21 results on '"Andrew T. Nishimoto"'
Search Results
2. Pneumolysin: Pathogenesis and Therapeutic Target
- Author
-
Andrew T. Nishimoto, Jason W. Rosch, and Elaine I. Tuomanen
- Subjects
Streptococcus pneumoniae ,pneumococcus ,pneumolysin ,cholesterol-dependent cytolysin ,invasive pneumococcal disease ,vaccine ,Microbiology ,QR1-502 - Abstract
Streptococcus pneumoniae is an opportunistic pathogen responsible for widespread illness and is a major global health issue for children, the elderly, and the immunocompromised population. Pneumolysin (PLY) is a cholesterol-dependent cytolysin (CDC) and key pneumococcal virulence factor involved in all phases of pneumococcal disease, including transmission, colonization, and infection. In this review we cover the biology and cytolytic function of PLY, its contribution to S. pneumoniae pathogenesis, and its known interactions and effects on the host with regard to tissue damage and immune response. Additionally, we review statins as a therapeutic option for CDC toxicity and PLY toxoid as a vaccine candidate in protein-based vaccines.
- Published
- 2020
- Full Text
- View/download PDF
3. Loss of Upc2p-Inducible ERG3 Transcription Is Sufficient To Confer Niche-Specific Azole Resistance without Compromising Candida albicans Pathogenicity
- Author
-
Arturo Luna-Tapia, Hubertine M. E. Willems, Josie E. Parker, Hélène Tournu, Katherine S. Barker, Andrew T. Nishimoto, P. David Rogers, Steven L. Kelly, Brian M. Peters, and Glen E. Palmer
- Subjects
azole resistance ,Candida albicans ,disseminated candidiasis ,ERG3 ,mouse models ,pathogenesis ,Microbiology ,QR1-502 - Abstract
ABSTRACT Inactivation of sterol Δ5,6-desaturase (Erg3p) in the prevalent fungal pathogen Candida albicans is one of several mechanisms that can confer resistance to the azole antifungal drugs. However, loss of Erg3p activity is also associated with deficiencies in stress tolerance, invasive hyphal growth, and attenuated virulence in a mouse model of disseminated infection. This may explain why relatively few erg3-deficient strains have been reported among azole-resistant clinical isolates. In this study, we examined the consequences of Erg3p inactivation upon C. albicans pathogenicity and azole susceptibility in mouse models of mucosal and disseminated infection. While a C. albicans erg3Δ/Δ mutant was unable to cause lethality in the disseminated model, it induced pathology in a mouse model of vaginal infection. The erg3Δ/Δ mutant was also more resistant to fluconazole treatment than the wild type in both models of infection. Thus, complete loss of Erg3p activity confers azole resistance but also niche-specific virulence deficiencies. Serendipitously, we discovered that loss of azole-inducible ERG3 transcription (rather than complete inactivation) is sufficient to confer in vitro fluconazole resistance, without compromising C. albicans stress tolerance, hyphal growth, or pathogenicity in either mouse model. It is also sufficient to confer fluconazole resistance in the mouse vaginal model, but not in the disseminated model of infection, and thus confers niche-specific azole resistance without compromising C. albicans pathogenicity at either site. Collectively, these results establish that modulating Erg3p expression or activity can have niche-specific consequences on both C. albicans pathogenicity and azole resistance. IMPORTANCE While conferring resistance to the azole antifungals in vitro, loss of sterol Δ5,6-desaturase (Erg3p) activity has also been shown to reduce C. albicans pathogenicity. Accordingly, it has been presumed that this mechanism may not be significant in the clinical setting. The results presented here challenge this assumption, revealing a more complex relationship between Erg3p activity, azole resistance, C. albicans pathogenicity, and the specific site of infection. Most importantly, we have shown that even modest changes in ERG3 transcription are sufficient to confer azole resistance without compromising C. albicans fitness or pathogenicity. Given that previous efforts to assess the importance of ERG3 as a determinant of clinical azole resistance have focused almost exclusively on detecting null mutants, its role may have been grossly underestimated. On the basis of our results, a more thorough investigation of the contribution of the ERG3 gene to azole resistance in the clinical setting is warranted.
- Published
- 2018
- Full Text
- View/download PDF
4. Transkingdom Interactions Important for the Pathogenesis of Human Viruses
- Author
-
Hannah M. Rowe, Nicholas Wohlgemuth, Stacey Schultz-Cherry, Jason W. Rosch, Valerie Cortez, and Andrew T. Nishimoto
- Subjects
0301 basic medicine ,Genetics ,viruses ,Viral pathogenesis ,030106 microbiology ,Supplement Articles ,Disease ,Biology ,medicine.disease_cause ,Pathogenesis ,03 medical and health sciences ,030104 developmental biology ,Infectious Diseases ,Immune system ,Tissue remodeling ,Influenza A virus ,medicine ,Immunology and Allergy ,Microbiome - Abstract
The bacterial, fungal, and helminthic species that comprise the microbiome of the mammalian host have profound effects on health and disease. Pathogenic viruses must contend with the microbiome during infection and likely have evolved to exploit or evade the microbiome. Both direct interactions between the virions and the microbiota and immunomodulation and tissue remodeling caused by the microbiome alter viral pathogenesis in either host- or virus-beneficial ways. Recent insights from in vitro and murine models of viral pathogenesis have highlighted synergistic and antagonistic, direct and indirect interactions between the microbiome and pathogenic viruses. This review will focus on the transkingdom interactions between human gastrointestinal and respiratory viruses and the constituent microbiome of those tissues.
- Published
- 2020
5. An Investigation into Clinically Relevant Determinants of Azole Resistance in Candida albicans
- Author
-
Andrew T. Nishimoto
- Subjects
chemistry.chemical_classification ,biology ,chemistry ,Zoonosis ,medicine ,Azole ,Azole resistance ,Candida albicans ,biology.organism_classification ,medicine.disease ,Microbiology - Published
- 2022
6. Molecular and genetic basis of azole antifungal resistance in the opportunistic pathogenic fungusCandida albicans
- Author
-
P. David Rogers, Andrew T. Nishimoto, and Cheshta Sharma
- Subjects
Azoles ,Microbiology (medical) ,Antifungal Agents ,Microbial Sensitivity Tests ,Review ,Biology ,medicine.disease_cause ,Microbiology ,Fungal Proteins ,Drug Resistance, Fungal ,Candida albicans ,medicine ,Humans ,Pharmacology (medical) ,Organism ,Pharmacology ,chemistry.chemical_classification ,Mutation ,Candidiasis ,Pathogenic fungus ,biology.organism_classification ,Corpus albicans ,Infectious Diseases ,chemistry ,Azole ,Efflux ,Fluconazole ,Transcription Factors ,medicine.drug - Abstract
Candida albicans is an opportunistic yeast and the major human fungal pathogen in the USA, as well as in many other regions of the world. Infections with C. albicans can range from superficial mucosal and dermatological infections to life-threatening infections of the bloodstream and vital organs. The azole antifungals remain an important mainstay treatment of candidiasis and therefore the investigation and understanding of the evolution, frequency and mechanisms of azole resistance are vital to improving treatment strategies against this organism. Here the organism C. albicans and the genetic changes and molecular bases underlying the currently known resistance mechanisms to the azole antifungal class are reviewed, including up-regulated expression of efflux pumps, changes in the expression and amino acid composition of the azole target Erg11 and alterations to the organism’s typical sterol biosynthesis pathways. Additionally, we update what is known about activating mutations in the zinc cluster transcription factor (ZCF) genes regulating many of these resistance mechanisms and review azole import as a potential contributor to azole resistance. Lastly, investigations of azole tolerance in C. albicans and its implicated clinical significance are reviewed.
- Published
- 2019
7. Impact of the Major Candida glabrata Triazole Resistance Determinants on the Activity of the Novel Investigational Tetrazoles VT-1598 and VT-1161
- Author
-
Andrew T. Nishimoto, Edward P. Garvey, Sarah G. Whaley, Robert J. Schotzinger, Christopher M. Yates, P. David Rogers, William J. Hoekstra, Nathan P. Wiederhold, and Qing Zhang
- Subjects
Antifungal Agents ,Pyridines ,Triazole ,Tetrazoles ,Candida glabrata ,Microbial Sensitivity Tests ,Microbiology ,Fungal Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,In vivo ,Drug Resistance, Fungal ,Mechanisms of Resistance ,Pharmacology (medical) ,030212 general & internal medicine ,Gene ,Pharmacology ,0303 health sciences ,biology ,030306 microbiology ,Transporter ,biology.organism_classification ,Phenotype ,In vitro ,Infectious Diseases ,chemistry ,Efflux ,Transcription Factors - 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.
- Published
- 2019
8. In Vitro Activities of the Novel Investigational Tetrazoles VT-1161 and VT-1598 Compared to the Triazole Antifungals against Azole-Resistant Strains and Clinical Isolates of Candida albicans
- Author
-
P. David Rogers, Stephanie A. Flowers, Joachim Morschhäuser, Steven L. Kelly, Edward P. Garvey, Christopher M. Yates, William J. Hoekstra, Robert J. Schotzinger, Qing Zhang, Nathan P. Wiederhold, and Andrew T. Nishimoto
- Subjects
Pharmacology ,chemistry.chemical_classification ,Voriconazole ,0303 health sciences ,Posaconazole ,biology ,030306 microbiology ,Itraconazole ,Triazole ,biology.organism_classification ,Corpus albicans ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,Infectious Diseases ,chemistry ,medicine ,Azole ,Experimental Therapeutics ,Pharmacology (medical) ,Candida albicans ,Fluconazole ,030304 developmental biology ,medicine.drug - Abstract
The fungal Cyp51-specific inhibitors VT-1161 and VT-1598 have emerged as promising new therapies to combat fungal infections, including Candida spp. To evaluate their in vitro activities compared to other azoles, MICs were determined by Clinical and Laboratory Standards Institute (CLSI) method for VT-1161, VT-1598, fluconazole, voriconazole, itraconazole, and posaconazole against 68 C. albicans clinical isolates well characterized for azole resistance mechanisms and mutant strains representing individual azole resistance mechanisms. VT-1161 and VT-1598 demonstrated potent activity (geometric mean MICs ≤0.15 μg/ml) against predominantly fluconazole-resistant (≥8 μg/ml) isolates. However, five of 68 isolates exhibited MICs greater than six dilutions (>2 μg/ml) to both tetrazoles compared to fluconazole-susceptible isolates. Four of these isolates likewise exhibited high MICs beyond the upper limit of the assay for all triazoles tested. A premature stop codon in ERG3 likely explained the high-level resistance in one isolate. VT-1598 was effective against strains with hyperactive Tac1, Mrr1, and Upc2 transcription factors and against most ERG11 mutant strains. VT-1161 MICs were elevated compared to the control strain SC5314 for hyperactive Tac1 strains and two strains with Erg11 substitutions (Y132F and Y132F&K143R) but showed activity against hyperactive Mrr1 and Upc2 strains. While mutations affecting Erg3 activity appear to greatly reduce susceptibility to VT-1161 and VT-1598, the elevated MICs of both tetrazoles for four isolates could not be explained by known azole resistance mechanisms, suggesting the presence of undescribed resistance mechanisms to triazole- and tetrazole-based sterol demethylase inhibitors.
- Published
- 2019
9. A Systematic Screen Reveals a Diverse Collection of Medications That Induce Antifungal Resistance in Candida Species
- Author
-
Christian DeJarnette, Andrew T. Nishimoto, Leanna R Estredge, Glen E. Palmer, Arielle Butts, Tracy L. Peters, P. David Rogers, Michael P. Veve, and Parker Reitler
- Subjects
Drug ,media_common.quotation_subject ,Pharmacology ,Candida parapsilosis ,Candida tropicalis ,03 medical and health sciences ,chemistry.chemical_compound ,Amphotericin B ,medicine ,Pharmacology (medical) ,030304 developmental biology ,media_common ,0303 health sciences ,biology ,Candida glabrata ,030306 microbiology ,business.industry ,biology.organism_classification ,Infectious Diseases ,chemistry ,Efflux ,Caspofungin ,business ,Fluconazole ,medicine.drug - Abstract
The increasing incidence of and high mortality rates associated with invasive fungal infections (IFIs) impose an enormous clinical, social, and economic burden on humankind. In addition to microbiological resistance to existing antifungal drugs, the large number of unexplained treatment failures is a serious concern. Due to the extremely limited therapeutic options available, it is critical to identify and understand the various causes of treatment failure if patient outcomes are to improve. In this study, we examined one potential source of treatment failure: antagonistic drug interactions. Using a simple screen, we systematically identified currently approved medications that undermine the antifungal activity of three major antifungal drugs-fluconazole, caspofungin, and amphotericin B-on four prevalent human fungal pathogens-Candida albicans, Candida glabrata, Candida parapsilosis, and Candida tropicalis This revealed that a diverse collection of structurally distinct drugs exhibit antagonistic interactions with fluconazole. Several antagonistic agents selected for follow-up studies induce azole resistance through a mechanism that depends on Tac1p/Pdr1p zinc-cluster transcription factors, which activate the expression of drug efflux pumps belonging to the ABC-type transporter family. Few antagonistic interactions were identified with caspofungin or amphotericin B, possibly reflecting their cell surface mode of action that should not be affected by drug efflux mechanisms. Given that patients at greatest risk of IFIs usually receive a multitude of drugs to treat various underlying conditions, these studies suggest that chemically inducible azole resistance may be much more common and important than previously realized.
- Published
- 2019
10. Contribution of Clinically Derived Mutations in the Gene Encoding the Zinc Cluster Transcription Factor Mrr2 to Fluconazole Antifungal Resistance and CDR1 Expression in Candida albicans
- Author
-
P. David Rogers, Brandon T. Hazlett, Qing Zhang, Andrew T. Nishimoto, and Joachim Morschhäuser
- Subjects
Pharmacology ,0303 health sciences ,medicine.medical_specialty ,biology ,030306 microbiology ,Drug resistance ,biology.organism_classification ,Corpus albicans ,Microbiology ,03 medical and health sciences ,Infectious Diseases ,Molecular genetics ,Gene expression ,medicine ,Pharmacology (medical) ,Efflux ,Candida albicans ,Gene ,Fluconazole ,030304 developmental biology ,medicine.drug - Abstract
Mutations in genes encoding zinc cluster transcription factors (ZCFs) such as TAC1, MRR1, and UPC2 play a key role in Candida albicans azole antifungal resistance. Artificial activation of the ZCF Mrr2 has shown increased expression of the gene encoding the Cdr1 efflux pump and resistance to fluconazole. Amino acid substitutions in Mrr2 have recently been reported to contribute to fluconazole resistance in clinical isolates. In the present study, 57 C. albicans clinical isolates with elevated fluconazole MICs were examined for mutations in MRR2 and expression of CDR1. Mutations in MRR2 resulting in 15 amino acid substitutions were uniquely identified among resistant isolates, including 4 substitutions (S466L, A468G, S469T, T470N) previously reported to reduce fluconazole susceptibility. Three additional, novel amino acid substitutions (R45Q, A459T, V486M) were also discovered in fluconazole-resistant isolates. When introduced into a fluconazole-susceptible background, no change in fluconazole MIC or CDR1 expression was observed for any of the mutations found in this collection. However, introduction of an allele leading to artificial activation of Mrr2 increased resistance to fluconazole as well as CDR1 expression. Moreover, Mrr2 amino acid changes reported previously to have the strongest effect on fluconazole susceptibility and CDR1 expression also exhibited no differences in fluconazole susceptibility or CDR1 expression relative to the parent strain. While all known fluconazole resistance mechanisms are represented within this collection of clinical isolates and contribute to fluconazole resistance to different extents, mutations in MRR2 do not appear to alter CDR1 expression or contribute to resistance in any of these isolates.
- Published
- 2019
11. Abrogation of Triazole Resistance upon Deletion of CDR1 in a Clinical Isolate of Candida auris
- Author
-
Jeffrey M. Rybak, P. David Rogers, Glen E. Palmer, Andrew T. Nishimoto, Laura A. Doorley, and Katherine S. Barker
- Subjects
Antifungal Agents ,Triazole ,Microbial Sensitivity Tests ,Genome ,Homology (biology) ,Microbiology ,Fungal Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,Mechanisms of Resistance ,Drug Resistance, Fungal ,CRISPR-Associated Protein 9 ,Gene Expression Regulation, Fungal ,Humans ,Pharmacology (medical) ,ATP Binding Cassette Transporter, Subfamily B, Member 1 ,Candida albicans ,Gene ,Pathogen ,Fluconazole ,030304 developmental biology ,Candida ,Pharmacology ,0303 health sciences ,biology ,030306 microbiology ,Candidiasis ,Membrane Transport Proteins ,Triazoles ,biology.organism_classification ,Infectious Diseases ,chemistry ,Candida auris ,Efflux ,Microorganisms, Genetically-Modified ,Gene Deletion - Abstract
Candida auris has rapidly emerged as a health care-associated and multidrug-resistant pathogen of global concern. In this work, we examined the relative expression of the four C. auris genes with the highest degree of homology to Candida albicans CDR1 and MDR1 among three triazole-resistant clinical isolates as compared to the triazole-susceptible genome reference clinical isolate. We subsequently utilized a novel Cas9-mediated system for genetic manipulations to delete C. auris CDR1 and MDR1 in both a triazole-resistant clinical isolate and a susceptible reference strain and observed that MICs for all clinically available triazoles decreased as much as 128-fold in the CDR1 deletion strains. The findings of this work reveal for the first time that C. auris CDR1 and MDR1 are more highly expressed among triazole-resistant clinical isolates of C. auris and that the overexpression of CDR1 is a significant contributor to clinical triazole resistance.
- Published
- 2019
12. The evolution of azole resistance in Candida albicans sterol 14α-demethylase (CYP51) through incremental amino acid substitutions
- Author
-
P. David Rogers, Claire L. Price, Diane E. Kelly, Andrew G. S. Warrilow, Andrew T. Nishimoto, Steven L. Kelly, Stephanie A. Flowers, and Josie E. Parker
- Subjects
Azoles ,Posaconazole ,Antifungal Agents ,Itraconazole ,Triazole ,Fungal Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,Sterol 14-Demethylase ,Mechanisms of Resistance ,Candida albicans ,medicine ,azole ,Pharmacology (medical) ,Amino Acid Sequence ,Fluconazole ,030304 developmental biology ,Pharmacology ,chemistry.chemical_classification ,0303 health sciences ,biology ,030306 microbiology ,Triazoles ,biology.organism_classification ,mutations ,Molecular biology ,Corpus albicans ,3. Good health ,Infectious Diseases ,Enzyme ,chemistry ,Mutation ,Azole ,Voriconazole ,Candida albicans CYP51 ,medicine.drug ,Protein Binding - Abstract
Recombinant Candida albicans CYP51 (CaCYP51) proteins containing 23 single and 5 double amino acid substitutions found in clinical strains and the wild-type enzyme were expressed in Escherichia coli and purified by Ni2+-nitrilotriacetic acid agarose chromatography. Catalytic tolerance to azole antifungals was assessed by determination of the concentration causing 50% enzyme inhibition (IC50) using CYP51 reconstitution assays., Recombinant Candida albicans CYP51 (CaCYP51) proteins containing 23 single and 5 double amino acid substitutions found in clinical strains and the wild-type enzyme were expressed in Escherichia coli and purified by Ni2+-nitrilotriacetic acid agarose chromatography. Catalytic tolerance to azole antifungals was assessed by determination of the concentration causing 50% enzyme inhibition (IC50) using CYP51 reconstitution assays. The greatest increase in the IC50 compared to that of the wild-type enzyme was observed with the five double substitutions Y132F+K143R (15.3-fold), Y132H+K143R (22.1-fold), Y132F+F145L (10.1-fold), G307S+G450E (13-fold), and D278N+G464S (3.3-fold). The single substitutions K143R, D278N, S279F, S405F, G448E, and G450E conferred at least 2-fold increases in the fluconazole IC50, and the Y132F, F145L, Y257H, Y447H, V456I, G464S, R467K, and I471T substitutions conferred increased residual CYP51 activity at high fluconazole concentrations. In vitro testing of select CaCYP51 mutations in C. albicans showed that the Y132F, Y132H, K143R, F145L, S405F, G448E, G450E, G464S, Y132F+K143R, Y132F+F145L, and D278N+G464S substitutions conferred at least a 2-fold increase in the fluconazole MIC. The catalytic tolerance of the purified proteins to voriconazole, itraconazole, and posaconazole was far lower and limited to increased residual activities at high triazole concentrations for certain mutations rather than large increases in IC50 values. Itraconazole was the most effective at inhibiting CaCYP51. However, when tested against CaCYP51 mutant strains, posaconazole seemed to be the most resistant to changes in MIC as a result of CYP51 mutation compared to itraconazole, voriconazole, or fluconazole.
- Published
- 2019
13. Contribution of Clinically Derived Mutations in the Gene Encoding the Zinc Cluster Transcription Factor Mrr2 to Fluconazole Antifungal Resistance and
- Author
-
Andrew T, Nishimoto, Qing, Zhang, Brandon, Hazlett, Joachim, Morschhäuser, and P David, Rogers
- Subjects
Azoles ,Fungal Proteins ,Drug Resistance, Fungal ,Mechanisms of Resistance ,Gene Expression Regulation, Fungal ,Candida albicans ,Mutation ,Microbial Sensitivity Tests ,Fluconazole ,Transcription Factors - Abstract
Mutations in genes encoding zinc cluster transcription factors (ZCFs) such as TAC1, MRR1, and UPC2 play a key role in Candida albicans azole antifungal resistance. Artificial activation of the ZCF Mrr2 has shown increased expression of the gene encoding the Cdr1 efflux pump and resistance to fluconazole. Amino acid substitutions in Mrr2 have recently been reported to contribute to fluconazole resistance in clinical isolates. In the present study, 57 C. albicans clinical isolates with elevated fluconazole MICs were examined for mutations in MRR2 and expression of CDR1. Mutations in MRR2 resulting in 15 amino acid substitutions were uniquely identified among resistant isolates, including 4 substitutions (S466L, A468G, S469T, T470N) previously reported to reduce fluconazole susceptibility. Three additional, novel amino acid substitutions (R45Q, A459T, V486M) were also discovered in fluconazole-resistant isolates. When introduced into a fluconazole-susceptible background, no change in fluconazole MIC or CDR1 expression was observed for any of the mutations found in this collection. However, introduction of an allele leading to artificial activation of Mrr2 increased resistance to fluconazole as well as CDR1 expression. Moreover, Mrr2 amino acid changes reported previously to have the strongest effect on fluconazole susceptibility and CDR1 expression also exhibited no differences in fluconazole susceptibility or CDR1 expression relative to the parent strain. While all known fluconazole resistance mechanisms are represented within this collection of clinical isolates and contribute to fluconazole resistance to different extents, mutations in MRR2 do not appear to alter CDR1 expression or contribute to resistance in any of these isolates.
- Published
- 2019
14. A Systematic Screen Reveals a Diverse Collection of Medications That Induce Antifungal Resistance in
- Author
-
Arielle, Butts, Parker, Reitler, Andrew T, Nishimoto, Christian, DeJarnette, Leanna R, Estredge, Tracy L, Peters, Michael P, Veve, P David, Rogers, and Glen E, Palmer
- Subjects
Azoles ,Echinocandins ,Antifungal Agents ,Drug Resistance, Fungal ,Mechanisms of Resistance ,Amphotericin B ,Morpholines ,Haloperidol ,Humans ,Candida - Abstract
The increasing incidence of and high mortality rates associated with invasive fungal infections (IFIs) impose an enormous clinical, social, and economic burden on humankind. In addition to microbiological resistance to existing antifungal drugs, the large number of unexplained treatment failures is a serious concern. Due to the extremely limited therapeutic options available, it is critical to identify and understand the various causes of treatment failure if patient outcomes are to improve. In this study, we examined one potential source of treatment failure: antagonistic drug interactions. Using a simple screen, we systematically identified currently approved medications that undermine the antifungal activity of three major antifungal drugs—fluconazole, caspofungin, and amphotericin B—on four prevalent human fungal pathogens—Candida albicans, Candida glabrata, Candida parapsilosis, and Candida tropicalis. This revealed that a diverse collection of structurally distinct drugs exhibit antagonistic interactions with fluconazole. Several antagonistic agents selected for follow-up studies induce azole resistance through a mechanism that depends on Tac1p/Pdr1p zinc-cluster transcription factors, which activate the expression of drug efflux pumps belonging to the ABC-type transporter family. Few antagonistic interactions were identified with caspofungin or amphotericin B, possibly reflecting their cell surface mode of action that should not be affected by drug efflux mechanisms. Given that patients at greatest risk of IFIs usually receive a multitude of drugs to treat various underlying conditions, these studies suggest that chemically inducible azole resistance may be much more common and important than previously realized.
- Published
- 2019
15. Loss of C-5 Sterol Desaturase Activity Results in Increased Resistance to Azole and Echinocandin Antifungals in a Clinical Isolate of Candida parapsilosis
- Author
-
Kayihura Manigaba, Ramin Homayouni, Josie E. Parker, Qing Zhang, Kelly E. Caudle, Jeffrey M. Rybak, P. David Rogers, Sujoy B. Roy, Andrew T. Nishimoto, Glen E. Palmer, C. Michael Dickens, Arturo Luna-Tapia, Steven L. Kelly, Thomas R. Sutter, Sarah G. Whaley, Nathan P. Wiederhold, and Katherine S. Barker
- Subjects
0301 basic medicine ,Azoles ,Antifungal Agents ,Candida parapsilosis ,Echinocandin ,030106 microbiology ,Gene Dosage ,Microbial Sensitivity Tests ,Biology ,Polymorphism, Single Nucleotide ,Sterol desaturase activity ,Microbiology ,03 medical and health sciences ,chemistry.chemical_compound ,Echinocandins ,Mechanisms of Resistance ,Drug Resistance, Multiple, Fungal ,Ergosterol ,medicine ,polycyclic compounds ,Humans ,Pharmacology (medical) ,Pharmacology ,chemistry.chemical_classification ,Cross Infection ,biology.organism_classification ,bacterial infections and mycoses ,C-5 sterol desaturase activity ,Infectious Diseases ,chemistry ,Azole ,Genome, Fungal ,Oxidoreductases ,Fungemia ,Fluconazole ,medicine.drug - Abstract
Among emerging non- albicans Candida species, Candida parapsilosis is of particular concern as a cause of nosocomial bloodstream infections in neonatal and intensive care unit patients. While fluconazole and echinocandins are considered effective treatments for such infections, recent reports of fluconazole and echinocandin resistance in C. parapsilosis indicate a growing problem. The present study describes a novel mechanism of antifungal resistance in this organism affecting susceptibility to azole and echinocandin antifungals in a clinical isolate obtained from a patient with prosthetic valve endocarditis. Transcriptome analysis indicated differential expression of several genes in the resistant isolate, including upregulation of ergosterol biosynthesis pathway genes ERG2 , ERG5 , ERG6 , ERG11 , ERG24 , ERG25 , and UPC2 . Whole-genome sequencing revealed that the resistant isolate possessed an ERG3 mutation resulting in a G111R amino acid substitution. Sterol profiles indicated a reduction in sterol desaturase activity as a result of this mutation. Replacement of both mutant alleles in the resistant isolate with the susceptible isolate's allele restored wild-type susceptibility to all azoles and echinocandins tested. Disruption of ERG3 in the susceptible and resistant isolates resulted in a loss of sterol desaturase activity, high-level azole resistance, and an echinocandin-intermediate to -resistant phenotype. While disruption of ERG3 in C. albicans resulted in azole resistance, echinocandin MICs, while elevated, remained within the susceptible range. This work demonstrates that the G111R substitution in Erg3 is wholly responsible for the altered azole and echinocandin susceptibilities observed in this C. parapsilosis isolate and is the first report of an ERG3 mutation influencing susceptibility to the echinocandins.
- Published
- 2017
16. Azole Antifungal Resistance in Candida albicans and Emerging Non-albicans Candida Species
- Author
-
Jeffrey M. Rybak, P. David Rogers, Andrew T. Nishimoto, Katherine S. Barker, Sarah G. Whaley, and Elizabeth L. Berkow
- Subjects
0301 basic medicine ,Microbiology (medical) ,chemistry.chemical_classification ,Candida glabrata ,030106 microbiology ,Biology ,Candida parapsilosis ,biology.organism_classification ,Microbiology ,Corpus albicans ,3. Good health ,Candida tropicalis ,03 medical and health sciences ,chemistry ,Candida krusei ,medicine ,Azole ,Candida albicans ,Fluconazole ,medicine.drug - Abstract
Within the limited antifungal armamentarium, the azole antifungals are the most frequent class used to treat Candida infections. Azole antifungals such as fluconazole are often preferred treatment for many Candida infections as they are inexpensive, exhibit limited toxicity, and are available for oral administration. There is, however, extensive documentation of intrinsic and developed resistance to azole antifungals among several Candida species. As the frequency of azole resistant Candida isolates in the clinical setting increases, it is essential to elucidate the mechanisms of such resistance in order to both preserve and improve upon the azole class of antifungals for the treatment of Candida infections. This review examines azole resistance in infections caused by C. albicans as well as the emerging non-albicans Candida species C. parapsilosis, C. tropicalis, C. krusei, and C. glabrata and in particular, describes the current understanding of molecular basis of azole resistance in these fungal species.
- Published
- 2017
17. Azole Antifungal Resistance in
- Author
-
Sarah G, Whaley, Elizabeth L, Berkow, Jeffrey M, Rybak, Andrew T, Nishimoto, Katherine S, Barker, and P David, Rogers
- Subjects
resistance ,Candida parapsilosis ,Candida albicans ,Candida krusei ,azole ,Candida glabrata ,Review ,Candida tropicalis ,Microbiology ,antifungal - Abstract
Within the limited antifungal armamentarium, the azole antifungals are the most frequent class used to treat Candida infections. Azole antifungals such as fluconazole are often preferred treatment for many Candida infections as they are inexpensive, exhibit limited toxicity, and are available for oral administration. There is, however, extensive documentation of intrinsic and developed resistance to azole antifungals among several Candida species. As the frequency of azole resistant Candida isolates in the clinical setting increases, it is essential to elucidate the mechanisms of such resistance in order to both preserve and improve upon the azole class of antifungals for the treatment of Candida infections. This review examines azole resistance in infections caused by C. albicans as well as the emerging non-albicans Candida species C. parapsilosis, C. tropicalis, C. krusei, and C. glabrata and in particular, describes the current understanding of molecular basis of azole resistance in these fungal species.
- Published
- 2016
18. Isavuconazole: Pharmacology, Pharmacodynamics, and Current Clinical Experience with a New Triazole Antifungal Agent
- Author
-
P. David Rogers, Andrew T. Nishimoto, Kayleigh Marx, and Jeffrey M. Rybak
- Subjects
Antifungal Agents ,Pyridines ,Population ,Triazole ,Pharmacology ,Aspergillosis ,chemistry.chemical_compound ,Nitriles ,medicine ,Humans ,Mucormycosis ,Pharmacology (medical) ,Candidiasis, Invasive ,education ,Voriconazole ,education.field_of_study ,medicine.diagnostic_test ,business.industry ,Candidemia ,Triazoles ,medicine.disease ,Isavuconazonium ,chemistry ,Therapeutic drug monitoring ,Pharmacodynamics ,business ,medicine.drug - Abstract
Coinciding with the continually increasing population of immunocompromised patients worldwide, the incidence of invasive fungal infections has grown over the past 4 decades. Unfortunately, infections caused by both yeasts such as Candida and molds such as Aspergillus or Mucorales remain associated with unacceptably high morbidity and mortality. In addition, the available antifungals with proven efficacy in the treatment of these infections remain severely limited. Although previously available second-generation triazole antifungals have significantly expanded the spectrum of the triazole antifungal class, these agents are laden with shortcomings in their safety profiles as well as formulation and pharmacokinetic challenges. Isavuconazole, administered as the prodrug isavuconazonium, is the latest second-generation triazole antifungal to receive U.S. Food and Drug Administration approval. Approved for the treatment of both invasive aspergillosis and invasive mucormycosis, and currently under investigation for the treatment of candidemia and invasive candidiasis, isavuconazole may have therapeutic advantages over its predecessors. With clinically relevant antifungal potency against a broad range of yeasts, dimorphic fungi, and molds, isavuconazole has a spectrum of activity reminiscent of the polyene amphotericin B. Moreover, clinical experience thus far has revealed isavuconazole to be associated with fewer toxicities than voriconazole, even when administered without therapeutic drug monitoring. These characteristics, in an agent available in both a highly bioavailable oral and a β-cyclodextrin-free intravenous formulation, will likely make isavuconazole a welcome addition to the triazole class of antifungals.
- Published
- 2015
19. Spatial and Temporal Requirements for huntingtin (Htt) in Neuronal Migration and Survival during Brain Development
- Author
-
Li Liu, Dan Goldowitz, Anton Reiner, Yiai Tong, Andrew T. Nishimoto, and Thomas J. Ha
- Subjects
Male ,congenital, hereditary, and neonatal diseases and abnormalities ,Time Factors ,Huntingtin ,Cell Survival ,Green Fluorescent Proteins ,Mice, Transgenic ,Nerve Tissue Proteins ,Biology ,Article ,Mice ,Cell Movement ,Pregnancy ,mental disorders ,Huntingtin Protein ,medicine ,Animals ,RNA, Small Interfering ,Gene knockout ,Neurons ,Mice, Inbred ICR ,Gene knockdown ,Neocortex ,Caspase 3 ,General Neuroscience ,Brain ,Gene Expression Regulation, Developmental ,Nuclear Proteins ,Cell migration ,Embryo, Mammalian ,Caspase 9 ,nervous system diseases ,Neuroepithelial cell ,medicine.anatomical_structure ,Bromodeoxyuridine ,nervous system ,Female ,Neural development ,Neuroscience - Abstract
Huntington's disease (HD), caused by an expanded triplet repeat in the huntingtin (Htt) gene, results in extensive neuropathology, but study of theHttgene in CNS development through gene knockout is problematic as the knockout leads to embryonic lethality in mice. Here, we report that the knockdown ofHttexpression in neuroepithelial cells of neocortex results in disturbed cell migration, reduced proliferation, and increased cell death that is relatively specific to early neural development. In the cerebellum, however,Httknockdown results in cell death but not perturbed migration. The cell death phenotype in cortex can be partially reversed with co-knockdown ofCasp9, indicating that mitochondria-mediated cell apoptotic processes are involved in the neuronal death. The timing of knockdown during early development is also an important variable. These results indicate a spatial and temporal requirement forHttexpression in neural development. Although it is uncertain whether the loss of wild-type huntingtin function contributes to pathogenesis in Huntington's disease, these results clearly contraindicate the use of nonspecific knockdown ofHttas a therapeutic measure in HD, particularlyin utero.
- Published
- 2011
20. Chapter 8. Biotechnology and Pharmacogenomics
- Author
-
Jeffrey M. Rybak, P. David Rogers, and Andrew T. Nishimoto
- Subjects
business.industry ,Pharmacogenomics ,Medicine ,Engineering ethics ,Pharmacology ,business - Published
- 2015
21. 20-Hydroxyeicosatetraenoic acid mediates angiotensin ii-induced phospholipase d activation in vascular smooth muscle cells
- Author
-
Kafait U. Malik, Jean-Hugues Parmentier, Mubarack M. Muthalif, and Andrew T. Nishimoto
- Subjects
Male ,medicine.medical_specialty ,Diacylglycerol lipase ,Organophosphonates ,Arachidonic Acids ,Glycerophospholipids ,Biology ,Phospholipase ,Ceramides ,Muscle, Smooth, Vascular ,chemistry.chemical_compound ,Phospholipase A2 ,Internal medicine ,Hydroxyeicosatetraenoic Acids ,Internal Medicine ,medicine ,Phospholipase D ,Animals ,Enzyme Inhibitors ,Protein kinase A ,Cells, Cultured ,Cyclohexanones ,Angiotensin II ,Oligonucleotides, Antisense ,20-Hydroxyeicosatetraenoic acid ,Molecular biology ,Propranolol ,Isoenzymes ,Endocrinology ,chemistry ,cardiovascular system ,biology.protein ,lipids (amino acids, peptides, and proteins) ,Arachidonic acid ,Rabbits ,Mitogen-Activated Protein Kinases - Abstract
Angiotensin II (Ang II) activates cytosolic phospholipase A 2 (cPLA 2 ) and phospholipase D (PLD) in rabbit vascular smooth muscle cells (VSMCs). Ang II also activates ras/mitogen-activated protein (MAP) kinase in VSMCs; this activation is mediated by 20-hydroxyeicosatetraenoic acid (HETE) and 12(S)-HETE, which are metabolites of arachidonic acid generated by cytochrome P450 4A and lipoxygenase, respectively, produced on activation of cPLA 2 . The purpose of this study was to determine if Ang II–induced PLD activation in VSMCs is mediated through the ras/extracellular signal-regulating kinase (ERK) pathway by arachidonic acid metabolites that are generated consequent to cPLA 2 stimulation. Inhibitors of PLD (C 2 ceramide), phosphatidate phosphohydrolase (propranolol), and diacylglycerol lipase (RHC 80267) attenuated Ang II–induced arachidonic acid release. Ang II–induced PLD activation, as measured by [ 3 H]phosphatidylethanol production, was inhibited by C 2 ceramide but not by propranolol or RHC 80267. Ang II–induced PLD activation was decreased by the inhibitor methyl arachidonylfluorophosphate (MAFP) and the antisense oligonucleotide of cPLA 2 . Inhibitors of lipoxygenases (baicalein) and cytochrome P450 4A (ODYA) attenuated Ang II–induced PLD activation. 20-HETE and 12(S)-HETE increased PLD activity. Inhibitors of ras farnesyltransferase (FPT III and BMS-191563) and MAP kinase kinase (UO126) attenuated the increase in PLD activity elicited by 20-HETE and Ang II. PLD2 was the main isoform activated by Ang II in VSMCs. These data suggest that the CYP4A metabolite 20-HETE, which is generated from arachidonic acid after cPLA 2 activation by Ang II, stimulates the ras/MAP kinase pathway, which in turn activates PLD2 and releases further arachidonic acid for prostaglandin synthesis through the phosphatidate phosphohydrolase/diacylglycerol lipase pathway.
- Published
- 2001
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.