scholarly journals Flucytosine-Fluconazole Cross-Resistance in Purine-Cytosine Permease-Deficient Candida lusitaniae Clinical Isolates: Indirect Evidence of a Fluconazole Uptake Transporter

2003 ◽  
Vol 47 (4) ◽  
pp. 1275-1284 ◽  
Author(s):  
Thierry Noël ◽  
Fabienne François ◽  
Patrick Paumard ◽  
Christiane Chastin ◽  
Daniel Brèthes ◽  
...  
Keyword(s):  
In Vitro Selection ◽  
Single Gene ◽  
Resistance Mechanism ◽  
Cytosine Deaminase ◽  
Indirect Evidence ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
Recessive Mutation ◽  
Candida Lusitaniae

ABSTRACT An unusual interaction between flucytosine and fluconazole was observed when a collection of 60 Candida lusitaniae clinical isolates was screened for cross-resistance. Among eight isolates resistant to flucytosine (MIC ≥ 128 μg/ml) and susceptible to fluconazole (0.5 < MIC < 2 μg/ml), four became flucytosine-fluconazole cross resistant when both antifungals were used simultaneously. Fluconazole resistance occurred only in the presence of high flucytosine concentrations, and the higher the fluconazole concentration used, the greater the flucytosine concentration necessary to trigger the cross-resistance. When the flucytosine- and fluconazole-resistant cells were grown in the presence of fluconazole alone, the cells reversed to fluconazole susceptibility. Genetic analyses of the progeny from crosses between resistant and sensitive isolates showed that resistance to flucytosine was derived from a recessive mutation in a single gene, whereas cross-resistance to fluconazole seemed to vary like a quantitative trait. We further demonstrated that the four clinical isolates were susceptible to 5-fluorouracil and that cytosine deaminase activity was unaffected. Kinetic transport studies with [14C]flucytosine showed that flucytosine resistance was due to a defect in the purine-cytosine permease. Our hypothesis was that extracellular flucytosine would subsequently behave as a competitive inhibitor of fluconazole uptake transport. Finally, in vitro selection of spontaneous and induced mutants indicated that such a cross-resistance mechanism could also affect other Candida species, including C. albicans, C. tropicalis, and C. glabrata. This is the first report of a putative fluconazole uptake transporter in Candida species and of a possible resistance mechanism associated with a deficiency in the uptake of this drug.

scholarly journals Flucytosine-Fluconazole Cross-Resistance in Purine-Cytosine Permease-Deficient Candida lusitaniae Clinical Isolates: Indirect Evidence of a Fluconazole Uptake Transporter

2003 ◽  
Vol 47 (6) ◽  
pp. 2062-2062
Author(s):  
Thierry Noël ◽  
Fabienne François ◽  
Patrick Paumard ◽  
Christiane Chastin ◽  
Daniel Brèthes ◽  
...  
Keyword(s):  
Indirect Evidence ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
Candida Lusitaniae

scholarly journals Nonsense and Missense Mutations in FCY2 and FCY1 Genes Are Responsible for Flucytosine Resistance and Flucytosine-Fluconazole Cross-Resistance in Clinical Isolates of Candida lusitaniae

2009 ◽  
Vol 53 (7) ◽  
pp. 2982-2990 ◽  
Author(s):  
Martine Florent ◽  
Thierry Noël ◽  
Gwenaël Ruprich-Robert ◽  
Bruno Da Silva ◽  
Valérie Fitton-Ouhabi ◽  
...  
Keyword(s):  
Nonsense Mutation ◽  
Molecular Mechanisms ◽  
Antifungal Susceptibility ◽  
Cytosine Deaminase ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
Nucleotide Sequencing ◽  
Missense Mutations ◽  
Wild Type ◽  
Candida Lusitaniae

ABSTRACT The aim of this work was to elucidate the molecular mechanisms of flucytosine (5FC) resistance and 5FC/fluconazole (FLC) cross-resistance in 11 genetically and epidemiologically unrelated clinical isolates of Candida lusitaniae. We first showed that the levels of transcription of the FCY2 gene encoding purine-cytosine permease (PCP) in the isolates were similar to that in the wild-type strain, 6936. Nucleotide sequencing of the FCY2 alleles revealed that 5FC and 5FC/FLC resistance could be correlated with a cytosine-to-thymine substitution at nucleotide 505 in the fcy2 genes of seven clinical isolates, resulting in a nonsense mutation and in a putative nonfunctional truncated PCP of 168 amino acids. Reintroducing a FCY2 wild-type allele at the fcy2 locus of a ura3 auxotrophic strain derived from the clinical isolate CL38 fcy2(C505T) restored levels of susceptibility to antifungals comparable to those of the wild-type strains. In the remaining four isolates, a polymorphic nucleotide was found in FCY1 where the nucleotide substitution T26C resulted in the amino acid replacement M9T in cytosine deaminase. Introducing this mutated allele into a 5FC- and 5FC/FLC-resistant fcy1Δ strain failed to restore antifungal susceptibility, while susceptibility was obtained by introducing a wild-type FCY1 allele. We thus found a correlation between the fcy1 T26C mutation and both 5FC and 5FC/FLC resistances. We demonstrated that only two genetic events occurred in 11 unrelated clinical isolates of C. lusitaniae to support 5FC and 5FC/FLC resistance: either the nonsense mutation C505T in the fcy2 gene or the missense mutation T26C in the fcy1 gene.

scholarly journals In Vitro Selection oframRandsoxRMutants Overexpressing Efflux Systems by Fluoroquinolones as Well as Cefoxitin in Klebsiella pneumoniae

2011 ◽  
Vol 55 (6) ◽  
pp. 2795-2802 ◽  
Author(s):  
Suzanne Bialek-Davenet ◽  
Estelle Marcon ◽  
Véronique Leflon-Guibout ◽  
Jean-Philippe Lavigne ◽  
Frédéric Bert ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
In Vitro Selection ◽  
Efflux Pump ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
Efflux System ◽  
Content Type ◽  
New Antibiotics ◽  
Regulator Genes

ABSTRACTThe relationship between efflux system overexpression and cross-resistance to cefoxitin, quinolones, and chloramphenicol has recently been reported inKlebsiella pneumoniae. In 3 previously published clinical isolates and 17in vitromutants selected with cefoxitin or fluoroquinolones, mutations in the potential regulator genes of the AcrAB efflux pump (acrR,ramR,ramA,marR,marA,soxR,soxS, androb) were searched, and their impacts on efflux-related antibiotic cross-resistance were assessed. All mutants but 1, and 2 clinical isolates, overexpressedacrB. No mutation was detected in the regulator genes studied among the clinical isolates and 8 of the mutants. For the 9 remaining mutants, a mutation was found in theramRgene in 8 of them and in thesoxRgene in the last one, resulting in overexpression oframAandsoxS, respectively. Transformation of theramRmutants and thesoxRmutant with the wild-typeramRandsoxRgenes, respectively, abolished overexpression ofacrBandramAin theramRmutants and ofsoxSin thesoxRmutant, as well as antibiotic cross-resistance. Resistance due to efflux system overexpression was demonstrated for 4 new antibiotics: cefuroxime, cefotaxime, ceftazidime, and ertapenem. This study shows that theramRandsoxRgenes control the expression of efflux systems inK. pneumoniaeand suggests the existence of efflux pumps other than AcrAB and of other loci involved in the regulation of AcrAB expression.

scholarly journals Gene mapping and cross-resistance in cyclodiene insecticide-resistant Drosophila melanogaster (Mg.).

1991 ◽  
Vol 57 (1) ◽  
pp. 17-21 ◽  
Author(s):  
R. H. Ffrench-Constant ◽  
R. T. Roush
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosomal Location ◽  
Major Gene ◽  
Single Gene ◽  
Resistance Mechanism ◽  
Cross Resistance ◽  
Cyclodiene Insecticide ◽  
Chromosome Iii ◽  
Resistance Spectrum ◽  
Mixed Function Oxidase Activity

SummaryResistance to the cyclodiene insecticide dieldrin maps to a single gene (Rdl) on the left arm of chromosome III in Drosophila melanogaster (Meigen). The gene was further mapped by the use of chromosomal deficiencies to a single letter sub-region, 66F, on the polytene chromosome. The cross-resistance spectrum of a backcrossed strain lacking elevated mixed function oxidase activity, a common resistance mechanism, was examined. Levels of resistance similar to those found in other insects were found to dieldrin, aldrin, endrin, lindane, and picrotoxinin. Strong similarity of this single major gene with that found in other cyclodiene resistant insects is suggested by its cross-resistance spectrum and chromosomal location, via homology with other Diptera. The significance of major genes in insecticide resistance is discussed.

Susceptibility of Candida spp. clinical isolates to antimycotics and disinfectants

2010 ◽  
Vol 5 (6) ◽  
pp. 821-826
Author(s):  
Monika Staniszewska ◽  
Beata Rozbicka ◽  
Aleksandra Rajnisz ◽  
Ewa Bocian ◽  
Ewa Wasińska ◽  
...  
Keyword(s):  
Clinical Isolates ◽  
Cross Resistance ◽  
Biocidal Activity ◽  
Candida Spp ◽  
In Vitro Susceptibility ◽  
Minimal Inhibitory Concentrations ◽  
Antiseptic Agent ◽  
Resistant Strains ◽  
Candida Infections

AbstractThe incidence of candidiasis among immunocompromised patients and emergence of antimycotics resistant strains has increased significantly. The aims of this study were: to examine the in vitro activity of antimycotics and biocides against Candida clinical isolates; to detect cross-resistance of fungi to these preparations and to estimate whether disinfectants applied in hospital areas are active against clinical Candida isolates. In vitro susceptibility of 102 Candida isolates to eight antimycotics was examined by Etest and ATB Fungus. Sensitivity of these strains to four disinfectants and an antiseptic agent was tested according to EN 1275:2005. Amphotericin B, caspofungin and 5-fluorocytosine were the most effective antimycotics against all Candida isolates. Resistance to itraconazole and fluconazole was observed among C. krusei and C. glabrata. The MICs (Minimal Inhibitory Concentrations) for ketoconazole, voriconazole and posaconazole against Candida albicans ranged: 0.003 - >32 μg/ml and one strain was resistant to three agents tested. All analysed Candida strains were sensitive to biocides containing either chlorine, aldehyde, alcohol mixtures, glucoprotamin or chlorhexidine gluconate with isopropanol. Sensitivity to these agents was observed at concentrations lower than those concentrations recommended by manufacturers to achieve proper biocidal activity to those preparations. Our data suggest that these disinfectants can be effectively applied in clinical wards to prevent nosocomial Candida infections.

scholarly journals In VitroActivity of AZD5847 against Geographically Diverse Clinical Isolates of Mycobacterium tuberculosis

2014 ◽  
Vol 58 (7) ◽  
pp. 4222-4223 ◽  
Author(s):  
Jim Werngren ◽  
Maria Wijkander ◽  
Nasrin Perskvist ◽  
V. Balasubramanian ◽  
Vasan K. Sambandamurthy ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Lavage Fluid ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
Drug Candidate ◽  
Content Type ◽  
Geographical Regions ◽  
Lung Biopsies

ABSTRACTThe MIC of the novel antituberculosis (anti-TB) drug AZD5847 was determined against 146 clinical isolates from diverse geographical regions, including eastern Europe, North America, Africa, and Asia, using the automated Bactec Mycobacterial Growth Indicator Tube (MGIT) 960 system. These isolates originated from specimen sources such as sputum, bronchial alveolar lavage fluid, pleural fluid, abscess material, lung biopsies, and feces. The overall MIC90was 1.0 mg/liter (range, 0.125 to 4 mg/liter). The MICs of AZD5847 for isolates ofMycobacterium tuberculosiswere similar among drug-sensitive strains, multidrug-resistant (MDR) strains, and extensively drug resistant (XDR) strains. The goodin vitroactivity of AZD5847 againstM. tuberculosisand the lack of cross-resistance make this agent a promising anti-TB drug candidate.

scholarly journals Resistance to Antimicrobial Peptides and Stress Response in Mycoplasma pulmonis

2005 ◽  
Vol 49 (10) ◽  
pp. 4154-4165 ◽  
Author(s):  
Lina Fassi Fehri ◽  
Pascal Sirand-Pugnet ◽  
Géraldine Gourgues ◽  
Gwenaël Jan ◽  
Henri Wróblewski ◽  
...  
Keyword(s):  
Stress Response ◽  
Antimicrobial Peptides ◽  
In Vitro Selection ◽  
Immune Defense ◽  
Negative Regulator ◽  
Respiratory Pathogen ◽  
Cross Resistance ◽  
Mycoplasma Pulmonis ◽  
Gramicidin D

ABSTRACT Antimicrobial peptides are widely distributed in nature, and in vertebrates, they play a key function in the innate immune defense system. It is generally agreed that these molecules may provide new antibiotics with therapeutic value. However, there are still many unsolved questions regarding the mechanisms underlying their antimicrobial activity as well as the mechanisms of resistance evolved by microorganisms against these molecules. The second point was addressed in this study. After determining the activity of 10 antimicrobial peptides against Mycoplasma pulmonis, a murine respiratory pathogen, the development of resistance was investigated. Following in vitro selection using subinhibitory concentrations of peptides, clones of this bacterium showing increased resistance to melittin or gramicidin D were obtained. For some of the clones, a cross-resistance was observed between these two peptides, in spite of their deep structural differences, and also with tetracycline. A proteomic analysis suggested that the stress response in these clones was constitutively activated, and this was confirmed by finding mutations in the hrcA gene; in mycoplasmas, bacteria which lack alternative sigma factors, the HrcA protein is supposed to play a key role as a negative regulator of heat shock proteins. By complementation of the hrcA mutants with the wild-type gene, the initial MICs of melittin and gramicidin D decreased to values close to the initial ones. This indicates that the resistance of M. pulmonis to these two antimicrobial peptides could result from a stress response involving HrcA-regulated genes.

Sign in / Sign up

Export Citation Format

Share Document