scholarly journals Carbapenem Resistance in Gram-negative Bacteria in South-western Nigeria: The Role of Extended-spectrum β-lactamase CTX-M-15

2018 ◽  
pp. 344-349
Author(s):  
Do Ogbolu ◽  
Ma Webber
Keyword(s):  
Outer Membrane ◽  
Antimicrobial Agents ◽  
Random Amplified Polymorphic Dna ◽  
Outer Membrane Proteins ◽  
Carbapenem Resistance ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Carbapenem Resistant ◽  
Extended Spectrum

Objective: To determine the role of extended-spectrum β-lactamases in carbapenem-resistant Gram-negative bacteria from south-western Nigeria. Methods: Twenty-seven carbapenem-resistant isolates that were found to be non-carbapenemase producers (15 Escherichia coli, 9 Klebsiella pneumoniae and 3 Pseudomonas aeruginosa) were further studied. These isolates were subjected to analysis including phenotypic and genotypic detection of various β-lactamases, efflux activity, outer membrane protein, plasmids replicon typing, detection of transferable genes and resistances and typing using random amplified polymorphic DNA tests. Results: No isolates demonstrated de-repression of efflux, but all showed either complete loss or reduced production of outer membrane proteins. Transconjugants from these strains contained various genes including plasmid-mediated quinolone resistance and extended-spectrum beta-lactamases. All the transconjugants carried the blaCTX-M-15 gene. The transconjugants had varying minimum inhibitory concentrations of carbapenems ranging from 0.03 μg/ml to 8 μg/ml. Varying resistances to other antimicrobial agents were also transferred with the plasmids. The donor isolates were not clonally related by molecular typing. Conclusion: Resistance to carbapenem antibiotics in this sample was not mediated only by carbapenemases but also by production of extended-spectrum β-lactamases (largely CTX-M-15), accompanied by protein loss. This was an important mechanism underpinning carbapenem resistance in these clinical isolates of various species.

scholarly journals Functions of the BamBCDE Lipoproteins Revealed by Bypass Mutations in BamA

2020 ◽  
Vol 202 (21) ◽  
Author(s):  
Elizabeth M. Hart ◽  
Thomas J. Silhavy
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Gram Negative Bacteria ◽  
Wild Type ◽  
Gram Negative ◽  
Bam Complex ◽  
Essential Function ◽  
The Individual

ABSTRACT The heteropentomeric β-barrel assembly machine (BAM complex) is responsible for folding and inserting a diverse array of β-barrel outer membrane proteins (OMPs) into the outer membrane (OM) of Gram-negative bacteria. The BAM complex contains two essential proteins, the β-barrel OMP BamA and a lipoprotein BamD, whereas the auxiliary lipoproteins BamBCE are individually nonessential. Here, we identify and characterize three bamA mutations, the E-to-K change at position 470 (bamAE470K), the A-to-P change at position 496 (bamAA496P), and the A-to-S change at position 499 (bamAA499S), that suppress the otherwise lethal ΔbamD, ΔbamB ΔbamC ΔbamE, and ΔbamC ΔbamD ΔbamE mutations. The viability of cells lacking different combinations of BAM complex lipoproteins provides the opportunity to examine the role of the individual proteins in OMP assembly. Results show that, in wild-type cells, BamBCE share a redundant function; at least one of these lipoproteins must be present to allow BamD to coordinate productively with BamA. Besides BamA regulation, BamD shares an additional essential function that is redundant with a second function of BamB. Remarkably, bamAE470K suppresses both, allowing the construction of a BAM complex composed solely of BamAE470K that is able to assemble OMPs in the absence of BamBCDE. This work demonstrates that the BAM complex lipoproteins do not participate in the catalytic folding of OMP substrates but rather function to increase the efficiency of the assembly process by coordinating and regulating the assembly of diverse OMP substrates. IMPORTANCE The folding and insertion of β-barrel outer membrane proteins (OMPs) are conserved processes in mitochondria, chloroplasts, and Gram-negative bacteria. In Gram-negative bacteria, OMPs are assembled into the outer membrane (OM) by the heteropentomeric β-barrel assembly machine (BAM complex). In this study, we probe the function of the individual BAM proteins and how they coordinate assembly of a diverse family of OMPs. Furthermore, we identify a gain-of-function bamA mutant capable of assembling OMPs independently of all four other BAM proteins. This work advances our understanding of OMP assembly and sheds light on how this process is distinct in Gram-negative bacteria.

scholarly journals Roles of β-Lactamases and Porins in Activities of Carbapenems and Cephalosporins against Klebsiella pneumoniae

1999 ◽  
Vol 43 (7) ◽  
pp. 1669-1673 ◽  
Author(s):  
Luis Martínez-Martínez ◽  
Alvaro Pascual ◽  
Santiago Hernández-Allés ◽  
Dolores Alvarez-Díaz ◽  
Ana Isabel Suárez ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Carbapenem Resistance ◽  
Clinical Isolates ◽  
Extended Spectrum ◽  
Inoculum Effect

ABSTRACT Two clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae were noted to be less susceptible than expected to imipenem. Both were missing outer membrane proteins that serve as channels for antibiotic entry. The role of β-lactamase in resistance was investigated by eliminating the original ESBL and introducing plasmids encoding various ESBLs and AmpC β-lactamase types, by studying the effect of an increased inoculum, and by evaluating interactions with β-lactamase inhibitors. The contribution of porin deficiency was investigated by restoring a functional ompK36 gene on a plasmid. Plasmids encoding AmpC-type β-lactamases provided resistance to imipenem (up to 64 μg/ml) and meropenem (up to 16 μg/ml) in strains deficient in porins. Carbapenem resistance showed little inoculum effect, was not affected by clavulanate but was blocked by BRL 42715, and was diminished if OmpK36 porin was restored. Plasmids encoding TEM- and SHV-type ESBLs conferred resistance to cefepime and cefpirome, as well as to earlier oxyimino-β-lactams. This resistance was magnified with an increased inoculum, was blocked by clavulanate, and was also lowered by OmpK36 porin restoration. In addition, SHV-2 β-lactamase had a small effect on carbapenem resistance (imipenem MIC, 4 μg/ml, increasing to 16 μg/ml with a higher inoculum) when porins were absent. In K. pneumoniae porin loss can thus augment resistance provided either by TEM- or SHV-type ESBLs or by plasmid-mediated AmpC enzymes to include the latest oxyimino-β-lactams and carbapenems.

scholarly journals MexAB-OprM Efflux Pump Interaction with the Peptidoglycan of Escherichia coli and Pseudomonas aeruginosa

2021 ◽  
Vol 22 (10) ◽  
pp. 5328
Author(s):  
Miao Ma ◽  
Margaux Lustig ◽  
Michèle Salem ◽  
Dominique Mengin-Lecreulx ◽  
Gilles Phan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Cell Division ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Efflux Pump ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Active Efflux

One of the major families of membrane proteins found in prokaryote genome corresponds to the transporters. Among them, the resistance-nodulation-cell division (RND) transporters are highly studied, as being responsible for one of the most problematic mechanisms used by bacteria to resist to antibiotics, i.e., the active efflux of drugs. In Gram-negative bacteria, these proteins are inserted in the inner membrane and form a tripartite assembly with an outer membrane factor and a periplasmic linker in order to cross the two membranes to expulse molecules outside of the cell. A lot of information has been collected to understand the functional mechanism of these pumps, especially with AcrAB-TolC from Escherichia coli, but one missing piece from all the suggested models is the role of peptidoglycan in the assembly. Here, by pull-down experiments with purified peptidoglycans, we precise the MexAB-OprM interaction with the peptidoglycan from Escherichia coli and Pseudomonas aeruginosa, highlighting a role of the peptidoglycan in stabilizing the MexA-OprM complex and also differences between the two Gram-negative bacteria peptidoglycans.

scholarly journals An overview of carbapenem, its resistance and therapeutic options for infections caused by carbapenem resistant bacteria

2020 ◽  
Vol 9 (9) ◽  
pp. 1454
Author(s):  
Hari P. Nepal ◽  
Rama Paudel
Keyword(s):  
Bacterial Infections ◽  
Carbapenem Resistance ◽  
Therapeutic Options ◽  
Resistant Bacteria ◽  
Gram Negative Bacteria ◽  
Beta Lactam ◽  
Gram Negative ◽  
Penicillin Binding Proteins ◽  
Carbapenem Resistant ◽  
The World

Carbapenems are beta-lactam drugs that have broadest spectrum of activity. They are commonly used as the drugs of last resort to treat complicated bacterial infections. They bind to penicillin binding proteins (PBPs) and inhibit cell wall synthesis in bacteria. Important members that are in clinical use include doripenem, ertapenem, imipenem, and meropenem. Unlike other members, imipenem is hydrolyzed significantly by renal dehydropeptidase; therefore, it is administered together with an inhibitor of renal dehydropeptidase, cilastatin. Carbapenems are usually administered intravenously due to their low oral bioavailability. Most common side effects of these drugs include nausea, vomiting, diarrhea, skin rashes, and reactions at the infusion sites. Increasing resistance to these antibiotics is being reported throughout the world and is posing a threat to public health.  Primary mechanisms of carbapenem resistance include expulsion of drug and inactivation of the drug by production of carbapenemases which may not only hydrolyze carbapenem, but also cephalosporin, penicillin, and aztreonam. Resistance especially among Gram negative bacteria is of much concern since there are only limited therapeutic options available for infections caused by carbapenem resistant Gram-negative bacterial pathogens. Commonly used drugs to treat such infections include polymyxins, fosfomycin and tigecycline.

Determination of carbapenemase genes in clinical isolates using Cepheid Xpert Carba-R

2021 ◽  
pp. 16-19
Author(s):  
N. I. Gabrielyan ◽  
V. G. Kormilitsyna ◽  
V. K. Zaletaeva ◽  
A. V. Krotevich ◽  
I. A. Miloserdov ◽  
...  
Keyword(s):  
Targeted Therapy ◽  
Infection Control ◽  
Resistance Genes ◽  
Carbapenem Resistance ◽  
Critical Issue ◽  
Sensitivity Study ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Carbapenem Resistant

Detection of carbapenem resistance genes is a critical issue for hospitals due to possible recommendations for infection control and targeted therapy. The Cepheid Xpert instrument, a Carba-R test for the detection and differentiation of five common carbapenemase genes, was tested from September 2020 to February 2021. As part of the approbation, 20 tests were provided. This review presents the results of the approbation of a relatively regular sensitivity study on Siemens WalkAway‑96 plus. Cepheid Xpert Carba-R analysis has been shown to be an accurate and fast tool for detecting colonization by carbapenem-resistant gram-negative bacteria, which can help limit the spread of these organisms in hospitals.

scholarly journals The gain-of-function allelebamAE470Kbypasses the essential requirement for BamD in β-barrel outer membrane protein assembly

2020 ◽  
Vol 117 (31) ◽  
pp. 18737-18743 ◽  
Author(s):  
Elizabeth M. Hart ◽  
Meera Gupta ◽  
Martin Wühr ◽  
Thomas J. Silhavy
Keyword(s):  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Protein Assembly ◽  
Gram Negative Bacteria ◽  
Gain Of Function ◽  
Essential Requirement ◽  
Gram Negative ◽  
Selective Permeability ◽  
Catalytic Role ◽  
Global Defect

The outer membrane (OM) of gram-negative bacteria confers innate resistance to toxins and antibiotics. Integral β-barrel outer membrane proteins (OMPs) function to establish and maintain the selective permeability of the OM. OMPs are assembled into the OM by the β-barrel assembly machine (BAM), which is composed of one OMP—BamA—and four lipoproteins—BamB, C, D, and E. BamB, C, and E can be removed individually with only minor effects on barrier function; however, depletion of either BamA or BamD causes a global defect in OMP assembly and results in cell death. We have identified a gain-of-function mutation,bamAE470K, that bypasses the requirement for BamD. AlthoughbamD::kanbamAE470Kcells exhibit growth and OM barrier defects, they assemble OMPs with surprising robustness. Our results demonstrate that BamD does not play a catalytic role in OMP assembly, but rather functions to regulate the activity of BamA.

Sign in / Sign up

Export Citation Format

Share Document