scholarly journals Unveiling azole resistance mechanisms in Candida glabrata clinical isolates encoding wild-type or gain-of-function CgPdr1 alleles

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Sara B. Salazar ◽  
Noémi Valez ◽  
Danielle Sotti-Novais ◽  
Rita Simões ◽  
José António Souza ◽  
...  
Keyword(s):  
Large Scale ◽  
Target Genes ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Azole Resistance ◽  
Gain Of Function ◽  
Resistance Phenotype ◽  
Rapid Acquisition ◽  
The One

The relevance of C. glabrata as a human pathogen is linked with its poor susceptibility to azoles as well as its extreme genomic plasticity that allows the rapid acquisition of resistance. Extensive characterization of azole-resistant C. glabrata strains unveiled the central role of the transcriptional regulator CgPdr1 in the resistance phenotype, with many strains encoding hyperactive (or gain-of-function; GOF) CgPdr1 alleles. Large scale profiling of a collection of clinical C. glabrata isolates recovered in hospitals of the Lisbon area, in Portugal, led to the identification of 11 strains exhibiting resistance to fluconazole and voriconazole, while 2 were only resistant to fluconazole. Among these strains, 10 were found to encode alleles of the CgPDR1 gene harbouring multiple non-synonymous SNPs that were not found in the alleles encoded by susceptible strains, including K274Q, I392M and I803T not previously described as GOF mutations. The isolates encoding these alleles were found to over-express several CgPdr1 target genes including the azole efflux pump CgCDR1 sustaining the idea that these represent new gain-of-function CgPdr1 alleles. Only one of the identified azole-resistant strains was found to encode a CgPDR1 allele fully identical to the one encoded by susceptible strains. To better understand the resistance phenotype of this strain, its transcriptome was compared with the one of a susceptible strain and of strains encoding CgPdr1 GOF alleles. The results of this comparative transcriptomic analysis will be discussed shedding light into the different azole-resistance mechanisms evolved by C. glabrata, including those independent of CgPdr1 GOF strains.

scholarly journals Novel ERG11 and TAC1b Mutations Associated with Azole Resistance in Candida auris

2021 ◽  
Vol 65 (5) ◽  
Author(s):  
Jizhou Li ◽  
Alix T. Coste ◽  
Maroussia Liechti ◽  
Daniel Bachmann ◽  
Dominique Sanglard ◽  
...  
Keyword(s):  
Invasive Candidiasis ◽  
Efflux Pump ◽  
Cumulative Effect ◽  
Resistance Mechanisms ◽  
Azole Resistance ◽  
Candida Auris ◽  
Content Type ◽  
Drug Classes ◽  
In The Wild

ABSTRACT Candida auris is a novel Candida species that has spread in all continents, causing nosocomial outbreaks of invasive candidiasis. C. auris has the ability to develop resistance to all antifungal drug classes. Notably, many C. auris isolates are resistant to the azole drug fluconazole, a standard therapy for invasive candidiasis. Azole resistance in C. auris can result from mutations in the azole target gene ERG11 and/or overexpression of the efflux pump Cdr1. TAC1 is a transcription factor controlling CDR1 expression in C. albicans. The role of TAC1 homologs in C. auris (TAC1a and TAC1b) remains to be better defined. In this study, we compared sequences of ERG11, TAC1a, and TAC1b between a fluconazole-susceptible and five fluconazole-resistant C. auris isolates of clade IV. Among four of the resistant isolates, we identified similar genotypes with concomitant mutations in ERG11 (F444L) and TAC1b (S611P). The simultaneous deletion of tandemly arranged TAC1a/TAC1b resulted in a decrease of MIC for fluconazole. Introduction of the ERG11 and TAC1b mutations separately and/or combined in the wild-type azole-susceptible isolate resulted in a significant increase of azole resistance with a cumulative effect of the two combined mutations. Interestingly, CDR1 expression was not significantly affected by TAC1a/TAC1b deletion or by the presence of the TAC1b S611P mutation, suggesting the existence of Tac1-dependent and Cdr1-independent azole resistance mechanisms. In conclusion, we demonstrated the role of two previously unreported mutations responsible for azole resistance in C. auris, which were a common signature among four azole-resistant isolates of clade IV.

scholarly journals Magnitude of Voriconazole Resistance in Clinical and Environmental Isolates of Aspergillus flavus and Investigation into the Role of Multidrug Efflux Pumps

2018 ◽  
Vol 62 (11) ◽  
Author(s):  
Raees A. Paul ◽  
Shivaprakash M. Rudramurthy ◽  
Manpreet Dhaliwal ◽  
Pankaj Singh ◽  
Anup K. Ghosh ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Azole Resistance ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Environmental Isolates ◽  
Content Type ◽  
Multidrug Efflux Pumps

ABSTRACT The magnitude of azole resistance in Aspergillus flavus and its underlying mechanism is obscure. We evaluated the frequency of azole resistance in a collection of clinical (n = 121) and environmental isolates (n = 68) of A. flavus by the broth microdilution method. Six (5%) clinical isolates displayed voriconazole MIC greater than the epidemiological cutoff value. Two of these isolates with non-wild-type MIC were isolated from same patient and were genetically distinct, which was confirmed by amplified fragment length polymorphism analysis. Mutations associated with azole resistance were not present in the lanosterol 14-α demethylase coding genes (cyp51A, cyp51B, and cyp51C). Basal and voriconazole-induced expression of cyp51A homologs and various efflux pump genes was analyzed in three each of non-wild-type and wild-type isolates. All of the efflux pump genes screened showed low basal expression irrespective of the azole susceptibility of the isolate. However, the non-wild-type isolates demonstrated heterogeneous overexpression of many efflux pumps and the target enzyme coding genes in response to induction with voriconazole (1 μg/ml). The most distinctive observation was approximately 8- to 9-fold voriconazole-induced overexpression of an ortholog of the Candida albicans ATP binding cassette (ABC) multidrug efflux transporter, Cdr1, in two non-wild-type isolates compared to those in the reference strain A. flavus ATCC 204304 and other wild-type strains. Although the dominant marker of azole resistance in A. flavus is still elusive, the current study proposes the possible role of multidrug efflux pumps, especially that of Cdr1B overexpression, in contributing azole resistance in A. flavus.

scholarly journals Mutations that increase expression of the EmrAB-TolC efflux pump confer increased resistance to nitroxoline in Escherichia coli

2019 ◽  
Author(s):  
Fabiola Puértolas-Balint ◽  
Omar Warsi ◽  
Marius Linkevicius ◽  
Po-Cheng Tang ◽  
Dan I Andersson
Keyword(s):  
Escherichia Coli ◽  
Target Genes ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Cross Resistance ◽  
Resistance Mutations ◽  
Double Knockout ◽  
Low Level ◽  
Resistant Mutants ◽  
Level Resistance

Abstract Objectives To determine the mechanism of resistance to the antibiotic nitroxoline in Escherichia coli. Methods Spontaneous nitroxoline-resistant mutants were selected at different concentrations of nitroxoline. WGS and strain reconstruction were used to define the genetic basis for the resistance. The mechanistic basis of resistance was determined by quantitative PCR (qPCR) and by overexpression of target genes. Fitness costs of the resistance mutations and cross-resistance to other antibiotics were also determined. Results Mutations in the transcriptional repressor emrR conferred low-level resistance to nitroxoline [nitroxoline MIC (MICNOX) = 16 mg/L] by increasing the expression of the emrA and emrB genes of the EmrAB-TolC efflux pump. These resistant mutants showed no fitness reduction and displayed cross-resistance to nalidixic acid. Second-step mutants with higher-level resistance (MICNOX = 32–64 mg/L) had mutations in the emrR gene, together with either a 50 kb amplification, a mutation in the gene marA, or an IS upstream of the lon gene. The latter mutations resulted in higher-level nitroxoline resistance due to increased expression of the tolC gene, which was confirmed by overexpressing tolC from an inducible plasmid in a low-level resistance mutant. Furthermore, the emrR mutations conferred a small increase in resistance to nitrofurantoin only when combined with an nfsAB double-knockout mutation. However, nitrofurantoin-resistant nfsAB mutants showed no cross-resistance to nitroxoline. Conclusions Mutations in different genes causing increased expression of the EmrAB-TolC pump lead to an increased resistance to nitroxoline. The structurally similar antibiotics nitroxoline and nitrofurantoin appear to have different modes of action and resistance mechanisms.

scholarly journals Evaluation the Expression of Efflux Pump Genes “Tap & P55 in Mycobacterium Tuberculosis Clinical Isolates in Fars, Iran

2020 ◽  
Author(s):  
Fardis Khoob ◽  
Milad Shahini Shams Abadi ◽  
Nahal Hadi ◽  
Farzaneh Avazzadeh ◽  
Zahra Zarei
Keyword(s):  
Drug Resistance ◽  
Mycobacterium Tuberculosis ◽  
Target Genes ◽  
Efflux Pump ◽  
Expression Level ◽  
Genetic Mutations ◽  
Antimicrobial Sensitivity ◽  
Probable Role ◽  
Tuberculosis Therapy

Abstract BackgroundThe increasing drug resistance in Mycobacterium tuberculosis isolates has become a global problem for tuberculosis therapy programs. Genetic mutations in rifampin (RIF), one of the key drugs in the treatment of tuberculosis are main mechanism of resistant to this drug in M. tuberculosis. Absence of mutation in target genes, other mechanisms such as efflux pump suggests possible role of drug resistant.The objective of this study was to find out mutations in rpoB genes in rifampin resistant isolates and to compare the expression level of tap and p55 efflux pump genes in non mutated isolates, mutated isolates in rpoB genes and susceptible isolates.MethodsIn this study, antimicrobial sensitivity test on first line drugs was performed on 200 M. tuberculosis isolates, obtained from TB center in Shiraz (IRAN) and genetic mutations were evaluated in rpoB gene in RIF resistant isolates by multiplex PCR, followed expression level evaluated by Real-time PCR.Resultsout of the 200 isolates tested, 23 (34.33%) showed resistant to RIF. 12 of 23 RIF resistant isolates have mutation in rpoB gene, and frequency of mutations in codons 516, 526 and 531 were 3 (25%), 4 (33.33%) and 5 (41.67%) respectively. The expression level of tap and p55 genes was considerably higher in resistant isolates which had no mutation compared to the expression level of genes in the isolates which had mutation in target genes.ConclusionThe accumulating data suggest the probable role of efflux pump in M. tuberculosis drug resistance, the validation of data needs further phenotypic assays of these pumps.

scholarly journals Two functionally redundant FK506-binding proteins regulate multidrug resistance gene expression and govern azole antifungal resistance

2021 ◽  
Author(s):  
Romila Moirangthem ◽  
Kundan Kumar ◽  
Rupinder Kaur
Keyword(s):  
Gene Expression ◽  
Binding Proteins ◽  
Target Genes ◽  
Fungal Infections ◽  
Antifungal Resistance ◽  
Azole Resistance ◽  
Multidrug Resistance Gene ◽  
Protein Levels ◽  
Fk506 Binding Proteins

Increasing resistance to antifungal therapy is an impediment to effective treatment of fungal infections. Candida glabrata is an opportunistic human fungal pathogen which is inherently less susceptible to cost-effective azole antifungals. Gain-of-function mutations in the Zn-finger pleiotropic drug resistance transcriptional activator-encoding gene, CgPDR1, are the most prevalent cause of azole resistance in clinical settings. CgPDR1 is also transcriptionally activated upon azole exposure, however, factors governing CgPDR1 gene expression are not yet fully understood. Here, we have uncovered a novel role for two FK506-binding proteins, CgFpr3 and CgFpr4, in regulation of the CgPDR1 regulon. We show that CgFpr3 and CgFpr4 possess peptidyl-prolyl isomerase domain, and act redundantly to control CgPDR1 expression, as Cgfpr3Δ4Δ mutant displayed elevated expression of CgPDR1 gene, along with overexpression of its target genes, CgCDR1, CgCDR2 and CgSNQ2, that code for ATP-binding cassette multidrug transporters. Further, CgFpr3 and CgFpr4 are required for maintenance of histone H3 and H4 protein levels, and fluconazole exposure leads to elevated H3 and H4 protein levels. Consistent with a role of histone proteins in azole resistance, disruption of genes coding for the histone demethylase CgRph1 and histone H3K36-specific methyltransferase CgSet2 leads to increased and decreased susceptibility to fluconazole, respectively, with Cgrph1Δ mutant displaying significantly lower basal expression of CgPDR1 and CgCDR1 genes. These data underscore a hitherto unknown role of histone methylation in modulating the most common azole antifungal resistance mechanism. Altogether, our findings establish a link between CgFpr-mediated histone homeostasis and CgPDR1 gene expression, and implicate CgFpr in virulence of C. glabrata.

Differential Expression of Resistant and Efflux Pump Genes in MDR-TB Isolates

2020 ◽  
Vol 20 (2) ◽  
pp. 271-287 ◽  
Author(s):  
Manaf AlMatar ◽  
Işıl Var ◽  
Begüm Kayar ◽  
Fatih Köksal
Keyword(s):  
Drug Resistance ◽  
Target Genes ◽  
Efflux Pump ◽  
Gene Mutations ◽  
Clinical Isolates ◽  
Pomegranate Juice ◽  
Drug Efflux ◽  
Mdr Tb ◽  
Drug Efflux Pump

Background: Numerous investigations demonstrate efflux as a worldwide bacterial mode of action which contributes to the resistance of drugs. The activity of antibiotics, which subjects to efflux, can be improved by the combined usage of efflux inhibitors. However, the efflux role to the overall levels of antibiotic resistance of clinical M. tuberculosis isolates is inadequately comprehended and is still disregarded by many. Method: Here, we assessed the contribution of resistant genes associated with isoniazid (INH) and rifampin (R) resistance to the levels of drug resistance in the (27) clinical isolates of MDR-TB. Additionally, the role of the resistance for six putative drug efflux pump genes to the antibiotics was investigated. The level of katG expression was down-regulated in 24/27 (88.88%) of MDR-TB isolates. Of the 27 MDR-TB isolates, inhA, oxyR-ahpC, and rpoB showed either overexpression or up-regulation in 8 (29.62%), 4 (14.81 %), and 24 (88.88%), respectively. Moreover, the efflux pump genes drrA, drrB, efpA, Rv2459, Rv1634, and Rv1250 were overexpressed under INH/RIF plus fresh pomegranate juice (FPJ) stress signifying the efflux pumps contribution to the overall levels of the resistance of MDR-TB isolates. Conclusion: These results displayed that the levels of drug resistance of MDR-TB clinical isolates are due to combination among drug efflux pump and the presence of mutations in target genes, a truth which is often ignored by the specialists of tuberculosis in favour of the almost undoubted significance of drug target- gene mutations for the resistance in M. tuberculosis.

scholarly journals Some Thoughts on the Role of the Critical Intellectual in Contemporary Germany

2005 ◽  
Vol 2 (2) ◽  
Author(s):  
Erich Steiner
Keyword(s):  
Large Scale ◽  
German Society ◽  
The Enlightenment ◽  
Current Usage ◽  
Agents Of Change ◽  
History Of ◽  
Professional Field ◽  
On Line ◽  
The One

The paper starts by relating the notion of the "critical intellectual" to the notion of "agent of social change" on the one hand, and to other potential types of agents of change on the other: women in revolt, artists, exiles and queer agencies. Proceeding to a brief characterisation of the socio-cultural and political context "Germany", we shall explore some meanings of attributes such as post-modern and consumer for contemporary German society and culture, arguing that these are cultural and economic terms, which denote current forms of expression for what continues to be a capitalist economy and a bourgeois democracy. One recurrent question will be what the contours might be of the figure of the "critical intellectual" under present day conditions. This is followed by a brief sketch of the meanings of "kritische(r) Intellektuelle(r)" in a historical ("geistesgeschichtlicher") perspective, mainly from the enlightenment onwards. We shall move on to a methodologically very different, but complementary, perspective, which is the consideration of current usage of the term with the help of large-scale electronic corpora of spoken language and an on-line search on the web. As we shall see, an important share and quality of the relevant meanings of a term lies in current usage, which may or may not be directly related to what we know from the history of ideas and/ or etymology. I shall then use examples from my own professional field of work for an exploration of what the role of a critical intellectual in a German context might be, discussing the field of natural language technologies. These examples will illustrate the fact that such a role has to involve participation in, rather than exclusively detached contemplation of, the sphere of production. They will also show that the role of the critical intellectual is, indeed, a locus of contestation in several respects. We finally broaden our perspective into a wider set of questions relating to the role of the critical intellectual, in German (and other) contexts. One of these questions will revolve around the notions of "values" and "ethics": Do we assume that the role of the critical intellectual is inherently connected to some systems of values, either in the sense of the enlightenment, and/or Marxism, and/or some other Weltanschauungs-system, or else do we believe that the position of a critical intellectual could be defined within some entirely market-driven ideology? Is there something like "truth", "progress" or "justice", other than what is successful on the market? Another one of these questions will focus on whether we can identify some force that motivates change in societies, and cultures, and what the role of the critical intellectual might be vis-à-vis such a force. One of our arguments here will be that among such forces may well be "contradictions", that this category of "contradiction" is in no way exhausted by the category of "difference" as currently debated. It will be argued, finally, that whereas the figure of the "critical intellectual", as we have tried to sketch it here, may be situated in a German context, its essential characteristics defy any attempts at claiming it for any one particular culture.

scholarly journals Investigation of Multiple Resistance Mechanisms in Voriconazole-Resistant Aspergillus flavus Clinical Isolates from a Chest Hospital Surveillance in Delhi, India

2018 ◽  
Vol 62 (3) ◽  
Author(s):  
Cheshta Sharma ◽  
Rakesh Kumar ◽  
Nitin Kumar ◽  
Aradhana Masih ◽  
Dinesh Gupta ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Target Genes ◽  
Empirical Therapy ◽  
Homology Model ◽  
Binding Pocket ◽  
Resistance Mechanisms ◽  
Drug Binding ◽  
Whole Genome Sequence ◽  
Azole Resistance ◽  
Content Type

ABSTRACT Invasive and allergic infections by Aspergillus flavus are more common in tropical and subtropical countries. The emergence of voriconazole (VRC) resistance in A. flavus impacts the management of aspergillosis, as azoles are used as the first-line and empirical therapy. We screened 120 molecularly confirmed A. flavus isolates obtained from respiratory and sinonasal specimens in a chest hospital in Delhi, India, for azole resistance using the CLSI broth microdilution (CLSI-BMD) method. Overall, 2.5% ( n = 3/120) of A. flavus isolates had VRC MICs above epidemiological cutoff values (>1 μg/ml). The whole-genome sequence analysis of three non-wild-type (WT) A. flavus isolates with high VRC MICs showed polymorphisms in azole target genes ( cyp51A , cyp51B , and cyp51C ). Further, four novel substitutions (S196F, A324P, N423D, and V465M) encoded in the cyp51C gene were found in a single non-WT isolate which also exhibited overexpression of cyp51 ( cyp51A , - B , and - C ) genes and transporter genes, namely, MDR1 , MDR2 , atrF , and mfs1 . The homology model of the non-WT isolate suggests that substitutions S196F and N423D exhibited major structural and functional effects on cyp51C drug binding. The substrate (drug) may not be able to bind to binding pocket due to changes in the pocket size or closing down or narrowing of cavities in drug entry channels. Notably, the remaining two VRC-resistant A. flavus isolates, including the one which had a pan-azole resistance phenotype (itraconazole and posaconazole), did not show upregulation of any of the analyzed target genes. These results suggest that multiple target genes and mechanisms could simultaneously contribute to azole resistance in A. flavus .

scholarly journals Prevalence and mechanisms of azole resistance in clinical isolates of Aspergillus section Fumigati species in a Canadian tertiary care centre, 2000 to 2013

2019 ◽  
Vol 75 (4) ◽  
pp. 849-858
Author(s):  
Maxime Parent-Michaud ◽  
Philippe J Dufresne ◽  
Eric Fournier ◽  
Benjamin Folch ◽  
Christine Martineau ◽  
...  
Keyword(s):  
Efflux Pump ◽  
Tertiary Care ◽  
Geographic Area ◽  
Resistance Mechanisms ◽  
Sensu Stricto ◽  
Azole Resistance ◽  
Intrinsic Resistance ◽  
Tertiary Care Centre ◽  
Combined Use ◽  
Aspergillus Section

Abstract Objectives Azole resistance among Aspergillus fumigatus isolates is a growing concern worldwide. Induction of mutations during azole therapy, environment-acquired mutations caused by azole fungicides and intrinsic resistance of cryptic Fumigati species all contribute to the burden of resistance. However, there is a lack of data in Canada on this emerging threat. Methods To gain insights into the magnitude and mechanisms of resistance, a 14 year collection of Aspergillus section Fumigati comprising 999 isolates from 807 patients at a Montreal hospital was screened for azole resistance, and resistance mechanisms were investigated with the combined use of genome sequencing, 3D modelling and phenotypic efflux pump assays. Results Overall azole resistance was low (4/807 patients; 0.5%). A single azole-resistant A. fumigatus sensu stricto strain, isolated from a patient with pulmonary aspergillosis, displayed efflux-pump-mediated resistance. Three patients were colonized or infected with azole-resistant cryptic Fumigati species (one Aspergillus thermomutatus, one Aspergillus lentulus and one Aspergillus turcosus). Evidence is presented that azole resistance is efflux-pump-mediated in the A. turcosus isolate, but not in the A. lentulus and A. thermomutatus isolates. Conclusions Azole resistance is rare in our geographic area and currently driven by cryptic Fumigati species. Continued surveillance of emergence of resistance is warranted.

scholarly journals New Insights into the Cyp51 Contribution to Azole Resistance in Aspergillus Section Nigri

2019 ◽  
Vol 63 (7) ◽  
Author(s):  
Alba Pérez-Cantero ◽  
Loida López-Fernández ◽  
Josep Guarro ◽  
Javier Capilla
Keyword(s):  
Resistance Mechanisms ◽  
Azole Resistance ◽  
Wild Type ◽  
Severe Condition ◽  
Content Type ◽  
Recommended Treatment ◽  
Highly Active ◽  
Expression Studies

ABSTRACT Invasive aspergillosis (IA) is a severe condition mainly caused by Aspergillus fumigatus, although other species of the genus, such as section Nigri members, can also be involved. Voriconazole (VRC) is the recommended treatment for IA; however, the prevalence of azole-resistant Aspergillus isolates has alarmingly increased in recent years, and the underlying resistance mechanisms in non-fumigatus species remain unclear. We have determined the in vitro susceptibility of 36 strains from section Nigri to VRC, posaconazole (POS), and itraconazole (ITC), and we have explored the role of Cyp51A and Cyp51B, both targets of azoles, in azole resistance. The three drugs were highly active; POS displayed the best in vitro activity, while ITC and VRC showed MICs above the established epidemiological cutoff values in 9 and 16% of the strains, respectively. Furthermore, expression studies of cyp51A and cyp51B in control condition and after VRC exposure were performed in 14 strains with different VRC susceptibility. We found higher transcription of cyp51A, which was upregulated upon VRC exposure, but no correlation between MICs and cyp51 transcription levels was observed. In addition, cyp51A sequence analyses revealed nonsynonymous mutations present in both, wild-type and non-wild-type strains of A. niger and A. tubingensis. Nevertheless, a few mutations were exclusively present in non-wild-type A. tubingensis strains. Altogether, our results suggest that azole resistance in section Nigri is not clearly explained by Cyp51A protein alteration or by cyp51 gene upregulation, which indicates that other mechanisms might be involved.

Sign in / Sign up

Export Citation Format

Share Document