infection of Diabetes Foot Caused by Carbapenem-Resistant Proteus penneri Mediated by a Novel Plasmid Containing blaNDM

Objective

A strain of Proteus penneri with carbapenem resistance was found in a patient with a diabetic foot infection. We studied drug resistance, genome, and homology of P. penneri to support clinical prevention and treatment of infection caused by carbapenem-resistant P. penneri (CR-PPE).

Methods

The strains were obtained through bacterial culture from purulence. VITEK 2 compact (GN13) and Kirby-Bauer (K-B) disk diffusion methods were used for antimicrobial susceptibility testing. Ceftriaxone, amikacin, gentamicin, ampicillin, aztreonam, ceftazidime, ciprofloxacin, levofloxacin, cefepime, trimethoprim-sulfamethoxazole, tobramycin, cefotetan, piperacillin-tazobactam, ampicillin-sulbactam, ertapenem, piperacillin, meropenem, cefuroxime, cefazolin, cefoperazone/sulbactam, cefoxitin, and imipenem were used for antimicrobial susceptibility testing. After bacterial genome extraction, sequencing, and sequence assembly, whole-genome sequencing (WGS) was performed to explore the CR-PPE genotype.

Results

CR-PPE was resistant to two carbapenems (imipenem and ertapenem), ceftriaxone, and cefazolin, and was sensitive to aztreonam, piperacillin-tazobactam, and cefotetan. WGS results depict that the resistant phenotype of CR-PPE is consistent with the genotype, without common virulence genes of Enterobacteriaceae bacteria detected (virulence factor database). The carbapenem resistance gene bla_NMD-1 is contained in a new plasmid, pWF127-NDM. The transposon Tn125 in pWF127-NDM carrying bla_NMD-1 has almost the same structure as Tn125 in the reference plasmid pHFK418-NDM (Accession: MH491967). In addition, through phylogenetic analysis, CR-PPE depicts the closest evolutionary relationship with GCF 024129515.1, which was found in Gallus gallus in the Czech Republic in 2019 (downloaded from National Center for Biotechnology Information database). According to the evolutionary tree, CR-PPE has high homology with the two P. penneri strains found in China.

Conclusion

CR-PPE exhibits strong drug resistance owing to the presence of multiple resistance genes. CR-PPE infection should receive more attention, especially in patients with underlying diseases, such as diabetes and weak immunity.

Adaptive Evolution Compensated for the Plasmid Fitness Costs Brought by Specific Genetic Conflicts

New Delhi metallo-β-lactamase (NDM)-carrying IncX3 plasmids is important in the transmission of carbapenem resistance in Escherichia coli. Fitness costs related to plasmid carriage are expected to limit gene exchange; however, the causes of these fitness costs are poorly understood. Compensatory mutations are believed to ameliorate plasmid fitness costs and enable the plasmid's wide spread, suggesting that such costs are caused by specific plasmid-host genetic conflicts. By combining conjugation tests and experimental evolution with comparative genetic analysis, we showed here that the fitness costs related to ndm/IncX3 plasmids in E. coli C600 are caused by co-mutations of multiple host chromosomal genes related to sugar metabolism and cell membrane function. Adaptive evolution revealed that mutations in genes associated with oxidative stress, nucleotide and short-chain fatty acid metabolism, and cell membranes ameliorated the costs associated with plasmid carriage. Specific genetic conflicts associated with the ndm/IncX3 plasmid in E. coli C600 involve metabolism and cell-membrane-related genes, which could be ameliorated by compensatory mutations. Collectively, our findings could explain the wide spread of IncX3 plasmids in bacterial genomes, despite their potential cost.

In Silico Characterization of blaNDM-Harboring Conjugative Plasmids in Acinetobacter Species

New Delhi metallo-β-lactamase (NDM)-producing clinical strains in Acinetobacter spp. have been recently reported in many countries and have received considerable attention. The vast majority of blaNDM cases occur on conjugative plasmids, which play a vital role in disseminating blaNDM. To characterize the conjugative plasmids bearing blaNDM genes in Acinetobacter spp., we analyzed the variants of blaNDM, conjugative transfer regions, genetic contexts of blaNDM, and the phylogenetic pattern of the 62 predicted blaNDM-positive plasmids, which were selected from 1,191 plasmids of Acinetobacter species from GenBank. We identified 30 conjugative plasmids from the 62 blaNDM-harboring plasmids in Acinetobacter species, with the oriT sites similar to plasmid pNDM-YR7 in our study, genes coding for relaxases of the MOBQ family, genes encoding type IV coupling proteins (T4CPs) of the TrwB/TraD subfamily, and VirB-like type IV secretion system (T4SS) gene clusters. The genome sizes of all 30 pNDM-YR7-like plasmids ranged from 39.36 kb to 49.65 kb, with a median size of 44.56 kb. The most common species of Acinetobacter containing the blaNDM-positive conjugative plasmids was A. baumannii, followed by Acinetobacter lwoffii and Acinetobacter indicus. Notably, pNDM-YR7 is the first report on a blaNDM-positive conjugative plasmid in Acinetobacter junii. Moreover, all 30 blaNDM-positive conjugative plasmids in Acinetobacter species were found to contain genetic contexts with the structure ISAba14-aph(3')-VI-ISAba125-blaNDM-ble. Our findings provide important insights into the phylogeny and evolution of blaNDM-positive plasmids of Acinetobacter species and further address their role in acquiring and spreading blaNDM genes in Acinetobacter species. IMPORTANCE Conjugative plasmids harboring the blaNDM gene play a vital role in disseminating carbapenem resistance. In this study, we first report a conjugative plasmid, pNDM-YR7, in Acinetobacter junii. Based on the genomic characteristics of the blaNDM-positive pNDM-YR7, we performed in silico typing and comparative analysis of blaNDM-positive plasmids using the 1,191 plasmids of Acinetobacter species available in the NCBI RefSeq database. We analyzed the characteristics of blaNDM-positive plasmids, including the variants of blaNDM, genetic features associated with blaNDM, conjugative transfer regions, and the phylogenetic pattern of the blaNDM-positive plasmids. All 30 blaNDM-positive conjugative plasmids were found to contain an ISAba14-aph(3')-VI-ISAba125-blaNDM-ble region. This study provides novel insights into the phylogeny and evolution of blaNDM-harboring conjugative plasmids and contributes to the repertoire of knowledge surrounding blaNDM-positive plasmids in the genus Acinetobacter.

Molecular epidemiology characteristics and detecting transmission of carbapenemase-producing enterobacterales in southwestern China

BACKGROUND

To investigate the genotype and clinical characteristics of carbapenem-resistant Enterobacteriaceae (CRE) strains in southwest China and provide information on the treatment stopping the spread of the infection.

METHODS

The clinical information of CRE isolates was collected from 19 hospitals in 12 cities across Sichuan Province, China, between June 2018 and April 2019. The isolates were detected by DNA sequencing of genes encoding carbapenem enzymes and multilocus sequence types (MLSTs).

RESULTS

A total of 166 nonrepetitive CRE isolates were isolated during the study period from sputum, blood, urine, and other samples. Klebsiella pneumoniae carbapenemase (KPC) was dominant in Klebsiella pneumoniae (53.9%), followed by New Delhi metallo-β-lactamase (NDM) (42.1%). A total of 43 STs were detected. The most common ST of K. pneumoniae was ST11, and that of Escherichia coli was ST410. Pairwise single nucleotide polymorphism (SNP) distances and the likelihood of local transmission by epidemiology were plotted for each species. About 65% of these pairs had ≤ 20 pairwise SNPs.

CONCLUSION

A large number of CRE strains carried carbapenemase. Although NDM-ST12 K. pneumoniae should not be disregarded, KPC-ST11is the predominant strain. Thus, the possibility of transmission between E. coli and K. pneumoniae could not be ignored.

New Delhi Metallo-Beta-Lactamase Facilitates the Emergence of Cefiderocol Resistance in Enterobacter cloacae

Cefiderocol is a promising novel siderophore cephalosporin for the treatment of multidrug-resistant Gram-negative bacilli and with stability against degradation by metallo-β-lactamases. Nonetheless, the emergence of cefiderocol in metallo-β-lactamase-producing Enterobacterales during therapy has been reported on more than one occasion. To understand the underlying mechanisms and factors facilitating the resistance development, we conducted an in vitro evolution experiment using clinical E. cloacae isolates via serial passaging under cefiderocol pressure. In this study, we showed that the presence of the New Delhi metallo-β-lactamase (NDM) facilitates the emergence of resistance via nonsynonymous mutations of the CirA catecholate siderophore receptor. Inhibition of metallo-β-lactamase activity using dipicolinic acid prevented the emergence of cefiderocol-resistant mutants successfully. This finding implies that caution should be taken when using cefiderocol for the treatment of infections caused by metallo-β-lactamase-producing bacteria.

Genotypic Distribution and Antimicrobial Susceptibilities of Carbapenemase-Producing Enterobacteriaceae Isolated From Rectal and Clinical Samples in Korean University Hospitals Between 2016 and 2019

Background

The emergence of carbapenemase-producing Enterobacteriaceae (CPE) represents a major clinical problem. Recently, the occurrence of CPE has increased globally, but epidemiological patterns vary across region. We report the trends in the genotypic distribution and antimicrobial susceptibility of CPE isolated from rectal and clinical samples during a four-year period.

Methods

Between January 2016 and December 2019, 1,254 nonduplicated CPE isolates were obtained from four university hospitals in Korea. Carbapenemase genotypes were determined by multiplex real-time PCR. Antimicrobial susceptibility was profiled using the Vitek 2 system (bioMérieux, Hazelwood, MO, USA) or MicroScan Walkaway-96 system (Siemens West Sacramento, CA, USA). The proportions of carbapenemase genotypes and nonsusceptibility were analyzed using Pearson’s chi-square test.

Results

Among the 1,254 CPE isolates, 486 (38.8%), 371 (29.6%), 357 (28.5%), 8 (0.6%), 8 (0.6%), and 24 (1.9%) were Klebsiella pneumoniae carbapenemase (KPC), oxacillinase (OXA)-48-like, New Delhi metallo-β-lactamase (NDM), imipenemase (IMP), Verona integron-encoded metallo-β-lactamase (VIM), and multiple producers, respectively. The predominant species was K. pneumoniae (72.6%), followed by Escherichia coli (6.5%). More than 90% of the isolates harboring KPC, NDM, and OXA-48-like were nonsusceptible to cephalosporins, aztreonam, and carbapenems.

Conclusions

The impact of CPE is primarily due to KPC-, NDM-, and OXA-48-like-producing K. pneumoniae isolates. Isolates carrying these carbapenemase are mostly multidrug-resistant. Control strategies based on these genotypic distributions and antimicrobial susceptibilities of CPE isolates are required.

Genetic Diversity and Characteristics of bla NDM-Positive Plasmids in Escherichia coli

New Delhi metallo-β-lactamases (NDMs), including at least 28 variants, are a rapidly emerging family of β-lactamases worldwide, with a variety of infections caused by NDM-positive strains usually associated with very poor prognosis and high mortality. NDMs are the most prevalent carbapenemases in Escherichia coli (E. coli) worldwide, especially in China. The vast majority of bla_NDM cases occur on plasmids, which play a vital role in the dissemination of bla_NDM. To systematically explore the relationships between plasmids and bla_NDM genes in E. coli and obtain an overall picture of the conjugative and mobilizable bla_NDM-positive plasmids, we analyzed the variants of bla_NDM, replicon types, phylogenetic patterns, conjugative transfer modules, host STs, and geographical distributions of 114 bla_NDM-positive plasmids, which were selected from 3786 plasmids from 1346 complete whole genomes of E. coli from the GenBank database. We also established links among the characteristics of bla_NDM-positive plasmids in E. coli. Eight variants of bla_NDM were found among the 114 bla_NDM-positive plasmids, with bla_NDM–5 (74 bla_NDM–5 genes in 73 plasmids), and bla_NDM–1 (31 bla_NDM–1 genes in 28 plasmids) being the most dominant. The variant bla_NDM–5 was mainly carried by the IncX3 plasmids and IncF plasmids in E. coli, the former were mainly geographically distributed in East Asia (especially in China) and the United States, and the latter were widely distributed worldwide. IncC plasmids were observed to be the predominant carriers of bla_NDM–1 genes in E. coli, which were mainly geographically distributed in the United States and China. Other bla_NDM–1-carrying plasmids also included IncM2, IncN2, and IncHI1. Moreover, the overall picture of the conjugative and mobilizable bla_NDM-positive plasmids in E. coli was described in our study. Our findings enhance our understanding of the genetic diversity and characteristics of bla_NDM-positive plasmids in in E. coli.

New Delhi Metallo-β-Lactamase-Producing Enterobacterales Bacteria, Switzerland, 2019-2020

Carbapenemase-producing Enterobacterales (CPE) bacteria are a critical global health concern; New Delhi metallo-β-lactamase (NDM) enzymes account for >25% of all CPE found in Switzerland. We characterized NDM-positive CPE submitted to the Swiss National Reference Center for Emerging Antibiotic Resistance during a 2-year period (January 2019–December 2020) phenotypically and by using whole-genome sequencing. Most isolates were either Klebsiella pneumoniae (59/141) or Escherichia coli (52/141), and >50% were obtained from screening swabs. Among the 108 sequenced isolates, NDM-1 was the most prevalent variant, occurring in 56 isolates, mostly K. pneumoniae (34/56); the next most prevalent was NDM-5, which occurred in 49 isolates, mostly E. coli (40/49). Fourteen isolates coproduced a second carbapenemase, predominantly an OXA-48-like enzyme, and almost one third of isolates produced a 16S rRNA methylase conferring panresistance to aminoglycosides. We identified successful plasmids and global lineages as major factors contributing to the increasing prevalence of NDMs in Switzerland.

Importance of Surveillance of New Delhi Metallo-Beta-Lactamase Klebsiella pneumoniae: Molecular Characterization and Clonality of Strains Isolated in the Lazio Region, Italy

Introduction

New Delhi metallo-β-lactamase producing Klebsiella pneumoniae (NDM-Kpn) strains have been causing healthcare-associated infections worldwide. The aim of this study was to describe the molecular mechanisms of antimicrobial resistance and to analyze the clonality of NDM-Kpn isolates collected between January 2019 and June 2020 from patients admitted to hospitals from the Lazio region, Italy.

Methods

We performed a retrospective cohort study. Whole-genome sequencing (WGS) was performed on all NDM-Kpn strains; clonality and genetic relationships were further investigated.

Results

During the surveillance period, 17 NDM-Kpn isolates were obtained from 17 patients admitted to seven different hospitals. Eight different sequence types (STs) were detected: ST147 (n = 4), ST383 (n = 4), ST15 (n = 3), ST11 (n = 2), ST17 (n = 1), ST29 (n = 1), ST307 (n = 1) and the newly identified ST4853 (n = 1). Genetic relationships were further investigated by the WGS-based core genome MLST (cgMLST) scheme, and 5 cluster types (CTs) were identified. Whereas a substantial overall heterogeneity among isolates was detected (8 different STs were identified out of 17 isolates), the strains within each cluster showed a very high level of genome similarity.

Discussion

Our study highlights the key role of surveillance, which allowed taking a picture of a part of the NDM-Kpn strains circulating in Italy, adding further insight into their molecular features.

Differences in chlorine and peracetic acid disinfection kinetics of Enterococcus faecalis and Escherichia fergusonii and their susceptible strains based on gene expressions and genomics

This study was conducted to investigate mechanisms of cross-resistance to chlorine and peracetic acid (PAA) disinfectants by antibiotic-resistant bacteria. Our study evaluated chlorine and PAA based disinfection kinetics of erythromycin-resistant Enterococcus faecalis, meropenem-resistant Escherichia fergusonii, and susceptible strains of these species. Using the integrated second-order disinfectant decay model and first-order Chick-Watson's Law, it was found that the meropenem-resistant Escherichia fergusonii strain showed significantly less log inactivation compared to the susceptible E. fergusonii strain in response to both chlorine and PAA disinfection (p-value = 0.059, 3.5 × 10^-6). On the other hand, the susceptible Enterococcus faecalis strain showed similar log inactivation compared to the erythromycin-resistant strain in response to either treatment (p-value = 0.075, 0.28). Meropenem-resistant E. fergusonii showed an increase in gene expression of New Delhi metallo-β-lactamase (bla_NDM-1) gene to chlorine, but there was no increase in expression to PAA. Whole genome sequencing (WGS) was then conducted to elucidate the differences in genes among both resistant and susceptible table E. fergusonii strains. The average nucleotide identity (ANI) analysis of the draft genomes (>97% similarity) suggests that meropenem-resistant E. fergusonii (S1) and meropenem-susceptible E. fergusonii (S2) are the same species but different strains. Both strains have the same genes for oxidative stress pathways, oxidative scavenger genes, and nearly 40 different antibiotic efflux pump genes. The chromosomal and plasmid draft genomes of meropenem-resistant and susceptible E. fergusonii strains each have 65 and 52 antibiotic resistance genes, respectively. Of these, the resistant E. fergusonii strain harbored the extended-spectrum beta-lactamases bla_CTX-M-15 and bla_TEM-1 genes located on the chromosome, and a bla_TEM-1 gene on the plasmid. The overall findings of this study are significant, as they reveal that antibiotic-resistant and susceptible strains of E. fergusonii exhibit different responses towards chlorine and PAA disinfection.

Synergy of the Polymyxin-Chloramphenicol Combination against New Delhi Metallo-β-Lactamase-Producing Klebsiella pneumoniae Is Predominately Driven by Chloramphenicol

Carbapenem-resistant Klebsiella pneumoniae has been classified as an Urgent Threat by the Centers for Disease Control and Prevention (CDC). The combination of two "old" antibiotics, polymyxin and chloramphenicol, displays synergistic killing against New Delhi metallo-β-lactamase (NDM)-producing K. pneumoniae. However, the mechanism(s) underpinning their synergistic killing are not well studied. We employed an in vitro pharmacokinetic/pharmacodynamic model to mimic the pharmacokinetics of the antibiotics in patients and examined bacterial killing against NDM-producing K. pneumoniae using a metabolomic approach. Metabolomic analysis was integrated with an isolate-specific genome-scale metabolic network (GSMN). Our results show that metabolic responses to polymyxin B and/or chloramphenicol against NDM-producing K. pneumoniae involved the inhibition of cell envelope biogenesis, metabolism of arginine and nucleotides, glycolysis, and pentose phosphate pathways. Our metabolomic and GSMN modeling results highlight the novel mechanisms of a synergistic antibiotic combination at the network level and may have a significant potential in developing precision antimicrobial chemotherapy in patients.

in Mahananda and Karala Rivers of India

In this study, we report a high incidence of New Delhi metallo-β-lactamase (NDM)-producing and ampicillin-catabolizing bacteria within carbapenem-resistant bacterial populations in the waters of two important rivers, Mahananda and Karala, bisecting two most populous towns, Siliguri and Jalpaiguri, respectively, in the northern West Bengal, India. Isolates producing NDM belonged to four genera, Acinetobacter, Escherichia, Proteus, and Pseudomonas; among which few were phylogenetically determined as putatively novel species. Class 1 integrons with the frequent presence of aadA and aac(6')-Ib gene cassettes in 50% of NDM-bearing isolates are indicative of possible selective pressures generated out of unregulated use of streptomycin, in agriculture practiced by the cultivators and tea planters living in locales drained by these two rivers, in their up- and downstream, and amikacin in the most crowded government-sponsored "sadar" and district hospitals of Siliguri and Jalpaiguri. NDM-delivering bacteria in rivers have genuine consequences for city inhabitants who are dependent on public water and sanitation facilities. Standard reconnaissance of antibiotic resistance, consolidating ecological sampling just as the assessment of clinical isolates, should be set up as a need.

First Report of blaNDM-1 Bearing IncX3 Plasmid in Clinically Isolated ST11 Klebsiella pneumoniae from Pakistan

The New Delhi Metallo-β-lactamase (NDM) is among the most threatening forms of carbapenemases produced by K. pneumoniae, well-known to cause severe worldwide infections. The molecular epidemiology of bla_NDM-1-harboring K. pneumoniae is not well elucidated in Pakistan. Herein, we aim to determine the antibiotics-resistance profile, genes type, molecular type, and plasmid analysis of 125 clinically isolated K. pneumoniae strains from urine samples during July 2018 to January 2019 in Pakistan. A total of 34 (27.2%) K. pneumoniae isolates were carbapenemases producers, and 23 (18.4%) harbored the bla_NDM-1 gene. The other carbapenemases encoding genes, i.e., bla_IMP-1 (7.2%), bla_VIM-1 (3.2%), and bla_OXA-48 (2.4%) were also detected. The Multi Locus Sequence Typing (MLST) results revealed that all bla_NDM-1-harboring isolates were ST11. The other sequence types detected were ST1, ST37, and ST105. The cluster analysis of Xbal Pulsed Field Gel Electrophoresis (PFGE) revealed variation amongst the clusters of the identical sequence type isolates. The bla_NDM-1 gene in all of the isolates was located on a 45-kb IncX3 plasmid, successfully transconjugated. For the first time, bla_NDM-1-bearing IncX3 plasmids were identified from Pakistan, and this might be a new primary vehicle for disseminating bla_NDM-1 in Enterobacteriaceae as it has a high rate of transferability.

Activity of meropenem/vaborbactam against international carbapenem-resistant Escherichia coli isolates in relation to clonal background, resistance genes, resistance to comparators and region

OBJECTIVES

Carbapenem resistance has emerged inEscherichia coli, including sequence type 131 (ST131) and its fluoroquinolone-resistant H30R subclone, the leading cause of extraintestinal E. coli infections globally. Meropenem/vaborbactam (MVB) is a recently approved carbapenem/β-lactamase inhibitor combination with broad-spectrum inhibition of β-lactamases, including serine carbapenemases. The activity of MVB against carbapenem-resistant (CR) E. coli infections in relation to phylogenetic background, resistance genotype and geographical region is unknown.

METHODS

We characterised 140 contemporary CR clinicalE. coli isolates from 17 non-US countries (2003-2017) for phylogroup, clonal group (including ST131, H30R and the CTX-M-15-associated H30Rx subset), relevant β-lactamase genes, and broth microdilution MICs for MVB and 11 comparators.

RESULTS

Overall, MVB was moderately active (66% susceptible), more so than all comparators except tigecycline and amikacin (100% and 74% susceptible, respectively). Most MVB-non-susceptible isolates carried metallo-β-lactamase or OXA-48 resistance genes. MVB's activity varied significantly in relation to phylogroup, clonal background, resistance genotype and global region: it was greatest among phylogroup F, ST131-H30R, H30Rx, Klebsiella pneumoniae carbapenemase (KPC)-positive and Latin American isolates, and lowest among phylogroup B1, metallo-β-lactamase gene-containing and Asia-West Pacific region isolates. Enhancement of meropenem's activity by vaborbactam was most evident for isolates from phylogroups B2, C and D, and those containing KPC. MVB retained appreciable (albeit somewhat reduced) activity against isolates resistant to comparator agents.

CONCLUSION

MVB should be useful for treating international CRE. coli infections, largely independent of other resistance phenotypes, although this likely will vary with the local prevalence of specific E. coli lineages and carbapenem resistance mechanisms.

The present danger of New Delhi metallo-β-lactamase: a threat to public health

The evolution of antimicrobial-resistant Gram-negative pathogens is a substantial menace to public health sectors, notably in developing countries because of the scarcity of healthcare facilities. New Delhi metallo-β-lactamase (NDM) is a potent β-lactam enzyme able to hydrolyze several available antibiotics. NDM was identified from the clinical isolates of Klebsiella pneumoniae and Escherichia coli from a Swedish patient in New Delhi, India. This enzyme horizontally passed on to various Gram-negative bacteria developing resistance against a variety of antibiotics which cause treatment crucial. These bacteria increase fatality rates and play an integral role in the economic burden. The efficient management of NDM-producing isolates requires the coordination between each healthcare setting in a region. In this review, we present the prevalence of NDM in children, fatality and the economic burden of resistant bacteria, the clonal spread of NDM harboring bacteria and modern techniques for the detection of NDM producing pathogens.

Global genotype distribution of human clinical isolates of New Delhi metallo-β-lactamase-producing Klebsiella pneumoniae; A systematic review

BACKGROUND AND AIM

The global rise of antimicrobial resistance among bacterial strains is a rapidly growing challenge and is becoming a major public health concern. This study documents the worldwide spread and genotype distribution of human clinical isolates of New Delhi metallo-β-lactamase-producing Klebsiella pneumoniae (NPKP).

METHODS

Several international databases, including Web of Science, Embase and Medline were searched (2010 - 2019) to identify studies addressing the frequency of NPKP regionally or worldwide.

RESULTS

Of 4779 articles identified, 202 studies fulfilled the eligibility criteria and were included in our analysis. The frequency of NPKP in Asia, Europe, America, Africa and Oceania was 64.6%, 20.1%, 9.0%, 5.6% and 0.4%, respectively. The most prevalent sequence types (STs) among NPKP were ST11, ST290, ST147, ST340, ST15, ST278 and ST14 based on published studies.

CONCLUSION

The dissemination of bla_NDM variants in different STs among NPKP in the various region of world is a serious concern to public health. The prevalence of NPKP should be controlled by comprehensive infection control measures and optimization of antibiotic therapy.

Molecular Bases of the Membrane Association Mechanism Potentiating Antibiotic Resistance by New Delhi Metallo-β-lactamase 1

Resistance to last-resort carbapenem antibiotics is an increasing threat to human health, as it critically limits therapeutic options. Metallo-β-lactamases (MBLs) are the largest family of carbapenemases, enzymes that inactivate these drugs. Among MBLs, New Delhi metallo-β-lactamase 1 (NDM-1) has experienced the fastest and largest worldwide dissemination. This success has been attributed to the fact that NDM-1 is a lipidated protein anchored to the outer membrane of bacteria, while all other MBLs are soluble periplasmic enzymes. By means of a combined experimental and computational approach, we show that NDM-1 interacts with the surface of bacterial membranes in a stable, defined conformation, in which the active site is not occluded by the bilayer. Although the lipidation is required for a long-lasting interaction, the globular domain of NDM-1 is tuned to interact specifically with the outer bacterial membrane. In contrast, this affinity is not observed for VIM-2, a natively soluble MBL. Finally, we identify key residues involved in the membrane interaction with NDM-1, which constitute potential targets for developing therapeutic strategies able to combat resistance granted by this enzyme.

Iminodiacetic Acid as a Novel Metal-Binding Pharmacophore for New Delhi Metallo-β-lactamase Inhibitor Development

The fungal natural product aspergillomarasmine A (AMA) has been identified as a noncompetitive inhibitor of New Delhi metallo-β-lactamase-1 (NDM-1) that inhibits by removing ZnII from the active-site. The nonselective metal-chelating properties and difficult synthesis and derivatization of AMA have hindered the development of this scaffold into a potent and selective inhibitor of NDM-1. Iminodiacetic acid (IDA) has been identified as the metal-binding pharmacophore (MBP) core of AMA that can be leveraged for inhibitor development. Herein, we report the use of IDA for fragment-based drug discovery (FBDD) of NDM-1 inhibitors. IDA (IC50 =120 μM) was developed into inhibitor 23 f (IC50 =8.6 μM, Ki =2.6 μM), which formed a ternary complex with NDM-1, as evidenced by protein thermal-shift and native-state electrospray ionization mass spectrometry (ESI-MS) experiments. Combining mechanistic analysis with inhibitor derivatization, the use of IDA as an alternative AMA scaffold for NDM-1 inhibitor development is detailed.

Novel Carbapenem-Resistant Klebsiella pneumoniae ST147 Coharboring bla NDM-1, bla OXA-48 and Extended-Spectrum β-Lactamases from Pakistan

Purpose

The emergence of multidrug-resistant Klebsiella pneumoniae (K. pneumoniae) is associated with the acquisition of multiple carbapenemases. Their clonal spread is a worldwide concern due to their critical role in nosocomial infections. Therefore, the identification of high-risk clones with antibiotic resistance genes is very crucial for controlling its global spread.

Materials and Methods

A total of 227 K. pneumoniae strains collected during April 2018 to November 2019 were confirmed by PCR. Carbapenemases and extended-spectrum β-lactamases (ESBL) were detected phenotypically. Confirmation of carbapenemases was carried out by PCR and Sanger sequencing. The clonal lineages were assigned to selected isolates by multilocus sequence typing (MLST), and the plasmid analysis was done by PCR-based detection of the plasmid replicon typing.

Results

Of the total K. pneumoniae, 117 (51.5%) were carbapenem resistant (CRKP) and 140 (61.7%) were identified as ESBL producers. Intermediate to high resistance was detected in the tested β-lactam drugs while polymyxin-B and tigecycline were found to be susceptible. Among CRKP, 91 (77.8%) isolates were detected as carbapenemase producing, while 55 (47%) were positive for bla_NDM-1 23.9% (n=28), bla_OXA-48 22.2% (n=26) and bla_VIM 0.85% (n=1) while 12.7% (n=7) carried both bla_NDM-1 and bla_OXA-48 genes. The CRKP coharboring bla_NDM-1 and bla_OXA-48 genes (n=7) were positive for bla_CTX-Mbla_SHV (n=3), bla_SHV (n=1) and bla_CTX-M (n=3). The novel CRKP with the coexistence of bla_NDM-1, bla_OXA-48, bla_CTX-M and bla_SHV genes were associated with the high-risk clone ST147 (n=5) and ST11 (n=2). The assigned replicon types were IncL/M, IncFII, IncA/C and IncH1.

Conclusion

This is the first report of the coexistence of bla_NDM-1, bla_OXA-48, bla_CTX-M and bla_SHV genes on a high-risk lineage ST147 from Pakistan. This study highlights the successful dissemination of carbapenemase resistance genes in the high-risk clones that emphasizes the importance of monitoring and controlling the spread of these diverse clones globally.

Transcriptomic responses of a New Delhi metallo-β-lactamase-producing Klebsiella pneumoniae isolate to the combination of polymyxin B and chloramphenicol

The combination of polymyxins and chloramphenicol possesses synergistic killing activity against New Delhi metallo-β-lactamase (NDM)-producing Klebsiella pneumoniae. This systems study examined the transcriptomic responses to the polymyxin/chloramphenicol combination in clinical NDM-producing K. pneumoniae isolate S01. Klebsiella pneumoniae S01 (initial inoculum ~10⁸ CFU/mL) was treated with polymyxin B (1 mg/L, continuous infusion) or chloramphenicol [maximum concentration (C_max) = 8 mg/L, half-life (t_1/2) = 4 h], alone or in combination, using an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model to mimic their pharmacokinetics in patients. Transcriptomic profiles of bacterial samples collected at 0, 0.25, 1, 4 and 24 h were examined using RNA sequencing (RNA-Seq). Chloramphenicol monotherapy significantly increased the expression of genes involved in ribosomal synthesis across the entire 24-h treatment, reflective of chloramphenicol-mediated inhibition of protein synthesis. The effect of polymyxin B was rapid and no major pathways were perturbed at later time points (4 h and 24 h). Combination treatment yielded the highest number of differentially expressed genes, including a large number observed following chloramphenicol monotherapy, in particular carbohydrate, nucleotide, amino acid and cell wall metabolism. Notably, chloramphenicol alone and in combination with polymyxin B significantly inhibited the expression of the arn operon that is responsible for lipid A modification and polymyxin resistance. These results indicate that the polymyxin/chloramphenicol combination displayed persistent transcriptomic responses over 24 h mainly on cell envelope synthesis and metabolism of carbohydrates, nucleotides and amino acids.

A New Delhi metallo-β-lactamase (NDM)-positive isolate of Klebsiella pneumoniae causing catheter-related bloodstream infection in an ambulatory hemodialysis patient

The New Delhi metallo-β-lactamase (NDM) is a mediator of broad antimicrobial resistance among the Enterobacteriaceae and other gram-negative pathogens that cause opportunistic and nosocomial infections. In the decade since its discovery, NDM has spread worldwide and represents an increasing threat to public health. NDM is capable of hydrolyzing nearly all known β-lactam antibiotics, including the carbapenems, and due to its zinc ion-dependent catalytic mechanism is unaffected by available β-lactamase inhibitors. We report a case of catheter-related bloodstream infection caused by a pan-resistant, NDM-positive isolate of Klebsiella pneumoniae in an ambulatory end-stage renal disease patient started on hemodialysis approximately 8 weeks prior. The absence of any recent hospitalization indicates that the infection was likely acquired from a hemodialysis center in the United States. This case demonstrates the increasing prevalence of antimicrobial resistance mechanisms in ambulatory as well as inpatient healthcare settings, and highlights the particular risk of the outpatient hemodialysis facility as an optimal environment for colonization with multidrug- and pandrug-resistant pathogens.

Diversity and Genetic Basis for Carbapenem Resistance in a Coastal Marine Environment

Resistance to the "last-resort" antibiotics, such as carbapenems, has led to very few antibiotics being left to treat infections by multidrug-resistant bacteria. Spread of carbapenem resistance (CR) has been well characterized for the clinical environment. However, there is a lack of information about its environmental distribution. Our study reveals that CR is present in a wide range of Gram-negative bacteria in the coastal seawater environment, including four phyla, eight classes, and 30 genera. These bacteria were likely introduced into seawater via stormwater flows. Some CR isolates found here, such as Acinetobacter junii, Acinetobacter johnsonii, Brevundimonas vesicularis, Enterococcus durans, Pseudomonas monteilii, Pseudomonas fulva, and Stenotrophomonas maltophilia, are further relevant to human health. We also describe a novel metallo-β-lactamase (MBL) for marine Rheinheimera isolates with CR, which has likely been horizontally transferred to Citrobacter freundii or Enterobacter cloacae In contrast, another MBL of the New Delhi type was likely acquired by environmental Variovorax isolates from Escherichia coli, Klebsiella pneumoniae, or Acinetobacter baumannii utilizing a plasmid. Our findings add to the growing body of evidence that the aquatic environment is both a reservoir and a vector for novel CR genes.IMPORTANCE Resistance against the "last-resort" antibiotics of the carbapenem family is often based on the production of carbapenemases, and this has been frequently observed in clinical samples. However, the dissemination of carbapenem resistance (CR) in the environment has been less well explored. Our study shows that CR is commonly found in a range of bacterial taxa in the coastal aquatic environment and can involve the exchange of novel metallo-β-lactamases from typical environmental bacteria to potential human pathogens or vice versa. The outcomes of this study contribute to a better understanding of how aquatic and marine bacteria can act as reservoirs and vectors for CR outside the clinical setting.

Characterization Of bla NDM-5-Positive Escherichia coli Prevalent In A University Hospital In Eastern China

Purpose

The emergence and spread of carbapenem-resistant Enterobacteriaceae deserves special concern worldwide. Unlike the epidemiological characteristics reported in other studies, we found that the production of New Delhi metallo-β-lactamase 5 was the main mechanism for the resistance of Escherichia coli to carbapenems.

Methods

All carbapenem-resistant strains were collected from July 2017 to July 2018 of the First Affiliated Hospital of Nanjing Medical University. The presence of carbapenemase-encoding genes was detected using PCR and gene sequencing. Genetic relatedness of the bla_NDM-5-positive E. coli strains was determined with PFGE and MLST. Susceptibility profiles were measured with broth microdilution method and E-test strips. Transferability features of bla_NDM-5 gene were assessed by conjugation experiments, S1-PFGE, southern blotting and PCR-based replicon typing methods. The genetic structures surrounding bla_NDM-5 were acquired by whole genome sequencing and PCR mapping.

Results

Among the 28 carbapenem-resistant E. coli strains, 18 (64%) were verified as NDM-5 producers. The 18 bla_NDM-5-positive E. coli strains showed high resistance to most antibiotics, but 100% were sensitive to colistin and tigecycline. In addition, the 18 bla_NDM-5-positive E. coli strains belonged to eight STs, among which ST167, ST410 and ST101 were found to cause clonal spread in the hospital. Further studies found that the bla_NDM-5 gene was located on an IncX3-type plasmid, and all plasmids harbored an IS3000-ΔISAba125-IS5-bla_NDM-5-bleMBL-trpF-dsbC-IS26 structure.

Conclusion

The clonal spread of bla_NDM-5-positive E. coli strains and horizontal dissemination via the pNDM-MGR 194-like plasmids should draw more attention. Appropriate infection control operations should be performed to prevent the further spread of bla_NDM-5.

Rapid Identification of New Delhi Metallo-β-Lactamase (NDM) Using Tryptic Peptides and LC-MS/MS

There is significant interest in the development of mass spectrometry (MS) methods for antimicrobial resistance protein detection, given the ability of these methods to confirm protein expression. In this work, we studied the performance of a liquid chromatography, tandem MS multiple-reaction monitoring (LC-MS/MS MRM) method for the direct detection of the New Delhi metallo-β-lactamase (NDM) carbapenemase in clinical isolates. Using a genoproteomic approach, we selected three unique peptides (SLGNLGDADTEHYAASAR, AFGAAFPK, and ASMIVMSHSAPDSR) specific to NDM that were efficiently ionized and spectrally well-defined. These three peptides were used to build an assay with turnaround time of 90 min. In a blind set, the assay detected 21/24 bla _NDM-containing isolates and 76/76 isolates with negative results, corresponding to a sensitivity value of 87.5% (95% confidence interval [CI], 67.6% to 97.3%) and a specificity value of 100% (95% CI, 95.3% to 100%). One of the missed identifications was determined by protein fractionation to be due to low (∼0.1 fm/μg) NDM protein expression (below the assay limit of detection). Parallel disk diffusion susceptibility testing demonstrated this isolate to be meropenem susceptible, consistent with low NDM expression. Total proteomic analysis of the other two missed identifications did not detect NDM peptides but detected other proteins expressed from the bla _NDM-containing plasmids, confirming that the plasmids were not lost. The measurement of relative NDM concentrations over the entire isolate test set demonstrated variability spanning 4 orders of magnitude, further confirming the remarkable range that may be seen in levels of NDM expression. This report highlights the sensitivity of LC-MS/MS to variations in NDM protein expression, with implications for how this technology may be used.

Frequency distribution, genotypes and prevalent sequence types of New Delhi metallo-β-lactamase-producing Escherichia coli among clinical isolates around the world: A review

OBJECTIVES

New Delhi metallo-β-lactamase (NDM)-producing Escherichia coli is perceived as one of the primary multidrug-resistant bacteria causing infections in hospitals and clinics. In this review, we present the frequency distribution, genotypes and most prevalent sequence types (STs) of NDM-producing E. coli among clinical isolates worldwide.

METHODS

Several international databases, including Medline, Embase, Scopus and Web of Science, were searched from 2008 to 2018 to identify studies addressing the prevalence of NDM-producing E. coli around the world.

RESULTS

Of 974 records identified from the databases, 110 studies fulfilled the eligibility criteria and were included in this analysis. The prevalence of NDM-producing E. coli was 82.6%, 12.9%, 1.5%, 1.0% and 2.0% in Asia, Europe, America, Africa and Oceania, respectively. The most common reported STs among NDM-producing E. coli were ST101, ST167, ST131, ST405, ST410 and ST648.

CONCLUSION

The spread of NDM variants among E. coli strains is a serious threat to global public health. In addition, the most prevalent E. coli clonal groups, such as ST101 and ST167, are one of the main causes of E. coli infection in different countries.

Investigation of Dipicolinic Acid Isosteres for the Inhibition of Metallo-β-Lactamases

New Delhi metallo-β-lactamase-1 (NDM-1) poses an immediate threat to our most effective and widely prescribed drugs, the β-lactam-containing class of antibiotics. There are no clinically relevant inhibitors to combat NDM-1, despite significant efforts toward their development. Inhibitors that use a carboxylic acid motif for binding the Zn^II ions in the active site of NDM-1 make up a large portion of the >500 inhibitors reported to date. New and structurally diverse scaffolds for inhibitor development are needed urgently. Herein we report the isosteric replacement of one carboxylate group of dipicolinic acid (DPA) to obtain DPA isosteres with good inhibitory activity against NDM-1 (and related metallo-β-lactamases, IMP-1 and VIM-2). It was determined that the choice of carboxylate isostere influences both the potency of NDM-1 inhibition and the mechanism of action. Additionally, we show that an isostere with a metal-stripping mechanism can be re-engineered into an inhibitor that favors ternary complex formation. This work provides a roadmap for future isosteric replacement of routinely used metal binding motifs (i.e., carboxylic acids) for the generation of new entities in NDM-1 inhibitor design and development.

Rapid detection of the commonly encountered carbapenemases (New Delhi metallo-β-lactamase, OXA-48/181) directly from various clinical samples using multiplex real-time polymerase chain reaction assay

Background

Resistance due to New Delhi metallo-β-lactamase (NDM) and OXA-48/181 continues to emerge as a threat which is associated with nosocomial outbreaks and is a serious healthcare concern. Phenotypic detection being laborious and time-consuming requires rapid detection of NDM and OXA-48/181, which is achieved through real-time polymerase chain reaction (RT-PCR).

Materials and Methods

In this study, RT-PCR assay was developed to simultaneously detect NDM and OXA-48/181. The assay was validated on 102 non-duplicate, phenotypically characterised clinical samples.

Results

The assay showed a sensitivity and specificity of 97% and 100% for the detection of carbapenemases in comparison to conventional PCR. The in-house developed multiplex RT-PCR would help to rule-in the presence of NDM and OXA-48/181.

Conclusions

Rapid detection of these carbapenemases would be assist in better patient management, in terms of accurate antimicrobial treatment, help in cohorting infected from uninfected patient to prevent spread.

Distribution of Clinical NDM-1-Producing Gram-Negative Bacteria in Brazil

New Delhi metallo-β-lactamase (NDM)-producing bacteria have been identified at a worrying rate in Brazil since 2013. Owing to the need to understand the extent of their spread, this study reports the dissemination of bla_NDM in different species of Gram-negative bacilli in different regions and states of Brazil. A total of 81 isolates from nine states were studied, including 11 species. All isolates carried bla_NDM-1 variant and were considered multidrug resistant. Colistin and amikacin were the agents with higher activity compared with the other drugs tested. The findings indicate that the NDM-1 enzyme is already widespread in the country.

The Reaction Mechanism of Metallo-β-Lactamases Is Tuned by the Conformation of an Active-Site Mobile Loop

Carbapenems are "last resort" β-lactam antibiotics used to treat serious and life-threatening health care-associated infections caused by multidrug-resistant Gram-negative bacteria. Unfortunately, the worldwide spread of genes coding for carbapenemases among these bacteria is threatening these life-saving drugs. Metallo-β-lactamases (MβLs) are the largest family of carbapenemases. These are Zn(II)-dependent hydrolases that are active against almost all β-lactam antibiotics. Their catalytic mechanism and the features driving substrate specificity have been matter of intense debate. The active sites of MβLs are flanked by two loops, one of which, loop L3, was shown to adopt different conformations upon substrate or inhibitor binding, and thus are expected to play a role in substrate recognition. However, the sequence heterogeneity observed in this loop in different MβLs has limited the generalizations about its role. Here, we report the engineering of different loops within the scaffold of the clinically relevant carbapenemase NDM-1. We found that the loop sequence dictates its conformation in the unbound form of the enzyme, eliciting different degrees of active-site exposure. However, these structural changes have a minor impact on the substrate profile. Instead, we report that the loop conformation determines the protonation rate of key reaction intermediates accumulated during the hydrolysis of different β-lactams in all MβLs. This study demonstrates the existence of a direct link between the conformation of this loop and the mechanistic features of the enzyme, bringing to light an unexplored function of active-site loops on MβLs.

Successful control of the first OXA-48 and/or NDM carbapenemase-producing Klebsiella pneumoniae outbreak in Slovenia 2014-2016

BACKGROUND

Carbapenemase-producing Enterobacteriaceae (CPE) occur only sporadically in Slovenia.

AIM

To describe the first Slovenian carbapenemase-producing (CP) Klebsiella pneumoniae and Escherichia coli outbreak which occurred at the tertiary teaching hospital University Medical Centre Ljubljana from October 2014 to April 2015.

METHODS

A CPE-positive case was defined as any patient infected or colonized with CPE. A strict definition of a contact patient was adopted. Measures to prevent cross-transmission included cohorting of all CPE carriers with strict contact precautions and assignment of dedicated healthcare workers, cohorting of all contact patients until obtaining the result of screening cultures, systematic rectal screening of contact patients, and tagging of all CPE-positive cases and their contacts. Educational campaigns on CPEs were implemented. Clinical specimens were processed using standard procedures. Pulsed-field gel electrophoresis (PFGE) was used to determine relatedness. Multi-locus sequence typing was performed on CP K. pneumoniae isolates that belonged to different pulsotypes.

FINDINGS

Before the outbreak was brought under control, 40 patients were colonized or infected with OXA-48 and/or New Delhi metallo-β-lactamase (NDM)-producing CPE; in 38 patients OXA-48 and/or NDM-producing K. pneumoniae was detected, in seven OXA-48 and/or NDM-producing E. coli was found together with K. pneumoniae, and in two patients only CP E. coli was isolated. The outbreak was oligoclonal with two major CP K. pneumoniae clusters belonging to ST437 and ST147 in epidemiologically linked patients.

CONCLUSION

Initial standard control measures failed to prevent the outbreak. Once the problem had been recognized, strict infection control measures and the education of healthcare workers contributed to the successful control of the outbreak.

Carbapenem Resistance in Clonally Distinct Clinical Strains of Vibrio fluvialis Isolated from Diarrheal Samples

These strains might acquire the bla_NDM-1 gene without exposure to antimicrobial drugs.

Carbapenems have been used for many years to treat severe nosocomial Enterobacteriaceae infections. The spread of resistance to these drugs among other bacterial families is an emerging problem worldwide, mostly caused by New Delhi metallo-β-lactamase (NDM-1). We screened for the prevalence of NDM-1–expressing enteric pathogens from hospitalized patients with acute diarrhea in Kolkata, India, and identified 27 Vibrio fluvialis–harboring bla_NDM-1 (NDM-VF) strains. These isolates were also resistant to all the tested antimicrobial drugs except doxycycline. The large plasmid of V. fluvialis harboring bla_NDM-1 could be easily transferred to other enteric pathogens. Genes flanking the bla_NDM-1 were found to be identical to the reported sequence from an Escherichia coli isolate. Analyses showed that the V. fluvialis possessing the NDM-VF region belonged to different clones. The pathogenicity of V. fluvialis to humans and its ubiquitous presence in the environment call for constant monitoring of this species for emerging antimicrobial drug resistance.

Detection of Antibiotic Resistance Determinants and Their Transmissibility among Clinically Isolated Carbapenem-Resistant Escherichia coli from South India

OBJECTIVES

The aim of this study was to analyze the prevalence of the CTX-M, TEM, SHV, VIM, NDM, and OXA genes in carbapenemase-producing Escherichia coli and their transmissibility at a tertiary care hospital in south India.

MATERIALS AND METHODS

Twenty-one carbapenem-resistant E. coli (carbapenem-resistant Enterobacteriaceae; CRE) were collected from the Sri Sathya Sai Institute of Higher Medical Sciences (Puttaparthi India). Resistance to antibiotics was analyzed by Vitek-2, and the identity of the isolates was confirmed by 16S rDNA sequencing. RAPD and enterobacterial repetitive intergenic consensus (ERIC)-PCR were performed for molecular typing. Metallo-β-lactamase production was confirmed by a double disc synergy test. The presence of the extended-spectrum β-lactamases CTX-M, TEM, and SHV and of the carbapenemases NDM, VIM, and OXA was determined by PCR. Carbapenemase variants were further confirmed by sequencing. The transmissibility of the genes was tested by conjugation.

RESULTS

Twelve of the 21 (57%) carbapenem-resistant E. coli isolates were community acquired, indicating the spread of CRE in environmental samples. TEM and NDM-5 were found to be the major β-lactamases produced by the pathogens. OXA-181 was found in 5 of the isolates. All 21 isolates were found to harbor more than one of the tested β-lactamases, and all of the isolates were found to have the capacity to participate in conjugation; 15 of the transconjugants were found to have acquired the tested β-lactamases, substantiating their ability to be transferred to other strains of bacteria.

CONCLUSION

Monitoring of community-acquired carbapenem-resistant bacteria is very important as the association of resistance determinants with mobile genetic elements would present a serious clinical challenge.

In Vitro Discordance with In Vivo Activity: Humanized Exposures of Ceftazidime-Avibactam, Aztreonam, and Tigecycline Alone and in Combination against New Delhi Metallo-β-Lactamase-Producing Klebsiella pneumoniae in a Murine Lung Infection Model

The management of infections with New Delhi metallo-beta-lactamase-1 (NDM)-producing bacteria remains clinically challenging given the multidrug resistant (MDR) phenotype associated with these bacteria. Despite resistance in vitro, ceftazidime-avibactam previously demonstrated in vivo activity against NDM-positive Enterobacteriaceae Herein, we observed in vitro synergy with ceftazidime-avibactam and aztreonam against an MDR Klebsiella pneumoniae harboring NDM. In vivo, humanized doses of ceftazidime-avibactam monotherapy resulted in >2 log10 CFU bacterial reduction; therefore, no in vivo synergy was observed.

ESBL- and Carbapenemase-Producing Enterobacteriaceae in Patients with Bacteremia, Yangon, Myanmar, 2014

Among 42 gram-negative bloodstream isolates from inpatients in 3 hospitals in Yangon, Myanmar, admitted during July-December 2014, 16 (38%) were extended-spectrum β-lactamase-producing Enterobacteriaceae and 6 (14%) produced carbapenemase. The high prevalence of multidrug-resistant gram-negative bacteria raises concerns about the empiric treatment of patients with sepsis in Yangon.

Multiclonal Expansion of Klebsiella pneumoniae Isolates Producing NDM-1 in Rio de Janeiro, Brazil

We characterized NDM-1-producing Klebsiella isolates from Rio de Janeiro, Brazil. PCR was applied for resistance and virulence determinants. The genetic context of bla_NDM was determined by S1 nuclease pulsed-field gel electrophoresis (PFGE) and hybridization. Genotyping was performed by PFGE and multilocus sequence typing (MLST). Most isolates carried multiple resistance genes and remained susceptible to amikacin, fosfomycin-trometamol, polymyxin B, and tigecycline. The spread of NDM-1-producing Klebsiella pneumoniae was not associated with clonal expansion and appears to be associated with Tn3000.

Antimicrobial resistance in Enterobacteriaceae in Brazil: focus on β-lactams and polymyxins

During the last 30 years there has been a dissemination of plasmid-mediated β-lactamases in Enterobacteriaceae in Brazil. Extended spectrum β-lactamases (ESBL) are widely disseminated in the hospital setting and are detected in a lower frequency in the community setting. Cefotaximases are the most frequently detected ESBL type and Klebsiella pneumoniae is the predominant species among ESBL producers. Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae became widely disseminated in Brazil during the last decade and KPC production is currently the most frequent resistance mechanism (96.2%) in carbapenem resistant K. pneumoniae. To date KPC-2 is the only variant reported in Brazil. Polymyxin B resistance in KPC-2-producing K. pneumoniae has come to an alarming rate of 27.1% in 2015 in São Paulo, the largest city in Brazil. New Delhi metallo-β-lactamase was detected in Brazil in 2013, has been reported in different Brazilian states but are not widely disseminated. Antimicrobial resistance in Enterobacteriaceae in Brazil is a very serious problem that needs urgent actions which includes both more strict adherence to infection control measures and more judicious use of antimicrobials.

Counting the cost of an outbreak of carbapenemase-producing Enterobacteriaceae: an economic evaluation from a hospital perspective

OBJECTIVE

To perform an economic evaluation on the cost associated with an outbreak of carbapenemase-producing Enterobacteriaceae (CPE).

METHODS

We performed an observational economic evaluation of an outbreak of CPE (NDM-producing Klebsiella pneumoniae) affecting 40 patients in a group of five hospitals across three sites in West London. Costs were split into actual expenditure (including anti-infective costs, enhanced CPE screening, contact precautions, temporary ward-based monitors of hand and environmental practice, and environmental decontamination), and 'opportunity cost' (staff time, bed closures and elective surgical missed revenue). Costs are estimated from the hospital perspective over the 10-month duration of the outbreak.

RESULTS

The outbreak cost €1.1m over 10 months (range €0.9-1.4m), comprising €312 000 actual expenditure, and €822 000 (range €631 000-€1.1m) in opportunity cost. An additional €153 000 was spent on Estates renovations prompted by the outbreak. Actual expenditure comprised: €54 000 on anti-infectives for 18 patients treated, €94 000 on laboratory costs for screening, €73 000 on contact precautions for 1831 contact precautions patient-days, €42 000 for hydrogen peroxide vapour decontamination of 24 single rooms, €43 000 on 2592 hours of ward-based monitors, and €6000 of expenditure related to ward and bay closures. Opportunity costs comprised: €244 000 related to 1206 lost bed-days (range 366-2562 bed-days, €77 000-€512 000), €349 000 in missed revenue from 72 elective surgical procedures, and €228 000 in staff time (range €205 000-€251 000). Reduced capacity to perform elective surgical procedures related to bed closures (€349 000) represented the greatest cost.

CONCLUSIONS

The cost estimates that we present suggest that CPE outbreaks are highly costly.

Modification and evaluation of the Carba NP test by use of paper strip for simple and rapid detection of carbapenemase-producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE) isolates have now emerged worldwide. We therefore modified the phenotypic Carba NP test by use of a filter paper strip for easily and rapidly identifying CPE in routine laboratory. A collection of 56 CPE and carbapenemase-producing Pseudomonas spp. isolates (including 28 NDM-1, 11 IMP-14a, 1 IMP-1, 1 IMP-4, 1 IMP-9, 1 IMP-15, 4 VIM-2, 1 VIM-1, 1 IMP-14a with VIM-2, 3 OXA-48, 3 OXA-181 and 1 KPC-2 producers) and 41 non-CPE isolates (including 19 ESBL, 7 pAmpC, 3 AmpC, 9 ESBL with pAmpC and 3 non-ESBL & non-AmpC producers) as confirmed by the PCR methods were tested by the paper strip method using pharmaceutical imipenem/cilastatin as a substrate. Bacterial colonies of each isolate were applied directly on filter paper strips dropped with either imipenem-phenol red (test strip) or phenol red solution alone (control strip). The reaction was read within 5 min. This test failed to detect 3 OXA-181, 2 OXA-48 and 3 IMP-14a producers (85.7 % sensitivity), whereas no false positives were seen (100 % specificity). Further evaluation of the paper strip test in 267 CPE screening-positive isolates from three hospitals by their medical technologists showed 92.0 % sensitivity (100 % for NDM producers) and 100 % specificity compared with the PCR methods. Because of its ease, rapidness and cost effective, the paper strip test has a potential for routine CPE testing in low-resource laboratories particularly in areas with high prevalence of NDM enzymes, leading to appropriate antimicrobial therapy and infection control strategy.

Impact of blaNDM-1 on fitness and pathogenicity of Escherichia coli and Klebsiella pneumoniae

The objective of this study was to determine whether acquisition of New Delhi metallo-β-lactamase-1 (NDM-1) has an impact on the fitness and virulence of Escherichia coli and Klebsiella pneumoniae. Growth kinetics and the cost of fitness of NDM-1 plasmid carriage were assessed in isogenic E. coli J53 and K. pneumoniae PRZ in vitro by pairwise competition assays. The pathogenicity of NDM-1-expressing E. coli and K. pneumoniae strains and their isogenic controls was analysed in vivo using a Galleria mellonella infection model. The cytotoxicity of NDM-1 was assessed in A549 human lung epithelial cells using the lactate dehydrogenase (LDH) assay. No differences in growth kinetics were recorded between NDM-1-expressing strains and controls (P = 0.92). A reduction in fitness of NDM-1-carrying strains was observed both for E. coli J53 and K. pneumoniae PRZ [selection rate constant (s) = -1.27 ± 0.27 for E. coli J53 and -0.19 ± 0.14 for K. pneumoniae PRZ; P < 0.0001]. Survival of G. mellonella larvae infected with NDM-1-expressing strains and controls was similar for E. coli J53 and K. pneumoniae PRZ. Cytotoxicity in A549 cells was not affected by NDM-1 expression (P > 0.05). The presence of blaNDM-1 did not increase the virulence or cytotoxicity of isogenic strains. However, there was a considerable cost of fitness incurred by carriage of the pNDM-1 plasmid. Interestingly, the cost of fitness was significantly higher in E. coli J53 compared with K. pneumoniae PRZ.