Global phylogeography and genomic characterization of blaKPC and blaNDM-positive clinical Klebsiella aerogenes isolates from China, 2016-2022

Carbapenem-resistant Klebsiella aerogenes (CRKA), being one of the members of carbapenem-resistant Enterobacteriaceae (CRE), has caused great public health concern, but with fewer studies compared to other CRE members. Furthermore, studies on phylogenetic analysis based on whole genome Single-Nucleotide Polymorphism (SNP) of CRKA were limited. Here, 20 CRKA isolates (11 blaKPC-2-bearing and 9 blaNDM-1/5-harboring) were characterized by antimicrobial susceptibility testing, conjugation assay, whole genome sequencing (WGS) and bioinformatics analysis. Additionally, the phylogeographic relationships of K. aerogenes were further investigated from public databases. All isolates were multidrug-resistant (MDR) bacteria, and they demonstrated susceptibility to colistin. Most blaKPC-2 or blaNDM-1/5-carrying plasmids were found to be conjugative. Phylogenetic analysis revealed the clonal dissemination of K. aerogenes primarily occurred within clinical settings. Notably, some strains in this study showed the potential for clonal transmission, sharing few SNPs between K. aerogenes and KPC- and/or NDM-positive K. aerogenes isolated from various countries. The STs of K. aerogenes strains had significant diversity. WGS analysis showed that the IncFIIK plasmid was the most prevalent carrier of blaKPC-2, and, blaNDM-1/5 were detected on the IncX3 plasmids. The Tn6296 and Tn3000 transposons were most common vehicles for facilitating the transmission of blaKPC-2 and blaNDM-1/5, respectively. This study highlights the importance of continuous screening and surveillance by WGS for analysis of drug-resistant strains in hospital settings, and provide clinical information that supports epidemiological and public health research on human pathogens.

Genomic insights into the adaptation of Acinetobacter johnsonii RB2-047 to the heavy metal-contaminated subsurface mine environment

The subsurface mine environments characterized by high levels of toxic metals and low nutrient availability represent an extreme threat to bacterial persistence. In recent study, the genomic analysis of the Acinetobacter johnsonii strain RB2-047 isolated from the Rozália Gold Mine in Slovakia was performed. As expected, the studied isolate showed a high level of heavy metal tolerance (minimum inhibitory concentrations were 500 mg/L for copper and nickel, 1,500 mg/L for lead, and 250 mg/L for zinc). The RB2-047 strain also showed noticeable resistance to several antibiotics (ampicillin, kanamycin, chloramphenicol, tetracycline and ciprofloxacin). The genomic composition analysis demonstrated a low number of antibiotic and metal resistance coding genes, but a high occurrence of efflux transporter genes located on the bacterial chromosome. The experimental inhibition of efflux pumps resulted in decreased tolerance to Zn and Ni (but not to Cu and Pb) and to all antibiotics tested. In addition, the H33342 dye-accumulation assay confirmed the high efflux activity in the RB2-047 isolate. These findings showed the important role of efflux pumps in the adaptation of Acinetobacter johsonii strain RB2-047 to metal polluted mine environment as well as in development of multi-antibiotic resistance.

Characterization of blaAFM-1-positive carbapenem-resistant strains isolated in Guangzhou, China

BACKGROUND

Carbapenemase-producing makes a great contribution to carbapenem resistance in Gram-negative bacilli. Bla_AFM-1 gene was first discovered by us in Alcaligenes faecalis AN70 strain isolated in Guangzhou of China and, was submitted to NCBI on 16 November 2018.

METHODS

Antimicrobial susceptibility testing was performed by broth microdilution assay using BD Phoenix 100. The phylogenetic tree of AFM and other B1 metallo-β-lactamases was visualized by MEGA7.0. Whole-genome sequencing technology was used to sequence carbapenem-resistant strains including the bla_AFM-1 gene. Cloning and expressing of bla_AFM-1 were designed to verify the function of AFM-1 to hydrolyze carbapenems and common β-lactamase substrates. Carba NP and Etest experiments were conducted to evaluate the activity of carbapenemase. Homology modeling was applied to predict the spatial structure of AFM-1. A conjugation assay was performed to test the ability of horizontal transfer of AFM-1 enzyme. The genetic context of bla_AFM-1 was performed by Blast alignment.

RESULTS

Alcaligenes faecalis strain AN70, Comamonas testosteroni strain NFYY023, Bordetella trematum strain E202, and Stenotrophomonas maltophilia strain NCTC10498 were identified as carrying the bla_AFM-1 gene. All of these four strains were carbapenem-resistant strains. Phylogenetic analysis revealed that AFM-1 shares little nucleotide and amino acid identity with other class B carbapenemases (the highest identity (86%) with NDM-1 at the amino acid sequence level). The spatial structure of the AFM-1 enzyme was predicted to be αβ/βα sandwich structure, with two zinc atoms at its active site structure. Cloning and expressing of bla_AFM-1 verified AFM-1 could hydrolyze carbapenems and common β-lactamase substrates. Carba NP test presented that the AFM-1 enzyme possesses carbapenemase activity. The successful transfer of pAN70-1(plasmid of AN70) to E.coli J53 suggested that the bla_AFM-1 gene could be disseminated by the plasmid. The genetic context of bla_AFM indicated that the downstream of the bla_AFM gene was always adjacent to trpF and ble_MBL. Comparative genome analysis revealed that bla_AFM appeared to have been mobilized by an ISCR27-related mediated event.

CONCLUSIONS

The bla_AFM-1 gene is derived from chromosome and plasmid, and the bla_AFM-1 gene derived from the pAN70-1 plasmid can transfer carbapenem resistance to susceptible strains through horizontal transfer. Several bla_AFM-1-positive species have been isolated from feces in Guangzhou, China.

NDM-5-Producing Escherichia coli Co-Harboring mcr-1 Gene in Companion Animals in China

Carbapenem and colistin are important antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative pathogens. Here, we isolated the blaNDM-5-harboring Escherichia coli in companion animals in healthy or diseased companion animals from veterinary clinics in six cities in China from July to November 2016. A total of 129 rectal swabs of healthy or diseased dogs and cats were collected from veterinary clinics in six different cities in China, and the isolates were subjected to carbapenem and colistin susceptibility testing. Resistance genes were confirmed using PCR. Conjugation experiments were conducted to determine the transferability of antibiotic resistance genes (ARGs) in the strains. The isolated rate of blaNDM-5-harboring E. coli strains was 3.88% (five strains). These five strains were multidrug resistant to at least three antibiotics and corresponded to four sequence types including ST101. The blaNDM-5 gene was located on 46 kb IncX3 plasmids in these five strains, and the genetic contexts were shared and were nearly identical to the K. pneumoniae plasmid pNDM5-IncX3 from China. In addition, one strain (CQ6-1) co-harbored blaNDM-5-encoding-IncX3 plasmid along with a mcr-1-encoding-IncX4 plasmid, and their corresponding genetic environments were identical to the blaNDM-5-IncX3 and mcr-1-IncX4 hybrid plasmid reported previously from the same area and from the same clinic. The results indicated that the similar genetic contexts were shared between these isolates from companion animals, and the IncX3-type plasmids played a key role in the spread of blaNDM-5 among these bacteria.

Antimicrobial Resistance Patterns and Clonal Distribution of E. coli, Enterobacter spp. and Acinetobacter spp. Strains Isolated from Two Hospital Wastewater Plants

The objective of this study was to determine the presence and persistence of antimicrobial-resistant enterobacteria and their clonal distribution in hospital wastewater. A descriptive cross-sectional study was carried out in wastewater from two Mexico City tertiary level hospitals. In February and March of 2020, eight wastewater samples were collected and 26 isolates of enterobacteria were recovered, 19 (73.1%) isolates were identified as E. coli, 5 (19.2%) as Acinetobacter spp. and 2 (7.7%) as Enterobacter spp. Antimicrobial susceptibility profiles were performed using the VITEK 2^® automated system and bacterial identification was performed by the Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometry (MALDI-TOF MS^®). ESBL genes were detected by polymerase chain reaction (PCR) and clonal distributions of isolates were determined by pulsed-field gel electrophoresis (PFGE). E. coli susceptibility to different classes of antimicrobials was analyzed and resistance was mainly detected as ESBLs and fluoroquinolones. One E. coli strain was resistant to doripenem, ertapenem, imipenem and meropenem. The analysis by PCR showed the presence of specific β-lactamases resistance genes (bla_KPC, bla_CTX-M). The PFGE separated the E. coli isolates into 19 different patterns (A–R). PFGE results of Acinetobacter spp. showed the presence of a majority clone A. Surveillance of antimicrobial resistance through hospital wastewater is an important tool for early detection of clonal clusters of clinically important bacteria with potential for dissemination.

Detection and Real-time PCR Assay for the Quantification of Carbapenemase Gene blablaNDM-1 in Hospital Effluent

This study aims to isolate gram-negative bacteria (GNB) harboring the gene NDM-1 from the tertiary care hospital effluents. Also, aims to evaluate the relative copy number of blaNDM-1 carried by the positive isolates. The study isolated 215 GNB from 40 effluent samples. The antibiotic susceptibility tests for carbapenems were performed using disc diffusion assay. The isolates resistant to either meropenem or imipenem were checked for the existence of MBL by phenotypic methods. The isolates carrying NDM-1 gene were genotypically confirmed by Polymerase chain reaction (PCR). The gene copy number of blaNDM- were determined by quantative real-time PCR. A total of 22 isolates showed phenotypic resistance to carbapenems and were characterized by biochemical methods. Among them, 12 harbored NDM-1 gene by PCR; these bacteria were subjected to qPCR for determining the absolute copy numbers of the NDM-1 gene on it. The gene abundance in the strains was in the range of 3.28× 105 to 6.05× 106 copies/ ng of DNA. Hospital effluents are important pool of antibiotic-resistant bacteria harboring the blaNDM-1 and infections caused by these bacteria are difficult to treat. Hence, the present study stresses the need for stringent antibiotic use and efficient wastewater treatment policies in these hospital settings, which is paramount in achieving sustainable health.

Antimicrobial resistance bacteria and genes detected in hospital sewage provide valuable information in predicting clinical antimicrobial resistance

Extensive use of antibiotics is significantly associated with development of antibiotic-resistant (AR) bacteria. However, their causal relationships have not been adequately investigated, especially in human population and hospitals. Our aims were to understand clinical AR through revealing co-occurrence patterns between antibiotic-resistant bacteria and genes (ARB and ARGs), and their association with antibiotic use, and to consider impact of ARB and ARGs on environmental and human health. Antibiotic usage was calculated based on the actual consumption in our target hospital. ARB was identified by culture. In isolates collected from hospital sewage, bacterial-specific DNA sequences and ARGs were determined using metagenomics. Our data revealed that the use of culture-based single-indicator-strain approaches only captured ARB in 16.17% of the infectious samples. On the other hand, 1573 bacterial species and 885 types of ARGs were detected in the sewage. Furthermore, hospital use of antibiotics influenced the resistance profiles, but the strength varied among bacteria. From our metagenomics analyses, ARGs for aminoglycosides were the most common, followed by sulfonamide, tetracycline, phenicol, macrolides, and quinolones, comprising 82.6% of all ARGs. Association analyses indicated that 519 pairs of ARGs were significantly correlated with ARB species (r > 0.8). The co-occurrence patterns of bacteria-ARGs mirrored the AR in the clinic. In conclusion, our systematic investigation further emphasized that antibiotic usage in hospital significantly influenced the abundance and types of ARB and ARGs in dose- and time-dependent manners which, in turn, mirrored clinical AR. In addition, our data provide novel information on development of certain ARB with multiple antibiotic resistance. These ARB and ARGs from sewage can also be disseminated into the environment and communities to create health problems. Therefore, it would be helpful to use such data to develop improved predictive risk model of AR, to enhance effective use of antibiotics, and to reduce environmental pollution.

Carbapenem Resistance among Marine Bacteria-An Emerging Threat to the Global Health Sector

The emergence of antibiotic resistance among pathogenic microorganisms is a major issue for global public health, as it results in acute or chronic infections, debilitating diseases, and mortality. Of particular concern is the rapid and common spread of carbapenem resistance in healthcare settings. Carbapenems are a class of critical antibiotics reserved for treatment against multidrug-resistant microorganisms, and resistance to this antibiotic may result in limited treatment against infections. In addition to in clinical facilities, carbapenem resistance has also been identified in aquatic niches, including marine environments. Various carbapenem-resistant genes (CRGs) have been detected in different marine settings, with the majority of the genes incorporated in mobile genetic elements, i.e., transposons or plasmids, which may contribute to efficient genetic transfer. This review highlights the potential of the marine environment as a reservoir for carbapenem resistance and provides a general overview of CRG transmission among marine microbes.

Detection of a NDM-5-producing Klebsiella pneumoniae sequence type 340 (CG258) high-risk clone in swine

The emergence and rapid increase of carbapenem-resistant Enterobacteriaceae among food-producing animals poses a serious threat to public health. The aim of this study was to investigate the presence and dissemination of bla_NDM-5 in porcine Klebsiella pneumoniae isolates. Of 19 meropenem-resistant K. pneumoniae isolates, 18 were bla_NDM-5-positive and one carried bla_NDM-1. Susceptibility testing indicated that all bla_NDM-carrying K. pneumoniae showed a multiple drug resistance (MDR) profile. The bla_NDM-5 gene was located on a conjugative IncX3 plasmid of ∼46-kb in all 18 bla_NDM-5-carrying isolates. MLST analysis revealed that ST340 (n = 8), a member of the worldwide existing high-risk epidemic clonal group 258 (CG258), was predominant. Furthermore, whole genome sequence (WGS) analysis for one representative ST340 K. pneumoniae Kp19110124 showed a MDR profile for a wide range of antimicrobial agents, including meropenem, various cephalosporins, azteonam, gentamicin, ciprofloxacin, and florfenicol. Phylogenetic analysis exhibited that K. pneumoniae ST340 strains were clustered into one branch, which had spread across host species and across continents. Among them, K. pneumoniae Kp19110124 displayed a very close relationship with a clinical isolate collected from a patient in Canada. In conclusion, these results reveal the presence of a bla_NDM-5-carrying conjugative IncX3 type plasmid into K. pneumoniae ST340 clone, which then may accelerate the dissemination of the bla_NDM-5 gene in porcine K. pneumoniae isolates. The detection of high-risk bla_NDM-5-carrying K. pneumoniae ST340 in food-producing animal poses a serious threat to public health.

β-Lactam Resistance Gene NDM-1 in the Aquatic Environment: A Review

New Delhi Metallo-β-lactamase-1 (NDM-1) offers carbapenem antibiotics resistance that creates an evolving challenge in treating bacterial infections. NDM-1-bearing strains were observed in surface waters around New Delhi in 2010 and after then identified globally. The usage of antibiotics may hasten the growth of the NDM-1-producing bacteria, which pose severe hazards to human and animal health. The emergence of the NDM-1 in the aquatic environment is turning out to be a growing concern worldwide. NDM-1 gene conferring resistance to a widespread class of antibiotics has been observed in bacteria disseminated in animal production wastewaters, hospital sewage, domestic sewage, industrial effluents, wastewater treatment plants, drinking water, surface water, and even in groundwater. This review recapitulates the currently published research studies on the prevalence and geographical distribution of the NDM-1 gene in the aquatic environment, its habitats, and healthcare risk associated with NDM-1-producing bacteria, in addition to molecular techniques employed to reveal the occurrence of the NDM-1 in the aquatic environment, including conventional polymerase chain reaction, real-time qPCR, DNA hybridization, and microarray-based methods.

Carbapenemase-producing Gram-negative bacteria in aquatic environments: a review

Antibiotic resistance is one of the greatest public-health challenges worldwide, especially with regard to Gram-negative bacteria (GNB). Carbapenems are the β-lactam antibiotics of choice with the broadest spectrum of activity and, in many cases, are the last-resort treatment for several bacterial infections. Carbapenemase-encoding genes, mainly carried by mobile genetic elements, are the main mechanism of resistance against carbapenems in GNB. These enzymes exhibit a versatile hydrolytic capacity and confer resistance to most β-lactam antibiotics. After being considered a clinical issue, increasing attention is being giving to the dissemination of such resistance mechanisms in the environment and especially through water. Aquatic environments are among the most significant microbial habitats on our planet, known as a favourable medium for antibiotic gene transfer, and they play a crucial role in the huge spread of drug resistance in the environment and the community. In this review, we present current knowledge regarding the spread of carbapenemase-producing isolates in different aquatic environments, which may help the implementation of control and prevention strategies against the spread of such dangerous resistant agents in the environment.

Characterization of Plasmid Co-Harboring NDM-1 and SHV-12 from a Multidrug-Resistant Citrobacter freundii Strain ZT01-0079 in China

Background

The emergence of multidrug-resistant Citrobacter freundii poses daunting challenges to the treatment of clinical infections. The purpose of this study was to characterize the genome of a C. freundii strain with an IncX3 plasmid encoding both the bla_NDM-1 and bla_SHV-12 genes.

Methods

Strain ZT01-0079 was isolated from a clinical urine sample. The Vitek2 system was used for identification and antimicrobial susceptibility testing. The presence of bla_NDM-1 was detected by PCR and sequencing. Conjugation experiments and Southern blotting were performed to determine the transferability of the bla_NDM-1- carrying plasmid. Nanopore and Illumina sequencing were performed to better understand the genomic characteristics of the strain.

Results

Strain ZT01-0079 was identified as C. freundii, and the coexistence of bla_NDM-1 and multiple drug resistance genes was confirmed. Electrophoresis and Southern blotting showed that bla_NDM-1 was located on a ~53kb IncX3 plasmid. The NDM-1-encoding plasmid was successfully transferred at a frequency of 1.68×10⁻³. Both the bla_NDM-1 and bla_SHV-12 genes were located on the self-transferable IncX3 plasmid.

Conclusion

The rapid spread of the IncX3 plasmid highlights the importance of continuous monitoring of the prevalence of NDM-1-encoding Enterobacteriaceae. Mutations of existing carbapenem resistance genes will bring formidable challenges to clinical treatment.

A catchment-scale assessment of the sanitary condition of treated wastewater and river water based on fecal indicators and carbapenem-resistant Acinetobacter spp

Urbanization and population growth have created considerable sanitation challenges in cities and communities in many parts of Europe and the world. As such, it is imperative to identify the most environmentally-harmful microbiological and chemical sources of pollution, these being wastewater treatment plants (WWTPs) which release wastewater of low quality. In the present manuscript, an extensive study was performed of the sanitary conditions of river water and treated wastewater from seventeen WWTPs of various sizes along the Pilica River catchment in central Poland, with the aim of identifying "hot spots" in terms of most serious sources of sanitary hazards. The bacteriological risk for the river, including fecal indicator bacteria (FIB) such as coliforms, E.coli, enterococci, C. perfringens, and carbapenem-resistant Acinetobacter spp. (CRA) were assessed using classical microbiological methods, and the physicochemical parameters were also tested. The WWTPs, particularly the small ones (<2000 people equivalent, PE) demonstrated significant variation regarding the physicochemical parameters. Carbapenem-resistant Acinetobacter spp. bacteria growing at 42 °C were found in the effluent wastewaters of all tested municipal WWTPs, and in most of the Pilica River water samples, presenting a potential hazard to public health. A positive correlation was identified between E. coli and CRA abundance in treated wastewater; however, no such relationship was found in river water. It was found that seven small treatment plants discharged wastewater with very different microbiological parameters. Moreover, three small treatment plants serving only 0.56% of the population in the studied area continuously released extremely high microbiological contamination, constituting as much as 54-82% of fecal indicator bacteria loads in the area studied. Our findings show that this type of comprehensive analysis may enable assessment of the use of the entire catchment area, thus identifying the most serious threats to surface water quality and guiding the actions needed to improve the worst operating WWTPs.

An Acinetobacter non-baumannii Population Study: Antimicrobial Resistance Genes (ARGs)

Acinetobacter non-baumannii species are becoming common etiologic agents of nosocomial infections. Furthermore, clinical isolates belonging to this group of bacteria are usually resistant to one or more antibiotics. The current information about antibiotic resistance genes in the different A. non-baumannii species has not yet been studied as a whole. Therefore, we did a comparative study of the resistomes of A. non-baumannii pathogens based on information available in published articles and genome sequences. We searched the available literature and sequences deposited in GenBank to identify the resistance gene content of A. calcoaceticus, A. lwoffii, A. junii, A. soli, A. ursingii, A. bereziniae, A. nosocomialis, A. portensis, A. guerrae, A. baylyi, A. calcoaceticus, A. disperses, A. johnsonii, A. junii, A. lwoffii, A. nosocomialis, A. oleivorans, A. oryzae, A. pittii, A. radioresistens, and A. venetianus. The most common genes were those coding for different β-lactamases, including the carbapenemase genes bla_NDM-1 and bla_OXA-58. A. pittii was the species with the most β-lactamase resistance genes reported. Other genes that were commonly found include those encoding some aminoglycoside modifying enzymes, the most common being aph(6)-Id, ant(3″)-IIa, and aph(3″)-Ib, and efflux pumps. All or part of the genes coding for the AdeABC, AdeFGH, and AdeIJK efflux pumps were the most commonly found. This article incorporates all the current information about A. non-baumannii resistance genes. The comparison of the different resistomes shows that there are similarities in the genes present, but there are also significant differences that could impact the efficiency of treatments depending on the etiologic agent. This article is a comprehensive resource about A. non-baumannii resistomes.

Antimicrobials and Antibiotic-Resistant Bacteria: A Risk to the Environment and to Public Health

The release of antibiotics to the environment, and the consequences of the presence of persistent antimicrobial residues in ecosystems, have been the subject of numerous studies in all parts of the world. The overuse and misuse of antibiotics is a common global phenomenon, which substantially increases the levels of antibiotics in the environment and the rates of their spread. Today, it can be said with certainty that the mass production and use of antibiotics for purposes other than medical treatment has an impact on both the environment and human health. This review aims to track the pathways of the environmental distribution of antimicrobials and identify the biological effects of their subinhibitory concentration in different environmental compartments; it also assesses the associated public health risk and government policy interventions needed to ensure the effectiveness of existing antimicrobials. The recent surge in interest in this issue has been driven by the dramatic increase in the number of infections caused by drug-resistant bacteria worldwide. Our study is in line with the global One Health approach.

The carbapenem resistance gene blaOXA-23 is disseminated by a conjugative plasmid containing the novel transposon Tn6681 in Acinetobacter johnsonii M19

Background

Carbapenem resistant Acinetobacter species have caused great difficulties in clinical therapy in the worldwide. Here we describe an Acinetobacter johnsonii M19 with a novel bla_OXA-23 containing transposon Tn6681 on the conjugative plasmid pFM-M19 and the ability to transferand carbapenem resistance.

Methods

A. johnsonii M19 was isolated under selection with 8 mg/L meropenem from hospital sewage, and the minimum inhibitory concentrations (MICs) for the representative carbapenems imipenem, meropenem and ertapenem were determined. The genome of A. johnsonii M19 was sequenced by PacBio RS II and Illumina HiSeq 4000 platforms. A homologous model of OXA-23 was generated, and molecular docking models with imipenem, meropenem and ertapenem were constructed by Discovery Studio 2.0. Type IV secretion system and conjugation elements were identified by the Pathosystems Resource Integration Center (PATRIC) server and the oriTfinder. Mating experiments were performed to evaluate transfer of OXA-23 to Escherichia coli 25DN.

Results

MICs of A. johnsonii M19 for imipenem, meropenem and ertapenem were 128 mg/L, 48 mg/L and 24 mg/L, respectively. Genome sequencing identified plasmid pFM-M19, which harbours the carbapenem resistance gene bla_OXA-23 within the novel transposon Tn6681. Molecular docking analysis indicated that the elongated hydrophobic tunnel of OXA-23 provides a hydrophobic environment and that Lys-216, Thr-217, Met-221 and Arg-259 were the conserved amino acids bound to imipenem, meropenem and ertapenem. Furthermore, pFM-M19 could transfer bla_OXA-23 to E. coli 25DN by conjugation, resulting in carbapenem-resistant transconjugants.

Conclusions

Our investigation showed that A. johnsonii M19 is a source and disseminator of bla_OXA-23 and carbapenem resistance. The ability to transfer bla_OXA-23 to other species by the conjugative plasmid pFM-M19 raises the risk of spread of carbapenem resistance.

Graphic abstract

The carbapenem resistance gene bla_OXA-23 is disseminated by a conjugative plasmid containing the novel transposon Tn6681 in Acinetobacter johnsonii M19.

Multidrug-resistant Acinetobacter baumannii outbreaks: a global problem in healthcare settings

INTRODUCTION

The increase in the prevalence of multidrug-resistant Acinetobacter baumannii infections in hospital settings has rapidly emerged worldwide as a serious health problem.

METHODS

This review synthetizes the epidemiology of multidrug-resistant A. baumannii, highlighting resistance mechanisms.

CONCLUSIONS

Understanding the genetic mechanisms of resistance as well as the associated risk factors is critical to develop and implement adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting.

Characterization of a Novel NDM-5-Harboring Plasmid from a Carbapenem-Resistant Escherichia coli Isolate from China

Background

A carbapenem-resistant Escherichia coli (sequence type 5415) strain was isolated from a male patient through routine surveillance in 2018 in Guangzhou, China.

Materials and Methods

Bacteria were isolated from a sputum culture and identified by using the Vitek 2 compact system. The bla_NDM-5 gene was amplified and confirmed by sequencing. Antimicrobial susceptibility testing was determined by a Vitek 2 compact system. The bla_NDM-5 gene was located by Southern blotting. Whole-genome sequencing was carried out using both Illumina MiSeq and Oxford Nanopore MinION.

Results

S1-PFGE and Southern blotting showed that the bla _NDM-5 gene was located on a novel 66-kb IncFII [F2:A-:B-] plasmid. Conjugation assays revealed that the bla _NDM-5-bearing plasmid was self-transferrable. Genomic sequencing and comparative analysis suggested that plasmid p2947-NDM5 likely originated from a combination of an IncFII-type backbone and the bla _NDM-5 flanking genetic elements.

Conclusion

This is the first report of an ST5414 E. coli strain expressing an NDM-5 β-lactamase. This study highlights the genetic complexity of bla _NDM-5 carrying plasmids and the urgent need for continuous active monitoring.

Multidrug Resistant Acinetobacter Isolates Release Resistance Determinants Through Contact-Dependent Killing and Bacteriophage Lysis

Antimicrobial resistance is an ancient bacterial defense mechanism that has rapidly spread due to the frequent use of antibiotics for disease treatment and livestock growth promotion. We are becoming increasingly aware that pathogens, such as members of the genus Acinetobacter, are precipitously evolving drug resistances through multiple mechanisms, including the acquisition of antibiotic resistance genes. In this study, we isolated three multidrug resistant Acinetobacter species from birds on a free-range farm. Acinetobacter radioresistens, Acinetobacter lwoffii, and Acinetobacter johnsonii were isolated from hens, turkeys and ducks and were resistant to 14 clinically relevant antibiotics, including several listed by the World Health Organization as essential medicines. Co-culturing any of the three Acinetobacter species with Acinetobacter baumannii resulted in contact-dependent release of intact resistance determinants. We also isolated several lytic bacteriophages and selected two of these phages to be included in this study based on differences in plaquing characteristics, nucleic acid content and viral morphology. Both phages released host DNA, including antibiotic resistance genes during cell lysis and we demonstrated that these resistance determinants were transferable to a naïve strain of Escherichia coli. This study demonstrates that contact-dependent competition between bacterial species can readily contribute to DNA release into the environment, including antibiotic resistance determinants. We also highlight that the constant lysis and turnover of bacterial populations during the natural lifecycle of a lytic bacteriophage is an underappreciated mechanism for the liberation of DNA and subsequent genetic exchange.

Phylogeographical Analyses and Antibiotic Resistance Genes of Acinetobacter johnsonii Highlight Its Clinical Relevance

Acinetobacter johnsonii has been severely understudied and its population structure and the presence of antibiotic resistance genes (ARGs) are very much uncertain. Our phylogeographical analysis shows that intercontinental transmission has occurred frequently and that different lineages are circulating within single countries; notably, clinical and nonclinical strains are not well differentiated from one another. Importantly, in this species recombination is a significant source of single nucleotide polymorphisms.

Acinetobacter johnsonii has been severely understudied and its population structure and the presence of antibiotic resistance genes (ARGs) are very much uncertain. Our phylogeographical analysis shows that intercontinental transmission has occurred frequently and that different lineages are circulating within single countries; notably, clinical and nonclinical strains are not well differentiated from one another. Importantly, in this species recombination is a significant source of single nucleotide polymorphisms. Furthermore, our results show this species could be an important reservoir of ARGs since it has a significant amount of ARGs, and many of them show signals of horizontal gene transfer. Thus, this study clearly points out the clinical importance of A. johnsonii and the urgent need to better appreciate its genomic diversity.

Occurrence and characterization of KPC-2-producing ST11 Klebsiella pneumoniae isolate and NDM-5-producing Escherichia coli isolate from the same horse of equestrian clubs in China

Carbapenem-resistant Enterobacteriaceae (CRE) have been rapidly increasing among animals in many countries and have been a great threat to public health. Horse riding is becoming increasingly popular worldwide; however, reports of CRE producing NDM or KPC-2, two prevalent types of carbapenemases, from horses of equestrian club are extremely scarce and KPC-2-producing Klebsiella pneumoniae in animals is still rarely characterized. In this study, we identified four NDM-5-producing Escherichia coli isolates from horses in equestrian club in Qingdao, China, and one horse possessing NDM-5-producing E. coli also carried ST11 KPC-2-producing K. pneumoniae. Transferability of the plasmids producing carbapenemases was determined by conjugation, and the sequences of all CRE isolates and their transconjugants were then analysed by using whole-genome sequencing. bla_NDM-5 was located on a highly similar ~ 46 kb self-transmissible IncX3 plasmid in all isolates, and these plasmids were nearly identical to IncX3 plasmids from different bacterial species of clinical patients in several countries, even including plasmid from clinical E. coli in Qingdao, China. The chromosome of the ST11 K. pneumoniae in this study was highly similar to ST11 clinical K. pneumoniae reported worldwide including the ST11 KPC-2-producing WCHKP020098 from Chengdu, China, and the bla_KPC-2 -bearing plasmid in our study was a novel F33:A-:B- non-conjugative multidrug resistance plasmid. The presence of CRE from horses in equestrian club is alarming due to the potential for transmitting these isolates to humans during horse riding, and the prevalence of CRE among equestrian clubs in the whole country requires further monitoring.

Hospital wastewater treatment reduces NDM-positive bacteria being discharged into water bodies

New Delhi metallo-β-lactamase-1 (NDM-1) is a novel type of metallo-β-lactamase (MBL) associated with Enterobacteriaceae constitutes an important growing public health threat. The present study aims to characterize the NDM-1 producing Gram-negative bacteria (GNB) from the effluents of two tertiary care hospitals in Mangalore, South India and to profile their antibiotic resistance pattern. A total of 134 GNB were isolated from 30 hospital wastewater samples (treated and untreated) and analyzed. High-level resistance among untreated effluent sample was found toward nalidixic acid (74.52%), followed by cefotaxime (72.64%) and ampicillin (66.03%). Among the treated effluent isolates, the high resistance was found toward ampicillin (85.71%) followed by cefotaxime (85.71%) and piperacillin-tazobactam (53.57%). From untreated effluent isolates, 9 were NDM-1 positive by PCR; no isolates from treated effluent samples harbored bla_NDM-1 . Untreated hospital wastewater is found to be important reservoirs of antibiotic-resistant bacteria carrying bla_NDM-1 , and the presence of such bacteria in the effluents is a matter of great concern because they can contribute the antibiotic resistance to the natural environment. However, the absence of NDM in treated effluents emphasizes the importance of effluent treatment in reducing the dissemination of antibiotic-resistant bacteria. PRACTITIONER POINTS: Hospital wastewater is the important reservoir of antibiotic-resistant bacteria especially metallo-β-lactamase producers (NDM-1). Wastewater treatment procedures in hospitals reduce the NDM isolates in the treated effluent. Thereby reduces the risk of resistance spread in the environment.

The Prevalence and Characterization of Extended-Spectrum β-Lactamase- and Carbapenemase-Producing Bacteria from Hospital Sewage, Treated Effluents and Receiving Rivers

Hospital sewage plays a key role in the dissemination of antibiotic-resistant genes (ARGs) by serving as an environmental antimicrobial resistance reservoir. In this study, we aimed to characterize the cephalosporin- and carbapenem-resistant isolates from hospital sewage and receiving rivers. The results showed that ESBL (bla_CTX-M) and carbapenemase genes (bla_NDM and bla_KPC) were widely detected in a number of different bacterial species. These resistance genes were mainly harbored in Enterobacteriaceae, followed by Acinetobacter and Aeromonas isolates. More attention should be given to these bacteria as important vectors of ARGs in the environment. Furthermore, we showed that the multidrug resistance phenotype was highly prevalent, which was found in 85.5% Enterobacteriaceae and 75% Acinetobacter strains. Notably, the presence of carbapenemase genes in isolates from treated effluents and receiving rivers indicates that the discharges of wastewater treatment plants could be an important source for high-risk resistance genes propagation to the environment. In conclusion, this study shows a high prevalence of ESBL- and carbapenemase-producing bacteria in hospital sewage and receiving rivers in China. These findings have serious implications for human health, and also suggest the need for more efforts to control the dissemination of resistant bacteria from hospital sewage into the environment.

Coexistence of Two bla NDM- 5 Genes Carried on IncX3 and IncFII Plasmids in an Escherichia coli Isolate Revealed by Illumina and Nanopore Sequencing

The emergence of carbapenem-resistant Enterobacteriaceae poses a significant threat to public health worldwide. Here, we reported a multidrug-resistant Escherichia coli strain with two different bla_NDM–5-carrying plasmids from China. Illumina short-read and MinION long-read whole genome sequencing were performed. Genomic analysis found that one bla_NDM–5 gene together with mphA was located on a 55-kb IncX3 plasmid, while the other bla_NDM–5 gene was on a novel 68-kb IncFII plasmid. Susceptibility testing and quantitative reverse transcription PCR results further indicated that the transconjugants with the IncX3 plasmid exhibited higher-level carbapenem resistance and expression of bla_NDM–5 than those with both plasmids or the IncFII plasmid. Two other β-lactamase genes (bla_CTX–M–15 and bla_OXA–1) were also detected on another 160-kb IncF plasmid. This is the first report of coexistence of two bla_NDM–5-carrying plasmids in a single bacterial isolate, highlighting the genetic complexity of NDM-5 carbapenemase circulation, and the urgent need for continued active surveillance.

Coexistence of the blaNDM-1-carrying plasmid pWLK-NDM and the blaKPC-2-carrying plasmid pWLK-KPC in a Raoultella ornithinolytica isolate

To date, bla_NDM and bla_KPC genes have been found predominantly in clinical settings around the world. In contrast, bacteria harbouring these two genes from natural environments are relatively less well studied compared to those found in clinical settings. In this study, a carbapenem-resistant Raoultella ornithinolytica strain, WLK218, was isolated from urban river sediment in Zhengzhou City, Henan Province, China. This isolate was subjected to PCR and antimicrobial susceptibility testing. PCR results showed that this isolate was positive for both the bla_NDM-1 and bla_KPC-2 genes. The antimicrobial susceptibility testing results showed that this isolate exhibited resistance or intermediate resistance to all the antibiotics tested except for streptomycin (susceptible) and cefepime (susceptible-dose dependent). The complete genome sequence of the WLK218 isolate was then determined by using a combination of the PacBio and Illumina sequencing technologies. The de novo assembly of the genome generated one chromosome and six plasmids. Among the six plasmids, the bla_NDM-1 gene was carried on the IncX3 plasmid pWLK-NDM, while the bla_KPC-2 gene was located on the untypeable plasmid pWLK-KPC. This is the first report of an environmental Raoultella ornithinolytica isolate co-harbouring the bla_NDM-1 and bla_KPC-2 genes.

The threat of carbapenem-resistant bacteria in the environment: Evidence of widespread contamination of reservoirs at a global scale

Environmental reservoirs of antibiotic resistance (AR) are a growing concern that are gathering more attention as potential sources for human infection. Carbapenem-resistant Enterobacteriaceae (CRE) are extremely dangerous, as carbapenems are often drugs of last resort that are used to treat multi-drug resistant infections. Among the genes capable of conferring carbapenem resistance to bacteria, the most transferrable are those that produce carbapenemase, an enzyme that hydrolyzes carbapenems and other β-lactam antibiotics. The goal of this review was to comprehensively identify global environmental reservoirs of carbapenemase-producing genes, as well as identify potential routes of transmission to humans. The genes of interest were Klebsiella pneumoniae carbapenemase (KPC), New Delhi Metallo-β-lactamase (NDM), Oxacillinase-48-type carbapenemases (OXA-48), and Verona Integron-Mediated Metallo-β-lactamase (VIM). Carbapenemase genes have been reported in the environment on almost every continent. Hospital and municipal wastewater, drinking water, natural waterways, sediments, recreational waters, companion animals, wildlife, agricultural environments, food animals, and retail food products were identified as current reservoirs of carbapenemase-producing bacteria and genes. Humans have been recorded as carrying CRE, without recent admittance to a hospital or long-term care facility in France, Egypt, and China. CRE infections from the environment have been reported in patients in Montpellier, France and Cairo, Egypt. This review demonstrates the need for 1) comprehensive monitoring of AR not only in waterways, but also other types of environmental matrices, such as aerosol, dusts, periphyton, and surfaces in indoor environments; and 2) action to reduce the prevalence and mitigate the effects of these potentially deadly resistance genes. In order to develop an accurate quantitative model for environmental dimensions of AR, longitudinal sampling and quantification of AR genes and bacteria are needed, using a One Health approach.

Metagenome of a polluted river reveals a reservoir of metabolic and antibiotic resistance genes

BACKGROUND

Yamuna, a major tributary of Ganga, which flows through the national capital region of Delhi, is among the major polluted rivers in India. The accumulation of various effluents, toxic chemicals, heavy metals, and increased organic load in the Yamuna directly affects the organisms that thrive inside or around this river. It also makes it an ideal site for studying the impact of pollution on the river microflora, which are sentinels of the water quality.

RESULTS

In this study, the microbial community structure and functional diversity of the Yamuna river water was assessed from the New Delhi region. The community structure of Yamuna during pre-monsoon (June) was found to be significantly different from the post-monsoon (November) time, with Acinetobacter being the most abundant genus during June, and Aeromonas during November. The functional characterization revealed the higher abundance of Methyl-accepting chemotaxis protein in the river water, which could be important for the microbial chemosensory adaptation in the environment. A higher abundance of genes related to nitrogen and sulfur metabolism, metal tolerance, and xenobiotic degradation, and complete degradation pathways of aromatic compounds such as toluene, xylene, benzene and phenol were identified. Further, the results showed the presence of a pool of antibiotic resistance genes in the bacterial microbiome in the Yamuna alongside a large number of broad-spectrum antibiotics, such as carbapenemases and metallo-β-lactamases. Efflux mechanism of resistance was found to dominate among these microbes conferring multi-drug resistance. The Principal Coordinate Analysis of the taxonomic composition of the Yamuna River water with publicly available freshwater and sewage datasets revealed significant differences in the two Yamuna samples and a greater resemblance of pre-monsoon Yamuna sample to sewage sample owing to the higher pollution levels in Yamuna in the pre-monsoon time.

CONCLUSION

The metagenomic study of the Yamuna river provides the first insights on the bacterial microbiome composition of this large polluted river, and also helps to understand the dynamics in the community structure and functions due to seasonal variations. The presence of antibiotic resistance genes and functional insights on the metabolic potential of a polluted river microbiome are likely to have several applications in health, biotechnology and bioremediation.

Key evolutionary events in the emergence of a globally disseminated, carbapenem resistant clone in the Escherichia coli ST410 lineage

There is an urgent need to understand the global epidemiological landscape of carbapenem-resistant Escherichia coli (CREC). Here we provide combined genomic and phenotypic characterization of the emergence of a CREC clone from the ST410 lineage. We show that the clone expands with a single plasmid, within which there is frequent switching of the carbapenemase gene type between blaNDM and blaOXA-181 with no impact on plasmid stability or fitness. A search for clone-specific traits identified unique alleles of genes involved in adhesion and iron acquisition, which have been imported via recombination. These recombination-derived allelic switches had no impact on virulence in a simple infection model, but decreased efficiency in binding to abiotic surfaces and greatly enhanced fitness in iron limited conditions. Together our data show a footprint for evolution of a CREC clone, whereby recombination drives new alleles into the clone which provide a competitive advantage in colonizing mammalian hosts.

Prevalence and molecular epidemiology characteristics of carbapenem-resistant Escherichia coli in Heilongjiang Province, China

Objective

This retrospective study was conducted to determine the prevalence and molecular epidemiology characteristics of carbapenem-resistant Escherichia coli (CRE).

Methods

A total of 593 Escherichia coli (E. coli) isolates were recovered from pigs and urban river from 2009 to 2014 in Heilongjiang Province of China. Forty CRE including 22 strains isolated from fecal samples of pigs and 18 strains isolated from water samples were selected. PCR detection of resistance determinants, multi-locus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and phylogenetic groups were performed to characterize CRE isolates. Conjugation experiments, plasmid stability testing, PCR-based replicon typing (PBRT), and PCR mapping were conducted to analyze bla_NDM-carrying plasmids. In vitro time–growth studies and competition experiments were carried out to assess the fitness impact of NDM carriage.

Results

Five NDM-1-positive E. coli isolates were identified from water samples. Genetic environment analysis revealed that a cluster of genes (ISAba125-bla_NDM-1-ble_MBL-ΔtrpF) was detected in all of the NDM-1-positive isolates. Conjugation assays showed that bla_NDM-1 could be successfully transferred to E. coli J53 from 5 donor strains at frequencies of 4.6×10⁻⁵ to 2.6×10⁻². The plasmids from all transconjugants belonged to different plasmid replicon types including IncA/C (n=2), IncFII (n=1) and IncX3 (n=2). In vitro time–growth studies revealed that bla_NDM-1 did not have a significant impact on cell proliferation. Meanwhile, competition experiments showed that the acquisition of bla_NDM-1 can place an energy burden on the bacterial host and incur fitness cost. However, plasmid stability testing showed that bla_NDM-1-carrying plasmid remained stable in the hosts after seven passages without antimicrobial selection.

Conclusion

The study revealed the early molecular epidemiology and dissemination characteristics of CRE. In addition, the overall antimicrobial resistance in E. coli recovered from water samples is higher than the strains isolated from fecal samples of pigs. Furthermore, we isolated and identified five NDM-1-producing E. coli strains from water samples.

NDM Metallo-β-Lactamases and Their Bacterial Producers in Health Care Settings

New Delhi metallo-β-lactamase (NDM) is a metallo-β-lactamase able to hydrolyze almost all β-lactams. Twenty-four NDM variants have been identified in >60 species of 11 bacterial families, and several variants have enhanced carbapenemase activity. Klebsiella pneumoniae and Escherichia coli are the predominant carriers of bla _NDM, with certain sequence types (STs) (for K. pneumoniae, ST11, ST14, ST15, or ST147; for E. coli, ST167, ST410, or ST617) being the most prevalent. NDM-positive strains have been identified worldwide, with the highest prevalence in the Indian subcontinent, the Middle East, and the Balkans. Most bla _NDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC). Commonly used phenotypic tests cannot specifically identify NDM. Lateral flow immunoassays specifically detect NDM, and molecular approaches remain the reference methods for detecting bla _NDM Polymyxins combined with other agents remain the mainstream options of antimicrobial treatment. Compounds able to inhibit NDM have been found, but none have been approved for clinical use. Outbreaks caused by NDM-positive strains have been reported worldwide, attributable to sources such as contaminated devices. Evidence-based guidelines on prevention and control of carbapenem-resistant Gram-negative bacteria are available, although none are specific for NDM-positive strains. NDM will remain a severe challenge in health care settings, and more studies on appropriate countermeasures are required.

Acinetobacter sichuanensis sp. nov., recovered from hospital sewage in China

A novel Acinetobacter strain, WCHAc060041^T, was recovered from hospital sewage at West China Hospital in Chengdu, Sichuan Province, China. The strain was Gram-negative coccobacillus, non-spore-forming, non-motile and strictly aerobic. The genomic DNA G+C content was 37.02 mol%. The 16S rRNA and rpoB gene sequences of the strain were ≤98.2 and≤89.5 % identical to the type strains of all known Acinetobacter species, respectively. The strain formed a distinct branch based on the genus-wide comparison of whole-cell mass fingerprints generated by matrix-assisted laser desorption/ionization-time-of flight mass spectrometry. Strain WCHAc060041^T was subjected to whole genome sequencing. The average nucleotide identity based on blast (ANIb) and in silico DNA-DNA hybridization (isDDH) values between strain WCHAc060041^T and type strains of other Acinetobacter species were ≤82.7 and ≤26.9 %, respectively. Strain WCHAc060041^T could be distinguished from all known Acinetobacter species by its ability to assimilate gentisate and levulinate, but not to citrate (Simmons'). Genotypic and phenotypic characteristics from this study indicate that strain WCHAc060041^T represents a novel species of the genus Acinetobacter, for which the name Acinetobacter sichuanensis sp. nov. is proposed. The type strain is WCHAc060041^T (=CCTCC AB 2018118^T=GDMCC 1.1383^T=KCTC 62575^T).

Multidrug-resistant Citrobacter freundii ST139 co-producing NDM-1 and CMY-152 from China

The emergence of carbapenemase-producing Citrobacter freundii poses a significant threat to public health worldwide. Here, we reported a C. freundii strain CWH001 which was resistant to all tested antimicrobials except tetracycline. Whole genome sequencing and analysis were performed. The strain, which belonged to a new sequence type ST139, showed close relationship with other foreign C. freundii strains through phylogenetic analysis. A novel variant of the intrinsic bla_CMY gene located on the chromosome was identified and designated as bla_CMY-152. Coexistence of bla_NDM-1 with qnrS1 was found on a conjugative IncN plasmid, which had a backbone appearing in various plasmids. Other class A ESBL genes (bla_VEB-3 and bla_TEM-1) were also detected on two different novel plasmids. The emergence of multidrug-resistant C. freundii is of major concern, causing great challenges to the treatment of clinical infections. Great efforts need to be taken for the specific surveillance of this opportunistic pathogen.

Characteristics of Carbapenem-Resistant Enterobacteriaceae in Ready-to-Eat Vegetables in China

Vegetables harboring bacteria resistant to antibiotics are a growing food safety issue. However, data concerning carbapenem-resistant Enterobacteriaceae (CRE) in ready-to-eat fresh vegetables is still rare. In this study, 411 vegetable samples from 36 supermarkets or farmer's markets in 18 cities in China, were analyzed for CRE. Carbapenemase-encoding genes and other resistance genes were analyzed among the CRE isolates. Plasmids carrying carbapenemase genes were studied by conjugation, replicon typing, S1-PFGE southern blot, restriction fragment length polymorphism (RFLP), and sequencing. CRE isolates were also analyzed by pulsed-field gel electrophoresis (PFGE). Ten vegetable samples yielded one or more CRE isolates. The highest detection rate of CRE (14.3%, 4/28) was found in curly endive. Twelve CRE isolates were obtained and all showed multidrug resistance: Escherichia coli, 5; Citrobacter freundii, 5; and Klebsiella pneumoniae, 2. All E. coli and C. freundii carried bla_NDM, while K. pneumoniae harbored bla_KPC−2. Notably, E. coli with bla_NDM and ST23 hypervirulent Klebsiella pneumoniae (hvKP) carrying bla_KPC−2 were found in the same cucumber sample and clonal spread of E. coli, C. freundii, and K. pneumoniae isolates were all observed between vegetable types and/or cities. IncX3 plasmids carrying bla_NDM from E. coli and C. freundii showed identical or highly similar RFLP patterns, and the sequenced IncX3 plasmid from cucumber was also identical or highly similar (99%) to the IncX3 plasmids from clinical patients reported in other countries, while bla_KPC−2 in K. pneumoniae was mediated by similar F35:A-:B1 plasmids. Our results suggest that both clonal expansion and horizontal transmission of IncX3- or F35:A-:B1-type plasmids may mediate the spread of CRE in ready-to-eat vegetables in China. The presence of CRE in ready-to-eat vegetables is alarming and constitutes a food safety issue. To our knowledge, this is the first report of either the C. freundii carrying bla_NDM, or K. pneumoniae harboring bla_KPC−2 in vegetables. This is also the first report of ST23 carbapenem-resistant hvKP strain in vegetables.

Sequence Type 273 Carbapenem-Resistant Klebsiella pneumoniae Carrying blaNDM-1 and blaIMP-4

A carbapenem-resistant Klebsiella pneumoniae isolate was recovered from human blood. Its whole-genome sequence was obtained using Illumina and long-read MinION sequencing. The strain belongs to sequence type 273 (ST273), which was found recently and caused an outbreak in Southeast Asia. It has two carbapenemase genes, bla_NDM-1 (carried by an ST7 IncN self-transmissible plasmid) and bla_IMP-4 (located on a self-transmissible IncHI5 plasmid). Non-KPC-producing ST237 may represent a lineage of carbapenem-resistant K. pneumoniae, which warrants further monitoring.

Cryptic transmission of ST405 Escherichia coli carrying bla NDM-4 in hospital

Three carbapenem-resistant Escherichia coli were recovered from rectal swabs of different patients in a tertiary hospital and were found carrying bla_NDM-4, an uncommon bla_NDM variant. Genome sequences of the isolates were obtained using Illumina technology and the long-read MinION sequencer. The isolates belonged to ST405 and phylogenetic group D, a globally distributed lineage associated with antimicrobial resistance. In addition to bla_NDM-4, the three isolates carried 14 known resistance genes including the extended-spectrum β-lactamase gene bla_CTX-M-15. There were only 1 or 2 SNPs between the isolates, suggesting a common origin and cryptic transmission in hospital. bla_NDM-4 was located on a 46.5-kb IncFIA self-transmissible plasmid, which may facilitate further dissemination of bla_NDM-4. Two copies of IS26 bracketed a 14.6-kb region containing bla_NDM-4 and have the potential to form a composite transposon for mediating the mobilization of bla_NDM-4.

In Vitro Activity of Neomycin, Streptomycin, Paromomycin and Apramycin against Carbapenem-Resistant Enterobacteriaceae Clinical Strains

We determined the in vitro susceptibility of four aminoglycosides, which are not of the 4,6-disubstituted deoxystreptamine (DOS) subclass against a collection of carbapenem-resistant Enterobacteriaceae (CRE). CRE clinical strains (n = 134) were collected from multiple hospitals in China and carried bla_NDM (bla_NDM−1, bla_NDM−5 or bla_NDM−7; n = 66), bla_KPC−2 (n = 62) or bla_IMP−4 (n = 7; including one carrying bla_NDM−1 and bla_IMP−4). MICs of neomycin, paromomycin, streptomycin and apramycin as well as three 4,6-disubstituted DOS aminoglycosides (amikacin, gentamicin and tobramycin) were determined using the broth microdilution with breakpoints defined by the Clinical Laboratory Standards Institute (for amikacin, gentamicin and tobramycin), US Food and Drug Administration (streptomycin), the National Antimicrobial Resistance Monitoring System (apramycin) or la Société Française de Microbiologie (neomycin and paromomycin). Apramycin-resistant strains were subjected to whole genome sequencing using Illumina X10 platform. Among CRE strains, 65.7, 64.9, 79.1, and 95.5% were susceptible to neomycin (MIC₅₀/MIC₉₀, 8/256 μg/ml), paromomycin (4/>256 μg/ml), streptomycin (16/256 μg/ml) and apramycin (4/8 μg/ml), respectively, while only 55.2, 28.4, and 35.1% were susceptible to amikacin (32/>256 μg/ml), gentamicin (128/>256 μg/ml) and tobramycin (64/>256 μg/ml), respectively. Six CRE strains including five Escherichia coli of different sequence types and one Klebsiella pneumoniae were resistant to apramycin and the apramycin-resistant gene aac(3)-IVa was detected in all of these strains. In conclusion, neomycin, paromomycin, streptomycin and apramycin retain activity against most CRE strains. Although none of these non-4,6-disubstituted DOS aminoglycosides are suitable for intravenous use in human at present, these agents warrant further investigations to be used against CRE infections.

Emergence of Klebsiella variicola positive for NDM-9, a variant of New Delhi metallo-β-lactamase, in an urban river in South Korea

Objectives

To examine the presence of pathogenic bacteria carrying New Delhi metallo-β-lactamase in the environment and to characterize the genome structures of these strains.

Methods

Phenotypic screening of antimicrobial susceptibility and WGS were conducted on three Klebsiella variicola strains possessing NDM-9 isolated from an urban river.

Results

Three carbapenem-resistant K. variicola isolated from Gwangju tributary were found to possess bla NDM-9 genes. Antimicrobial susceptibility testing indicated resistance of these strains to aminoglycosides, carbapenems, cephems, folate pathway inhibitors, fosfomycin and penicillins, but susceptibility to fluoroquinolones, phenicols, tetracyclines and miscellaneous agents. WGS revealed that the 108 kb IncFII(Y)-like plasmids carry bla NDM-9 sandwiched between IS 15 for the GJ1 strain, IS 26 for the GJ2 strain, IS 15D1 for the GJ3 strain and IS Vsa3 , and further bracketed by IS 26 and Tn AS3 along with the mercury resistance operon upstream and the class 1 integron composed of gene cassettes of aadA2 , dfrA12 and sul1 downstream. An aph(3')-Ia gene conferring resistance to aminoglycosides is located after the integrons. Chromosomally encoded bla LEN-13 , fosA , aqxA and oqxB genes, as well as plasmid-mediated bla TEM-1B and bla CTX-M-65 encoding ESBL, ant(3')-Ia and mph (A) genes, were also identified.

Conclusions

The findings of the present study provide us with the information that NDM-9 has been spreading into the environment. Dissemination of NDM-9 in the environment has raised a health risk alarm as this variant of NDM carries MDR genes with highly transferable mobile genetic elements, increasing the possibility of resistance gene transfer among microorganisms in the environment.

Acinetobacter defluvii sp. nov., recovered from hospital sewage

A Gram-stain-negative, non-motile Acinetobacter strain, WCHA30T, was isolated from hospital sewage in West China Hospital of Sichuan University in Chengdu, south-western China. Strain WCHA30T was a non-spore-forming, catalase-positive, oxidase-negative, strictly aerobic coccobacillus. The DNA G+C content was 38 mol%. Phylogenetic analysis based on 16S rRNA, rpoB and gyrB gene sequences revealed that the strain was distinct from any previously described species of the genus Acinetobacter. Strain WCHA30T could be distinguished from all known Acinetobacter species by its ability to assimilate β-alanine but not l-glutamate. Genotypic and phenotypic characteristics from this study indicate that strain WCHA30T should be considered to represent a novel species of the genus Acinetobacter, for which the name Acinetobacter defluvii sp. nov. is proposed. The type strain is WCHA30T (=CCTCC AB 2016203T=GDMCC 1.1101T=KCTC 52503T).

Characterization of NDM-5-positive extensively resistant Escherichia coli isolates from dairy cows

The aim of this study was to investigate the prevalence of bla_NDM-5 gene in Escherichia coli isolates from dairy cows and to characterize the molecular traits of the bla_NDM-5-positive isolates. A total of 169 cows were sampled (169 feces and 169 raw milk samples) in three dairy farms in Jiangsu Province and 203 E. coli isolates were recovered. Among these strains, three isolates carried bla_NDM-5 gene, including one co-harboring mcr-1, which belonged to sequence type 446 and the other two belonged to ST2. Susceptibility testing revealed that the three bla_NDM-5-positive isolates showed extensive resistance to antimicrobials. The bla_NDM-5 gene was located on a ∼46-kb IncX3 transferrable pNDM-MGR194-like plasmid in all three isolates, while mcr-1 was located on a ∼260-kb IncHI2 plasmid pXGE1mcr. Competition experiments revealed that acquisition of bla_NDM-5 or mcr-1-bearing plasmid can incur fitness cost of bacterial host, however, plasmid stability testing showed that both bla_NDM-5 and mcr-1-carrying plasmid maintained stable in the hosts after ten passages without antimicrobial selection. Whole genome sequencing revealed that the mcr-1 gene coexisted with multiple resistance genes in pXGE1mcr and the backbone of this plasmid was similar to that of previously reported mcr-1-positive plasmid pHNSHP45-2. Moreover, pXGE1mcr could be conjugated into clinical NDM-5-positive E. coli isolates in vitro, thereby generating strains that approached pan-resistance. Active surveillance efforts are imperative to monitor the prevalence of bla_NDM-5 and mcr-1 in carbapenem-resistant Enterobacteriaceae from dairy farms throughout China.

High Incidence of Escherichia coli Strains Coharboring mcr-1 and blaNDM from Chickens

This study investigated the characteristics of Escherichia coli isolates carrying mcr-1-bla_NDM from a chicken farm in China. Of the 78 E. coli isolates, 21 clonally unrelated isolates carried mcr-1-bla_NDM Diverse IncI2 plasmids disseminated mcr-1, while the dissemination of bla_NDM was mediated by diverse IncB/O plasmids. More striking was the colocalization of resistance genes mcr-1 and bla_NDM-4 in an IncHI2/ST3 plasmid, which might pose a great challenge for public health.

Draft Genome Sequence of a Colistin-Resistant Klebsiella pneumoniae Clinical Strain Carrying the blaNDM-1 Carbapenemase Gene

Klebsiella pneumoniae strain WCHKP1845, recovered from the sputum of a patient with pneumonia, was resistant to colistin and carried the carbapenemase gene bla_NDM-1 Here, we report its 5.4-Mb draft genome sequence, comprising 140 contigs with an average 57.33% G+C content. The genome contains 5,118 coding sequences and 88 tRNA genes.

Draft Genome Sequence of a Sequence Type 11 Klebsiella pneumoniae Clinical Strain Carrying a blaKPC-2 Carbapenemase Gene and an rmtB 16S rRNA Methylase Gene

Klebsiella pneumoniae strain WCHKP649, recovered from a human wound, carried the carbapenemase gene bla_KPC-2 and 16S rRNA methylase gene rmtB. Here, we report its 5.6-Mb draft genome sequence, comprising 171 contigs with an average 57.34% G+C content. The genome contained 5,284 coding sequences and 84 tRNA genes.

Emergence of Colistin Resistance Gene mcr-1 in Cronobacter sakazakii Producing NDM-9 and in Escherichia coli from the Same Animal

We report the presence of mcr-1 in Escherichia coli and carbapenem-resistant Cronobacter sakazakii from the same diseased chicken. The mcr-1 gene linked with ISApl1 was located on two different IncI2 plasmids, including one multidrug plasmid in E. coli, whereas fosA3-bla_NDM-9 was on an IncB/O plasmid in C. sakazakii The development of the fosA3-bla_NDM-9 resistance region was mediated by IS26 The colocation of mcr-1 or bla_NDM-9 with other resistance genes will accelerate the dissemination of the two genes.

Emergence of Acinetobacter pittii harboring New Delhi metallo-beta-lactamase genes in Daejeon, Korea

Carbapenemase production has been reported worldwide in gram-negative bacteria, including Acinetobacter species. We detected carbapenemase-producing Acinetobacter pittii in clinical isolates in Daejeon, Korea. Twenty-one ertapenem-resistant A. pittii isolates screened with a disk diffusion method were characterized by using the Epsilon test, four multiplex PCR assays, and a multilocus sequence typing (MLST) scheme. A total of 21 A. pittii isolates harbored the metallo-β-lactamase (MBL) gene bla(IMP-1) or bla(NDM-1). Nineteen isolates containing bla(IMP-1) were resistant to imipenem and meropenem, but two isolates harboring bla(NDM-1) were susceptible to them. The sequence types (STs) of the two New Delhi MBL (NDM-1)-producing A. pittii isolates were ST70 and ST207, which differed from the STs (ST63, ST119, ST396, and a novel ST) of the IMP-1-producing A. pittii. This is the first report on NDM-1-producing A. pittii isolates in Korea. Our results emphasize that the study of NDM-1-producing gram-negative bacteria should involve carbapenem-susceptible as well as carbapenem-resistant isolates.

Draft Genome Sequence of a Pseudomonas sp. Strain Carrying blaIMP-25 and blaVIM-2 Carbapenemase Genes from Hospital Sewage

Pseudomonas strain WCHP16 recovered from hospital sewage in West China Hospital, Chengdu, China was found to carry two carbapenemase genes bla_IMP-25 and bla_VIM-2. Here, we report its 5.7-Mb draft genome sequence, comprising 141 contigs and an average 59.53% G+C content. The genome contained 5,504 coding sequences and 67 tRNA genes.