The emerging NDM carbapenemases

Antimicrobial resistance and COVID-19: Intersections and implications

Before the coronavirus 2019 (COVID-19) pandemic began, antimicrobial resistance (AMR) was among the top priorities for global public health. Already a complex challenge, AMR now needs to be addressed in a changing healthcare landscape. Here, we analyse how changes due to COVID-19 in terms of antimicrobial usage, infection prevention, and health systems affect the emergence, transmission, and burden of AMR. Increased hand hygiene, decreased international travel, and decreased elective hospital procedures may reduce AMR pathogen selection and spread in the short term. However, the opposite effects may be seen if antibiotics are more widely used as standard healthcare pathways break down. Over 6 months into the COVID-19 pandemic, the dynamics of AMR remain uncertain. We call for the AMR community to keep a global perspective while designing finely tuned surveillance and research to continue to improve our preparedness and response to these intersecting public health challenges.

Mechanistic Basis of OXA-48-like β-Lactamases' Hydrolysis of Carbapenems

Carbapenem-hydrolyzing class D β-lactamases (CHDLs) are an important source of resistance to these last resort β-lactam antibiotics. OXA-48 is a member of a group of CHDLs named OXA-48-like enzymes. On the basis of sequence similarity, OXA-163 can be classified as an OXA-48-like enzyme, but it has altered substrate specificity. Compared to OXA-48, it shows impaired activity for carbapenems but displays an enhanced hydrolysis of oxyimino-cephalosporins. Here, we address the mechanistic and structural basis for carbapenem hydrolysis by OXA-48-like enzymes. Pre-steady-state kinetic analysis indicates that the rate-limiting step for OXA-48 and OXA-163 hydrolysis of carbapenems is deacylation and that the greatly reduced carbapenemase activity of OXA-163 compared to that of OXA-48 is due entirely to a slower deacylation reaction. Furthermore, our structural data indicate that the positioning of the β5-β6 loop is necessary for carbapenem hydrolysis by OXA-48. A major difference between the OXA-48 and OXA-163 complexes with carbapenems is that the 214-RIEP-217 deletion in OXA-163 creates a large opening in the active site that is absent in the OXA-48/carbapenem structures. We propose that the larger active site results in less constraint on the conformation of the 6α-hydroxyethyl group in the acyl-enzyme. The acyl-enzyme intermediate assumes multiple conformations, most of which are incompatible with rapid deacylation. Consistent with this hypothesis, molecular dynamics simulations indicate that the most stable complex is formed between OXA-48 and imipenem, which correlates with the OXA-48 hydrolysis of imipenem being the fastest observed. Furthermore, the OXA-163 complexes with imipenem and meropenem are the least stable and show significant conformational fluctuations, which correlates with the slow hydrolysis of these substrates.

Genetic Plurality of OXA/NDM-Encoding Features Characterized From Enterobacterales Recovered From Czech Hospitals

The aim of this study was to characterize four Enterobacterales co-producing NDM- and OXA-48-like carbapenemases from Czech patients with travel history or/and previous hospitalization abroad. Klebsiella pneumoniae isolates belonged to “high risk” clones ST147, ST11, and ST15, while the Escherichia coli isolate was assigned to ST167. All isolates expressed resistance against most β-lactams, including carbapenems, while retaining susceptibility to colistin. Furthermore, analysis of WGS data showed that all four isolates co-produced OXA-48- and NDM-type carbapenemases, in different combinations (Kpn47733: bla_NDM–5 + bla_OXA–181; Kpn50595: bla_NDM–1 + bla_OXA–181; Kpn51015: bla_NDM–1 + bla_OXA–244; Eco52418: bla_NDM–5 + bla_OXA–244). In Kpn51015, the bla_OXA–244 was found on plasmid p51015_OXA-244, while the respective gene was localized in the chromosomal contig of E. coli Eco52418. On the other hand, bla_OXA–181 was identified on a ColKP3 plasmid in isolate Kpn47733, while a bla_OXA–181-carrying plasmid being an IncX3-ColKP3 fusion was identified in Kpn50595. The bla_NDM–1 gene was found on two different plasmids, p51015_NDM-1 belonging to a novel IncH plasmid group and p51015_NDM-1 being an IncF_K1-FIB replicon. Furthermore, the bla_NDM–5 was found in two IncFII plasmids exhibiting limited nucleotide similarity to each other. In both plasmids, the genetic environment of bla_NDM–5 was identical. Finally, in all four carbapenemase-producing isolates, a diverse number of additional replicons, some of these associated with important resistance determinants, like bla_CTX–M–15, arr-2 and ermB, were identified. In conclusion, this study reports the first description of OXA-244-producing Enterobacterales isolated from Czech hospitals. Additionally, our findings indicated the genetic plurality involved in the acquisition and dissemination of determinants encoding OXA/NDM carbapenemases.

Increasing New Delhi metallo-β-lactamase-positive Escherichia coli among carbapenem non-susceptible Enterobacteriaceae in Taiwan during 2016 to 2018

New Delhi metallo-β-lactamase (NDM) had been reported to be the predominant carbapenemase among Escherichia coli in Taiwan. However, studies focusing on the clonal background and epidemiology of plasmids carrying NDM genes were limited. Between 2016 and 2018, all clinical E. coli and Klebsiella pneumoniae isolates that were non-susceptible to ertapenem, meropenem, and imipenem were tested for carbapenemase-encoding genes (CEGs) and antimicrobial susceptibilities. Molecular typing was performed on all carbapenemase-producing isolates. Whole genome sequencing (WGS) was performed on all NDM-positive E. coli isolates. Twenty-three (29.5%) of 78 carbapenem non-susceptible E. coli and 108 (35.3%) of 306 carbapenem non-susceptible K. pneumoniae isolates carried CEGs. The most prevalent CEGs in carbapenemase-producing E. coli (CPEc) were bla_NDM (39.1%) and bla_IMP-8 (30.4%), while that in carbapenemase-producing K. pneumoniae was Klebsiella pneumoniae carbapenemase (KPC) (72.2%). Fifteen sequence types were identified among 23 CPEc, and 55.6% of NDM-positive E. coli isolates belonged to ST410. WGS showed ST410 isolates were highly clonal and similar to those from other countries. All NDM-5-positive E. coli isolates carried identical IncX3 plasmid harboring bla_NDM-5 but no other antimicrobial resistance (AMR) genes. In each of the four NDM-1-positive E. coli isolates, the bla_NDM-1 was present in a ∼ 300 kb IncHI2/IncHI2A plasmid which carried an array of AMR genes. NDMs are the most prevalent carbapenemase among CPEc in Taiwan. Awareness should be raised as the prevalence of NDM-positive E. coli might increase rapidly with IncX3 plasmid and globally distributed strain ST410 being the potential vectors for wide dissemination.

Multidrug-resistant Klebsiella quasipneumoniae subsp. similipneumoniae carrying blaNDM-blaCTX-M15 isolated from flies in Rio de Janeiro, Brazil

OBJECTIVES

Flies have been implicated in the dispersal of medically important bacteria including members of the genus Klebsiella between different environmental compartments. The aim of this study was to retrieve and characterize antibiotic-resistant bacteria from flies collected near to hospitals.

METHODS

Flies were collected in the vicinity of medical facilities and examined for bacteria demonstrating phenotypic resistance to ceftriaxone, followed by determination of phenotypic and genotypic resistance profiles. In addition, whole genome sequencing followed by phylogenetic analysis and resistance genotyping were performed with the multidrug-resistant (MDR) strain Lemef23, identified as Klebsiella quasipneumoniae subsp. similipneumoniae.

RESULTS

The strain Lemef23, classified by multiple locus sequence typing as novel ST 3397, harboured numerous resistance genes. The bla_NDM was located on a Tn3000 element, a common genetic platform for the carriage of this gene in Brazil. Inference of phylogenetic orthology of strain Lemef23 and other clinical isolates suggested an anthropogenic origin.

CONCLUSIONS

The findings of this study support the role of flies as vectors of MDR bacteria of clinical importance and provide the first record of bla_NDM-1 and bla_CTXM-15 in a Brazilian isolate of K. quasipneumoniae subsp. similipneumoniae, demonstrating the value of surveying insects as reservoirs of antibiotic resistance.

NDM-1-Positive K. pneumoniae at a Teaching Hospital in Southwestern China: Clinical Characteristics, Antimicrobial Resistance, Molecular Characterization, Biofilm Assay, and Virulence

Background

The emergence of the NDM-1-positive Klebsiella pneumoniae (K. pneumoniae) strains has led to limited therapeutic options for clinical treatment. Understanding the clinical characteristics, antimicrobial resistance, biofilm assay, and the virulence genes of these isolated strains is of great significance.

Methods

The polymerase chain reaction (PCR) was used to screen isolated NDM-1-positive K. pneumoniae. The clinical information of the patients was collected from medical records. The NDM-1-positive K. pneumoniae isolates were subjected to antimicrobial susceptibility testing and multilocus sequence typing. Sixty strains of NDM-1-negative K. pneumoniae isolated during the same period were collected as the control group for the virulence analysis. The virulence phenotype of the strains was preliminarily evaluated by the string test and crystal violet semiquantitative biofilm formation experiment. PCR combined with gene sequencing was used to detect common high toxicity capsule genes (K1, K2, K5, K20, K54, and K57) and common virulence-related genes (entB, ybtS, ureA, ycf, WabG, FimH, uge, iutA, KfuB, aerobactin, rmpA, magA, Alls, IrnN, and VatD).

Results

In the 30 nonduplicated NDM-1-positive K. pneumoniae isolates, 43.33% (13/30) of the patients had a history of a stay in the neonatal intensive care unit (NICU). All of the isolates exhibited multidrug resistance. Nine STs were identified, 77% (10/13) strains from the NICU were ST11. The NDM-1-positive K. pneumoniae string tests were all negative, and 35% (21/60) NDM-1-negative K. pneumoniae were positive. The ratios of NDM-1-positive K. pneumoniae isolates biofilm formation ability according to strong, medium, and weak classification were 67%, 23%, and 10%, respectively. NDM-1-negative K. pneumoniae isolates were 60%, 25%, and 15%, respectively. There was no statistical difference between the two groups (t = 0.61, P=0.2723). The virulence-associated genes with more than 80% of detection rates among the 30 NDM-1-positive K. pneumoniae isolates included entB (100%, 30/30), ybtS (93.33%, 28/30), ureA (90%, 27/30), ycf (83.33%, 25/30), and wabG (90%, 27/30). KfuB and iutA were detected at prevalence of 3.33% and 13.33%. vatD, allS, iroN, aerobactin, and rmpA were not detected. In the NDM-1-negative K. pneumoniae, all other 14 virulence genes except VatD were detected. After statistical analysis, FimH, WabG, ycf, iutA, kfuB, aerobactin, rmpA, and Alls virulence genes, P < 0.005, there was a statistical difference.

Conclusion

NDM-1-positive K. pneumoniae exhibited multidrug resistance, MLST typing is mainly ST11, there is small clonal dissemination in the NICU in the hospital, and the NDM-1-positive K. pneumoniae virulence genes carrier rate is lower than the NDM-1-negative K. pneumoniae virulence genes carrier rate.

Struggle To Survive: the Choir of Target Alteration, Hydrolyzing Enzyme, and Plasmid Expression as a Novel Aztreonam-Avibactam Resistance Mechanism

Aztreonam-avibactam is a promising antimicrobial combination against multidrug-resistant organisms, such as carbapenemase-producing Enterobacterales Resistance to aztreonam-avibactam has been found, but the resistance mechanism remains poorly studied. We recovered three Escherichia coli isolates of an almost identical genome but exhibiting varied aztreonam-avibactam resistance. The isolates carried a cephalosporinase gene, bla _CMY-42, on IncIγ plasmids with a single-nucleotide variation in an antisense RNA-encoding gene, inc, of the replicon. The isolates also had four extra amino acids (YRIK) in penicillin-binding protein 3 (PBP3) due to a duplication of a 12-nucleotide (TATCGAATTAAC) stretch in pbp3 By cloning and plasmid-curing experiments, we found that elevated CMY-42 cephalosporinase production or amino acid insertions in PBP3 alone mediated slightly reduced susceptibility to aztreonam-avibactam, but their combination conferred aztreonam-avibactam resistance. We show that the elevated CMY-42 production results from increased plasmid copy numbers due to mutations in inc We also verified the findings using in vitro mutation assays, in which aztreonam-avibactam-resistant mutants also had mutations in inc and elevated CMY-42 production compared with the parental strain. This choir of target modification, hydrolyzing enzyme, and plasmid expression represents a novel, coordinated, complex antimicrobial resistance mechanism and also reflects the struggle of bacteria to survive under selection pressure imposed by antimicrobial agents.IMPORTANCE Carbapenemase-producing Enterobacterales (CPE) is a serious global challenge with limited therapeutic options. Aztreonam-avibactam is a promising antimicrobial combination with activity against CPE producing serine-based carbapenemases and metallo-β-lactamases and has the potential to be a major option for combatting CPE. Aztreonam-avibactam resistance has been found, but resistance mechanisms remain largely unknown. Understanding resistance mechanisms is essential for optimizing treatment and developing alternative therapies. Here, we found that either penicillin-binding protein 3 modification or the elevated expression of cephalosporinase CMY-42 due to increased plasmid copy numbers does not confer resistance to aztreonam-avibactam, but their combination does. We demonstrate that increased plasmid copy numbers result from mutations in antisense RNA-encoding inc of the IncIγ replicon. The findings reveal that antimicrobial resistance may be due to concerted combinatorial effects of target alteration, hydrolyzing enzyme, and plasmid expression and also highlight that resistance to any antimicrobial combination will inevitably emerge.

Faecal carriage of extended spectrum beta-lactamase (ESBL) and New Delhi metallo beta-lactamase(NDM) producing Escherichia coli between piglets and pig farmworkers

A cross-sectional study on five organized pig farms was conducted to assess the faecal carriage of ESBL and blaNDM carbapenemase-producing E. coli in piglets and pig farmworkers. Faecal samples from piglets (n = 155) and pig farmworkers (n = 21) were processed for isolation and characterization of E. coli. A total of 124 E. coli isolates from piglets and 21 E. coli isolates pig farmworkers were recovered and screening for ESBL production showed that 44.4 % (55/124) of the isolates from piglets and 42.9 % (9/21) of the isolates from farmworkers were ESBL positive. The ESBL positive isolates from piglets and farmworkers harbored blaCTX-M and also co-harbored other beta-lactams, sulphonamide, quinolone and tetracycline resistance genes. Diarrhoeic (50%, 49/98) and crossbred piglets (52.7%, 39/74) harbored a significantly higher number of ESBL producing isolates than non-diarrhoeic (23.1 %, 6/26) and purebred piglets (32%, 16/50) (p < 0.05). Piglets and pig farmworkers harbored nine and two carbapenem-resistant isolates, respectively. Interestingly, two isolates from piglets and one isolate from farmworkers harbored the blaNDM gene. The blaNDM positive E. coli isolated from piglets and farmworkers of the same farm revealed similar antibacterial resistance patterns, resistant genes, sequence (ST-167) and plasmid type (IncX3). In India, carbapenems are not used in food animal treatment, hence carbapenem resistant E. coli in piglets possibly originated from the human contact or common environment and is of public health importance.

Treatment and Outcomes of Infections Caused by Diverse Carbapenemase-Producing Carbapenem-Resistant Enterobacterales

Background: Diverse sequence types (ST) and various carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE) infections, which complicate treatment strategies, have emerged in Singapore. We aim to describe these CP-CRE infections and clinical outcomes according to their carbapenemase types and determine the hierarchy of predictors for mortality that are translatable to clinical practice.

Methods: Clinically significant CP-CRE infections were identified in Singapore General Hospital between 2013 and 2016. Retrospectively, all clinically relevant data were retrieved from electronic medical records from the hospital. Univariate analysis was performed. To further explore the relationship between the variables and mortality in different subsets of patients with CP-CRE, we conducted recursive partitioning analysis on all study variables using the “rpart” package in R.

Results: One hundred and fifty five patients were included in the study. Among them, 169 unique CP-CRE were isolated. Thirty-day all-cause in-hospital mortality was 35.5% (n = 55). There was no difference in the severity of illness, or any clinical outcomes exhibited by patients between the various carbapenemases. Root node began with patients with Acute Physical and Chronic Health Evaluation (APACHEII) score ≥ 15 (n = 98; mortality risk = 52.0%) and <15 (n = 57; mortality risk = 9.0%). Patients with APACHEII score ≥ 15 are further classified based on presence (n = 27; mortality risk = 23.0%) and absence (n = 71, mortality risk = 62.0%) of bacterial eradication. Without bacterial eradication, absence (n = 54) and presence (n = 17) of active source control yielded 70.0 and 35.0% mortality risk, respectively. Without active source control, the mortality risk was higher for the patients with non-receipt of definite combination therapy (n = 36, mortality risk = 83.0%) when compared to those who received (n = 18, mortality risk = 47.0%). Overall, the classification tree has an area under receiver operating characteristic curve of 0.92, with a sensitivity of 0.87 and specificity of 0.91.

Conclusion: Different mortality risks were observed with different treatment strategies. Effective source control and microbial eradication were associated with a lower mortality rate but not active empiric therapy for CP-CRE infection. When source control was impossible, definitive antibiotic combination appeared to be associated with a reduction in mortality.

Evolving trends of New Delhi Metallo-betalactamse (NDM) variants: A threat to antimicrobial resistance

The rapid emergence of carbapenemase producing Gram-negative bacterial strains exhibit broad-spectrum β-lactam resistance, especially New Delhi metallo-β-lactamase (NDM-1). It is a major public health threat as it catalyses the hydrolysis of a vast variety of β-lactam antibiotics, including carbapenems, which is the last choice for physicians to treat infections. NDM-1 and its variants are continuously spreading worldwide, in spite of constant efforts to control. Its clinical treatment remains challenging due to continuous evolution of new variants. A thorough structural study of all variants is required to develop new and effective inhibitors. This review focuses on the dissemination, position of substitution and carbapenemases activity of all the 28 NDM variants so far reported.

Inhibitory Potential of Polyclonal Camel Antibodies against New Delhi Metallo-β-lactamase-1 (NDM-1)

New Delhi Metallo-β-lactamase-1 (NDM-1) is the most prevalent type of metallo-β-lactamase, able to hydrolyze almost all antibiotics of the β-lactam group, leading to multidrug-resistant bacteria. To date, there are no clinically relevant inhibitors to fight NDM-1. The use of dromedary polyclonal antibody inhibitors against NDM-1 represents a promising new class of molecules with inhibitory activity. In the current study, immunoreactivities of dromedary Immunoglobulin G (IgG) isotypes containing heavy-chain and conventional antibodies were tested after successful immunization of dromedary using increasing amounts of the recombinant NDM-1 enzyme. Inhibition kinetic assays, performed using a spectrophotometric method with nitrocefin as a reporter substrate, demonstrated that IgG1, IgG2, and IgG3 were able to inhibit not only the hydrolytic activity of NDM-1 but also Verona integron-encoded metallo-β-lactamase (VIM-1) (subclass B1) and L1 metallo-β-lactamase (L1) (subclass B3) with inhibitory concentration (IC₅₀₎ values ranging from 100 to 0.04 μM. Investigations on the ability of IgG subclasses to reduce the growth of recombinant Escherichia coli BL21(DE3)/codon plus cells containing the recombinant plasmid expressing NDM-1, L1, or VIM-1 showed that the addition of IgGs (4 and 8 mg/L) to the cell culture was unable to restore the susceptibility of carbapenems. Interestingly, IgGs were able to interact with NDM-1, L1, and VIM-1 when tested on the periplasm extract of each cultured strain. The inhibitory concentration was in the micromolar range for all β-lactams tested. A visualization of the 3D structural basis using the three enzyme Protein Data Bank (PDB) files supports preliminarily the recorded inhibition of the three MBLs.

Emergence of NDM-producing Klebsiella pneumoniae and Escherichia coli in Spain: phylogeny, resistome, virulence and plasmids encoding blaNDM-like genes as determined by WGS

OBJECTIVES

NDM carbapenemases have spread worldwide. However, little information exists about the impact of NDM-producing Enterobacteriaceae in Spain. By WGS, we sought to elucidate the population structure of NDM-like-producing Klebsiella pneumoniae and Escherichia coli in Spain and to determine the plasmids harbouring blaNDM-like genes.

METHODS

High-resolution SNP typing, core-genome MLST and plasmid reconstruction (PlasmidID) were performed on 59 NDM-like-producing K. pneumoniae and 8 NDM-like-producing E. coli isolated over an 8 year period in Spain.

RESULTS

Five major epidemic clones of NDM-producing K. pneumoniae caused five important nationwide outbreaks: ST437/NDM-7, ST437/NDM-1, ST147/NDM-1, ST11/NDM-1 and ST101/NDM-1; in contrast, the spread of NDM-producing E. coli was polyclonal. Three blaNDM types were identified: blaNDM-1, 61.2%; blaNDM-7, 32.8%; and blaNDM-5, 6%. Five K. pneumoniae isolates co-produced other carbapenemases (three blaOXA-48 and two blaVIM-1). The average number of acquired resistance genes was higher in K. pneumoniae than in E. coli. The plasmids encoding blaNDM-like genes belonged to IncFII, IncFIB, IncX3, IncR, IncN and IncC types, of which IncF, IncR and IncC were associated with MDR. The genetic surroundings of blaNDM-like genes showed a highly variable region upstream of ISAba125.

CONCLUSIONS

In recent years NDM-producing K. pneumoniae and E. coli have emerged in Spain; the spread of a few high-risk K. pneumoniae clones such as ST437/NDM-7, ST437/NDM-1, ST147/NDM-1, ST11/NDM-1 and ST101/NDM-1 have caused several interregional outbreaks. In contrast, the spread of NDM-producing E. coli has been polyclonal. Plasmid types IncFII, IncFIB, IncX3, IncR, IncN and IncC carried blaNDM, and the same IncX3 plasmid was detected in K. pneumoniae and E. coli.

Characteristics of dual carbapenemase-producing Klebsiella pneumoniae strains from an outbreak in Venezuela: a retrospective study

Objective.

To characterize carbapenemase-producing Klebsiella pneumoniae isolated from patients treated at a hospital in Cumaná, Sucre, Venezuela.

Methods.

This was a retrospective study conducted at the general hospital in Cumaná where 58 K. pneumoniae strains were analyzed for resistance to antimicrobials, specifically carbapenems, in January – June 2015. Production of metallo-β-lactamases and serine carbapenemases was determined by the double-disc synergy test, using EDTA-sodium mercaptoacetic acid and 3-aminophenyl boronic acid discs, respectively. Multiplex-PCR was used to detect genes coding for carbapenemases. Molecular typing using ERIC-PCR determined the presence of clones.

Results.

Four strains of K. pneumoniae resistant to carbapenems were identified. Phenotypic methods for detection of metallo-β-lactamases and serine carbapenemases were positive, and PCR demonstrated the co-presence of bla_NDM and bla_KPC genes in all four strains. ERIC-PCR identified two clones circulating in the hospital.

Conclusions.

Infection control strategies are needed at the central hospital in Cumaná and its surrounding areas to prevent the spread of these pathogens, especially given the high levels of migration from Venezuela to other countries in South America.

Prevalence and Distribution Characteristics of blaKPC-2 and blaNDM-1 Genes in Klebsiella pneumoniae

Background

Carbapenem-resistant Klebsiella pneumoniae infections have caused major concern and posed a global threat to public health. As bla_KPC-2 and bla_NDM-1 genes are the most widely reported carbapenem resistant genes in K. pneumonia, it is crucial to study the prevalence and geographical distribution of these two genes for further understanding of their transmission mode and mechanism.

Purpose

Here, we investigated the prevalence and distribution of bla_KPC-2 and bla_NDM-1 genes in carbapenem-resistant K. pneumoniae strains from a tertiary hospital and from 1579 genomes available in the NCBI database, and further analyzed the possible core structure of bla_KPC-2 or bla_NDM-1 genes among global genome data.

Materials and Methods

K. pneumoniae strains from a tertiary hospital in China during 2013–2018 were collected and their antimicrobial susceptibility testing for 28 antibiotics was determined. Whole-genome sequencing of carbapenem-resistant K. pneumoniae strains was used to investigate the genetic characterization. The phylogenetic relationships of these strains were investigated through pan-genome analysis. The epidemiology and distribution of bla_KPC-2 and bla_NDM-1 genes in K. pneumoniae based on 1579 global genomes and carbapenem-resistant K. pneumoniae strains from hospital were analyzed using bioinformatics. The possible core structure carrying bla_KPC-2 or bla_NDM-1 genes was investigated among global data.

Results

A total of 19 carbapenem-resistant K. pneumoniae were isolated in a tertiary hospital. All isolates had a multi-resistant pattern and eight kinds of resistance genes. The phylogenetic analysis showed all isolates in the hospital were dominated by two lineages composed of ST11 and ST25, respectively. ST11 and ST25 were the major ST type carrying bla_KPC-2 and bla_NDM-1 genes, respectively. Among 1579 global genomes data, 147 known ST types (1195 genomes) have been identified, while ST258 (23.6%) and ST11 (22.1%) were the globally prevalent clones among the known ST types. Genetic environment analysis showed that the ISKpn7-dnaA/ISKpn27 -bla_KPC-2-ISkpn6 and bla_NDM-1-ble-trpf-nagA may be the core structure in the horizontal transfer of bla_KPC-2 and bla_NDM-1, respectively. In addition, DNA transferase (hin) may be involved in the horizontal transfer or the expression of bla_NDM-1.

Conclusion

There was clonal transmission of carbapenem-resistant K. pneumoniae in the tertiary hospital in China. The prevalence and distribution of bla_KPC-2 and bla_NDM-1 varied by countries and were driven by different transposons carrying the core structure. This study shed light on the genetic environment of bla_KPC-2 and bla_NDM-1 and offered basic information about the mechanism of carbapenem-resistant K. pneumoniae dissemination.

Whole-genome sequencing disproves two suspected transmission events of blaNDM between Pseudomonas aeruginosa and Enterobacterales in hospitalized patients

New Delhi metallo-β-lactamase (bla_NDM) acquisition by Gram-negative bacteria is a primary concern due to its broad-host-range distribution. This study investigated two potential in-vivo horizontal gene transfers (HGTs) of bla_NDM between Enterobacterales and Pseudomonas aeruginosa, initially indicated by polymerase chain reaction. Whole-genome sequencing showed independent parallel acquisition of two different bla_NDM variants (NDM-1 and NDM-5) in P. aeruginosa and Enterobacterales, respectively. The data show that short-read sequencing provides the necessary resolution to confirm or dispute HGT by the comparison of genetic elements surrounding the gene of interest, and thus provide a timely response to potential outbreaks.

Emergence of Escherichia coli isolates producing NDM-1 carbapenemase from waterfowls in Hainan island, China

Carbapenems are traditionally recognized to be the last resort drugs to treat infections due to MDR organisms such as E. coli. As such, the emergence of New Delhi metallo-β-lactamase-producing E. coli strains have become a challenging threat to the public health. In this regard, we examined the molecular characteristics of carbapenem-resistant E. coli (CRE) isolated from waterfowls in China's tropical island, Hainan. A total of 311 single E. coli strains were obtained from 20 various farms of healthy ducks and geese in 2 districts of Hainan island. The CRE strains were initially identified via phenotypic resistance and modified Hodge test. PCR assay and subsequent nucleotide sequencing were used to detect different types of carbapenemase encoding genes (bla_NDM, bla_VIM, bla_IMP, bla_OXA and bla_KPC). In addition, MLST and PFGE analyses were also performed. Among the 311 E. coli strains, 8 strains were detected to produce a single type of carbapenemase i.e. NDM-1 (2.6%). A total of 5 sequence types (STs) were observed, of which ST10 was the most prevalent accounting for 37.5% (3/8). Moreover, these 8 isolates yielded 6 different PFGE clusters but showed approximately related PFGE types, suggesting the propagation of similar clone between the farms. This is the first report on the identification of NDM-1-producing E. coli from waterfowls in Hainan island, China. Our results emphasize the need for better efforts to control the further spread of NDM-1-producing E. coli strains in this tropical island.

Drugs for Gram-Negative Bugs From 2010-2019: A Decade in Review

A literature review spanning January 1, 2010, to December 31, 2019, was conducted using the PubMed and ISI Web of Science databases to determine the breadth of publication activity in the area of gram-negative bacteria antimicrobial therapy. The number of articles was used as a reflection of scholarly activity. First, PubMed was searched using the following Medical Subject Headings (MeSH): antibacterial agents, Enterobacteriaceae, Acinetobacter, and Pseudomonas. A total of 12 643 articles were identified within PubMed, and 77 862 articles were identified within ISI Web of Science that included these terms. Second, these articles were categorized by antibiotic class to identify relative contributions to the literature by drug category. Third, these studies were used to identify key trends in the treatment of gram-negative bacterial infections from the past decade. This review highlights advances made in the past 10 years in antibacterial pharmacotherapy and some of the challenges that await the next decade of practice.

Prevalence of Extended-Spectrum β-lactamases in Enterobacteriaceae Isolated from Polluted Wild Fish

Background:

Antibiotic resistance is becoming a major public health concern worldwide. In marine animals, pollution is associated with the emergence of extended-spectrum β-lactamase (ESBL)-expressing bacteria, resulting in antibiotic resistance. However, the prevalence of these bacteria in wild fish has not been reported.

Objective:

Accordingly, in this study, we explored the influence of pollution oxidative stress on the incidence of ESBL-expressing Enterobacteriaceae in the gut of wild fish species from the Red Sea coastal region of Jeddah City, Saudi Arabia. Additionally, we evaluated the incidence of varied ESBL genes contributing to the ESBL+ phenotype.

Methods:

Antibiotic susceptibility tests were performed using cephalosporins and carbapenems against ESBL- and carbapenem-resistant Enterobacteriaceae (CRE)-producing bacteria. Frequent genes contributing to the ESBL+ phenotype were analyzed. Primers targeting ESBLs (e.g., blaCTX, blaSHV, blaTEM, and blaOXA) were used in polymerase chain reaction assays to detect the ESBL+ phenotype.

Results:

Screening results from the polluted site revealed ESBL-resistant Klebsiella pneumoniae B8 and CRE-resistant Morganella morganii A4. The evolution of the blaCTX-M gene in M. morganii was a consequence of aquatic pollution. The other isolates Acinetobacter pittii and Providencia rettgeri were found in the clean reference site. The isolate M. morganii showed resistance to most mutual antibiotics and expressed some β-lactamase genes.

Conclusion:

Our findings provide useful data for selecting marine molecular genomic biomarkers caused by aquatic pollution.

A novel incompatibility group X3 plasmid carrying bla NDM-1 encodes a small RNA that regulates host fucose metabolism and biofilm formation

The emergence of New Delhi metallo-beta-lactamase (NDM-1) has become a major health threat to clinical managements of gram-negative bacteria infections. A novel incompatibility group X3 plasmid (IncX3) pNDM-HN380 carrying bla _NDM-1 has recently been found to epidemiologically link with multiple geographical areas in China. In this paper, we studied the metabolic responses of host bacteria E. coli J53 upon introduction of pNDM-HN380. A reduction of bacterial motility was observed in J53/pNDM-HN380. We profiled the RNA repertoires of the transconjugants and found a downregulation of genes involved in flagella and chemotaxis metabolic pathways at logarithmic (log) phase. We also identified a novel intragenic region (IGR) small RNA plas2. The plasmid-transcribed sRNA IGR plas2 was further characterized as a regulator of fucRwhich controls the fucose metabolism. By knockdown of IGR plas2 using an antisense decoy, we managed to inhibit the formation of bacterial biofilm of the host. Our study demonstrated a potential way of utilizing plasmid-transcribed sRNA against infectious bacteria.

NMR Characterization of the Influence of Zinc(II) Ions on the Structural and Dynamic Behavior of the New Delhi Metallo-β-Lactamase-1 and on the Binding with Flavonols as Inhibitors

New Delhi metallo-β-lactamase-1 (NDM-1) has recently emerged as a global threat because of its ability to confer resistance to all common β-lactam antibiotics. Understanding the molecular basis of β-lactam hydrolysis by NDM is crucial for designing NDM inhibitors or β-lactams resistant to their hydrolysis. In this study, for the first time, NMR was used to study the influence of Zn(II) ions on the dynamic behavior of NDM-1. Our results highlighted that the binding of Zn(II) in the NDM-1 active site induced several structural and dynamic changes on active site loop 2 (ASL2) and L9 loops and on helix α2. We subsequently studied the interaction of several flavonols: morin, quercetin, and myricetin were identified as natural and specific inhibitors of NDM-1. Quercetin conjugates were also synthesized in an attempt to increase the solubility and bioavailability. Our NMR investigations on NDM-1/flavonol interactions highlighted that both Zn(II) ions and the residues of the NDM-1 ASL1, ASL2, and ASL4 loops are involved in the binding of flavonols. This is the first NMR interaction study of NDM-1/inhibitors, and the models generated using HADDOCK will be useful for the rational design of more active inhibitors, directed against NDM-1.

A Cephalosporin Prochelator Inhibits New Delhi Metallo-β-lactamase 1 without Removing Zinc

Antibacterial drug resistance is a rapidly growing clinical threat, partially due to expression of β-lactamase enzymes, which confer resistance to bacteria by hydrolyzing and inactivating β-lactam antibiotics. The increasing prevalence of metallo-β-lactamases poses a unique challenge, as currently available β-lactamase inhibitors target the active site of serine β-lactamases but are ineffective against the zinc-containing active sites of metallo-β-lactamases. There is an urgent need for metallo-β-lactamase inhibitors and antibiotics that circumvent resistance mediated by metallo-β-lactamases in order to extend the utility of existing β-lactam antibiotics for treating infection. Here we investigated the antibacterial chelator-releasing prodrug PcephPT (2-((((6R,7R)-2-carboxy-8-oxo-7-(2-phenylacetamido)-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl)methyl)thio) pyridine 1-oxide) as an inhibitor of New Delhi metallo-β-lactamase 1 (NDM-1). PcephPT is an experimental compound that we have previously shown inhibits growth of β-lactamase-expressing E. coli using a mechanism that is dependent on both copper availability and β-lactamase expression. Here, we found that PcephPT, in addition to being a copper-dependent antibacterial compound, inhibits hydrolysis activity of purified NDM-1with an IC₅₀ of 7.6 μM without removing zinc from the active site and restores activity of the carbapenem antibiotic meropenem against NDM-1-producing E. coli. This work demonstrates that targeting a metal-binding pharmacophore to β-lactamase-producing bacteria is a promising strategy for inhibition of both bacterial growth and metallo-β-lactamases.

Multidrug-resistant Klebsiella pneumoniae in hospital-acquired infections: Concomitant analysis of antimicrobial resistant strains

BACKGROUND

Hospital-acquired infections caused by K pneumoniae are difficult to eradicate since K pneumoniae carries resistance genes for many antimicrobials, including carbapenems. The study aimed to determine the prevalence of hospital-acquired infections caused by multiple drug-resistant K pneumoniae and identify carbapenem and fluoroquinolone resistance by phenotypic and genotypic methods amongst hospitalised patients.

METHODS

Two hundred and fifty samples from patients with hospital-acquired infections were included. Identification and susceptibility testing for K pneumoniae isolates was performed by standard methods. The detection of carbapenemase resistance (bla_KPC , bla_VIM-1 and bla_OXA-48 ) and plasmid-mediated quinolone resistance (PMQR; qnrA, qnrB and qnrS) genes was performed using PCR assay.

RESULTS

Out of 250 samples, 42 (16.8%) were multiple drug-resistant K pneumoniae, and the frequency of K Pneumoniae isolation was higher in urine samples, in the age group (<10 years), in ICU and in patients with longer hospital stay. Twenty-four (57%) of the isolates were resistant to Meropenem, 13 (31%) were resistant to Imipenem and 35 (83.3%) were resistant to Ciprofloxacin. bla_OXA-48 gene was detected in 9 (21.4%) of isolates, and bla_VIM-1 gene was detected in 6 (14.3%) of isolates. However, no isolate harboured bla_KPC gene. PMQR genes were detected in 100% of ciprofloxacin resistant isolates, and qnrS was the dominant.

CONCLUSION

Multidrug-resistant K pneumoniae isolates harbouring bla_OXA-48, bla_VIM-1 and PMQR genes are emerging in hospitals particularly with long hospital stays.

Role of plasmid carrying bla NDM in mediating antibiotic resistance among Acinetobacter baumannii clinical isolates from Egypt

We investigated antibiotic resistance levels among bla_NDM-positive (n = 9) and -negative (n = 65) A. baumannii clinical isolates collected in 2010 and 2015 from Alexandria Main University Hospital, Egypt using disc diffusion and minimum inhibitory concentration (MIC) determination. Plasmids from bla_NDM-positive isolates were transformed into a carbapenem-susceptible A. baumannii (CS-AB) isolate to assess the role of plasmid transfer in mediating carbapenem resistance. Imipenem, meropenem, and ertapenem MIC90 values against bla_NDM-positive isolates were 128, > 256, and 256 µg/mL, respectively. Plasmid isolation and polymerase chain reaction revealed that bla_NDM was plasmid mediated. The plasmids were electroporated into the cells of a CS-AB isolate at an efficiency of 1.3 × 10^–8 to 2.6 × 10^–7, transforming them to bla_NDM-positive carbapenem-resistant cells with an imipenem MIC increase of 256-fold. In addition to carbapenem resistance, the bla_NDM-positive isolates also exhibited higher levels of cephalosporins, tetracycline, aminoglycosides, fluoroquinolones, and colistin resistance than the bla_NDM-negative isolates. Acquisition of bla_NDM-carrying plasmids dramatically increased imipenem resistance among A. baumannii isolates. Intriguingly, bla_NDM-positive isolates also showed a high degree of resistance to antibiotics of different classes. The potential co-existence of different resistance determinants on A. baumannii plasmids and their possible transfer owing to the natural competence of the pathogen are especially alarming. More effective infection control and antibiotic stewardship programs are needed to curb the spread and treat such infections in both hospital and community settings.

Epidemiology of carbapenem-resistant Escherichia coli and first report of blaVIM carbapenemases gene in calves from India

A cross-sectional study on six dairy farms was conducted to ascertain the occurrence of carbapenem-resistant Escherichia coli in calves. Two-hundred and seventy-nine isolates of E. coli were recovered from 90 faecal samples from apparently healthy (45) and diarrhoeal (45) calves. The isolates were screened for phenotypic susceptibility to carbapenems and production of metallo β-lactamase, as well as five carbapenemase resistance genes by PCR, and overexpression of efflux pumps. Eighty-one isolates (29.03%) were resistant to at least one of three carbapenem antibiotics [meropenem (23.30%), imipenem (2.15%) and ertapenem (1.43%)], and one isolate was positive for the blaVIM gene which was located on an Incl1 plasmid of a novel sequence type (ST 297) by multilocus sequence typing. The majority (83.95%) of isolates had an active efflux pump. Calves housed on concrete floors were approximately seven times more likely to acquire meropenem-resistant isolates than those housed on earthen floors (95% CI 1.27–41.54). In India, carbapenem drugs are not used in food animal treatment, hence carbapenem-resistant strains in calves possibly originate from the natural environment or human contact and is of public health importance. To our knowledge, this is the first report of blaVIM carbapenemases gene in calves from India.

Fitness Cost of blaNDM-5-Carrying p3R-IncX3 Plasmids in Wild-Type NDM-Free Enterobacteriaceae

The wide dissemination of New Delhi metallo-β-lactamase genes (bla_NDM) has resulted in the treatment failure of most available β-lactam antibiotics, with IncX3-type bla_NDM-5-carrying plasmids recognised as having spread worldwide. In China, bacteria carrying these plasmids are increasingly being detected from diverse samples, including hospitals, communities, livestock and poultry, and the environment, suggesting that IncX3 plasmids are becoming a vital vehicle for bla_NDM dissemination. To elucidate the fitness cost of these plasmids on the bacterial host, we collected bla_NDM-negative strains from different sources and tested their ability to acquire the bla_NDM-5-harboring p3R-IncX3 plasmid. We then measured changes in antimicrobial susceptibility, growth kinetics, and biofilm formation following plasmid acquisition. Overall, 70.7% (29/41) of our Enterobacteriaceae recipients successfully acquired the bla_NDM-5-harboring p3R-IncX3 plasmid. Contrary to previous plasmid burden theory, 75.9% (22/29) of the transconjugates showed little fitness cost as a result of plasmid acquisition, with 6.9% (2/29) of strains exhibiting enhanced growth compared with their respective wild-type strains. Following plasmid acquisition, all transconjugates demonstrated resistance to most β-lactams, while several strains showed enhanced biofilm formation, further complicating treatment and prevention measures. Moreover, the highly virulent Escherichia coli sequence type 131 strain that already harbored mcr-1 also demonstrated the ability to acquire the bla_NDM-5-carrying p3R-IncX3 plasmid, resulting in further limited therapeutic options. This low fitness cost may partly explain the rapid global dissemination of bla_NDM-5-harboring IncX3 plasmids. Our study highlights the growing threat of IncX3 plasmids in spreading bla_NDM-5.

First Report of Extended-Spectrum Betalactamase-Producing Klebsiella pneumoniae Among Fecal Carriage in Iran: High Diversity of Clonal Relatedness and Virulence Factor Profiles

Increasing rate of silent intestinal carriers with extended-spectrum betalactamase (ESBL)-producing Klebsiella pneumonia (ESBL-KP) has given rise to a serious healthcare problem in clinical settings. Various epidemiological studies are being conducted to determine clonal relatedness among carriers. In this study, we investigated the intestinal carriage of ESBL-KP and clonal relatedness among ESBL-KP isolated from fecal carriage in Iran for the first time. A total of 120 rectal swabs (RSs) were collected including 61 from inpatients of intensive care unit and 59 from outpatients. ESBL-KP screening was performed using MacConkey agar supplemented with cefotaxime. PCR was done for detection of ESBL, carbapenemase, and virulence factor genes. Conjugation experiments and PCR-based replicon typing were performed. Clonal relatedness was investigated by multilocus sequence typing (MLST) and multiple locus variable number tandem repeat analysis (MLVA). Out of a total of 120 RSs, 18.3% (22/120) ESBL-KP were isolated. The rate of bla_CTXM-15 was 81%. ompk35 was the most prevalent virulence gene detected in 86.3% of the isolates. In conjugation experiments, three out of five tested isolates had conjugative plasmids. The most prevalent plasmid types belonged to IncL/M, IncA/C, and Inc FII. The MLST analysis showed that the main sequence types (STs) identified among ESBL-KP isolates were ST147, ST15, and ST16. The isolates were characterized into 4 miniclusters and 11 singletons using MLVA. High heterogeneity among ESBL-KP isolates indicated that this bacterium could be colonized in different sites and easily transferred. Screening of carriers in hospitals and community could help in controlling of infection in the healthcare and community settings.

The evolutionary puzzle of Escherichia coli ST131

The abrupt expansion of Escherichia coli sequence type (ST) 131 is unmatched among Gram negative bacteria. In many ways, ST131 can be considered a real-world model for the complexities involved in the evolution of a multidrug resistant pathogen. While much progress has been made on our insights into the organism's population structure, pathogenicity and drug resistance profile, significant gaps in our knowledge remain. Whole genome studies have shed light on key mutations and genes that have been selected against the background of antibiotics, but in most cases such events are inferred and not supported by experimental data. Notable examples include the unknown fitness contribution made by specific plasmids, genomic islands and compensatory mutations. Furthermore, questions remain like why this organism in particular achieved such considerable success in such a short time span, compared to other more pathogenic and resistant clones. Herein, we document what is known regarding the genetics of this organism since its first description in 2008, but also highlight where work remains to be done for a truly comprehensive understanding of the biology of ST131, in order to account for its dramatic rise to prominence.

Bacteriophages of Klebsiella spp., their diversity and potential therapeutic uses

Klebsiella spp. are commensals of the human microbiota, and a leading cause of opportunistic nosocomial infections. The incidence of multidrug resistant (MDR) strains of Klebsiella pneumoniae causing serious infections is increasing, and Klebsiella oxytoca is an emerging pathogen. Alternative strategies to tackle infections caused by these bacteria are required as strains become resistant to last-resort antibiotics such as colistin. Bacteriophages (phages) are viruses that can infect and kill bacteria. They and their gene products are now being considered as alternatives or adjuncts to antimicrobial therapies. Several in vitro and in vivo studies have shown the potential for lytic phages to combat MDR K. pneumoniae infections. Ready access to cheap sequencing technologies has led to a large increase in the number of genomes available for Klebsiella-infecting phages, with these phages being heterogeneous at the whole-genome level. This review summarizes our current knowledge on phages of Klebsiella spp. and highlights technological and biological issues relevant to the development of phage-based therapies targeting these bacteria.

A review on bacterial resistance to carbapenems: epidemiology, detection and treatment options

Carbapenems are a class of antimicrobial agents reserved for infections caused by multidrug-resistant microorganisms. The emergence of carbapenem resistance has become a serious public health threat. This type of antimicrobial resistance is spreading at an alarming rate, resulting in major outbreaks and treatment failure of community-acquired and nosocomial infections caused by the clinically relevant carbapenem-producing Enterobacteriaceae or carbapenem-resistant Enterobacteriaceae. This review is focused on carbapenem resistance, including mechanisms of resistance, history and epidemiology, phenotypic and genotypic detection in the clinically relevant bacterial pathogens and the possible treatment options available.

Complete Nucleotide Sequence of Plasmids of Two Escherichia coli Strains Carrying bla NDM- 5 and bla NDM - 5 and bla OXA - 181 From the Same Patient

Aim of this study was to genetically characterize two carbapenemase-producing Escherichia coli strains obtained from a pediatric patient affected by diarrhea, expressing OXA-181 and/or NDM-5 type enzymes. The above microorganisms were collected in the same Desenzano hospital (Northern Italy) where the bla_NDM–5 gene was detected for the first time in Italy 3 years ago. One strain (5P), belonged to sequence type ST405/ST477 (according to Pasture/Oxford schemes) and serotype O102:H6. It was characterized by a 130562 bp multi-replicon plasmid IncFII/IncFIA/IncFIB (pVSI_NDM-5) enclosing two main antibiotic resistance islands: (i) ARI-I, 10030 bp in size, carried genes coding for β-lactam- (bla_OXA–1, bla_CTX–M–15), fluoroquinolone/aminoglycoside- (aac(6′)-lb-cr) and phenicol- resistance (catB3), (ii) ARI-II, 15326 bp in size, carried genes coding for sulfonamide- (sul1), β-lactam- (bla_NDM–5, bla_TEM–1B), phenicol- (catB3), trimethoprim- (dfrA17), antiseptic- (qacEΔ1), and aminoglycoside- (aadA5, rmtB) resistance. The other isolate (5M), belonged to sequence type ST2659/ST759 and serotype O50/02:H18, and carried four plasmids: a 153866 bp multi-replicon IncFII/IncFIA/IncFIB (pISV_IncFII_NDM-5), an 89866 bp IncI1 plasmid, a 51480 bp IncX3 plasmid (pISV_IncX3_OXA181), and a 41143 bp IncI plasmid (pISV_IncI_CMY-42). pISV_IncFII_NDM-5 carried two main antibiotic resistance islands: (i) ARI-III, 12220 bp in size, carried genes coding for β-lactam- (bla_OXA–1), fluoroquinolone/aminoglycoside- (aac(6′)-lb-cr), tetracycline- (tet(B)) and phenicol- resistance (catB3, catA1), and ii) ARI-IV, 26527 bp in size, carried determinants coding for macrolide- (erm(B), mph(A)), sulfonamide- (sul1), beta-lactam- (bla_NDM–5, bla_TEM–1B), trimethoprim- (dfrA14, dfrA12), antiseptic- (qacEΔ1), and aminoglycoside- resistance (aadA5). pISV_IncI_CMY-42 harbored the bla_CMY–42 gene coding for beta-lactam resistance, pISV_IncX3_OXA181 harbored genes encoding fluoroquinolone- (qnrS1) and beta-lactams- resistance (bla_OXA–181). In conclusion, the detection of two different NDM-5 E. coli strains from a pediatric patient with a history of travel to the Far East countries strongly highlight an increasing trend and risk of importation from such areas.

Epidemiological characteristics of carbapenem-resistant Enterobacteriaceae collected from 17 hospitals in Nanjing district of China

Objective

In total, 97 carbapenem-resistant Enterobacteriaceae (CRE) were collected from 17 hospitals located in Nanjing, Southeast China, and analyzed for epidemiological characteristics.

Methods

Antimicrobial susceptibility was determined; followed by determination of the prevalence of resistance determinants, including extended-spectrum β-lactamase (ESBLs), plasmid-mediated AmpC enzyme (pAmpCs), plasmid-mediated quinolone resistance genes (PMQRs), fosfomycin resistance gene and exogenously acquired 16S rRNA methyltransferase (16S-RMTase) using PCR and DNA sequencing. The sequence types (STs) of CRE were determined by multi-locus sequence typing (MLST). The plasmid profiles were detected by PCR-based replicon typing (PBRT).

Results

All the CRE strains displayed high MIC₅₀ and MIC₉₀ for nearly all clinical available antibiotics, except for aztreonam/avibactam, minocycline, ceftazidime/avibactam, tigecycline, and colistin. KPC-2 (79.4%) and NDM (19.6%) were the main carbapenemases, CTX-M (76.3%) and SHV (60.8%) were the predominant ESBLs. In addition, oqxAB (70.1%) and qnr (63.9%) were the major PMQRs; rmtB (47.4%) was the main 16S-RMTase; fosA (76.3%) and fosA3 (37.1%) were the fosfomycin resistance gene. PBRT analysis showed presence of IncR (66.0%) and IncFII (64.9%) replicon types in the majority of the isolates, followed by IncFIB (46.4%) and IncX3 (16.5%). The IncFII and IncR replicon-types were found mainly in K. pneumoniae (68.8%), whereas the IncX3 replicons dominated in E. coli isolates (100.0%). The three dominating MLST-types ST11, ST15 and ST268 comprised 68.0% of the 77 K. pneumoniae. Seven distinct STs were identified among 8 E. coli.

Conclusions

The treatment for infections caused by CRE isolates is challenged by the presence of multiple resistance determinants and plasmid replicons. Our results highlighted the expansion of blaKPC-2 carrying K. pneumoniae ST11, the new emergency of single blaNDM-5 carrying K. oxytoca ST36, as well as blaIMP-4 and blaNDM-1 co-carrying E. cloacae ST418, which alert us on the urgency for antimicrobial resistant surveillance, to prevent dissemination of these highly transmissible and dangerous lineages.

IS26-Mediated Transfer of bla NDM-1 as the Main Route of Resistance Transmission During a Polyclonal, Multispecies Outbreak in a German Hospital

One of the most demanding challenges in infection control is the worldwide dissemination of multidrug-resistant (MDR) bacteria in clinical settings. Especially the increasing prevalence of carbapenemase producing Gram-negative pathogens poses an urgent threat to public health, as these enzymes confer resistance to almost all β-lactam antibiotics including carbapenems. In this study, we report a prolonged nosocomial outbreak of various NDM-1-producing Enterobacterales species due to clonal spread and cross-species exchange of plasmids and possibly transposons. Between July 2015 and September 2017, a total of 51 carbapenemase-positive isolates were collected from 38 patients and three environmental sources in a single German hospital. Combining molecular typing methods and whole genome sequencing, the metallo-β-lactamase gene bla _NDM-1 was found to be present in 35 isolates of which seven additionally carried the carbapenemase gene bla _KPC-2. Core genome MLST (cgMLST) revealed different clusters of closely related isolates of Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Morganella morganii or Enterobacter cloacae indicating clonal spread. The detailed reconstruction of the plasmid sequences revealed that in all outbreak-associated isolates bla_NDM-1 was located on similar composite transposons, which were also very similar to Tn125 previously described for Acinetobacter baumannii. In contrast to Tn125, these structures were flanked by IS26 elements, which could facilitate horizontal gene transfer. Moreover, the identical plasmid was found to be shared by E. coli and M. morganii isolates. Our results highlight the importance of detailed genome-based analyses for complex nosocomial outbreaks, allowing the identification of causal genetic determinants and providing insights into potential mechanisms involved in the dissemination of antibiotic resistances between different bacterial species.

Coexistence of bla NDM-1 and rmtC on a Transferrable Plasmid of a Novel ST192 Klebsiella aerogenes Clinical Isolate

Introduction

The occurrence and development of antibiotic resistance are mainly caused by the spread of large plasmids carrying multiple antibiotic resistance genes. Recently, the association between 16S rRNA methyltransferase genes and β-lactamase genes carried by the same plasmid is of concern.

Methods

The Klebsiella aerogenes 1564 was isolated from the catheter tip of a patient in a tertiary hospital, Shanghai, China. The presence of the bla _NDM-1 and rmtC genes were assessed by PCR. Complete sequence of plasmid p1564 was determined. The K. aerogenes 1564 was characterized by antimicrobial susceptibility testing, Carbapenemase phenotype confirmation testing, conjugation experiment, S1-PFGE and multilocus sequence typing (MLST).

Results

Herein, we found that a New Delhi Metallo-β-lactamase-1 gene (bla _NDM-1) and a 16S rRNA methyltransferase gene (rmtC) coexisted on a transferrable plasmid of a carbapenem-resistant K. aerogenes clinical isolate. The K. aerogenes clinical isolate was found to belong to a novel sequence type 192 (ST192) determined by MLST. The sequencing results of the plasmid p1564 carrying bla _NDM-1 gene and rmtC gene showed that the size and guanine-cytosine content of the plasmid were 136, 902 bp and 51.8%, with 164 putative ORFs and two multidrug resistance gene islands. In addition to bla _NDM-1and rmtC, the plasmid contained bleomycin resistance gene (ble _MBL), CMY-6β-lactamase gene (bla _CMY-6), quaternary ammonium compound resistance gene (sugE), truncated quaternary ammonium compound resistance gene (qacEΔ1), aminoglycoside resistance gene (aacA4) and sulfonamide resistance gene (sul1). By comparison, p1564 has high homology with pHS36-NDM from Salmonella enterica subsp. enterica serovar Stanley reported in China, with similar size and both belonging to plasmid incompatibility group A/C.

Conclusion

The present study demonstrated for the first time the co-existence of rmtC and bla _NDM-1 in a novel ST192 K. aerogenes. The spread of plasmids harboring both bla _NDM-1 and rmtC may occur among Enterobacteriaceae in China.

The Inc FII Plasmid and its Contribution in the Transmission of blaNDM-1 and blaKPC-2 in Klebsiella pneumoniae in Egypt

The emergence of bla_KPC-2 and bla_NDM-1 producing Klebsiella pneumoniae represents a great problem in many Egyptian hospitals. One hundred and twenty-six K. pneumoniae isolates from patients admitted to Assiut University Hospital were identified by an API20E kit. Carbapenemase-producing K. pneumoniae (CPKP) was detected by the modified carbapenem inactivation method (mCIM), the EDTA-modified carbapenem inactivation method (eCIM), and an E-test. Based on the polymerase chain reaction, all isolates were negative for bla-_VIM-1 and bla-_IMP-1, fifteen of these isolates were positive for both bla_KPC-2 and bla_NDM-1, two isolates were positive for bla_KPC-2 only, and twenty-eight isolates were positive for bla-_NDM-1 only. Although one isolate was positive for the string test, all CPKP isolates were negative for capsular genes. Only 71.1% of CPKP transferred their plasmids to their corresponding transconjugants (E. coli J53). The resistance patterns of the clinical isolates and their transconjugates were similar, except for 12 isolates, which showed differences with their transconjugates in the resistance profile of four antibiotics. Molecular typing of the plasmids based on replicon typing showed that Inc FIIK and FII plasmids predominated in isolates and their transconjugants carrying bla_KPC-2 and/or bla_NDM-1. Conjugative Inc FII plasmids play an important role in the spread of CPKP, and their recognition is essential to limit their spread.

Expanding medicinal chemistry into 3D space: metallofragments as 3D scaffolds for fragment-based drug discovery

Fragment-based drug discovery (FBDD) is a powerful strategy for the identification of new bioactive molecules. FBDD relies on fragment libraries, generally of modest size, but of high chemical diversity. Although good chemical diversity in FBDD libraries has been achieved in many respects, achieving shape diversity - particularly fragments with three-dimensional (3D) structures - has remained challenging. A recent analysis revealed that >75% of all conventional, organic fragments are predominantly 1D or 2D in shape. However, 3D fragments are desired because molecular shape is one of the most important factors in molecular recognition by a biomolecule. To address this challenge, the use of inert metal complexes, so-called 'metallofragments' (mFs), to construct a 3D fragment library is introduced. A modest library of 71 compounds has been prepared with rich shape diversity as gauged by normalized principle moment of inertia (PMI) analysis. PMI analysis shows that these metallofragments occupy an area of fragment space that is unique and highly underrepresented when compared to conventional organic fragment libraries that are comprised of orders of magnitude more molecules. The potential value of this metallofragment library is demonstrated by screening against several different types of proteins, including an antiviral, an antibacterial, and an anticancer target. The suitability of the metallofragments for future hit-to-lead development was validated through the determination of IC50 and thermal shift values for select fragments against several proteins. These findings demonstrate the utility of metallofragment libraries as a means of accessing underutilized 3D fragment space for FBDD against a variety of protein targets.

Pterostilbene restores carbapenem susceptibility in New Delhi metallo-β-lactamase-producing isolates by inhibiting the activity of New Delhi metallo-β-lactamases

BACKGROUND AND PURPOSE

Bacteria producing New Delhi metallo-β-lactamase-1 (NDM-1) are an increasing clinical threat. NDM-1 can inactivate almost all β-lactams and is not sensitive to any existing β-lactamase inhibitors. To identify effective inhibitors of the NDM-1 enzyme and clarify the mechanism of action, a "lead compound" for developing more potent NDM-1 inhibitors needs to be provided.

EXPERIMENTAL APPROACH

Natural compounds were tested by enzyme inhibition screening to find potential inhibitors. MIC assays, growth curve assays, and time-kill assays were conducted to evaluate the in vitro antibacterial activity of pterostilbene and the combination of pterostilbene and meropenem. A murine thigh model and a mouse pneumonia model were used to evaluate the in vivo efficacy of combined therapy. Molecular modelling and a mutational analysis were used to clarify the mechanism of action.

KEY RESULTS

Pterostilbene significantly inhibited NDM-1 hydrolysis activity in enzyme inhibition screening assays and effectively restored the effectiveness of meropenem in vitro with NDM-expressing isolates in antibacterial activity assays. In addition, the combined therapy effectively reduced the bacterial burden in a murine thigh model and protected mice from pneumonia caused by Klebsiella pneumoniae. By means of molecular dynamics simulation, we observed that pterostilbene localized to the catalytic pocket of NDM-1, hindering substrate binding to NDM-1 and reducing NDM-1 activity.

CONCLUSIONS AND IMPLICATIONS

These findings indicated that pterostilbene combined with meropenem may offer a new safe and potential "lead compound" for the further development of NDM-1 inhibitors.

Sewage from Airplanes Exhibits High Abundance and Diversity of Antibiotic Resistance Genes

Airplane sanitary facilities are shared by an international audience. We hypothesized the corresponding sewage to be an extraordinary source of antibiotic-resistant bacteria (ARB) and resistance genes (ARG) in terms of diversity and quantity. Accordingly, we analyzed ARG and ARB in airplane-borne sewage using complementary approaches: metagenomics, quantitative polymerase chain reaction (qPCR), and cultivation. For the purpose of comparison, we also quantified ARG and ARB in the inlets of municipal treatment plants with and without connection to airports. As expected, airplane sewage contained an extraordinarily rich set of mobile ARG, and the relative abundances of genes were mostly increased compared to typical raw sewage of municipal origin. Moreover, combined resistance against third-generation cephalosporins, fluorochinolones, and aminoglycosides was unusually common (28.9%) among Escherichia coli isolated from airplane sewage. This percentage exceeds the one reported for German clinical isolates by a factor of 8. Our findings suggest that airplane-borne sewage can effectively contribute to the fast and global spread of antibiotic resistance.

New Delhi Metallo-β-Lactamase 1-Producing Klebsiella pneumoniae ST719 Isolated from a Neonate in China

The spread of carbapenem-resistant Klebsiella pneumoniae has become a significant problem for public health in recent years. In this study, we reported a New Delhi metallo-β-lactamase 1 (NDM-1)-producing K. pneumoniae strain KP14003 from a neonate in Beijing, China. Whole-genome sequencing was performed. The strain belonged to sequence type ST719. Coexistence of bla_NDM-1 and bla_SHV-12 was found on a self-transferable plasmid, which had a typical IncX3 backbone. The horizontal transfer of bla_NDM-1 was associated with Tn125 followed by possible transposition events. Other class A extended-spectrum β-lactamase genes (bla_SHV-27 and bla_TEM-1) were also identified on chromosome or plasmid. The dissemination of NDM-1-producing K. pneumoniae causes great challenges to the treatment of clinical infections. Effective actions need to be taken to control the further spread of this pathogen.

Co-existence of virulence factors and antibiotic resistance in new Klebsiella pneumoniae clones emerging in south of Italy

Background

Endemic presence of Klebsiella pneumoniae resistant to carbapenem in Italy has been due principally to the clonal expansion of CC258 isolates; however, recent studies suggest an ongoing epidemiological change in this geographical area.

Methods

50 K. pneumoniae strains, 25 carbapenem-resistant (CR-Kp) and 25 susceptible (CS-Kp), collected from march 2014 to march 2016 at the Laboratory of Bacteriology of the Paolo Giaccone Polyclinic University hospital of Palermo, Italy, were characterized for antibiotic susceptibility and fully sequenced by next generation sequencing (NGS) for the in silico analysis of resistome, virulome, multi-locus sequence typing (MLST) and core single nucleotide polymorphism (SNP) genotypes

Results

MLST in silico analysis of CR-Kp showed that 52% of isolates belonged to CC258, followed by ST395 (12%), ST307 (12%), ST392 (8%), ST348 (8%), ST405 (4%) and ST101 (4%). In the CS-Kp group, the most represented isolate was ST405 (20%), followed by ST392 and ST15 (12%), ST395, ST307 and ST1727 (8%). The in silico β-lactamase analysis of the CR-Kp group showed that the most detected gene was blaSHV (100%), followed by blaTEM (92%), blaKPC (88%), blaOXA (88%) and blaCTX-M (32%). The virulome analysis detected mrk operon in all studied isolates, and wzi-2 was found in three CR-Kp isolates (12%). Furthermore, the distribution of virulence genes encoding for the yersiniabactin system, its receptor fyuA and the aerobactin system did not show significant distribution differences between CR-Kp and CS-Kp, whereas the Klebsiella ferrous iron uptake system (kfuA, kfuB and kfuC genes), the two-component system kvgAS and the microcin E495 were significantly (p < 0.05) prevalent in the CS-Kp group compared to the CR-Kp group.

Core SNP genotyping, correlating with the MLST data, allowed greater strain tracking and discrimination than MLST analysis.

Conclusions

Our data support the idea that an epidemiological change is ongoing in the Palermo area (Sicily, Italy). In addition, our analysis revealed the co-existence of antibiotic resistance and virulence factors in CR-Kp isolates; this characteristic should be considered for future genomic surveillance studies.

Isolation of five Enterobacteriaceae species harbouring blaNDM-1 and mcr-1 plasmids from a single paediatric patient

In Argentina, NDM metallo-β-lactamase was first reported in 2013. By now, it has disseminated throughout the country in diverse Gram negative bacteria. Here, we report the case of a paediatric patient that underwent a 1-year hospitalisation due to erythrodermic psoriasis in 2014 and received multiple antimicrobial treatments. During his stay, five isolates were obtained from rectal swabs (rs) or blood culture (bc) suspicious of carbapenemase production: a K. quasipneumoniae subsp. quasipneumoniae (rs), Citrobacter freundii (rs), Escherichia coli (bc), Enterobacter cloacae (rs), and a Serratia marcescens (bc). The isolates were studied with broth microdilution, biparental conjugation and plasmid and whole genome sequencing (Illumina). All isolates harboured an 138,998-bp type 1 IncC plasmid that carried bla_NDM-1, ble_MBL, bla_CMY-6, rmtC, aac(6’)-Ib, and sul1 resistance genes. Additionally, the bla_NDM-plasmids contained ISKpn8 an insertion sequence previously described as associated only to bla_KPC. One isolate, a colistin-resistant E. coli, also carried a mcr-1-containing an IncI2 plasmid, which did not harbour additional resistance. The whole genome of K. quasipneumoniae subsp. quasipneumoniae isolate was fully sequenced. This isolate harboured, additionally to bla_NDM, three plasmid-mediated quinolone resistance genes: qnrB4, qnrB52 and aac(6’)-Ib-cr1. The E. cloacae isolate also harboured qnrA1. These findings alert to the underestimated horizontal dissemination of multidrug-resistant plasmids limiting treatment options with last resort antimicrobials.

Resistome and a Novel blaNDM-1-Harboring Plasmid of an Acinetobacter haemolyticus Strain from a Children's Hospital in Puebla, Mexico

Acinetobacter calcoaceticus-baumannii complex isolates have been frequently associated with hospital and community infections, with A. baumannii being the most common. Other Acinetobacter spp. not belonging to this complex also cause infections in hospital settings, and the incidence has increased over the past few years. Some species of the Acinetobacter genus possess a great diversity of antibiotic resistance mechanisms, such as efflux pumps, porins, and resistance genes that can be acquired and disseminated by mobilizable genetic elements. By means of whole-genome sequencing, we describe in the clinical Acinetobacter haemolyticus strain AN54 different mechanisms of resistance that involve bla_OXA-265, bla_NDM-1, aphA6, aac(6’)-Ig, and a resistance-nodulation-cell division-type efflux pump. This strain carries six plasmids, of which the plasmid pAhaeAN54e contains bla_NDM-1 in a Tn125-like transposon that is truncated at the 3′ end. This strain also has an insertion sequence IS91 and seven genes encoding hypothetical proteins. The pAhaeAN54e plasmid is nontypable and different from other plasmids carrying bla_NDM-1 that have been reported in Mexico and other countries. The presence of these kinds of plasmids in an opportunistic pathogen such as A. haemolyticus highlights the role that these plasmids play in the dissemination of antibiotic resistance genes, especially against carbapenems, in Mexican hospitals.

Outbreak of blaNDM-5-Harboring Klebsiella pneumoniae ST290 in a Tertiary Hospital in China

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has posed a great threat to public health. Among 133 nonduplicated CRKP isolates collected between September 2016 and November 2017 in a tertiary hospital in China, 89 (89/133, 66.9%) and 31 (31/133, 23.3%) were positive for bla_NDM-5 and bla_KPC-2. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) revealed that ST290 represented the majority of NDM-5 producers (67/89, 75.3%) and PFGE cluster E accounted for 50 (50/67, 74.6%) ST290 isolates from the burn ward, suggesting that K. pneumoniae ST290 clone carrying bla_NDM-5 resulted in an outbreak in this hospital. Whole genome sequencing of the plasmid carrying bla_NDM-5 showed that the resistance gene bla_NDM-5 was located in a ∼49 kb multireplicon plasmid with a peculiar insertion of ISKpn19 of the IncX3-type plasmid. To the best of our knowledge, this is the first report of outbreak of K. pneumoniae ST290 clone carrying bla_NDM-5.

Satellite tracking of gulls and genomic characterization of faecal bacteria reveals environmentally mediated acquisition and dispersal of antimicrobial-resistant Escherichia coli on the Kenai Peninsula, Alaska

Gulls (Larus spp.) have frequently been reported to carry Escherichia coli exhibiting antimicrobial resistance (AMR E. coli); however, the pathways governing the acquisition and dispersal of such bacteria are not well described. We equipped 17 landfill-foraging gulls with satellite transmitters and collected gull faecal samples longitudinally from four locations on the Kenai Peninsula, Alaska to assess: (a) gull attendance and transitions between sites, (b) spatiotemporal prevalence of faecally shed AMR E. coli, and (c) genomic relatedness of AMR E. coli isolates among sites. We also sampled Pacific salmon (Oncorhynchus spp.) harvested as part of personal-use dipnet fisheries at two sites to assess potential contamination with AMR E. coli. Among our study sites, marked gulls most commonly occupied the lower Kenai River (61% of site locations) followed by the Soldotna landfill (11%), lower Kasilof River (5%) and upper Kenai River (<1%). Gulls primarily moved between the Soldotna landfill and the lower Kenai River (94% of transitions among sites), which were also the two locations with the highest prevalence of AMR E. coli. There was relatively high spatial and temporal variability in AMR E. coli prevalence in gull faeces and there was no evidence of contamination on salmon harvested in personal-use fisheries. We identified E. coli sequence types and AMR genes of clinical importance, with some isolates possessing genes associated with resistance to as many as eight antibiotic classes. Our findings suggest that gulls acquire AMR E. coli at habitats with anthropogenic inputs and subsequent movements may represent pathways through which AMR is dispersed.

First identification of blaNDM-1 carbapenemase in blaOXA-94-producing Acinetobacter baumannii ST85 in Spain

INTRODUCTION

NDM-1 carbapenemase is spreading rapidly all over the world, but this metallo-beta-lactamase has just been detected for the first time in an Acinetobacter baumannii (Ab) isolate of the ST85 clone in Spain. The aim of this study was to characterize a NDM-1-producing carbapenem-resistant A. baumannii (CR-Ab) isolate submitted to the Andalusian PIRASOA [infection prevention program] referral laboratory.

METHODS

Carbapenemases were detected by PCR and Sanger DNA sequencing. Whole genome sequencing was performed by NGS (Miseq, Illumina). Resistance genes were identified with RESfinder, while MLSTfinder was used for sequence typing (ST). The genetic location of bla_NDM-1 was determined by nuclease S-1/PFGE/hybridization with specific probe.

RESULTS

The isolate was susceptible to amikacin and tigecycline and belonged to the ST85 clone. bla_OXA-94 and bla_NDM-1 were identified by PCR and Sanger DNA sequencing, respectively. The resistance genes aadB, bla_ADC-25, bla_NDM-1, bla_OXA-94, msr(E), mph(E) and floR,sul2 were identified by NGS. The chromosome of the isolate contained a defective Tn125 transposon with bla_NDM-1 flanked by the insertion sequences ISAbA125 and ISAba14. The bla_NDM-1 gene was only detected in the chromosomal DNA.

CONCLUSION

This is the first time that bla_NDM-1 has been detected and characterized in a bla_OXA-94-producing CR-Ab isolate belonging to the ST85 clone in Spain.

Emergence of IncFIA Plasmid-Carrying blaNDM-1 Among Klebsiella pneumoniae and Enterobacter cloacae Isolates in a Tertiary Referral Hospital in Mexico

The emergence of New Delhi metallo-β-lactamase 1 on carbapenemase-producing bacteria has raised a major worldwide public health concern. This study reports the dissemination of bla_NDM-1 in carbapenem-resistant isolates that caused nosocomial infections in a tertiary hospital in Mexico City. Seven Enterobacter cloacae and three Klebsiella pneumoniae nosocomial isolates from the same time period harbored the bla_NDM-1 gene. The resistance phenotype and the bla_NDM-1 gene were transferred through conjugative plasmids belonging to the incompatibility group IncFIA of 85, 101, and 195 kb in E. cloacae and 95 and 101 kb in K. pneumoniae isolates. Restriction fragment length polymorphism analysis showed that bla_NDM-1 was carried in similar plasmids with molecular sizes of 101 and 85 kb, each one in three isolates of E. cloacae and one of 101 kb on two isolates of K. pneumoniae. During a 9-month period, six of the seven isolates of E. cloacae analyzed harbored bla_NDM-1 and belonged to clone E1. Similarly, over a 5-month period, two of the three K. pneumoniae isolates that harbored bla_NDM-1 belonged to clone K1. These results demonstrate the horizontal transfer of bla_NDM-1 between different bacterial species, dissemination of clones with high levels of resistance to carbapenems, and underscore the need for heightened measures to control their further spread.

Evaluation of co-transfer of plasmid-mediated fluoroquinolone resistance genes and bla NDM gene in Enterobacteriaceae causing neonatal septicaemia

Background

The bla_NDM-1 (New Delhi Metallo-β-lactamase-1) gene has disseminated around the globe. NDM-1 producers are found to co-harbour resistance genes against many antimicrobials, including fluoroquinolones. The spread of large plasmids, carrying both bla_NDM and plasmid-mediated fluoroquinolone resistance (PMQR) markers, is one of the main reasons for the failure of these essential antimicrobials.

Methods

Enterobacteriaceae (n = 73) isolated from the blood of septicaemic neonates, admitted at a neonatal intensive care unit (NICU) in Kolkata, India, were identified followed by PFGE, antibiotic susceptibility testing and determination of MIC values for meropenem and ciprofloxacin. Metallo-β-lactamases and PMQRs were identified by PCR. NDM-positive isolates were studied for mutations in GyrA & ParC and for co-transmission of bla_NDM and PMQR genes (aac(6′)-Ib-cr, qnrB, qnrS) through conjugation or transformation. Plasmid types, integrons, plasmid addiction systems, and genetic environment of the bla_NDM gene in NDM-positive isolates and their transconjugants/ transformants were studied.

Results

Isolated Enterobacteriaceae comprised of Klebsiella pneumoniae (n = 55), Escherichia coli (n = 16), Enterobacter cloacae (n = 1) and Enterobacter aerogenes (n = 1). The rates of ciprofloxacin (90%) and meropenem (49%) non-susceptibility were high. NDM was the only metallo-β-lactamase found in this study. NDM-1 was the predominant metallo-β-lactamase but NDM-5, NDM-7, and NDM-15 were also found. There was no significant difference in ciprofloxacin non-susceptibility (97% vs 85%) and the prevalence of PMQRs (85% vs 77%) between NDM-positive and NDM-negative isolates. Among the PMQRs, aac(6′)-Ib-cr was predominant followed by qnrB1 and qnrS1. Twenty-nine isolates (40%) co-harboured PMQRs and bla_NDM, of which 12 co-transferred PMQRs along with bla_NDM in large plasmids of IncFIIK, IncA/C, and IncN types. Eighty-two percent of NDM-positive isolates possessed GyrA and/or ParC mutations. Plasmids carrying only bla_NDM were of IncHIB-M type predominantly. Most of the isolates had ISAba125 in the upstream region of the bla_NDM gene.

Conclusion

We hypothesize that the spread of PMQRs was independent of the spread of NDM-1 as their co-transfer was confirmed only in a few isolates. However, the co-occurrence of these genes poses a great threat to the treatment of neonates.

Electronic supplementary material

The online version of this article (10.1186/s13756-019-0477-7) contains supplementary material, which is available to authorized users.