April 21, 2020  |  

Tracking short-term changes in the genetic diversity and antimicrobial resistance of OXA-232-producing Klebsiella pneumoniae ST14 in clinical settings.

To track stepwise changes in genetic diversity and antimicrobial resistance in rapidly evolving OXA-232-producing Klebsiella pneumoniae ST14, an emerging carbapenem-resistant high-risk clone, in clinical settings.Twenty-six K. pneumoniae ST14 isolates were collected by the Korean Nationwide Surveillance of Antimicrobial Resistance system over the course of 1 year. Isolates were subjected to whole-genome sequencing and MIC determinations using 33 antibiotics from 14 classes.Single-nucleotide polymorphism (SNP) typing identified 72 unique SNP sites spanning the chromosomes of the isolates, dividing them into three clusters (I, II and III). The initial isolate possessed two plasmids with 18 antibiotic-resistance genes, including blaOXA-232, and exhibited resistance to 11 antibiotic classes. Four other plasmids containing 12 different resistance genes, including blaCTX-M-15 and strA/B, were introduced over time, providing additional resistance to aztreonam and streptomycin. Moreover, chromosomal integration of insertion sequence Ecp1-blaCTX-M-15 mediated the inactivation of mgrB responsible for colistin resistance in four isolates from cluster III. To the best of our knowledge, this is the first description of K. pneumoniae ST14 resistant to both carbapenem and colistin in South Korea. Furthermore, although some acquired genes were lost over time, the retention of 12 resistance genes and inactivation of mgrB provided resistance to 13 classes of antibiotics.We describe stepwise changes in OXA-232-producing K. pneumoniae ST14 in vivo over time in terms of antimicrobial resistance. Our findings contribute to our understanding of the evolution of emerging high-risk K. pneumoniae clones and provide reference data for future outbreaks.Copyright © 2019 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.


April 21, 2020  |  

Potent LpxC Inhibitors with In Vitro Activity Against Multi-Drug Resistant Pseudomonas aeruginosa.

New drugs with novel mechanisms of resistance are desperately needed to address both community and nosocomial infections due to Gram-negative bacteria. One such potential target is LpxC, an essential enzyme that catalyzes the first committed step of Lipid A biosynthesis. Achaogen conducted an extensive research campaign to discover novel LpxC inhibitors with activity against Pseudomonas aeruginosa We report here the in vitro antibacterial activity and pharmacodynamics of ACHN-975, the only molecule from these efforts and the first ever LpxC inhibitor to be evaluated in Phase 1 clinical trials. In addition, we describe the profile of three additional LpxC inhibitors that were identified as potential lead molecules. These efforts did not produce an additional development candidate with a sufficiently large therapeutic window and the program was subsequently terminated.Copyright © 2019 American Society for Microbiology.


April 21, 2020  |  

Early emergence of mcr-1-positive Enterobacteriaceae in gulls from Spain and Portugal.

We tested extended-spectrum ß-lactamase producing bacteria from wild gulls (Larus spp.) sampled in 2009 for the presence of mcr-1. We report the detection of mcr-1 and describe genome characteristics of four Escherichia coli and one Klebsiella pneumoniae isolate from Spain and Portugal that also exhibited colistin resistance. Results represent the earliest evidence for colistin-resistant bacteria in European wildlife.Published 2019. This article is a U.S. Government work and is in the public domain in the USA.


April 21, 2020  |  

Plasmid-encoded tet(X) genes that confer high-level tigecycline resistance in Escherichia coli.

Tigecycline is one of the last-resort antibiotics to treat complicated infections caused by both multidrug-resistant Gram-negative and Gram-positive bacteria1. Tigecycline resistance has sporadically occurred in recent years, primarily due to chromosome-encoding mechanisms, such as overexpression of efflux pumps and ribosome protection2,3. Here, we report the emergence of the plasmid-mediated mobile tigecycline resistance mechanism Tet(X4) in Escherichia coli isolates from China, which is capable of degrading all tetracyclines, including tigecycline and the US FDA newly approved eravacycline. The tet(X4)-harbouring IncQ1 plasmid is highly transferable, and can be successfully mobilized and stabilized in recipient clinical and laboratory strains of Enterobacteriaceae bacteria. It is noteworthy that tet(X4)-positive E.?coli strains, including isolates co-harbouring mcr-1, have been widely detected in pigs, chickens, soil and dust samples in China. In vivo murine models demonstrated that the presence of Tet(X4) led to tigecycline treatment failure. Consequently, the emergence of plasmid-mediated Tet(X4) challenges the clinical efficacy of the entire family of tetracycline antibiotics. Importantly, our study raises concern that the plasmid-mediated tigecycline resistance may further spread into various ecological niches and into clinical high-risk pathogens. Collective efforts are in urgent need to preserve the potency of these essential antibiotics.


April 21, 2020  |  

Complete Whole-Genome Sequences of Two Raoultella terrigena Strains, NCTC 13097 and NCTC 13098, Isolated from Human Cases.

Raoultella terrigena is a bacterial species associated with soil and aquatic environments; however, sporadic cases of opportunistic disease in humans have been reported. Here, we report the first two complete genome sequences from clinical strains isolated from human sources that have been deposited in the National Collection of Type Cultures (NCTC). © Crown copyright 2019.


April 21, 2020  |  

Advantage of the F2:A1:B- IncF Pandemic Plasmid over IncC Plasmids in In Vitro Acquisition and Evolution of blaCTX-M Gene-Bearing Plasmids in Escherichia coli.

Despite a fitness cost imposed on bacterial hosts, large conjugative plasmids play a key role in the diffusion of resistance determinants, such as CTX-M extended-spectrum ß-lactamases. Among the large conjugative plasmids, IncF plasmids are the most predominant group, and an F2:A1:B- IncF-type plasmid encoding a CTX-M-15 variant was recently described as being strongly associated with the emerging worldwide Escherichia coli sequence type 131 (ST131)-O25b:H4 H30Rx/C2 sublineage. In this context, we investigated the fitness cost of narrow-range F-type plasmids, including the F2:A1:B- IncF-type CTX-M-15 plasmid, and of broad-range C-type plasmids in the K-12-like J53-2 E. coli strain. Although all plasmids imposed a significant fitness cost to the bacterial host immediately after conjugation, we show, using an experimental-evolution approach, that a negative impact on the fitness of the host strain was maintained throughout 1,120 generations with the IncC-IncR plasmid, regardless of the presence or absence of cefotaxime, in contrast to the F2:A1:B- IncF plasmid, whose cost was alleviated. Many chromosomal and plasmid rearrangements were detected after conjugation in transconjugants carrying the IncC plasmids but not in transconjugants carrying the F2:A1:B- IncF plasmid, except for insertion sequence (IS) mobilization from the fliM gene leading to the restoration of motility of the recipient strains. Only a few mutations occurred on the chromosome of each transconjugant throughout the experimental-evolution assay. Our findings indicate that the F2:A1:B- IncF CTX-M-15 plasmid is well adapted to the E. coli strain studied, contrary to the IncC-IncR CTX-M-15 plasmid, and that such plasmid-host adaptation could participate in the evolutionary success of the CTX-M-15-producing pandemic E. coli ST131-O25b:H4 lineage.Copyright © 2019 Mahérault et al.


April 21, 2020  |  

Circulation of Plasmids Harboring Resistance Genes to Quinolones and/or Extended-Spectrum Cephalosporins in Multiple Salmonella enterica Serotypes from Swine in the United States.

Nontyphoidal Salmonella enterica (NTS) poses a major public health risk worldwide that is amplified by the existence of antimicrobial-resistant strains, especially those resistant to quinolones and extended-spectrum cephalosporins (ESC). Little is known on the dissemination of plasmids harboring the acquired genetic determinants that confer resistance to these antimicrobials across NTS serotypes from livestock in the United States. NTS isolates (n?=?183) from U.S. swine clinical cases retrieved during 2014 to 2016 were selected for sequencing based on their phenotypic resistance to enrofloxacin (quinolone) or ceftiofur (3rd-generation cephalosporin). De novo assemblies were used to identify chromosomal mutations and acquired antimicrobial resistance genes (AARGs). In addition, plasmids harboring AARGs were identified using short-read assemblies and characterized using a multistep approach that was validated by long-read sequencing. AARGs to quinolones [qnrB15, qnrB19, qnrB2, qnrD, qnrS1, qnrS2, and aac(6′)Ib-cr] and ESC (blaCMY-2, blaCTX-M-1, blaCTX-M-27, and blaSHV-12) were distributed across serotypes and were harbored by several plasmids. In addition, chromosomal mutations associated with resistance to quinolones were identified in the target enzyme and efflux pump regulation genes. The predominant plasmid harboring the prevalent qnrB19 gene was distributed across serotypes. It was identical to a plasmid previously reported in S. enterica serovar Anatum from swine in the United States (GenBank accession number KY991369.1) and similar to Escherichia coli plasmids from humans in South America (GenBank accession numbers GQ374157.1 and JN979787.1). Our findings suggest that plasmids harboring AARGs encoding mechanisms of resistance to critically important antimicrobials are present in multiple NTS serotypes circulating in swine in the United States and can contribute to resistance expansion through horizontal transmission.Copyright © 2019 American Society for Microbiology.


April 21, 2020  |  

Dynamics of Resistance Plasmids in Extended-Spectrum-ß-Lactamase-Producing Enterobacteriaceae during Postinfection Colonization.

Extended-spectrum ß-lactamase-producing Enterobacteriaceae (EPE) are a major cause of bloodstream infections, and the colonization rate of EPE in the gut microbiota of individuals lacking prior hospitalization or comorbidities is increasing. In this study, we performed an in-depth investigation of the temporal dynamics of EPE and their plasmids during one year by collecting fecal samples from three patients initially seeking medical care for urinary tract infections. In two of the patients, the same strain that caused the urinary tract infection (UTI) was found at all consecutive samplings from the gut microbiota, and no other EPEs were detected, while in the third patient the UTI strain was only found in the initial UTI sample. Instead, this patient presented a complex situation where a mixed microbiota of different EPE strain types, including three different E. coli ST131 variants, as well as different bacterial species, was identified over the course of the study. Different plasmid dynamics were displayed in each of the patients, including the spread of plasmids between different strain types over time and the transposition of blaCTX-M-15 from the chromosome to a plasmid, followed by subsequent loss through homologous recombination. Small cryptic plasmids were found in all isolates from all patients, and they appear to move frequently between different strains in the microbiota. In conclusion, we could demonstrate an extensive variation of EPE strain types, plasmid composition, rearrangements, and horizontal gene transfer of genetic material illustrating the high dynamics nature and interactive environment of the gut microbiota during post-UTI carriage.Copyright © 2019 American Society for Microbiology.


April 21, 2020  |  

Detection of VIM-1-Producing Enterobacter cloacae and Salmonella enterica Serovars Infantis and Goldcoast at a Breeding Pig Farm in Germany in 2017 and Their Molecular Relationship to Former VIM-1-Producing S. Infantis Isolates in German Livestock Production.

In 2011, VIM-1-producing Salmonella enterica serovar Infantis and Escherichia coli were isolated for the first time in four German livestock farms. In 2015/2016, highly related isolates were identified in German pig production. This raised the issue of potential reservoirs for these isolates, the relation of their mobile genetic elements, and potential links between the different affected farms/facilities. In a piglet-producing farm suspicious for being linked to some blaVIM-1 findings in Germany, fecal and environmental samples were examined for the presence of carbapenemase-producing Enterobacteriaceae and Salmonella spp. Newly discovered isolates were subjected to Illumina whole-genome sequencing (WGS) and S1 pulsed-field gel electrophoresis (PFGE) hybridization experiments. WGS data of these isolates were compared with those for the previously isolated VIM-1-producing Salmonella Infantis isolates from pigs and poultry. Among 103 samples, one Salmonella Goldcoast isolate, one Salmonella Infantis isolate, and one Enterobacter cloacae isolate carrying the blaVIM-1 gene were detected. Comparative WGS analysis revealed that the blaVIM-1 gene was part of a particular Tn21-like transposable element in all isolates. It was located on IncHI2 (ST1) plasmids of ~290 to 300?kb with a backbone highly similar (98 to 100%) to that of reference pSE15-SA01028. SNP analysis revealed a close relationship of all VIM-1-positive S Infantis isolates described since 2011. The findings of this study demonstrate that the occurrence of the blaVIM-1 gene in German livestock is restricted neither to a certain bacterial species nor to a certain Salmonella serovar but is linked to a particular Tn21-like transposable element located on transferable pSE15-SA01028-like IncHI2 (ST1) plasmids, being present in all of the investigated isolates from 2011 to 2017.IMPORTANCE Carbapenems are considered one of few remaining treatment options against multidrug-resistant Gram-negative pathogens in human clinical settings. The occurrence of carbapenemase-producing Enterobacteriaceae in livestock and food is a major public health concern. Particularly the occurrence of VIM-1-producing Salmonella Infantis in livestock farms is worrisome, as this zoonotic pathogen is one of the main causes for human salmonellosis in Europe. Investigations on the epidemiology of those carbapenemase-producing isolates and associated mobile genetic elements through an in-depth molecular characterization are indispensable to understand the transmission of carbapenemase-producing Enterobacteriaceae along the food chain and between different populations to develop strategies to prevent their further spread.Copyright © 2019 Roschanski et al.


April 21, 2020  |  

Spreading Patterns of NDM-Producing Enterobacteriaceae in Clinical and Environmental Settings in Yangon, Myanmar.

The spread of carbapenemase-producing Enterobacteriaceae (CPE), contributing to widespread carbapenem resistance, has become a global concern. However, the specific dissemination patterns of carbapenemase genes have not been intensively investigated in developing countries, including Myanmar, where NDM-type carbapenemases are spreading in clinical settings. In the present study, we phenotypically and genetically characterized 91 CPE isolates obtained from clinical (n = 77) and environmental (n = 14) samples in Yangon, Myanmar. We determined the dissemination of plasmids harboring genes encoding NDM-1 and its variants using whole-genome sequencing and plasmid analysis. IncFII plasmids harboring blaNDM-5 and IncX3 plasmids harboring blaNDM-4 or blaNDM-7 were the most prevalent plasmid types identified among the isolates. The IncFII plasmids were predominantly carried by clinical isolates of Escherichia coli, and their clonal expansion was observed within the same ward of a hospital. In contrast, the IncX3 plasmids were found in phylogenetically divergent isolates from clinical and environmental samples classified into nine species, suggesting widespread dissemination of plasmids via horizontal transfer. Half of the environmental isolates were found to possess IncX3 plasmids, and this type of plasmid was confirmed to transfer more effectively to recipient organisms at a relatively low temperature (25°C) compared to the IncFII plasmid. Moreover, various other plasmid types were identified harboring blaNDM-1, including IncFIB, IncFII, IncL/M, and IncA/C2, among clinical isolates of Klebsiella pneumoniae or Enterobacter cloacae complex. Overall, our results highlight three distinct patterns of the dissemination of blaNDM-harboring plasmids among CPE isolates in Myanmar, contributing to a better understanding of their molecular epidemiology and dissemination in a setting of endemicity.Copyright © 2019 American Society for Microbiology.


April 21, 2020  |  

Diverse Vectors and Mechanisms Spread New Delhi Metallo-ß-Lactamases among Carbapenem-Resistant Enterobacteriaceae in the Greater Boston Area.

New Delhi metallo-beta-lactamases (NDMs) are an uncommon but emerging cause of carbapenem resistance in the United States. Genomic factors promoting their domestic spread remain poorly characterized. A prospective genomic surveillance program among Boston-area hospitals identified multiple new occurrences of NDM-carrying strains of Escherichia coli and Enterobacter cloacae complex in inpatient and outpatient settings, representing the first occurrences of NDM-mediated resistance since initiating genomic surveillance in 2011. Cases included domestic patients with no international exposures. PacBio sequencing of isolates identified strain characteristics, resistance genes, and the complement of mobile vectors mediating spread. Analyses revealed a common 3,114-bp region containing the blaNDM gene, with carriage of this conserved region among unique strains by diverse transposon and plasmid backbones. Functional studies revealed a broad capacity for blaNDM transmission by conjugation, transposition, and complex interplasmid recombination events. NDMs represent a rapidly spreading form of drug resistance that can occur in inpatient and outpatient settings and in patients without international exposures. In contrast to Tn4401-based spread of Klebsiella pneumoniae carbapenemases (KPCs), diverse transposable elements mobilize NDM enzymes, commonly with other resistance genes, enabling naive strains to acquire multi- and extensively drug-resistant profiles with single transposition or plasmid conjugation events. Genomic surveillance provides effective means to rapidly identify these gene-level drivers of resistance and mobilization in order to inform clinical decisions to prevent further spread.Copyright © 2019 American Society for Microbiology.


April 21, 2020  |  

One Health Genomic Surveillance of Escherichia coli Demonstrates Distinct Lineages and Mobile Genetic Elements in Isolates from Humans versus Livestock.

Livestock have been proposed as a reservoir for drug-resistant Escherichia coli that infect humans. We isolated and sequenced 431 E. coli isolates (including 155 extended-spectrum ß-lactamase [ESBL]-producing isolates) from cross-sectional surveys of livestock farms and retail meat in the East of England. These were compared with the genomes of 1,517 E. coli bacteria associated with bloodstream infection in the United Kingdom. Phylogenetic core genome comparisons demonstrated that livestock and patient isolates were genetically distinct, suggesting that E. coli causing serious human infection had not directly originated from livestock. In contrast, we observed highly related isolates from the same animal species on different farms. Screening all 1,948 isolates for accessory genes encoding antibiotic resistance revealed 41 different genes present in variable proportions in human and livestock isolates. Overall, we identified a low prevalence of shared antimicrobial resistance genes between livestock and humans based on analysis of mobile genetic elements and long-read sequencing. We conclude that within the confines of our sampling framework, there was limited evidence that antimicrobial-resistant pathogens associated with serious human infection had originated from livestock in our region. IMPORTANCE The increasing prevalence of E. coli bloodstream infections is a serious public health problem. We used genomic epidemiology in a One Health study conducted in the East of England to examine putative sources of E. coli associated with serious human disease. E. coli from 1,517 patients with bloodstream infections were compared with 431 isolates from livestock farms and meat. Livestock-associated and bloodstream isolates were genetically distinct populations based on core genome and accessory genome analyses. Identical antimicrobial resistance genes were found in livestock and human isolates, but there was limited overlap in the mobile elements carrying these genes. Within the limitations of sampling, our findings do not support the idea that E. coli causing invasive disease or their resistance genes are commonly acquired from livestock in our region. Copyright © 2019 Ludden et al.


April 21, 2020  |  

Genetic variation in the conjugative plasmidome of a hospital effluent multidrug resistant Escherichia coli strain.

Bacteria harboring conjugative plasmids have the potential for spreading antibiotic resistance through horizontal gene transfer. It is described that the selection and dissemination of antibiotic resistance is enhanced by stressors, like metals or antibiotics, which can occur as environmental contaminants. This study aimed at unveiling the composition of the conjugative plasmidome of a hospital effluent multidrug resistant Escherichia coli strain (H1FC54) under different mating conditions. To meet this objective, plasmid pulsed field gel electrophoresis, optical mapping analyses and DNA sequencing were used in combination with phenotype analysis. Strain H1FC54 was observed to harbor five plasmids, three of which were conjugative and two of these, pH1FC54_330 and pH1FC54_140, contained metal and antibiotic resistance genes. Transconjugants obtained in the absence or presence of tellurite (0.5?µM or 5?µM), arsenite (0.5?µM, 5?µM or 15?µM) or ceftazidime (10?mg/L) and selected in the presence of sodium azide (100?mg/L) and tetracycline (16?mg/L) presented distinct phenotypes, associated with the acquisition of different plasmid combinations, including two co-integrate plasmids, of 310 kbp and 517 kbp. The variable composition of the conjugative plasmidome, the formation of co-integrates during conjugation, as well as the transfer of non-transferable plasmids via co-integration, and the possible association between antibiotic, arsenite and tellurite tolerance was demonstrated. These evidences bring interesting insights into the comprehension of the molecular and physiological mechanisms that underlie antibiotic resistance propagation in the environment. Copyright © 2019 Elsevier Ltd. All rights reserved.


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