Y229W substitution in #NDM-1/L209F variant restores the hydrolytic activity of the enzyme towards #penicillins, #cephalosporins and #carbapenems: kinetic profile and molecular dynamic studies (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Y229W substitution in NDM-1/L209F variant restores the hydrolytic activity of the enzyme towards penicillins, cephalosporins and carbapenems: kinetic profile and molecular dynamic studies

Alessandra Piccirilli, Fabrizia Brisdelli, Massimiliano Aschi, Giuseppe Celenza, Gianfranco Amicosante, Mariagrazia Perilli

DOI: 10.1128/AAC.02270-18



NDM-1 enzyme is the most common metallo-β-lactamase identified in many Gram-negative bacteria causing severe nosocomial infections. The aim of this study was to focus the attention on non-active site residues, L209 and Y229, of NDM-1 and to investigate their role in the catalytic mechanism. Specifically, the effect of Y229W substitution in L209F variant was evaluated by antimicrobial susceptibility testing, kinetic and molecular dynamic (MD) studies. The Y229W single mutant and L209F/Y229W double mutant were generated by site-directed mutagenesis. The Km, kcat and kcat/Km kinetic constants, calculated for the two mutants, were compared with those of NDM-1 and L209F variants. Compared to L209F single mutant, L209F/Y229W mutant showed a remarkable increase of kcat values of 100-, 240-, 250- and 420-fold for imipenem, meropenem, benzylpenicillin and cefepime, respectively. In L209F/Y229W enzyme we observed a remarkable increase of kcat/Km of 370-, 140- and 80-fold for cefepime, meropenem and cefazolin, respectively. The same behavior was stated by antimicrobial susceptibility test. MD simulations were carried out on both L209F and L209F/Y229W enzymes complexed with benzylpenicillin focusing the attention on the overall mechanical features and on the differences between the two systems. With respect to L209F variant, the L209F/Y229W double mutant showed a mechanical stabilization of Loop 10 and N-terminal region but a destabilization of C-terminal and 149-154 regions. The epistatic effect of Y229W mutation jointly with stabilization of Loop 10 lead to a better catalytic efficiency of β-lactams. NDM numbering is used in order to facilitate the comparison with other NDM-1 studies.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Antibiotics; Drugs Resistance; Carbapenem; Beta-lactams; NDM1; Imipenem; Meropenem; Penicillins.



Dose-dependent Synergistic Interactions of #Colistin with #Rifampicin, #Meropenem and #Tigecycline against #Carbapenem-resistant #Klebsiella pneumoniae #Biofilms (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Dose-dependent Synergistic Interactions of Colistin with Rifampicin, Meropenem and Tigecycline against Carbapenem-resistant Klebsiella pneumoniae Biofilms

Anastasia Geladari, Maria Simitsopoulou, Charalampos Antachopoulos, Emmanuel Roilides

DOI: 10.1128/AAC.02357-18



Carbapenem-resistant Klebsiella pneumoniae (CR-Kp) can cause biofilm-related bloodstream infections associated with significant morbidity and mortality worldwide. We investigated the bactericidal activities of colistin (CST), rifampicin (RIF), meropenem (MEM), gentamicin (GEN) and tigecycline (TGC) alone and that of CST in combination with RIF, MEM, GEN or TGC against CR-Kp mature biofilms. Twenty CR-Kp blood isolates were derived from equal number of bloodstream infections in adult patients. Biofilm formation was assessed by staining with 0.4% crystal violet and measuring optical density spectrophotometrically at 545 nm. Biofilm damage was measured as % reduction of metabolic activity by XTT assay. MIC50 for biofilms was determined as the minimum concentration that caused ≥50% bacterial damage compared to that for untreated controls. Antibacterial drug interactions were analyzed by the Bliss independence model. Four of the twenty CR-Kp isolates were biofilm producers. Biofilm MIC50’s of CST, RIF, MEM, GEN and TGC for these isolates were 64, 8, >256, 128 and 8 mg/L, respectively. Synergistic interactions were observed at 32-64 mg/L of CST combined with 0.25-4 mg/L of RIF, at 32 mg/L of CST combined with 0.007-0.25 mg/L of MEM, and at 16-32 mg/L of CST combined with 16-64 mg/L of TGC. The synergy was highest for CST+RIF, with %ΔE±SE 49.87±9.22 compared to 29.52±4.97 for CST+MEM (p<0.001) and 32.44±6.49 for CST+TGC (p<0.001). Indifferent results were exhibited by CST+GEN. None of the combinations exhibited antagonism. These drug interactive findings, especially that of CST with RIF, may be of importance in the treatment of biofilm-related CR-Kp infections.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Antibiotics; Drugs Resistance; Carbapene; Klebsiella pneumoniae; Colistin; Gentamicin; Tigecycline; Meropenem; Rifampicin.


Molecular characterisation of the #NDM-1-encoding #plasmid p2189-NDM in an #Escherichia coli ST410 clinical isolate from #Ghana (PLoS One, abstract)

[Source: PLoS One, full page: (LINK). Abstract, edited.]


Molecular characterisation of the NDM-1-encoding plasmid p2189-NDM in an Escherichia coli ST410 clinical isolate from Ghana

Alafate Ayibieke, Wakana Sato, Samiratu Mahazu, Isaac Prah, John Addow-Thompson, Mitsuko Ohashi, Toshihiko Suzuki, Shiroh Iwanaga, Anthony Ablordey, Ryoichi Saito

Published: December 21, 2018 / DOI: https://doi.org/10.1371/journal.pone.0209623



Global dissemination of New Delhi metallo-β-lactamase (NDM)-producing bacteria has become a major health threat. However, there are few reports regarding the identification and characterisation of NDM-producing bacteria from West Africa, including Ghana. An Escherichia coli strain with resistance to meropenem was isolated from the Tamale Teaching Hospital in Ghana. Its identification and determination of antibiotic susceptibility profile were carried out using commercial systems. The antibiotic resistance mechanism was analysed by phenotypic detection kits, PCR, and DNA sequencing. Conjugation experiments, S1 nuclease pulsed field gel electrophoresis, and Southern blotting were performed. Finally, the NDM-1-harbouring plasmid was characterised using next-generation sequencing and phylogenetic analysis. The meropenem-resistant Escherichia coli strain EC2189 harboured blaNDM-1 and belonged to sequence type 410. blaNDM-1 was located on the IncHI type transferrable plasmid p2189-NDM (248,807 bp long), which co-carried multiple resistance genes, such as blaCTX-M-15, aadA1, aac(6′)-Ib, sul3, dfrA12, and cmlA1. p2189-NDM phylogenetically differed from previously identified blaNDM-1-positive IncHI type plasmids. A truncated Tn125 containing blaNDM-1 was bracketed by an ISSm-1-like insertion sequence upstream and by a site-specific integrase downstream. To the best of our knowledge, we have, for the first time identified and molecularly characterised an NDM-1-producing Enterobacteriaceae strain in Ghana with blaNDM-1 that had a novel genetic structure. Our findings indicate a possibility of NDM-1 dissemination in Ghana and underscore the need for constant monitoring of carbapenemase-producing bacteria.


Citation: Ayibieke A, Sato W, Mahazu S, Prah I, Addow-Thompson J, Ohashi M, et al. (2018) Molecular characterisation of the NDM-1-encoding plasmid p2189-NDM in an Escherichia coli ST410 clinical isolate from Ghana. PLoS ONE 13(12): e0209623. https://doi.org/10.1371/journal.pone.0209623

Editor: Yung-Fu Chang, Cornell University, UNITED STATES

Received: September 26, 2018; Accepted: December 7, 2018; Published: December 21, 2018

Copyright: © 2018 Ayibieke et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: This study was supported by the Japan Agency for Medical Research and Development (AMED, URL: http://www.amed.go.jp/en/) under Grant Number 17fm0108010h0003 (MO, TS, SI, RS). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Keywords: Antibiotics; Drugs resistance; NMD1; Carbapene; Ghana.


Diverse #vectors and mechanisms #spread #NDM beta-lactamases among #carbapenem resistant #Enterobacteriaceae in the Greater #Boston area (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Diverse vectors and mechanisms spread NDM beta-lactamases among carbapenem resistant Enterobacteriaceae in the Greater Boston area

Nicole Pecora, Xiaomin Zhao, Kathleen Nudel, Maria Hoffmann, Ning Li, Andrew B. Onderdonk, Deborah Yokoe, Eric Brown, Marc Allard, Lynn Bry

DOI: 10.1128/AAC.02040-18



New Delhi metallo-beta-lactamases (NDMs) are an uncommon but emerging cause of carbapenem resistance in the United States. Genomic factors promoting their domestic spread remain poorly characterized. A prospective genomic surveillance program among Boston-area hospitals identified multiple new occurrences of NDM carrying strains of E. coli and E. cloacaecomplex in inpatient and outpatient settings, representing the first occurrences of NDM-mediated resistance since initiating genomic surveillance in 2011. Cases included domestic patients with no international exposures. PacBio sequencing of isolates identified strain characteristics, resistance genes, and the complement of mobile vectors mediating spread. Analyses revealed a common 3114-bp region containing the blaNDM gene, with carriage of this conserved region among unique strains by diverse transposon and plasmid backbones. Functional studies revealed broad capacity for blaNDM transmission by conjugation, transposition, and complex inter-plasmid recombination events. NDMs represent a rapidly spreading form of drug resistance that can occur in inpatient and outpatient settings and in patients without international exposures. In contrast to Tn4401-based spread of Klebsiella pneumoniae carbapenemases (KPCs), diverse transposable elements mobilize NDM enzymes, commonly with other resistance genes, enabling naïve strains to acquire multi- and extensively-drug resistance profiles with single transposition or plasmid conjugation events. Genomic surveillance provides effective means to rapidly identify these gene-level drivers of resistance and mobilization, to inform clinical decisions to prevent further spread.

Copyright © 2018 American Society for Microbiology. All Rights Reserved.

Keywords: Antibiotics; Drugs Resistance; Carbapenem; NDM1; USA; Enterobacteriaceae.


#Spreading #patterns of #NDM-producing #Enterobacteriaceae in clinical and #environmental settings in #Yangon, #Myanmar (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Spreading patterns of NDM-producing Enterobacteriaceae in clinical and environmental settings in Yangon, Myanmar

Yo Sugawara, Yukihiro Akeda, Hideharu Hagiya, Noriko Sakamoto, Dan Takeuchi, Rathina Kumar Shanmugakani, Daisuke Motooka, Isao Nishi, Khwar Nyo Zin, Mya Mya Aye, Thuzar Myint,Kazunori Tomono, Shigeyuki Hamada

DOI: 10.1128/AAC.01924-18



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

Copyright © 2018 American Society for Microbiology. All Rights Reserved.

Keywords: Antibiotics; Drugs Resistance; Carbapenem; Myanmar; Enterobacteriaceae.


#Cefiderocol versus #imipenem-cilastatin for the #treatment of complicated #UTIs caused by Gram-negative #uropathogens: a phase 2, randomised, double-blind, non-inferiority trial (Lancet Infect Dis., abstract)

[Source: The Lancet Infectious Diseases, full page: (LINK). Abstract, edited.]

Cefiderocol versus imipenem-cilastatin for the treatment of complicated urinary tract infections caused by Gram-negative uropathogens: a phase 2, randomised, double-blind, non-inferiority trial

Simon Portsmouth, MD,  David van Veenhuyzen, MBChB, Roger Echols, MD, Mitsuaki Machida, MS, Juan Camilo Arjona Ferreira, MD, Mari Ariyasu, BPharm, Prof Peter Tenke, MD, Tsutae Den Nagata, MD

Published: October 25, 2018 / DOI: https://doi.org/10.1016/S1473-3099(18)30554-1




Carbapenem-resistant Gram-negative bacteria represent the highest priority for addressing global antibiotic resistance. Cefiderocol (S-649266), a new siderophore cephalosporin, has broad activity against Enterobacteriaceae and non-fermenting bacteria, such asPseudomonas aeruginosa and Acinetobacter baumannii, including carbapenem-resistant strains. We assessed the efficacy and safety of cefiderocol versus imipenem-cilastatin for the treatment of complicated urinary tract infection in patients at risk of multidrug-resistant Gram-negative infections.


We did a phase 2, multicentre, double-blind, parallel-group non-inferiority trial at 67 hospitals in 15 countries. Adults (≥18 years) admitted to hospital with a clinical diagnosis of complicated urinary tract infection with or without pyelonephritis or those with acute uncomplicated pyelonephritis were randomly assigned (2:1) by an interactive web or voice response system to receive 1 h intravenous infusions of cefiderocol (2 g) or imipenem-cilastatin (1 g each) three times daily, every 8 h for 7–14 days. Patients were excluded if they had a baseline urine culture with more than two uropathogens, a fungal urinary tract infection, or pathogens known to be carbapenem resistant. The primary endpoint was the composite of clinical and microbiological outcomes at test of cure (ie, 7 days after treatment cessation), which was used to establish non-inferiority (15% and 20% margins) of cefiderocol versus imipenem-cilastatin. The primary efficacy analysis was done on a modified intention-to-treat population, which included all randomly assigned individuals who received at least one dose of study drug and had a qualifying Gram-negative uropathogen (≥1 × 10 5 colony-forming units [CFU]/mL). Safety was assessed in all randomly assigned individuals who received at least one dose of study drug, according to the treatment they received. This study is registered withClinicalTrials.gov, number NCT02321800.


Between Feb 5, 2015, and Aug 16, 2016, 452 patients were randomly assigned to cefiderocol (n=303) or imipenem-cilastatin (n=149), of whom 448 patients (n=300 in the cefiderocol group; n=148 in the imipenem-cilastatin group) received treatment. 371 patients (n=252 patients in the cefiderocol group; n=119 patients in the imipenem-cilastatin group) had qualifying Gram-negative uropathogen (≥1 × 105 CFU/mL) and were included in the primary efficacy analysis. At test of cure, the primary efficacy endpoint was achieved by 183 (73%) of 252 patients in the cefiderocol group and 65 (55%) of 119 patients in the imipenem-cilastatin group, with an adjusted treatment difference of 18·58% (95% CI 8·23–28·92; p=0·0004), establishing the non-inferiority of cefiderocol. Cefiderocol was well tolerated. Adverse events occurred in 122 (41%) of 300 patients in the cefiderocol group and 76 (51%) of 148 patients in the imipenem-cilastatin group, with gastrointestinal disorders (ie, diarrhoea, constipation, nausea, vomiting, and abdominal pain) the most common adverse events for both treatment groups (35 [12%] patients in the cefiderocol group and 27 [18%] patients in the imipenem-cilastatin group).


Intravenous infusion of cefiderocol (2 g) three times daily was non-inferior compared with imipenem-cilastatin (1 g each) for the treatment of complicated urinary tract infection in people with multidrug-resistant Gram-negative infections. The results of this study will provide the basis for submission of a New Drug Application to the US Food and Drug Administration. Clinical trials of hospital-acquired pneumonia and carbapenem-resistant infections are ongoing.


Shionogi & Co Ltd, Shionogi Inc.

Keywords: Antibiotics; Drugs Resistance; Carbapenem; Imipenem-Cilastatin; Cefiderocol.


Impact of Combination #Therapy vs Monotherapy on #Mortality from #Carbapenem-Resistant #Enterobacteriaceae #Bacteremia: A Retrospective Observational Study from a Chinese Network (Antimicrob Agents Chemother., abstract)

[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]

Impact of Combination Therapy vs Monotherapy on Mortality from Carbapenem-Resistant Enterobacteriaceae Bacteremia: A Retrospective Observational Study from a Chinese Network

Xiaojuan Wang, Qi Wang, Bin Cao, Shijun Sun, Yawei Zhang, Bing Gu, Binbin Li, Kang Liao, Feng Zhao, Liang Jin, Chunmei Jin, Chunxia Yang, Fengyan Pei, Zhijie Zhang, Hui Wang

DOI: 10.1128/AAC.01511-18



A total of 164 bloodstream infection cases due to carbapenem-resistant Enterobacteriaceae (CRE) in 2013-2017 were retrospectively collected from 36 tertiary hospitals in 19 provinces in China to evaluate outcomes and risk factors for mortality by univariable and multivariable analysis. The most frequent infected species was Klebsiella pneumoniae (69.5%, 114/164). The overall in-hospital and 14-day mortality were 32.9% (54/164) and 31.1% (42/135), respectively. Multivariable analysis revealed that septic shock (adjusted odds ratio [aOR] 6.339, 95% confidence interval [CI] 1.586-25.332, P = 0.009), Pitt bacteremia score (aOR 1.300, 95% CI 1.009-1.676, P = 0.042), and Charlson comorbidity index (aOR 1.392, 95% CI 1.104-1.755, P = 0.005) were independently associated with hazard effect on mortality. Combination therapy, especially tigecycline-based combination therapy had the lowest in-hospital mortality and rates of bacterial clearance. Survival analysis revealed that appropriate therapy was associated with lower 14-day mortality than inappropriate therapy (including non-active therapy, P = 0.022); combination therapy was superior to monotherapy (P = 0.036); metallo-β-lactamase producers resulted in lower 14-day mortality than strains without carbapenemases or KPC-2 producers (P= 0.009); strains with minimum inhibitory concentrations (MICs) > 8 mg/L for meropenem were associated with higher 14-day mortality than that with MICs ≤ 8 mg/L (P = 0.037). Collectively, severity of illness, meropenem MICs > 8 mg/L, carbapenemase-producing types are associated with clinical outcome. Early detection of carbapenemase type and initiating appropriate combination therapy within 96 h might be helpful for improving survival.

Copyright © 2018 American Society for Microbiology. All Rights Reserved.

Keywords: Antibiotics; Drugs Resistance; Carbapenem; Tigecycline; Enterobacteriaceae; China.