scholarly journals MSH2Gene Point Mutations Are Not Antifungal Resistance Markers inCandida glabrata

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
María Ángeles Bordallo-Cardona ◽  
Caroline Agnelli ◽  
Ana Gómez-Nuñez ◽  
Carlos Sánchez-Carrillo ◽  
Emilio Bouza ◽  
...  
Keyword(s):  
Point Mutations ◽  
Gene Mutations ◽  
Housekeeping Genes ◽  
Antifungal Resistance ◽  
Content Type ◽  
Fluconazole Resistant ◽  
Patient Prognosis ◽  
Antifungal Use

ABSTRACTThe high rates of antifungal resistance inCandida glabratamay be facilitated by the presence of alterations in theMSH2gene. We aimed to study the sequence of theMSH2gene in 124 invasiveC. glabrataisolates causing incident episodes of candidemia (n= 81), subsequent candidemia episodes (n= 9), endocarditis (n= 2), andin vitro-generated echinocandin-resistant isolates (n= 32) and assessed its relationship with genotypes, acquisition of antifungal resistancein vivoandin vitro, and patient prognosis. TheMSH2gene was sequenced, and isolates were genotyped using six microsatellite markers and multilocus sequence typing (MLST) based on six housekeeping genes. According to EUCAST, isolates causing candidemia (n= 90) were echinocandin susceptible, and four of them were fluconazole resistant (MIC ≥64 mg/liter). One isolate obtained from a heart valve was resistant to micafungin and anidulafungin (MICs, 2 mg/liter and 1 mg/liter, respectively).MSH2gene mutations were present in 44.4% of the incident isolates, the most common being V239L. The presence ofMSH2mutations was not correlated within vitroorin vivoantifungal resistance. Microsatellite and MLST revealed 27 genotypes and 17 sequence types, respectively. Fluconazole-resistant isolates were unrelated. MostMSH2mutations were found in cluster isolates; conversely, some mutations were found in more than one genotype. No clinical differences, including previous antifungal use, were found between patients infected by wild-typeMSH2gene isolates and isolates with any point mutation. The presence ofMSH2gene mutations inC. glabrataisolates causing candidemia is not correlated with specific genotypes, the promotion of antifungal resistance, or the clinical outcome.

scholarly journals Molecular Basis of In Vivo Resistance to Sulfadoxine-Pyrimethamine in African Adult Patients Infected withPlasmodium falciparum Malaria Parasites

1998 ◽  
Vol 42 (7) ◽  
pp. 1811-1814 ◽  
Author(s):  
Leonardo K. Basco ◽  
Rachida Tahar ◽  
Pascal Ringwald
Keyword(s):  
Dihydrofolate Reductase ◽  
Point Mutations ◽  
Gene Mutations ◽  
Adult Patients ◽  
Wild Type ◽  
Dihydropteroate Synthase ◽  
Reductase Gene ◽  
Parasite Populations

ABSTRACT In vitro sulfadoxine and pyrimethamine resistance has been associated with point mutations in the dihydropteroate synthase and dihydrofolate reductase domains, respectively, but the in vivo relevance of these point mutations has not been well established. To analyze the correlation between genotype and phenotype, 10 Cameroonian adult patients were treated with sulfadoxine-pyrimethamine and followed up for 28 days. After losses to follow-up (n = 1) or elimination of DNA samples due to mixed parasite populations with pyrimethamine-sensitive and pyrimethamine-resistant profiles (n = 3), parasite genomic DNA from day 0 blood samples of six patients were analyzed by DNA sequencing. Three patients who were cured had isolates characterized by a wild-type or mutant dihydrofolate reductase gene (with one or two mutations) and a wild-type dihydropteroate synthase gene. Three other patients who failed to respond to sulfadoxine-pyrimethamine treatment carried isolates with triple dihydrofolate reductase gene mutations and either a wild-type or a mutant dihydropteroate synthase gene. Three dihydrofolate reductase gene codons (51, 59, and 108) may be reliable genetic markers that can accurately predict the clinical outcome of sulfadoxine-pyrimethamine treatment in Africa.

scholarly journals Elevated Cell Wall Chitin in Candida albicans Confers Echinocandin ResistanceIn Vivo

2011 ◽  
Vol 56 (1) ◽  
pp. 208-217 ◽  
Author(s):  
Keunsook K. Lee ◽  
Donna M. MacCallum ◽  
Mette D. Jacobsen ◽  
Louise A. Walker ◽  
Frank C. Odds ◽  
...  
Keyword(s):  
Weight Loss ◽  
Cell Wall ◽  
Candida Albicans ◽  
Point Mutations ◽  
Low Frequency ◽  
Normal Cells ◽  
Content Type ◽  
Echinocandin Resistance

ABSTRACTCandida albicanscells with increased cell wall chitin have reduced echinocandin susceptibilityin vitro. The aim of this study was to investigate whetherC. albicanscells with elevated chitin levels have reduced echinocandin susceptibilityin vivo. BALB/c mice were infected withC. albicanscells with normal chitin levels and compared to mice infected with high-chitin cells. Caspofungin therapy was initiated at 24 h postinfection. Mice infected with chitin-normal cells were successfully treated with caspofungin, as indicated by reduced kidney fungal burdens, reduced weight loss, and decreasedC. albicansdensity in kidney lesions. In contrast, mice infected with high-chitinC. albicanscells were less susceptible to caspofungin, as they had higher kidney fungal burdens and greater weight loss during early infection. Cells recovered from mouse kidneys at 24 h postinfection with high-chitin cells had 1.6-fold higher chitin levels than cells from mice infected with chitin-normal cells and maintained a significantly reduced susceptibility to caspofungin when testedin vitro. At 48 h postinfection, caspofungin treatment induced a further increase in chitin content ofC. albicanscells harvested from kidneys compared to saline treatment. Some of the recovered clones had acquired, at a low frequency, a point mutation inFKS1resulting in a S645Y amino acid substitution, a mutation known to confer echinocandin resistance. This occurred even in cells that had not been exposed to caspofungin. Our results suggest that the efficacy of caspofungin againstC. albicanswas reducedin vivodue to either elevation of chitin levels in the cell wall or acquisition ofFKS1point mutations.

scholarly journals Impact of the Major Candida glabrata Triazole Resistance Determinants on the Activity of the Novel Investigational Tetrazoles VT-1598 and VT-1161

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Andrew T. Nishimoto ◽  
Sarah G. Whaley ◽  
Nathan P. Wiederhold ◽  
Qing Zhang ◽  
Christopher M. Yates ◽  
...  
Keyword(s):  
Candida Glabrata ◽  
Opportunistic Pathogen ◽  
Resistance Mechanisms ◽  
Invasive Infection ◽  
Content Type ◽  
Zinc Cluster ◽  
Transcription Factor Genes ◽  
Fluconazole Resistant

ABSTRACT VT-1161 and VT-1598 are promising investigational tetrazole antifungals that have shown in vitro and in vivo activity against Candida and other fungi. Candida glabrata is a problematic opportunistic pathogen that is associated with high mortality in invasive infection, as well as both intrinsic and rapidly acquired antifungal resistance. The MICs of VT-1161 and VT-1598 were determined by CLSI methodology to evaluate their in vitro activities against clinical C. glabrata isolates and strains containing individual deletions of the zinc cluster transcription factor genes PDR1 and UPC2A as well as the efflux transporter genes CDR1, PDH1, and SNQ2. Overall, both tetrazoles demonstrated relative activities comparable to those of the tested triazole antifungals against clinical C. glabrata isolates (MIC range, 0.25 to 2 mg/liter and 0.5 to 2 μg/ml for VT-1161 and VT-1598, respectively). Deletion of the PDR1 gene in fluconazole-resistant matched clinical isolate SM3 abolished the decreased susceptibility phenotype completely for both VT-1161 and VT-1598, similarly to the triazoles. UPC2A deletion also increased susceptibility to both triazoles and tetrazoles but to a lesser extent than PDR1 deletion. Of the three major transporter genes regulated by Pdr1, CDR1 deletion resulted in the largest MIC reductions for all agents tested, while PDH1 and SNQ2 deletion individually impacted MICs very little. Overall, both VT-1161 and VT-1598 have comparable activities to those of the available triazoles, and decreased susceptibility to these tetrazoles in C. glabrata is driven by many of the same known resistance mechanisms.

scholarly journals Enantioselective Regulation of Lactate Racemization by LarR in Lactobacillus plantarum

2014 ◽  
Vol 197 (1) ◽  
pp. 219-230 ◽  
Author(s):  
Benoît Desguin ◽  
Philippe Goffin ◽  
Nordine Bakouche ◽  
Aurélie Diman ◽  
Eric Viaene ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactobacillus Plantarum ◽  
Point Mutations ◽  
Racemic Mixture ◽  
Content Type ◽  
Sugar Fermentation ◽  
Gel Retardation ◽  
Positive Effect

Lactobacillus plantarumis a lactic acid bacterium that produces a racemic mixture ofl- andd-lactate from sugar fermentation. The interconversion of lactate isomers is performed by a lactate racemase (Lar) that is transcriptionally controlled by thel-/d-lactate ratio and maximally induced in the presence ofl-lactate. We previously reported that the Lar activity depends on the expression of two divergently oriented operons: (i) thelarABCDEoperon encodes the nickel-dependent lactate racemase (LarA), its maturases (LarBCE), and a lactic acid channel (LarD), and (ii) thelarR(MN)QOoperon encodes a transcriptional regulator (LarR) and a four-component ABC-type nickel transporter [Lar(MN), in which the M and N components are fused, LarQ, and LarO]. LarR is a novel regulator of the Crp-Fnr family (PrfA group). Here, the role of LarR was further characterizedin vivoandin vitro. We show that LarR is a positive regulator that is absolutely required for the expression of Lar activity. Using gel retardation experiments, we demonstrate that LarR binds to a 16-bp palindromic sequence (Lar box motif) that is present in thelarR-larAintergenic region. Mutations in the Lar box strongly affect LarR binding and completely abolish transcription from thelarApromoter (PlarA). Two half-Lar boxes located between the Lar box and the −35 box of PlarApromote LarR multimerization on DNA, and point mutations within one or both half-Lar boxes inhibit PlarAinduction byl-lactate. Gel retardation and footprinting experiments indicate thatl-lactate has a positive effect on the binding and multimerization of LarR, whiled-lactate antagonizes the positive effect ofl-lactate. A possible mechanism of LarR regulation by lactate enantiomers is proposed.

scholarly journals Mycobacterium tuberculosis embBCodon 306 Mutations Confer Moderately Increased Resistance to Ethambutol In Vitro and In Vivo

2011 ◽  
Vol 55 (6) ◽  
pp. 2891-2896 ◽  
Author(s):  
Claudia Plinke ◽  
Kerstin Walter ◽  
Sahar Aly ◽  
Stefan Ehlers ◽  
Stefan Niemann
Keyword(s):  
Resistance Mechanism ◽  
Point Mutations ◽  
Fold Increase ◽  
Wild Type ◽  
Content Type ◽  
First Line Therapy ◽  
The One ◽  
The Impact

ABSTRACTEthambutol (EMB) is a major component of the first-line therapy of tuberculosis. Mutations in codon 306 ofembB(embB306) were suggested as a major resistance mechanism in clinical isolates. To directly analyze the impact of individualembB306 mutations on EMB resistance, we used allelic exchange experiments to generateembB306 mutants ofM. tuberculosisH37Rv. The level of EMB resistance conferred by particular mutations was measuredin vitroandin vivoafter EMB therapy by daily gavage in a mouse model of aerogenic tuberculosis. The wild-typeembB306 ATG codon was replaced byembB306 ATC, ATA, or GTG, respectively. All of the obtainedembB306 mutants exhibited a 2- to 4-fold increase in EMB MIC compared to the wild-type H37Rv.In vivo, the one selectedembB306 GTG mutant required a higher dose of ethambutol to restrict its growth in the lung compared to wild-type H37Rv. These experiments demonstrate thatembB306 point mutations enhance the EMB MICin vitroto a moderate, but significant extent, and reduce the efficacy of EMB treatment in the animal model. We propose that conventional EMB susceptibility testing, in combination withembB306 genotyping, may guide dose adjustment to avoid clinical treatment failure in these low-level resistant strains.

scholarly journals Compensatory mechanisms in resistant Anopheles gambiae AcerKis and KdrKis neurons modulate insecticide-based mosquito control

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Stéphane Perrier ◽  
Eléonore Moreau ◽  
Caroline Deshayes ◽  
Marine El-Adouzi ◽  
Delphine Goven ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Anopheles Gambiae ◽  
Calcium Concentration ◽  
Mosquito Control ◽  
Point Mutations ◽  
Resting Membrane Potential ◽  
Compensatory Mechanisms ◽  
Pyrethroid Insecticides

AbstractIn the malaria vector Anopheles gambiae, two point mutations in the acetylcholinesterase (ace-1R) and the sodium channel (kdrR) genes confer resistance to organophosphate/carbamate and pyrethroid insecticides, respectively. The mechanisms of compensation that recover the functional alterations associated with these mutations and their role in the modulation of insecticide efficacy are unknown. Using multidisciplinary approaches adapted to neurons isolated from resistant Anopheles gambiae AcerKis and KdrKis strains together with larval bioassays, we demonstrate that nAChRs, and the intracellular calcium concentration represent the key components of an adaptation strategy ensuring neuronal functions maintenance. In AcerKis neurons, the increased effect of acetylcholine related to the reduced acetylcholinesterase activity is compensated by expressing higher density of nAChRs permeable to calcium. In KdrKis neurons, changes in the biophysical properties of the L1014F mutant sodium channel, leading to enhance overlap between activation and inactivation relationships, diminish the resting membrane potential and reduce the fraction of calcium channels available involved in acetylcholine release. Together with the lower intracellular basal calcium concentration observed, these factors increase nAChRs sensitivity to maintain the effect of low concentration of acetylcholine. These results explain the opposite effects of the insecticide clothianidin observed in AcerKis and KdrKis neurons in vitro and in vivo.

scholarly journals Characterization of LDD-2633 as a Novel RET Kinase Inhibitor with Anti-Tumor Effects in Thyroid Cancer

2021 ◽  
Vol 14 (1) ◽  
pp. 38
Author(s):  
Hyo Jeong Lee ◽  
Pyeonghwa Jeong ◽  
Yeongyu Moon ◽  
Jungil Choi ◽  
Jeong Doo Heo ◽  
...  
Keyword(s):  
Thyroid Cancer ◽  
Thyroid Carcinoma ◽  
Kinase Inhibitor ◽  
Point Mutations ◽  
Carcinoma Cells ◽  
Medullary Thyroid ◽  
Potent Inhibition ◽  
Kinase Inhibitory Activity

Rearranged during transfection (RET), a receptor tyrosine kinase, is activated by glial cell line-derived neurotrophic factor family ligands. Chromosomal rearrangement or point mutations in RET are observed in patients with papillary thyroid and medullary thyroid carcinomas. Oncogenic alteration of RET results in constitutive activation of RET activity. Therefore, inhibiting RET activity has become a target in thyroid cancer therapy. Here, the anti-tumor activity of a novel RET inhibitor was characterized in medullary thyroid carcinoma cells. The indirubin derivative LDD-2633 was tested for RET kinase inhibitory activity. In vitro, LDD-2633 showed potent inhibition of RET kinase activity, with an IC50 of 4.42 nM. The growth of TT thyroid carcinoma cells harboring an RET mutation was suppressed by LDD-2633 treatment via the proliferation suppression and the induction of apoptosis. The effects of LDD-2633 on the RET signaling pathway were examined; LDD-2633 inhibited the phosphorylation of the RET protein and the downstream molecules Shc and ERK1/2. Oral administration of 20 or 40 mg/kg of LDD-2633 induced dose-dependent suppression of TT cell xenograft tumor growth. The in vivo and in vitro experimental results supported the potential use of LDD-2633 as an anticancer drug for thyroid cancers.

scholarly journals Diffuse intrinsic pontine glioma: current insights and future directions

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Dilakshan Srikanthan ◽  
Michael S. Taccone ◽  
Randy Van Ommeren ◽  
Joji Ishida ◽  
Stacey L. Krumholtz ◽  
...  
Keyword(s):  
Brain Tumor ◽  
Gene Mutations ◽  
Pediatric Brain Tumor ◽  
Diffuse Intrinsic Pontine Glioma ◽  
Pontine Glioma ◽  
Current Standard ◽  
In Vivo Models ◽  
Landscape Models

AbstractDiffuse intrinsic pontine glioma (DIPG) is a lethal pediatric brain tumor and the leading cause of brain tumor–related death in children. As several clinical trials over the past few decades have led to no significant improvements in outcome, the current standard of care remains fractionated focal radiation. Due to the recent increase in stereotactic biopsies, tumor tissue availabilities have enabled our advancement of the genomic and molecular characterization of this lethal cancer. Several groups have identified key histone gene mutations, genetic drivers, and methylation changes in DIPG, providing us with new insights into DIPG tumorigenesis. Subsequently, there has been increased development of in vitro and in vivo models of DIPG which have the capacity to unveil novel therapies and strategies for drug delivery. This review outlines the clinical characteristics, genetic landscape, models, and current treatments and hopes to shed light on novel therapeutic avenues and challenges that remain.

scholarly journals Inhibition of RANKL-Induced Osteoclastogenesis by Novel Mutant RANKL

2021 ◽  
Vol 22 (1) ◽  
pp. 434
Author(s):  
Yuria Jang ◽  
Hong Moon Sohn ◽  
Young Jong Ko ◽  
Hoon Hyun ◽  
Wonbong Lim
Keyword(s):  
Nuclear Translocation ◽  
Critical Role ◽  
Osteoclast Differentiation ◽  
Point Mutations ◽  
Tartrate Resistant Acid Phosphatase ◽  
Mice Model ◽  
Gsk 3Β ◽  
Rank Signaling

Background: Recently, it was reported that leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4, also called GPR48) is another receptor for RANKL and was shown to compete with RANK to bind RANKL and suppress canonical RANK signaling during osteoclast differentiation. The critical role of the protein triad RANK–RANKL in osteoclastogenesis has made their binding an important target for the development of drugs against osteoporosis. In this study, point-mutations were introduced in the RANKL protein based on the crystal structure of the RANKL complex and its counterpart receptor RANK, and we investigated whether LGR4 signaling in the absence of the RANK signal could lead to the inhibition of osteoclastogenesis.; Methods: The effects of point-mutated RANKL (mRANKL-MT) on osteoclastogenesis were assessed by tartrate-resistant acid phosphatase (TRAP), resorption pit formation, quantitative real-time polymerase chain reaction (qPCR), western blot, NFATc1 nuclear translocation, micro-CT and histomorphological assay in wild type RANKL (mRANKL-WT)-induced in vitro and in vivo experimental mice model. Results: As a proof of concept, treatment with the mutant RANKL led to the stimulation of GSK-3β phosphorylation, as well as the inhibition of NFATc1 translocation, mRNA expression of TRAP and OSCAR, TRAP activity, and bone resorption, in RANKL-induced mouse models; and Conclusions: The results of our study demonstrate that the mutant RANKL can be used as a therapeutic agent for osteoporosis by inhibiting RANKL-induced osteoclastogenesis via comparative inhibition of RANKL. Moreover, the mutant RANKL was found to lack the toxic side effects of most osteoporosis treatments.

scholarly journals Exogenous Alginate Protects Staphylococcus aureus from Killing by Pseudomonas aeruginosa

2019 ◽  
Vol 202 (8) ◽  
Author(s):  
Courtney E. Price ◽  
Dustin G. Brown ◽  
Dominique H. Limoli ◽  
Vanessa V. Phelan ◽  
George A. O’Toole
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Physical Space ◽  
Late Time ◽  
Protective Effects ◽  
Content Type ◽  
Alginate Production ◽  
The Impact

ABSTRACT Cystic fibrosis (CF) patients chronically infected with both Pseudomonas aeruginosa and Staphylococcus aureus have worse health outcomes than patients who are monoinfected with either P. aeruginosa or S. aureus. We showed previously that mucoid strains of P. aeruginosa can coexist with S. aureus in vitro due to the transcriptional downregulation of several toxic exoproducts typically produced by P. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here, we demonstrate that exogenous alginate protects S. aureus from P. aeruginosa in both planktonic and biofilm coculture models under a variety of nutritional conditions. S. aureus protection in the presence of exogenous alginate is due to the transcriptional downregulation of pvdA, a gene required for the production of the iron-scavenging siderophore pyoverdine as well as the downregulation of the PQS (Pseudomonas quinolone signal) (2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that coculture of mucoid P. aeruginosa with nonmucoid P. aeruginosa strains can mitigate the killing of S. aureus by the nonmucoid strain of P. aeruginosa, indicating that the mechanism that we describe here may function in vivo in the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability to kill S. aureus at late time points and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the S. aureus-protective effects of mucoidy in a strain-specific manner. IMPORTANCE CF patients are chronically infected by polymicrobial communities. The two dominant bacterial pathogens that infect the lungs of CF patients are P. aeruginosa and S. aureus, with ∼30% of patients coinfected by both species. Such coinfected individuals have worse outcomes than monoinfected patients, and both species persist within the same physical space. A variety of host and environmental factors have been demonstrated to promote P. aeruginosa-S. aureus coexistence, despite evidence that P. aeruginosa kills S. aureus when these organisms are cocultured in vitro. Thus, a better understanding of P. aeruginosa-S. aureus interactions, particularly mechanisms by which these microorganisms are able to coexist in proximal physical space, will lead to better-informed treatments for chronic polymicrobial infections.

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