NDM-producing Enterobacteriaceae in a Chinese hospital, 2014-2015: identification of NDM-producing Citrobacterwerkmanii and acquisition of blaNDM-1-carrying plasmid in vivo in a clinical Escherichia coli isolate

Identification of Providencia spp. clinical isolates co-producing carbapenemases IMP-27, OXA-24, and OXA-58 in Mexico

Providencia rettgeri, belonging to the genus Providencia, had gained significant interest due to its increasing prevalence as a common pathogen responsible for healthcare-associated infections in hospitals. P. rettgeri isolates producing carbapenemases have been reported to reduce the efficiency of carbapenems in clinical antimicrobial therapy. However, coexistence with other resistance determinants is rarely reported. The goal of this study was the molecular characterization of carbapenemase-producing Providencia spp. clinical isolates. Among 23 Providencia spp. resistant to imipenem, 21 were positive to blaNDM-1; one positive to blaNDM-1 and blaOXA-58 like; and one isolate co-producing blaIMP-27, blaOXA-24/40 like, and blaOXA-58 like were identified. We observed a low clonal relationship, and the incompatibility groups Col3M and ColRNAI were identified in the plasmid harboring blaNDM-1. We report for the first time a P. rettgeri strain co-producing blaIMP-27, blaOXA-24-like, and blaOXA-58 like. The analysis of these resistance mechanisms in carbapenemase co-producing clinical isolates reflects the increased resistance.

Horizontal transmission of a multidrug-resistant IncN plasmid isolated from urban wastewater

Wastewater treatment plants (WWTPs) are considered reservoirs of antibiotic resistance genes (ARGs). Given that plasmid-mediated horizontal gene transfer plays a critical role in disseminating ARGs in the environment, it is important to inspect the transfer potential of transmissible plasmids to have a better understanding of whether these mobile ARGs can be hosted by opportunistic pathogens and should be included in One Health's considerations. In this study, we used a fluorescent-reporter-gene based exogenous isolation approach to capture extended-spectrum beta-lactamases encoding mobile determinants from sewer microbiome samples that enter an urban water system (UWS) in Denmark. After screening and sequencing, we isolated a ∼73 Kbp IncN plasmid (pDK_DARWIN) that harboured and expressed multiple ARGs. Using a dual fluorescent reporter gene system, we showed that this plasmid can transfer into resident urban water communities. We demonstrated the transfer of pDK_DARWIN to microbiome members of both the sewer (in the upstream UWS compartment) and wastewater treatment (in the downstream UWS compartment) microbiomes. Sequence similarity search across curated plasmid repositories revealed that pDK_DARWIN derives from an IncN backbone harboured by environmental and nosocomial Enterobacterial isolates. Furthermore, we searched for pDK_DARWIN sequence matches in UWS metagenomes from three countries, revealing that this plasmid can be detected in all of them, with a higher relative abundance in hospital sewers compared to residential sewers. Overall, this study demonstrates that this IncN plasmid is prevalent across Europe and an efficient vector capable of disseminating multiple ARGs in the urban water systems.

A critical role of outer membrane vesicles in antibiotic resistance in carbapenem-resistant Klebsiella pneumoniae

BACKGROUND

This study aimed to illustrate the status of carbapenem-resistant Enterobacterales (CRE) infections in a Chinese tertiary hospital and to investigate the role of outer membrane vesicles (OMVs) in antibiotic resistance in carbapenem-resistant Klebsiella pneumoniae (CRKP).

METHODS

The data of CRE infections was collected from laboratory records, and the CRE isolates from two distinct periods (2015/07 to 2017/07 and 2020/04 to 2021/04) were enrolled to detect the carbapenemase genes by polymerase chain reaction (PCR). Multilocus sequence typing (MLST) was used to analyze the molecular characterization of CRKP. The conjugation assay was performed to verify the transmission of the antibiotic resistance plasmid. The OMVs of CRKP were isolated with a method combining an electrophoretic technique with a 300 kDa cut-off dialysis bag. The protein components in CRKP OMVs were analyzed by liquid chromatography tandem-mass spectrometry (LC-MS/MS), and the meropenem-hydrolyzing bioactivity of KPC in CRKP OMVs was determined with different treatments in vitro.

RESULTS

A total of 178 CRE isolates, including 100 isolates from 2015/07 to 2017/07 and 78 isolates from 2020/04 to 2021/04, were collected for the detection of carbapenemase genes. We found that the carbapenemase gene blaKPC was the most prevalent, followed by blaNDM. By MLST, we found that sequence type (ST) 11 CRKP (96.1%) was the leading type during 2015/07 to 2017/07 and that the ST15 CRKP increased to 46.2% in the late period of 2020/04 to 2021/04. The diameters of Klebsiella pneumoniae OMVs ranged from 100 to 200 nm, and by proteomics analysis the most proteins from OMVs belonged to the "enzyme" group. The KPC enzyme was found in the OMVs from CRKP, and the OMVs could protect inside KPC from proteinase K digestion. Moreover, the KPC enzymes within OMVs, which could be released after Triton X-100 treatment, could hydrolyze meropenem.

CONCLUSIONS

CRE has increasingly caused infections in hospitals, and blaKPC-positive CRKP infections have constituted a major proportion of infections in the past decade. The OMVs play a critical role in antibiotic resistance in CRKP.

Whole genome-based genetic insights of blaNDM producing clinical E. coli isolates in hospital settings of Pakistan

Carbapenem resistance among Enterobacterales has become a global health concern. Clinical Escherichia coli isolates producing the metallo β-lactamase NDM have been isolated from two hospitals in Faisalabad, Pakistan. These E. coli strains were characterized by MALDI-TOF, PCR, antimicrobial susceptibility testing, XbaI and S1 nuclease pulsed-field gel electrophoresis (PFGE), conjugation assay, DNA hybridization, whole genome sequencing, bioinformatic analysis, and Galleria mellonella experiments. Thirty-four blaNDM producing E. coli strains were identified among 52 nonduplicate carbapenem-resistant strains. More than 90% of the isolates were found to be multidrug resistant by antimicrobial susceptibility testing. S1 PFGE confirmed the presence of blaNDM gene on plasmids ranging from 40 kbps to 250 kbps, and conjugation assays demonstrated transfer frequencies of blaNDM harboring plasmids ranging from 1.59 × 10-1 to 6.46 × 10-8 per donor. Whole genome sequencing analysis revealed blaNDM-5 as the prominent NDM subtype with the highest prevalence of blaOXA-1, blaCTX-M-15, aadA2, aac(6')-Ib-cr, and tet(A) associated resistant determinants. E. coli sequence types: ST405, ST361, and ST167 were prominent, and plasmid Inc types: FII, FIA, FIB, FIC, X3, R, and Y, were observed among all isolates. The genetic environment of blaNDM region on IncF plasmids included partial ISAba125, the bleomycin ble gene, and a class I integron. The virulence genes terC, traT, gad, fyuA, irp2, capU, and sitA were frequently observed, and G. mellonella experiments showed that virulence correlated with the number of virulence determinants. A strong infection control management in the hospital is necessary to check the emergence of carbapenem resistance in Gram-negative bacteria.IMPORTANCEWe describe a detailed analysis of highly resistant clinical E. coli isolates from two tertiary care centers in Pakistan including carbapenem resistance as well as common co-resistance mechanisms. South Asia has a huge problem with highly resistant E. coli. However, we find that though these isolates are very difficult to treat they are of low virulence. Thus the Western world has an increasing problem with virulent E. coli that are mostly of low antibiotic resistance, whereas, South Asia has an increasing problem with highly resistant E. coli that are of low virulence potential. These observations allow us to start to devise methodologies to limit both virulence and resistance and combat problems in developing nations as well as the Western world.

Whole Genome Sequencing of an Extensively Drug-Resistant Raoultella planticola Isolate Containing blaKPC-2, blaNDM-1, and blaCTX-M-15

Raoultella planticola harboring genes that confer resistance to antimicrobials, such as carbapenems, have been associated with severe infections in immunocompromised patients. In this study, we reported the first whole genome sequence of a Brazilian isolate of R. planticola and the genomic context of antibiotic resistance markers. By whole-genome sequencing (WGS) of a carbapenem-resistant R. planticola isolate, RpHUM1, we found 23 resistance-encoding genes belonging to 9 classes of antibiotics (aminoglycosides, β-lactams, fluoroquinolones, fosfomycin, macrolides, phenicols, sulfonamides, tetracycline, and diaminopyrimidine derivatives) and 3 plasmids (RpHUM1pEaer-4382s, RpHUM1_pFDAARGOS_440, and RpHUM1pRSF1010). This isolate coharbored the genes blaKPC-2, which is carried by the plasmid RpHUM1pEaer-4382s, and blaNDM-1 and blaCTX-M-15 all located in the accessory genome. In addition, these genes were associated with, at least, one mobile genetic element. This comprehensive knowledge is of great importance for implementation of control measures to prevent the rapid dissemination of this neglected microorganism and their genetic resistance background.

Detection of NDM-1 and OXA-10 Co-Producing Providencia rettgeri Clinical Isolate

Background

The coexistence of blaNDM-1 with other resistance determinants is rarely reported for Providencia rettgeri. Therefore, this study investigates the phenotypic and genetic characteristics of a multidrug-resistant P. rettgeri strain YQ150713.

Methods

P. rettgeri YQ150713 was identified as carrying blaNDM-1. S1-pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, and conjugation experiments were used to determine plasmid characteristics. An antimicrobial susceptibility test was conducted. The complete genomic sequence of YQ150713 was obtained using Illumina NovaSeq 6000 and Oxford nanopore platforms. To further characterize the phylogenetic structure of P. rettgeri YQ150713, average nucleotide identity (ANI) and phylogenetic analyses were conducted.

Results

The S1-PFGE, Southern blot, and conjugation assays have confirmed that the isolate P. rettgeri YQ150713 contains the blaNDM-1 gene on a conjugative plasmid pYQ150713-NDM-1. Antimicrobial susceptibility testing has indicated that strain YQ150713 was resistant to various common antibiotics, except aztreonam and fosfomycin. Bioinformatics analysis has further shown that pYQ150713-NDM-1 was a novel plasmid with a size of 265,883 bp, and blaNDM-1 and blaOXA-10 were co-located on it. Phylogenetic analysis suggesting P. rettgeri has spread widely throughout the world.

Conclusion

In this study, blaNDM-1 and blaOXA-10 were co-localized on a novel plasmid pYQ150713-NDM-1 with a horizontal transfer function. To reduce the risk of the dissemination of such P. rettgeri isolates in clinical settings, more surveillance will be required in the future.

Genomic characterization of carbapenem-resistant Klebsiella oxytoca complex in China: a multi-center study

Carbapenem-resistant (CR) Klebsiella oxytoca complex can be associated with high mortality, emerging as a new threat to the public health. K. oxytoca complex is phylogenetically close to K. pneumoniae, one of most common species associated with multidrug resistance in Enterobacterale. The latest research showed that K. oxytoca is a complex of six species. Currently, the epidemiological and genomic characteristics of CR K. oxytoca complex in China are still unclear. Here, we conducted a multi-center study on 25 CR K. oxytoca complex collected from five representative regions in China. These isolates were, respectively, recovered from respiratory tract (12 cases, 48.0%), abdominal cavity (5 cases, 20.0%), blood (4 cases, 16.0%), urine tract (3 cases, 12.0%) and skin or soft tissue (1 cases, 4.0%). Among them, 32.0% (8/25) of patients infected with K. oxytoca complex had a poor prognosis. In this study, three K. oxytoca complex species were detected, namely K. michiganensis, K. oxytoca and K. pasteurii, among which K. michiganensis was the most common. Three carbapenemase genes were identified, including bla_NDM-1 (10, 38.5%), bla_KPC-2 (9, 34.6%) and bla_IMP (6 bla_IMP-4 and 1 bla_IMP-8; 7, 26.9%). Subsequent multilocus sequence typing identified various sequence types (STs), among which ST43, ST92 and ST145 were relatively common. Different from the clonal dissemination of high-risk carbapenem-resistant K. pneumoniae strains, our research revealed a polyclonal dissemination characteristic of CR K. oxytoca complex in China. S1-nuclease PFGE and Southern blot experiment showed that carbapenemase genes were encoded in plasmids of different sizes. Two bla_NDM-harboring plasmids were subsequently sequenced, and were characterized to be IncX3 and IncC incompatibility groups, respectively. This is the first multi-center study of CR K. oxytoca complex in China, which improved our understanding of the prevalence and antimicrobial resistance characteristics of CR K. oxytoca complex in China.

High prevalence and genomic characteristics of carbapenem-resistant Enterobacteriaceae and colistin-resistant Enterobacteriaceae from large-scale rivers in China

The widespread presence of carbapenem-resistant Enterobacteriaceae (CRE) and mcr-positive Escherichia coli (MCREC) poses a huge threat to both animal and human health. River water environments are vital reservoirs of antibiotic resistance genes, however, the prevalence and characteristics of CRE and MCREC from large-scale rivers in China have not been reported. In the current study, we sampled 86 rivers from four cities in Shandong Province, China in 2021 and analyzed the prevalence of CRE and MCREC. The bla_NDM/bla_KPC-2/mcr-positive isolates were characterized with methods including PCR, antimicrobial susceptibility testing, conjugation, replicon typing, whole-genome sequencing and phylogenetic analysis. We found that the prevalence of CRE and MCREC in 86 rivers was 16.3% (14/86) and 27.9% (24/86), respectively and eight rivers carried both mcr-1 and bla_NDM/bla_KPC-2. A total of 48 Enterobacteriaceae isolates (10 ST11 Klebsiella pneumoniae with bla_KPC-2, 12 bla_NDM-positive E. coli and 26 MCREC carrying only mcr-1) were obtained in this study and 47 displayed multidrug resistance (MDR). Notably, 10 of the 12 bla_NDM-positive E. coli isolates also harbored the mcr-1 gene. The bla_KPC-2 gene was located within mobile element ISKpn27-bla_KPC-2-ISKpn6 on novel F33:A-:B- non-conjugative MDR plasmids in ST11 K. pneumoniae. The dissemination of bla_NDM was mediated by transferable MDR IncB/O plasmids or IncX3 plasmids while mcr-1 was primarily disseminated by highly similar IncI2 plasmids. Notably, these waterborne IncB/O, IncX3 and IncI2 plasmids were all highly similar to previously identified plasmids from animal and human isolates. A phylogenomic analysis revealed that the CRE and MCREC isolates from water environments might be derived from animals and trigger infections in humans. The high prevalence of CRE and MCREC in large-scale environmental rivers is alarming and needs sustained surveillance due to the potential risk for transmission to humans via the food chain (irrigation) or direct contact.

Emergence of blaNDM-1, blaNDM-5, blaKPC-2 and blaIMP-4 carrying plasmids in Raoultella spp. in the environment

To date, carbapenem-resistant Enterobacteriaceae have been found predominantly in clinical settings worldwide. Raoultella belongs to the Enterobacteriaceae family which can cause hospital-acquired infections, and carbapenem-resistant Raoultella spp. (CRR) is sporadically reported in the environment. We investigated the distribution and underlying resistance mechanisms of CRR in a wastewater treatment plant (WWTP) from eastern China between January 2018 and February 2019. A total of 17 CRR were isolated from 324 environmental samples, including Raoultella ornithinolytica (n = 15) and Raoultella planticola (n = 2). The detection of CRR was more frequent in the water inlet compared to anaerobic tank, aerobic tank, sludge thickener, activated sludge, mud cake storage area, and water outlet, and CRR was detected in mud cake stacking area. All CRR were resistant to imipenem, meropenem, ampicillin, piperacillin-tazobactam, cefotaxime, ceftazidime, trimethoprim-sulfamethoxazole and fosfomycin. Four different carbapenemase genes were identified, including bla_KPC-2 (n = 13), bla_NDM-1 (n = 8), bla_NDM-5 (n = 1), bla_IMP-4 (n = 1). Interestingly, isolated R. ornithinolytica from the WWTP were closely related to those reported from human samples in China. Plasmid analysis indicated that IncFII(Yp), IncP6, and IncU mediated bla_KPC-2 spread, IncX3 and IncN2 mediated bla_NDM spread in the environment. The core structure of the Tn3-ISKpn27-bla_KPC-2-ISKpn6, ISAba125-bla_NDM-ble_MBL-trpF-dsbD were identified. The study provides evidence that Raoultella spp. may spread alarming carbapenem resistance in the environment and, therefore, the continuous surveillance for carbapenem resistance in the WWTP should be conducted, especially sludge.

Description of a new non-Tn4401 element (NTEKPC-IIe) harboured on IncQ plasmid in Citrobacter werkmanii from recreational coastal water

OBJECTIVES

Here we describe an IncQ1-like plasmid carrying blaKPC-2 in a new non-Tn4401 element found in Citrobacter werkmanii recovered from coastal water.

METHODS

In vitro and in silico approaches were used to assess antimicrobial resistance determinants, as well as blaKPC-2 vicinities.

RESULTS

The LB-887 isolate showed a multidrug-resistant phenotype and was identified as C. werkmanii. Resistome analysis identified further acquired resistance determinants to β-lactams, aminoglycosides, sulphonamides/trimethoprim, tetracyclines, chloramphenicol, macrolides, rifampicin and fluoroquinolones. Plasmidome included incompatibility groups IncA, IncC2, IncR, Col and IncQ families. The blaKPC-2 was inserted on a new variant of NTEKPC-II, called here NTEKPC-IIe, carried by an InQ1-like plasmid of 7930 kb (pKPC-LB887). NTEKPC-IIe differed from NTEKPC-IId by the complete absence of ISKpn6-tnpA. The InQ1-like backbone harbouring this element had been described in Enterobacterales recovered from clinical and environmental settings.

CONCLUSION

Unravelling genetic structures related to blaKPC dissemination in different settings may provide clues on the main forces driving evolution of this important resistance determinant. Indeed, the occurrence of blaKPC in a new NTEKPC variant from an environmental source highlights the ongoing evolution of this mobile genetic element. In addition, blaKPC carriage on a small and highly mobilizable IncQ plasmid in C. freundii complex from recreational water, similar to others found in clinical isolates, may suggest its relevance for blaKPC-2 dissemination among different compartments.

Persistence and Dissemination Capacities of a BlaNDM-5-Harboring IncX-3 Plasmid in Escherichia coli Isolated from an Urban River in Montpellier, France

To investigate the capacities of persistence and dissemination of bla_NDM-5 within Escherichia coli and in aquatic environment, we characterized E. coli (sequence type 636) strains B26 and B28 isolated one month apart from the same urban river in Montpellier, France. The two isolates carried a pTsB26 plasmid, which sized 45,495 Kb, harbored bla_NDM-5 gene and belonged to IncX-3 incompatibility group. pTsB26 was conjugative in vitro at high frequency, it was highly stable after 400 generations and it exerted no fitness cost on its host. bla_NDM-5harboring plasmids are widely dispersed in E. coli all around the world, with no lineage specialization. The genomic comparison between B26 and B28 stated that the two isolates probably originated from the same clone, suggesting the persistence of pTsB26 in an E. coli host in aquatic environment.

Occurrence of NDM-1, VIM-1, and OXA-10 Co-Producing Providencia rettgeri Clinical Isolate in China

Providencia rettgeri is a nosocomial pathogen associated with urinary tract infections related to hospital-acquired Infections. In recent years, P. rettgeri clinical strains producing New Delhi Metallo-β-lactamase (NDM) and other β-lactamase which reduce the efficiency of antimicrobial therapy have been reported. However, there are few reports of P. rettgeri co-producing two metallo-β-lactamases in one isolate. Here, we first reported a P. rettgeri strain (P138) co-harboring bla_NDM-1, bla_VIM-1, and bla_OXA-10. The specie were identified using MALDI-TOF MS. The results of antimicrobial susceptibility testing by broth microdilution method indicated that P. rettgeri P138 was resistant to meropenem (MIC = 64μg/ml), imipenem (MIC = 64μg/ml), and aztreonam (MIC = 32μg/ml). Conjugation experiments revealed that the bla_NDM-1-carrying plasmid was transferrable. The carbapenemase genes were detected using PCR and confirmed by PCR-based sequencing. The complete genomic sequence of the P. rettgeri was identified using Illumina (Illumina, San Diego, CA, USA) short-read sequencing (150bp paired-end reads), and many common resistance genes had been identified, including bla_NDM-1, bla_VIM-1, bla_OXA-10, aac(6’)-Il, aadA5, ant(2’’)-Ia, aadA1, aac(6’)-Ib3, aadA1, aph(3’)-Ia, aac(6’)-Ib-cr, qnrD1, qnrA1, and catA2. The bla_NDM-1 gene was characterized by the following structure: IS110–TnpA–IntI1–aadB–IS91–GroEL–GroES–DsbD–PAI–ble–bla_NDM-1–IS91–QnrS1–IS110. Blast comparison revealed that the bla_NDM-1 gene structure shared >99% similarity with plasmid p5_SCLZS62 (99% nucleotide identity and query coverage). In summary, we isolated a P. rettgeri strain coproducing bla_NDM-1, bla_VIM-1, and blaOXA-10. To the best of our acknowledge, this was first reported in the world. The occurrence of the strain needs to be closely monitored.

Using Whole Genome Sequencing to Trace, Control and Characterize a Hospital Infection of IMP-4-Producing Klebsiella pneumoniae ST2253 in a Neonatal Unit in a Tertiary Hospital, China

Background: The purpose of this study is to use whole genome sequencing (WGS) combined with epidemiological data to track a hospital infection of the carbapenem-resistant Klebsiella pneumoniae (CRKP), which affected 3 neonatal patients in the neonatal intensive care unit (NICU). Methods: The minimum inhibitory concentrations for the antimicrobial agents were determined according to the guidelines of the Clinical and Laboratory Standards Institute. Beta-lactamases were investigated using the polymerase chain reaction and DNA sequencing. The transferability of the plasmid was investigated by a conjugation experiment. The clonal relationships were evaluated using multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). WGS and single nucleotide polymorphisms (SNPs) analysis were performed on the CRKP isolates to investigate how the infection might progress. Results: Nine CRKP isolates were obtained from the NICU, seven from three patients, one from a duster cloth and one from the hand of a nurse, they all harbored blaIMP-4. Other resistance genes including blaKPC-2, blaIMP-4, blaSHV-1, blaTEM-1, blaCTX-M-15, and blaDHA-1 were also detected. PFGE analysis showed that IMP-4-producing K. pneumoniae were clonally related, and MLST assigned them to a new sequence type 2253. The SNP variations throughout the genome divided the 9 strains into three clades. Clade 1 comprised 7 strains (K1- K2 and K4-K8), whereas clade 2 and 3 consisted of only one strain each: K3 and K9, respectively.The sputum isolate K3 from patient 3 was the most distinct one differing from the other eight isolates by 239-275 SNPs. Conclusions: This is a report of using WGS to track a hospital infecion of IMP-4-producing K. pneumoniae ST2253 among neonates. Nosocomial surveillance systems are needed to limit the spread of the infection caused by these pathogens resulting from the environmental exposure in NICUs.

Klebsiella oxytoca Complex: Update on Taxonomy, Antimicrobial Resistance, and Virulence

Klebsiella oxytoca is actually a complex of nine species-Klebsiella grimontii, Klebsiella huaxiensis, Klebsiella michiganensis, K. oxytoca, Klebsiella pasteurii, Klebsiella spallanzanii, and three unnamed novel species. Phenotypic tests can assign isolates to the complex, but precise species identification requires genome-based analysis. The K. oxytoca complex is a human commensal but also an opportunistic pathogen causing various infections, such as antibiotic-associated hemorrhagic colitis (AAHC), urinary tract infection, and bacteremia, and has caused outbreaks. Production of the cytotoxins tilivalline and tilimycin lead to AAHC, while many virulence factors seen in Klebsiella pneumoniae, such as capsular polysaccharides and fimbriae, have been found in the complex; however, their association with pathogenicity remains unclear. Among the 5,724 K. oxytoca clinical isolates in the SENTRY surveillance system, the rates of nonsusceptibility to carbapenems, ceftriaxone, ciprofloxacin, colistin, and tigecycline were 1.8%, 12.5%, 7.1%, 0.8%, and 0.1%, respectively. Resistance to carbapenems is increasing alarmingly. In addition to the intrinsic bla_OXY, many genes encoding β-lactamases with varying spectra of hydrolysis, including extended-spectrum β-lactamases, such as a few CTX-M variants and several TEM and SHV variants, have been found. bla_KPC-2 is the most common carbapenemase gene found in the complex and is mainly seen on IncN or IncF plasmids. Due to the ability to acquire antimicrobial resistance and the carriage of multiple virulence genes, the K. oxytoca complex has the potential to become a major threat to human health.

Recent research and development of NDM-1 inhibitors

Bacteria carrying New Delhi metallo-β-lactamase-1 (New Delhi metallo-β-lactamase, NDM-1) resistance gene is a new type of "superbug", which can hydrolyze almost all β-lactam antibiotics, rapidly spread among the same species and even spread among different species. NDM-1 belongs to the class B1 broad-spectrum enzyme of β-lactamase. The two positively charged zinc ions in the active center have electrostatic interaction with the hydroxyl ions in them to seize the hydrogen atom near the water molecule to form a bridging ring water molecule, which strengthens its nucleophilicity and attacks the carbonyl group on the lactam ring; thus, catalyzing the hydrolysis of β-lactam antibiotics. Since NDM-1 has an open active site and unique electrostatic structure, it essentially provides a wider range of substrate specificity. Due to its flexible hydrolysis mechanism and more and more variants also aggravate the threat of drug-resistant bacteria infection, there is still no effective inhibitor in clinic, which is a serious threat to human health and public health safety. The electron-rich substituents of NDM-1 inhibitors coordinate with two positively charged zinc ions in the active center of the enzyme through ion-dipole interaction to produce NDM-1 inhibitory activity. In this review, the research progress of NDM-1 enzyme and its inhibitors in the past 5 years was reviewed. The crystal structure, active center structure, surrounding important amino acid residues, newly discovered inhibitors and their action mechanism are classified and summarized in detail, which can be used as a reference for the development of effective drugs against drug-resistant bacteria targeting NDM-1.

Whole Genomic analysis of a clinical isolate of Uropathogenic Escherichia coli strain of Sequence Type - 101 carrying the drug resistance NDM-7 in IncX3 plasmid

The emerging NDM-producing Enterobactereciae is a major threat to public health. The association of NDM-7 with sequence type 101 E.coli is identified in very few numbers. Therefore, it is of interest to analyse the whole genome sequence of NDM-producing uropathogenic E. coli XA31 that was found to carry numerous drug resistance genes of different antibiotic classes. The isolate E. coli belongs to ST-101 carrying blaNDM-7 coexisting with several resistance genes blaOXA-1, blaTEM1-A, blaCTX-M15, aac(6')-Ib-cr, catB3, tetB. Resfinder predicts this and four other plasmid replicons were identified using the Plasfinder in the CGE platform. The high transferable IncX3 plasmid was found to carry the NDM-7 gene. Thus, we the report the combination of NDM-7-ST101-IncX3 in India. The combination of this epidemic clone with NDM-7 is highly required to develop an effective infection control strategy.

First report of a blaNDM-resistant gene in a Klebsiella aerogenes clinical isolate from Brazil

INTRODUCTION:

Carbapenemase-resistant enterobacteria that produce the bla_NDM gene are found worldwide. However, this is the first report of bla_NDM in Klebsiella aerogenes in Brazil.

METHODS:

The identification of bacterial species was performed using anautomated system and confirmed by biochemical tests, 16S rRNA gene sequencing, and detection of resistance genes.

RESULTS:

The clinical isolate showed minimum inhibitory concentration resistance to meropenem and polymyxin B at 8mg/L and 4mg/L, respectively. Only the bla_NDM gene was detected.

CONCLUSIONS:

The current report of the bla_NDM gene in isolated MDR enterobacteria indicates that this gene can spread silently in a hospital setting.

The Hydric Environment: A Hub for Clinically Relevant Carbapenemase Encoding Genes

Carbapenems are β-lactams antimicrobials presenting a broad activity spectrum and are considered as last-resort antibiotic. Since the 2000s, carbapenemase producing Enterobacterales (CPE) have emerged and are been quickly globally spreading. The global dissemination of carbapenemase encoding genes (CEG) within clinical relevant bacteria is attributed in part to its location onto mobile genetic elements. During the last decade, carbapenemase producing bacteria have been isolated from non-human sources including the aquatic environment. Aquatic ecosystems are particularly impacted by anthropic activities, which conduce to a bidirectional exchange between aquatic environments and human beings and therefore the aquatic environment may constitute a hub for CPE and CEG. More recently, the isolation of autochtonous aquatic bacteria carrying acquired CEG have been reported and suggest that CEG exchange by horizontal gene transfer occurred between allochtonous and autochtonous bacteria. Hence, aquatic environment plays a central role in persistence, dissemination and emergence of CEG both within environmental ecosystem and human beings, and deserves to be studied with particular attention.

Epidemiology of Enterobacter cloacae strains producing a carbapenemase or metallo-beta-lactamase in Vietnamese clinical settings in 2014-2017

Introduction. Little is known about the epidemiology of Enterobacter cloacae strains producing a carbapenemase or metallo-beta-lactamase in Vietnamese hospitals.Aim. This study analysed E. cloacae strains resistant to imipenem or meropenem that had been isolated from patients admitted to one of the largest hospitals in Vietnam in 2014-2017.Methodology. Eighteen Vietnamese (VN) strains were subjected to whole-genome sequencing and their sequences compared with those of 17 E. cloacae strains carrying a carbapenemase or metallo-beta-lactamase in the database (db strains).Results. Although the distribution of virulence factors did not differ significantly between VN and db strains, all 18 VN isolates harboured blaNDM-1, phylogenetic analysis revealed a high clonality of the VN strains. Bayesian phylogenetic analysis suggested that the VN strains speciated relatively recently.Conclusions. Several prevalent clones of carbapenem-resistant E. cloacae have circulated within Vietnamese hospitals. Adequate measures are needed to prevent their further spread.

Resistance of Klebsiella pneumoniae Strains Carrying bla NDM-1 Gene and the Genetic Environment of bla NDM-1

OBJECTIVE

Regional dissemination is the major cause of the widespread prevalence of a plasmid-encoding NDM-1 enzyme. We investigated the drug resistance, joint efficiency, and gene environment of a Klebsiella pneumoniae strain carrying bla NDM-1 gene.

MATERIALS AND METHODS

Carbapenem-non-susceptible strains were analyzed using the VITEK 2 Compact. Strains carrying bla NDM-1 were identified using polymerase chain reaction and sequencing. Antimicrobial susceptibility testing and plasmid conjugation experiments were then conducted. Strains carrying bla NDM-1 were subjected to Southern blot analysis. After the gene mapping of bla NDM-1, library construction, and sequencing, plasmids were subsequently spliced and genotyped using the software Glimmer 3.0, and then analyzed using Mauve software.

RESULTS

Among 1735 carbapenem-non-susceptible strains, 54 strains of bla NDM-1-positive bacteria were identified, which consisted of 44 strains of K. pneumoniae, 8 strains of Acinetobacter baumannii and 2 strains of Escherichia coli. Strains carrying bla NDM-1 had a resistance rate of more than 50% in most antibiotics. Plasmid conjugation between strains carrying bla NDM-1 and E. coli strain J53 had a success rate of 50%. Southern blot analysis indicated that each strain had multiple plasmids containing bla NDM-1. Among the five plasmids containing bla NDM-1 in K. pneumoniae for sequencing, two plasmids with complete sequences were obtained. The findings were as follows: (i) The p11106 and p12 plasmids were highly similar to pNDM-BTR; (ii) the p11106 and p12 plasmids showed differences in the 20-30 kb region (orf00032-orf00043) from the other six plasmids; and (iii) bla NDM-1 was located at orf00037, while ble was found at orf00038. Two tnpA genes were located in the upstream region, and orf00052 (tnpA) in the 36 kb region was in the downstream sequence.

CONCLUSION

bla NDM-1-containing bacteria exhibit multidrug resistance, which rapidly spreads and is transferred through efficient plasmid conjugation; the multidrug resistance of these bacteria may be determined by analyzing their drug-resistant plasmids. The presence of ble and tnpA genes suggests a possible hypothesis that bla NDM-1 originates from A. baumannii, which is retained in K. pneumoniae over a long period by transposition of mobile elements.

NDM-1-producing Escherichia coli isolated from pigs induces persistent infection with limited pathogenicity

NDM-1-producing Enterobacteriaceae are multidrug-resistant bacteria, also called superbacteria, that have become important global human health threats in recent years. However, data about NDM-1-producing bacteria in animals are rare. In this study, an NDM-1-producing Escherichia coli isolate (designated E120413) was obtained from pigs in Henan province, China in 2012. The susceptibility of E. coli E120413 to antimicrobial agents was determined using Kirby-Bauer disk diffusion and micro-dilution methods. Susceptibility tests indicated that E. coli E120413 was resistant to almost all common antibiotics with high MIC values obtained for most antibiotics tested. E. coli E120413 was detected in the heart, liver, spleen, lung, kidney, brain, stomach, duodenum, mesenteric lymph nodes, and fecal samples of piglets in both cohabitation and experimental groups and the bacteria persisted for more than 2 weeks. However, no obvious clinical symptoms or serious pathological lesions were observed. This is the first investigation of NDM-1-producing E. coli isolate from pigs in China. Although no significant pathological lesions were observed, NDM-1-producing E. coli was found to be highly transmissible and to cause persistent infection in pigs.

Simultaneous three Enterobacteriaceae with different bla NDM-1-encoding plasmids in a patient transferred from mainland China to Taiwan

New-Delhi metallo-β-lactamase1 (NDM-1) Enterobacteriaceae are increasing worldwide. Herein, we describe a single patient who carried three unusual NDM-1 carbapenem-resistant Enterobacteriaceae – Enterobacter cloacae (E. cloacae) yielded from a urine specimen and Klebsiella pneumoniae (K. pneumoniae) and Escherichia coli (E. coli) from stool specimens. For E. cloacae, its bla NDM-1-encoding plasmid was pKP04NDM with a size of ~54 kb replicons with an IncN backbone. For K. pneumoniae, its bla_NDM-1-encoding plasmid was pNDM-BTR with a size of ~59.6 kb and belonged to IncN. For E. coli, its main bla_NDM-1-encoding plasmid was pIMP-HK1500, and the NDM-1 gene was obtained from a part of pNDM-BTR (8439 bp). These three clinical strains are reported for the first time and are assumed to be imported from mainland China to Taiwan. The three different plasmids were never reported in K. pneumoniae, E. coli, and Citrobacter spp before. Owing to their associated multidrug resistance, appropriate measures of periodic, targeted surveillance, and development of new antimicrobial agents are urgently needed.

Occurrence of blaNDM Variants Among Enterobacteriaceae From a Neonatal Intensive Care Unit in a Northern India Hospital

Carbapenem-resistance among enterobacteriaceae has become a global health concern. The objective of this study was to understand NDM producing enterobacteriaceae and their genetic basis of resistance, spreading in neonatal intensive care unit. Carbapenem resistant NDM producing enterobacteriaceae isolates were recovered from rectal swab and blood sample of infants admitted in NICU. These were determined by using Carba-NP test. All isolates were identified using BD Phoenix^TM−100 and MICs were determined by broth microdilution method. The bla_NDM and associated resistant markers were checked by PCR followed by sequencing. Moreover, ERIC-PCR and genetic environment of bla_NDM gene were also performed for the analysis of clonal relationship and genetic surrounding of the strains. We characterized 44 isolates with bla_NDM variants in Escherichia coli (45.5%), Klebsiella pneumoniae (40.9%), Citrobacter freundii (4.5%), Citrobacter braakii (2.3%), Klebsiella oxytoca (2.3%), Enterobacter cloacae (2.3%), Enterobacter aerogenes (2.2%) from NICU, showing resistance against all antibiotics except colistin and polymixin B. ISAba125 and bleomycin gene were found surrounding all bla_NDM variants, besides class I integron on plasmid. (ERIC)-PCR data revealed non-clonal relatedness among most of the isolates. The transfer of resistant markers was confirmed by conjugation experiment. The PCR-based replicon typing was carried out using DNA of transconjugants. These isolates carried NDM-1 (20.45%), NDM-4 (36.36%), NDM-5 (38.64%), NDM-7 (4.55%), along with OXA, CMY, and SHV variants on conjugative plasmid of IncFIA, IncFIC, IncF, IncK, IncFIB, IncB/O, IncHI1, IncP, IncY, IncFIIA, IncI1, and IncN types. An increased number of carbapenem-resistant NDM producing enterobacteriaceae isolates recovered from NICU which is alarming signal for health workers and policy makers. Hence, it is utmost important to think about infection control measures.

Molecular characterization of clinical IMP-producing Klebsiella pneumoniae isolates from a Chinese Tertiary Hospital

BACKGROUND

IMP-producing Klebsiella pneumoniae (IMPKpn) exhibits sporadic prevalence in China. The mechanisms related to the spread of IMPKpn remain unclear.

METHODS

Carbapenem non-susceptible K. pneumoniae isolates were collected from our hospital. The genetic relatedness, antimicrobial susceptibility, as well as sequence types (ST) were analyzed by pulsed-field gel electrophoresis (PFGE), VITEK 2 AST test Kit, and multilocus sequence typing (MLST), respectively. S1-PFGE, Southern blot analysis and multiple PCR amplification were used for plasmid profiling.

RESULTS

Between October 2009 and June 2016, 25 non-repetitive IMPKpn isolates were identified. PFGE results showed that these isolates belonged to 20 genetically unrelated IMPKpn strains. Diverse STs were identified by MLST. Most strains carried bla IMP-4, followed by bla IMP-1. Four incompatibility types of bla IMP-carrying plasmids were identified, which included A/C (n = 2), B/O (n = 2), L/M (n = 1) and N (n = 14), while type of other one plasmid failed to be determined.

CONCLUSIONS

The IMPKpn isolates exhibited sporadic prevalence in our hospital. IncN types of plasmids with various sizes have emerged as the main platform mediating the spread of the bla IMP genes in our hospital.

Structure, Genetics and Worldwide Spread of New Delhi Metallo-β-lactamase (NDM): a threat to public health

Background

The emergence of carbapenemase producing bacteria, especially New Delhi metallo-β-lactamase (NDM-1) and its variants, worldwide, has raised amajor public health concern. NDM-1 hydrolyzes a wide range of β-lactam antibiotics, including carbapenems, which are the last resort of antibiotics for the treatment of infections caused by resistant strain of bacteria.

Main body

In this review, we have discussed bla_NDM-1variants, its genetic analysis including type of specific mutation, origin of country and spread among several type of bacterial species. Wide members of enterobacteriaceae, most commonly Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and gram-negative non-fermenters Pseudomonas spp. and Acinetobacter baumannii were found to carry these markers. Moreover, at least seventeen variants of bla_NDM-type gene differing into one or two residues of amino acids at distinct positions have been reported so far among different species of bacteria from different countries. The genetic and structural studies of these variants are important to understand the mechanism of antibiotic hydrolysis as well as to design new molecules with inhibitory activity against antibiotics.

Conclusion

This review provides a comprehensive view of structural differences among NDM-1 variants, which are a driving force behind their spread across the globe.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-1012-8) contains supplementary material, which is available to authorized users.

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.

Outbreak of nosocomial NDM-1-producing Klebsiella pneumoniae ST1419 in a neonatal unit

OBJECTIVES

The aim of this study was to characterise carbapenem-resistant Klebsiella pneumoniae isolates recovered from neonatal clinical specimens over a 4-month period.

METHODS

Seven carbapenem-resistant K. pneumoniae isolates were analysed. Antibiotic susceptibilities of the isolates were determined by the agar dilution method, and the drug resistance genes were evaluated by PCR. Clonal relatedness of the isolates was assessed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Conjugation experiments and Southern blot hybridisation were performed to determine the transferability of the plasmids.

RESULTS

All of the K. pneumoniae isolates carried the bla_NDM-1 gene but were negative for all other carbapenemases tested. All of the isolates harboured bla_SHV-12, and five isolates also carried bla_CTX-M-15 and/or bla_TEM-1. All of the isolates exhibited multidrug resistance. The isolates belonged to sequence types ST1419 and ST101 and formed three different PFGE patterns. Plasmids carrying bla_NDM-1 were successfully transferred from six of the seven isolates to the Escherichia coli recipient. These six NDM-1-producing K. pneumoniae were clonal and carried bla_NDM-1 on the same plasmid, but one isolate possibly carried chromosomal bla_NDM-1.

CONCLUSIONS

This is the first report of NDM-1-positive K. pneumoniae ST1419 from neonates in China. Closer attention should be paid to monitoring bla_NDM-1 gene dissemination because it is potentially transferred horizontally.