Preservation of Acquired Colistin Resistance in Gram-Negative Bacteria

ABSTRACTColistin-resistant mutants were obtained from 17 colistin-susceptible strains ofAcinetobacter baumannii,Pseudomonas aeruginosa,Klebsiella pneumoniae, andEscherichia coli. The stability of colistin resistance in these mutants was investigated. Three of four colistin-resistantP. aeruginosamutants recovered colistin susceptibility in colistin-free medium; however, colistin-susceptible revertants were obtained from only one strain each ofA. baumanniiandE. coli. No susceptible revertants were obtained fromK. pneumoniaemutants.

Download Full-text

Heterogeneous and Flexible Transmission ofmcr-1in Hospital-AssociatedEscherichia coli

mBio ◽

10.1128/mbio.00943-18 ◽

2018 ◽

Vol 9 (4) ◽

Cited By ~ 23

Author(s):

Yingbo Shen ◽

Zuowei Wu ◽

Yang Wang ◽

Rong Zhang ◽

Hong-Wei Zhou ◽

...

Keyword(s):

Escherichia Coli ◽

Genomic Analysis ◽

Multidrug Resistant ◽

Fluoroquinolone Resistance ◽

Gram Negative Bacteria ◽

Colistin Resistance ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Genes Encoding

ABSTRACTThe recent emergence of a transferable colistin resistance mechanism, MCR-1, has gained global attention because of its threat to clinical treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, the possible transmission route ofmcr-1amongEnterobacteriaceaespecies in clinical settings is largely unknown. Here, we present a comprehensive genomic analysis ofEscherichia coliisolates collected in a hospital in Hangzhou, China. We found thatmcr-1-carrying isolates from clinical infections and feces of inpatients and healthy volunteers were genetically diverse and were not closely related phylogenetically, suggesting that clonal expansion is not involved in the spread ofmcr-1. Themcr-1gene was found on either chromosomes or plasmids, but in most of theE. coliisolates,mcr-1was carried on plasmids. The genetic context of the plasmids showed considerable diversity as evidenced by the different functional insertion sequence (IS) elements, toxin-antitoxin (TA) systems, heavy metal resistance determinants, and Rep proteins of broad-host-range plasmids. Additionally, the genomic analysis revealed nosocomial transmission ofmcr-1and the coexistence ofmcr-1with other genes encoding β-lactamases and fluoroquinolone resistance in theE. coliisolates. These findings indicate thatmcr-1is heterogeneously disseminated in both commensal and pathogenic strains ofE. coli, suggest the high flexibility of this gene in its association with diverse genetic backgrounds of the hosts, and provide new insights into the genome epidemiology ofmcr-1among hospital-associatedE. colistrains.IMPORTANCEColistin represents one of the very few available drugs for treating infections caused by extensively multidrug-resistant Gram-negative bacteria. The recently emergentmcr-1colistin resistance gene threatens the clinical utility of colistin and has gained global attention. Howmcr-1spreads in hospital settings remains unknown and was investigated by whole-genome sequencing ofmcr-1-carryingEscherichia coliin this study. The findings revealed extraordinary flexibility ofmcr-1in its spread among genetically diverseE. colihosts and plasmids, nosocomial transmission ofmcr-1-carryingE. coli, and the continuous emergence of novel Inc types of plasmids carryingmcr-1and newmcr-1variants. Additionally,mcr-1was found to be frequently associated with other genes encoding β-lactams and fluoroquinolone resistance. These findings provide important information on the transmission and epidemiology ofmcr-1and are of significant public health importance as the information is expected to facilitate the control of this significant antibiotic resistance threat.

Download Full-text

National Surveillance of Antimicrobial Susceptibility of Bacteremic Gram-Negative Bacteria with Emphasis on Community-Acquired Resistant Isolates: Report from the 2019 Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART)

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01089-20 ◽

2020 ◽

Vol 64 (10) ◽

Author(s):

Po-Yu Liu ◽

Yu-Lin Lee ◽

Min-Chi Lu ◽

Pei-Lan Shao ◽

Po-Liang Lu ◽

...

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Antimicrobial Resistance ◽

Klebsiella Pneumoniae ◽

Gram Negative Bacteria ◽

National Surveillance ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Carbapenem Resistant

ABSTRACT A multicenter collection of bacteremic isolates of Escherichia coli (n = 423), Klebsiella pneumoniae (n = 372), Pseudomonas aeruginosa (n = 300), and Acinetobacter baumannii complex (n = 199) was analyzed for susceptibility. Xpert Carba-R assay and sequencing for mcr genes were performed for carbapenem- or colistin-resistant isolates. Nineteen (67.8%) carbapenem-resistant K. pneumoniae (n = 28) and one (20%) carbapenem-resistant E. coli (n = 5) isolate harbored blaKPC (n = 17), blaOXA-48 (n = 2), and blaVIM (n = 1) genes.

Download Full-text

Nonclonal Emergence of Colistin Resistance Associated with Mutations in the BasRS Two-Component System in Escherichia coli Bloodstream Isolates

mSphere ◽

10.1128/msphere.00143-20 ◽

2020 ◽

Vol 5 (2) ◽

Cited By ~ 2

Author(s):

Axel B. Janssen ◽

Toby L. Bartholomew ◽

Natalia P. Marciszewska ◽

Marc J. M. Bonten ◽

Rob J. L. Willems ◽

...

Keyword(s):

Escherichia Coli ◽

Lipid A ◽

Gram Negative Bacteria ◽

Colistin Resistance ◽

Anionic Lipid ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Two Component ◽

Resistant Strains

ABSTRACT Infections by multidrug-resistant Gram-negative bacteria are increasingly common, prompting the renewed interest in the use of colistin. Colistin specifically targets Gram-negative bacteria by interacting with the anionic lipid A moieties of lipopolysaccharides, leading to membrane destabilization and cell death. Here, we aimed to uncover the mechanisms of colistin resistance in nine colistin-resistant Escherichia coli strains and one Escherichia albertii strain. These were the only colistin-resistant strains of 1,140 bloodstream Escherichia isolates collected in a tertiary hospital over a 10-year period (2006 to 2015). Core-genome phylogenetic analysis showed that each patient was colonized by a unique strain, suggesting that colistin resistance was acquired independently in each strain. All colistin-resistant strains had lipid A that was modified with phosphoethanolamine. In addition, two E. coli strains had hepta-acylated lipid A species, containing an additional palmitate compared to the canonical hexa-acylated E. coli lipid A. One E. coli strain carried the mobile colistin resistance (mcr) gene mcr-1.1 on an IncX4-type plasmid. Through construction of chromosomal transgene integration mutants, we experimentally determined that mutations in basRS, encoding a two-component signal transduction system, contributed to colistin resistance in four strains. We confirmed these observations by reversing the mutations in basRS to the sequences found in reference strains, resulting in loss of colistin resistance. While the mcr genes have become a widely studied mechanism of colistin resistance in E. coli, sequence variation in basRS is another, potentially more prevalent but relatively underexplored, cause of colistin resistance in this important nosocomial pathogen. IMPORTANCE Multidrug resistance among Gram-negative bacteria has led to the use of colistin as a last-resort drug. The cationic colistin kills Gram-negative bacteria through electrostatic interaction with the anionic lipid A moiety of lipopolysaccharides. Due to increased use in clinical and agricultural settings, colistin resistance has recently started to emerge. In this study, we used a combination of whole-genome sequence analysis and experimental validation to characterize the mechanisms through which Escherichia coli strains from bloodstream infections can develop colistin resistance. We found no evidence of direct transfer of colistin-resistant isolates between patients. The lipid A of all isolates was modified by the addition of phosphoethanolamine. In four isolates, colistin resistance was experimentally verified to be caused by mutations in the basRS genes, encoding a two-component regulatory system. Our data show that chromosomal mutations are an important cause of colistin resistance among clinical E. coli isolates.

Download Full-text

Correct Sorting of Lipoproteins into the Inner and Outer Membranes ofPseudomonas aeruginosaby theEscherichia coliLolCDE Transport System

mBio ◽

10.1128/mbio.00194-19 ◽

2019 ◽

Vol 10 (2) ◽

Cited By ~ 4

Author(s):

Christian Lorenz ◽

Thomas J. Dougherty ◽

Stephen Lory

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Outer Membrane ◽

Transport Systems ◽

Gram Negative Bacteria ◽

Inner Membrane ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Outer Membranes

ABSTRACTBiogenesis of the outer membrane of Gram-negative bacteria depends on dedicated macromolecular transport systems. The LolABCDE proteins make up the machinery for lipoprotein trafficking from the inner membrane (IM) across the periplasm to the outer membrane (OM). The Lol apparatus is additionally responsible for differentiating OM lipoproteins from those for the IM. InEnterobacteriaceae, a default sorting mechanism has been proposed whereby an aspartic acid at position +2 of the mature lipoproteins prevents Lol recognition and leads to their IM retention. In other bacteria, the conservation of sequences immediately following the acylated cysteine is variable. Here we show that inPseudomonas aeruginosa, the three essential Lol proteins (LolCDE) can be replaced with those fromEscherichia coli. TheP. aeruginosalipoproteins MexA, OprM, PscJ, and FlgH, with different sequences at their N termini, were correctly sorted by either theE. coliorP. aeruginosaLolCDE. We further demonstrate that an inhibitor ofE. coliLolCDE is active againstP. aeruginosaonly when expressing theE. coliorthologues. Our work shows that Lol proteins recognize a wide range of signals, consisting of an acylated cysteine and a specific conformation of the adjacent domain, determining IM retention or transport to the OM.IMPORTANCEGram-negative bacteria build their outer membranes (OM) from components that are initially located in the inner membrane (IM). A fraction of lipoproteins is transferred to the OM by the transport machinery consisting of LolABCDE proteins. Our work demonstrates that the LolCDE complexes of the transport pathways ofEscherichia coliandPseudomonas aeruginosaare interchangeable, with theE. coliorthologues correctly sorting theP. aeruginosalipoproteins while retaining their sensitivity to a small-molecule inhibitor. These findings question the nature of IM retention signals, identified inE. colias aspartate at position +2 of mature lipoproteins. We propose an alternative model for the sorting of IM and OM lipoproteins based on their relative affinities for the IM and the ability of the promiscuous sorting machinery to deliver lipoproteins to their functional sites in the OM.

Download Full-text

A High-Throughput Approach To Identify Compounds That Impair Envelope Integrity in Escherichia coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00537-16 ◽

2016 ◽

Vol 60 (10) ◽

pp. 5995-6002 ◽

Cited By ~ 7

Author(s):

Kristin R. Baker ◽

Bimal Jana ◽

Henrik Franzyk ◽

Luca Guardabassi

Keyword(s):

Escherichia Coli ◽

High Throughput ◽

High Throughput Screening ◽

Gram Negative Bacteria ◽

Chromogenic Substrate ◽

Intrinsic Resistance ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Screening Platform

ABSTRACTThe envelope of Gram-negative bacteria constitutes an impenetrable barrier to numerous classes of antimicrobials. This intrinsic resistance, coupled with acquired multidrug resistance, has drastically limited the treatment options against Gram-negative pathogens. The aim of the present study was to develop and validate an assay for identifying compounds that increase envelope permeability, thereby conferring antimicrobial susceptibility by weakening of the cell envelope barrier in Gram-negative bacteria. A high-throughput whole-cell screening platform was developed to measureEscherichia colienvelope permeability to a β-galactosidase chromogenic substrate. The signal produced by cytoplasmic β-galactosidase-dependent cleavage of the chromogenic substrate was used to determine the degree of envelope permeabilization. The assay was optimized by using known envelope-permeabilizing compounds andE. coligene deletion mutants with impaired envelope integrity. As a proof of concept, a compound library comprising 36 peptides and 45 peptidomimetics was screened, leading to identification of two peptides that substantially increased envelope permeability. Compound 79 reduced significantly (from 8- to 125-fold) the MICs of erythromycin, fusidic acid, novobiocin and rifampin and displayed synergy (fractional inhibitory concentration index, <0.2) with these antibiotics by checkerboard assays in two genetically distinctE. colistrains, including the high-risk multidrug-resistant, CTX-M-15-producing sequence type 131 clone. Notably, in the presence of 0.25 μM of this peptide, both strains were susceptible to rifampin according to the resistance breakpoints (R> 0.5 μg/ml) for Gram-positive bacterial pathogens. The high-throughput screening platform developed in this study can be applied to accelerate the discovery of antimicrobial helper drug candidates and targets that enhance the delivery of existing antibiotics by impairing envelope integrity in Gram-negative bacteria.

Download Full-text

Emergence of Colistin Resistant Gram-Negative Bacteria in a Tertiary Care Rural Hospital in 2019

KYAMC Journal ◽

10.3329/kyamcj.v11i2.48421 ◽

2020 ◽

Vol 11 (2) ◽

pp. 87-90

Author(s):

Abdullah Akhtar Ahmed ◽

Nusrat Akhtar Juyee ◽

SM Ali Hasan

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Tertiary Care ◽

Salmonella Typhi ◽

Rural Hospital ◽

Gram Negative Bacteria ◽

Bacterial Isolates ◽

Colistin Resistance ◽

Sensitivity Testing ◽

Gram Negative

Background: Colistin-resistant Gram-negative bacteria is a rapidly emerging global threatgenerated a sense of public alarm. Objective: To combat this challenge a study was designedto evaluate the fast spreading infections by colistin-resistant pathogens in the tertiary care rural hospital of Bangladesh. Materials and Methods: To study isolation ofpathogenic gram-negative bacilli,clinical sample (n-640) of hospitalized patients of Khwaja Yunus Ali Medical College Hospital in Enayetpur, Bangladesh during the 1st quarter of the year 2019 were used. The bacterial isolates were screened for meropenem and colistin-resistance. Results: A total of 156 bacterial isolates were studied which included Escherichia coli (n-112), Klebsiella pneumoniae (n-14), Pseudomonas aeruginosa (n-27), and Salmonella typhi (n-3). Antibiotic sensitivity testing showed that 32/156(20%) and 119/156 (76%) isolates were resistant to meropenem and colistin, respectively. whereas 50/156 (32%) isolates were resistant to both antibiotics. Escherichia coli, K. pneumoniae, pseudomonas aeruginosa, and Salmonella typhi isolates respectivelywere 112/156 (72%), 14/156 (9%). 27/156 (17%), and 3/156 (2%). Conclusion: Colistin is typically used as salvage therapy, or last-line treatment, for MDR gramnegative infections.But there is worrisome therapeutic scenario in our study finding of colistin resistance is 76% in Gram-negative bacteria of the clinical isolates. The restricted and rational use of colistin drug is the need of hour. KYAMC Journal Vol. 11, No.-2, July 2020, Page 87-90

Download Full-text

Bacterial Metal Resistance: Coping with Copper without Cooperativity?

mBio ◽

10.1128/mbio.00653-21 ◽

2021 ◽

Author(s):

Nicholas P. Greene ◽

Vassilis Koronakis

Keyword(s):

Escherichia Coli ◽

Cell Division ◽

Cell Envelope ◽

Metal Resistance ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Rnd Transporter ◽

Entire Cell

In Escherichia coli and other Gram-negative bacteria, tripartite efflux pumps (TEPs) span the entire cell envelope and serve to remove noxious molecules from the cell. CusBCA is a TEP responsible for copper and silver detoxification in E. coli powered by the resistance-nodulation-cell division (RND) transporter, CusA.

Download Full-text

Synergistic Interactions of Vancomycin with Different Antibiotics against Escherichia coli: Trimethoprim and Nitrofurantoin Display Strong Synergies with Vancomycin against Wild-Type E. coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.03502-14 ◽

2014 ◽

Vol 59 (1) ◽

pp. 276-281 ◽

Cited By ~ 38

Author(s):

Alice Zhou ◽

Tina Manzhu Kang ◽

Jessica Yuan ◽

Casey Beppler ◽

Caroline Nguyen ◽

...

Keyword(s):

Escherichia Coli ◽

The Other ◽

Gram Negative Bacteria ◽

Functional Categories ◽

Wild Type ◽

Gram Negative ◽

Content Type ◽

E Coli ◽

Synergistic Interactions ◽

Pairwise Interactions

ABSTRACTGram-negative bacteria are normally resistant to the antibiotic vancomycin (VAN), which cannot significantly penetrate the outer membrane. We usedEscherichia colimutants that are partially sensitive to VAN to study synergies between VAN and 10 other antibiotics representing six different functional categories. We detected strong synergies with VAN and nitrofurantoin (NTR) and with VAN and trimethoprim (TMP) and moderate synergies with other drugs, such as aminoglycosides. These synergies are powerful enough to show the activity of VAN against wild-typeE. coliat concentrations of VAN as low as 6.25 μg/ml. This suggests that a very small percentage of exogenous VAN does enterE. colibut normally has insignificant effects on growth inhibition or cell killing. We used the results of pairwise interactions with VAN and the other 10 antibiotics tested to place VAN into a functional category of its own, as previously defined by Yeh et al. (P. Yeh, A. I. Tschumi, and R. Kishony, Nat Genet 28:489–494, 2006,http://dx.doi.org/10.1038/ng1755).

Download Full-text

Biotinylation Facilitates the Uptake of Large Peptides by Escherichia coli and Other Gram-Negative Bacteria

Applied and Environmental Microbiology ◽

10.1128/aem.71.4.1850-1855.2005 ◽

2005 ◽

Vol 71 (4) ◽

pp. 1850-1855 ◽

Cited By ~ 16

Author(s):

Jennifer R. Walker ◽

Elliot Altman

Keyword(s):

Escherichia Coli ◽

Amino Acids ◽

Pseudomonas Aeruginosa ◽

Gram Negative Bacteria ◽

Cell Fractionation ◽

Peptide Antibiotics ◽

Small Peptides ◽

Gram Negative ◽

E Coli ◽

Serovar Typhimurium

ABSTRACT Gram-negative bacteria such as Escherichia coli can normally only take up small peptides less than 650 Da, or five to six amino acids, in size. We have found that biotinylated peptides up to 31 amino acids in length can be taken up by E. coli and that uptake is dependent on the biotin transporter. Uptake could be competitively inhibited by free biotin or avidin and blocked by the protonophore carbonyl m-chlorophenylhydrazone and was abolished in E. coli mutants that lacked the biotin transporter. Biotinylated peptides could be used to supplement the growth of a biotin auxotroph, and the transported peptides were shown to be localized to the cytoplasm in cell fractionation experiments. The uptake of biotinylated peptides was also demonstrated for two other gram-negative bacteria, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa. This finding may make it possible to create new peptide antibiotics that can be used against gram-negative pathogens. Researchers have used various moieties to cause the illicit transport of compounds in bacteria, and this study demonstrates the illicit transport of the largest known compound to date.

Download Full-text

Colonization and Resistance Dynamics of Gram-Negative Bacteria in Patients during and after Hospitalization

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.7.2879-2886.2005 ◽

2005 ◽

Vol 49 (7) ◽

pp. 2879-2886 ◽

Cited By ~ 34

Author(s):

P. Margreet G. Filius ◽

Inge C. Gyssens ◽

Irma M. Kershof ◽

Patty J. E. Roovers ◽

Alewijn Ott ◽

...

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Susceptibility Testing ◽

General Ward ◽

Gram Negative Bacteria ◽

Icu Patients ◽

Gram Negative ◽

E Coli ◽

General Wards ◽

Colonization Rates

ABSTRACT The colonization and resistance dynamics of aerobic gram-negative bacteria in the intestinal and oropharyngeal microfloras of patients admitted to intensive care units (ICU) and general wards were investigated during and after hospitalization. A total of 3,316 specimens were obtained from patients upon admission, once weekly during hospitalization, at discharge from the ICU, at discharge from the hospital, and 1 and 3 months after discharge from the hospital. Five colonies per specimen were selected for identification and susceptibility testing. In both patient populations, the gram-negative colonization rates in oropharyngeal specimens increased during hospitalization and did not decrease in the 3 months after discharge. In rectal specimens, colonization rates decreased during hospitalization and increased after discharge. There was a change in species distribution among the dominant microfloras during hospitalization. Klebsiella spp., Enterobacter spp., Serratia marcescens, and Pseudomonas aeruginosa were isolated more often, whereas the frequency of Escherichia coli declined. The percentage of ICU patients colonized with ampicillin- and/or cephalothin-resistant fecal E. coli was significantly increased at discharge from the hospital and did not change in the 3 months after discharge. The emergence of multidrug resistance was observed for E. coli during patient stays in the ICU. Resistance frequencies in E. coli significantly increased with the length of stay in the ICU. For the general ward population, no significant changes in resistance frequencies were found during hospitalization. From a population perspective, the risk of dissemination of resistant gram-negative bacteria into the community through hospitalized patients appears to be low for general ward patients but is noticeably higher among ICU patients.

Download Full-text