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Abstract
Candida albicans, the most pervasive fungal pathogen that colonizes humans, forms biofilms that are architecturally complex. They consist of a basal yeast cell polylayer and an upper region of hyphae encapsulated in extracellular matrix. However, biofilms formed in vitro vary as a result of the different conditions employed in models, the methods used to assess biofilm formation, strain differences, and, in a most dramatic fashion, the configuration of the mating type locus (MTL). Therefore, integrating data from different studies can lead to problems of interpretation if such variability is not taken into account. Here we review the conditions and factors that cause biofilm variation, with the goal of engendering awareness that more attention must be paid to the strains employed, the methods used to assess biofilm development, every aspect of the model employed, and the configuration of the MTL locus. We end by posing a set of questions that may be asked in comparing the results of different studies and developing protocols for new ones. This review should engender the notion that not all biofilms are created equal.
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Affiliation(s)
- David R Soll
- Developmental Studies Hybridoma Bank, Department of Biology, The University of Iowa, Iowa City, Iowa, USA
| | - Karla J Daniels
- Developmental Studies Hybridoma Bank, Department of Biology, The University of Iowa, Iowa City, Iowa, USA
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152
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In vitro antifungal and antibiofilm activities of halogenated quinoline analogues against Candida albicans and Cryptococcus neoformans. Int J Antimicrob Agents 2016; 48:208-11. [DOI: 10.1016/j.ijantimicag.2016.04.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/08/2016] [Accepted: 04/16/2016] [Indexed: 11/18/2022]
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153
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Abstract
In humans, microbial cells (including bacteria, archaea, and fungi) greatly outnumber host cells. Candida albicans is the most prevalent fungal species of the human microbiota; this species asymptomatically colonizes many areas of the body, particularly the gastrointestinal and genitourinary tracts of healthy individuals. Alterations in host immunity, stress, resident microbiota, and other factors can lead to C. albicans overgrowth, causing a wide range of infections, from superficial mucosal to hematogenously disseminated candidiasis. To date, most studies of C. albicans have been carried out in suspension cultures; however, the medical impact of C. albicans (like that of many other microorganisms) depends on its ability to thrive as a biofilm, a closely packed community of cells. Biofilms are notorious for forming on implanted medical devices, including catheters, pacemakers, dentures, and prosthetic joints, which provide a surface and sanctuary for biofilm growth. C. albicans biofilms are intrinsically resistant to conventional antifungal therapeutics, the host immune system, and other environmental perturbations, making biofilm-based infections a significant clinical challenge. Here, we review our current knowledge of biofilms formed by C. albicans and closely related fungal species.
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Affiliation(s)
- Clarissa J Nobile
- Department of Molecular and Cell Biology, School of Natural Sciences, University of California, Merced, California 95343;
| | - Alexander D Johnson
- Department of Microbiology and Immunology, University of California, San Francisco, California 94143;
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154
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Gao L, Jiang S, Sun Y, Deng M, Wu Q, Li M, Zeng T. Evaluation of the Effects of Photodynamic Therapy Alone and Combined with Standard Antifungal Therapy on Planktonic Cells and Biofilms of Fusarium spp. and Exophiala spp. Front Microbiol 2016; 7:617. [PMID: 27199946 PMCID: PMC4847004 DOI: 10.3389/fmicb.2016.00617] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/14/2016] [Indexed: 12/02/2022] Open
Abstract
Infections of Fusarium spp. and Exophiala spp. are often chronic, recalcitrant, resulting in significant morbidity, causing discomfort, disfigurement, social isolation. Systemic disseminations happen in compromised patients, which are often refractory to available antifungal therapies and thereby lead to death. The antimicrobial photodynamic therapy (aPDT) has been demonstrated to effectively inactivate multiple pathogenic fungi and is considered as a promising alternative treatment for mycoses. In the present study, we applied methylene blue (8, 16, and 32 μg/ml) as a photosensitizing agent and light emitting diode (635 ± 10 nm, 12 and 24 J/cm2), and evaluated the effects of photodynamic inactivation on five strains of Fusarium spp. and five strains of Exophiala spp., as well as photodynamic effects on in vitro susceptibility to itraconazole, voriconazole, posaconazole and amphotericin B, both planktonic and biofilm forms. Photodynamic therapy was efficient in reducing the growth of all strains tested, exhibiting colony forming unit-reductions of up to 6.4 log10 and 5.6 log10 against planktonic cultures and biofilms, respectively. However, biofilms were less sensitive since the irradiation time was twice longer than that of planktonic cultures. Notably, the photodynamic effects against Fusarium strains with high minimal inhibitory concentration (MIC) values of ≥16, 4-8, 4-8, and 2-4 μg/ml for itraconazole, voriconazole, posaconazole and amphotericin B, respectively, were comparable or even superior to Exophiala spp., despite Exophiala spp. showed relatively better antifungal susceptibility profile. MIC ranges against planktonic cells of both species were up to 64 times lower after aPDT treatment. Biofilms of both species showed high sessile MIC50 (SMIC50) and SMIC80 of ≥16 μg/ml for all azoles tested and variable susceptibilities to amphotericin B, with SMIC ranging between 1 and 16 μg/ml. Biofilms subjected to aPDT exhibited a distinct reduction in SMIC50 and SMIC80 compared to untreated groups for both species, except SMIC80 of itraconazole against Fusarium biofilms. In conclusion, in vitro photodynamic therapy was efficient in inactivation of Fusarium spp. and Exophiala spp., both planktonic cultures and biofilms. In addition, the combination of aPDT and antifungal drugs represents an attractive alternative to the current antifungal strategies. However, further investigations are warranted for the reliable and safe application in clinical practice.
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Affiliation(s)
- Lujuan Gao
- Department of Dermatology, Zhongshan Hospital Fudan University Shanghai, China
| | - Shaojie Jiang
- Department of Gastroenterology, Jingzhou Central Hospital, The Second Clinical Medical College, Yangtze University Jingzhou, China
| | - Yi Sun
- Department of Dermatology, Jingzhou Central Hospital, The Second Clinical Medical College, Yangtze University Jingzhou, China
| | - Meiqi Deng
- The Second Clinical Medical College, Yangtze University Jingzhou, China
| | - Qingzhi Wu
- Department of Dermatology, Jingzhou Central Hospital, The Second Clinical Medical College, Yangtze University Jingzhou, China
| | - Ming Li
- Department of Dermatology, Zhongshan Hospital Fudan University Shanghai, China
| | - Tongxiang Zeng
- Department of Dermatology, Jingzhou Central Hospital, The Second Clinical Medical College, Yangtze University Jingzhou, China
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155
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Sanglard D. Emerging Threats in Antifungal-Resistant Fungal Pathogens. Front Med (Lausanne) 2016; 3:11. [PMID: 27014694 PMCID: PMC4791369 DOI: 10.3389/fmed.2016.00011] [Citation(s) in RCA: 233] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 03/03/2016] [Indexed: 12/15/2022] Open
Abstract
The use of antifungal drugs in the therapy of fungal diseases can lead to the development of antifungal resistance. Resistance has been described for virtually all antifungal agents in diverse pathogens, including Candida and Aspergillus species. The majority of resistance mechanisms have also been elucidated at the molecular level in these pathogens. Drug resistance genes and genome mutations have been identified. Therapeutic choices are limited for the control of fungal diseases, and it is tempting to combine several drugs to achieve better therapeutic efficacy. In the recent years, several novel resistance patterns have been observed, including antifungal resistance originating from environmental sources in Aspergillus fumigatus and the emergence of simultaneous resistance to different antifungal classes (multidrug resistance) in different Candida species. This review will summarize these current trends.
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Affiliation(s)
- Dominique Sanglard
- Institute of Microbiology, University Hospital Center, University of Lausanne , Lausanne , Switzerland
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156
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Affiliation(s)
- Priya Uppuluri
- The Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-University of California Los Angeles (UCLA) Medical Center, Los Angeles, California, United States of America
- * E-mail:
| | - Jose L. Lopez-Ribot
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, United States of America
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157
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Bujdáková H. Management of Candida biofilms: state of knowledge and new options for prevention and eradication. Future Microbiol 2016; 11:235-51. [PMID: 26849383 DOI: 10.2217/fmb.15.139] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Biofilms formed by Candida species (spp.) on medical devices represent a potential health risk. The focus of current research is searching for new options for the treatment and prevention of biofilm-associated infections using different approaches including modern nanotechnology. This review summarizes current information concerning the most relevant resistance/tolerance mechanisms to conventional drugs and a role of additional factors contributing to these phenomena in Candida spp. (mostly Candida albicans). Additionally, it provides an information update in prevention and eradication of a Candida biofilm including experiences with 'lock' therapy, potential utilization of small molecules in biomedical applications, and perspectives of using photodynamic inactivation in the control of a Candida biofilm.
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Affiliation(s)
- Helena Bujdáková
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology & Virology, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovak Republic
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158
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Ajdačić V, Senerovic L, Vranić M, Pekmezovic M, Arsic-Arsnijevic V, Veselinovic A, Veselinovic J, Šolaja BA, Nikodinovic-Runic J, Opsenica IM. Synthesis and evaluation of thiophene-based guanylhydrazones (iminoguanidines) efficient against panel of voriconazole-resistant fungal isolates. Bioorg Med Chem 2016; 24:1277-91. [PMID: 26867487 DOI: 10.1016/j.bmc.2016.01.058] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 01/21/2016] [Accepted: 01/29/2016] [Indexed: 12/31/2022]
Abstract
A series of new thiophene-based guanylhydrazones (iminoguanidines) were synthesized in high yields using a straightforward two-step procedure. The antifungal activity of compounds was evaluated against a wide range of medicaly important fungal strains including yeasts, molds, and dermatophytes in comparison to clinically used drug voriconazole. Cytotoxic properties of compounds were also determined using human lung fibroblast cell line and hemolysis assay. All guanylhydrazones showed significant activity against broad spectrum of clinically important species of Candida spp., Aspergillus fumigatus, Fusarium oxysporum, Microsporum canis and Trichophyton mentagrophytes, which was in some cases comparable or better than activity of voriconazole. More importantly, compounds 10, 11, 13, 14, 18 and 21 exhibited excellent activity against voriconazole-resistant Candida albicans CA5 with very low minimal inhibitory concentration (MIC) values <2 μg mL(-1). Derivative 14, bearing bromine on the phenyl ring, was the most effective compound with MICs ranging from 0.25 to 6.25 μg mL(-1). However, bis-guanylhydrazone 18 showed better selectivity in terms of therapeutic index values. In vivo embryotoxicity on zebrafish (Danio rerio) showed improved toxicity profile of 11, 14 and 18 in comparison to that of voriconazole. Most guanylhydrazones also inhibited C. albicans yeast to hyphal transition, essential for its biofilm formation, while 11 and 18 were able to disperse preformed Candida biofilms. All guanylhydrazones showed the equal potential to interact with genomic DNA of C. albicans in vitro, thus indicating a possible mechanism of their action, as well as possible mechanism of observed cytotoxic effects. Tested compounds did not have significant hemolytic effect and caused low liposome leakage, which excluded the cell membrane as a primary target. On the basis of computational docking experiments using both human and cytochrome P450 from Candida it was concluded that the most active guanylhydrazones had minimal structural prerequisites to interact with the cytochrome P450 14α-demethylase (CYP51). Promising guanylhydrazone derivatives also showed satisfactory pharmacokinetic profile based on molecular calculations.
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Affiliation(s)
- Vladimir Ajdačić
- Faculty of Chemistry, University of Belgrade, Studentski trg 16, PO Box 51, 11158 Belgrade, Serbia
| | - Lidija Senerovic
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11000 Belgrade, Serbia
| | - Marija Vranić
- Faculty of Chemistry, University of Belgrade, Studentski trg 16, PO Box 51, 11158 Belgrade, Serbia
| | - Marina Pekmezovic
- National Reference Medical Mycology Laboratory, Institute of Microbiology and Immunology, Faculty of Medicine, University of Belgrade, Dr Subotica 1, 11000 Belgrade, Serbia
| | - Valentina Arsic-Arsnijevic
- National Reference Medical Mycology Laboratory, Institute of Microbiology and Immunology, Faculty of Medicine, University of Belgrade, Dr Subotica 1, 11000 Belgrade, Serbia
| | | | - Jovana Veselinovic
- Faculty of Medicine, Department of Chemistry, University of Niš, 18000 Niš, Serbia
| | - Bogdan A Šolaja
- Faculty of Chemistry, University of Belgrade, Studentski trg 16, PO Box 51, 11158 Belgrade, Serbia
| | - Jasmina Nikodinovic-Runic
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11000 Belgrade, Serbia.
| | - Igor M Opsenica
- Faculty of Chemistry, University of Belgrade, Studentski trg 16, PO Box 51, 11158 Belgrade, Serbia.
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159
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Jennings JA, Beenken KE, Parker AC, Smith JK, Courtney HS, Smeltzer MS, Haggard WO. Polymicrobial Biofilm Inhibition Effects of Acetate-Buffered Chitosan Sponge Delivery Device. Macromol Biosci 2016; 16:591-8. [DOI: 10.1002/mabi.201500347] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 11/04/2015] [Indexed: 12/14/2022]
Affiliation(s)
- Jessica Amber Jennings
- Department of Biomedical Engineering; University of Memphis; 330 Engineering Technology Building Memphis TN 38152 USA
| | - Karen E. Beenken
- Department of Orthopaedics; University of Arkansas for Medical Sciences; 4301 W. Markham St. Little Rock AR 72205 USA
| | - Ashley C. Parker
- Department of Biomedical Engineering; University of Memphis; 330 Engineering Technology Building Memphis TN 38152 USA
| | - James Keaton Smith
- Department of Biomedical Engineering; University of Memphis; 330 Engineering Technology Building Memphis TN 38152 USA
| | - Harry S. Courtney
- Department of Medicine; University of Tennessee Health Science Center; Coleman Building Suite D334, 956 Court Avenue Memphis TN 38163 USA
| | - Mark S. Smeltzer
- Department of Orthopaedics; University of Arkansas for Medical Sciences; 4301 W. Markham St. Little Rock AR 72205 USA
| | - Warren O. Haggard
- Department of Biomedical Engineering; University of Memphis; 330 Engineering Technology Building Memphis TN 38152 USA
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160
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Vriens K, Cools TL, Harvey PJ, Craik DJ, Braem A, Vleugels J, De Coninck B, Cammue BPA, Thevissen K. The radish defensins RsAFP1 and RsAFP2 act synergistically with caspofungin against Candida albicans biofilms. Peptides 2016; 75:71-9. [PMID: 26592804 DOI: 10.1016/j.peptides.2015.11.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 11/09/2015] [Accepted: 11/09/2015] [Indexed: 01/28/2023]
Abstract
The radish defensin RsAFP2 was previously characterized as a peptide with potent antifungal activity against several plant pathogenic fungi and human pathogens, including Candida albicans. RsAFP2 induces apoptosis and impairs the yeast-to-hypha transition in C. albicans. As the yeast-to-hypha transition is considered important for progression to mature biofilms, we analyzed the potential antibiofilm activity of recombinant (r)RsAFP2, heterologously expressed in Pichia pastoris, against C. albicans biofilms. We found that rRsAFP2 prevents C. albicans biofilm formation with a BIC-2 (i.e., the minimal rRsAFP2 concentration that inhibits biofilm formation by 50% as compared to control treatment) of 1.65 ± 0.40 mg/mL. Moreover, biofilm-specific synergistic effects were observed between rRsAFP2 doses as low as 2.5 μg/mL to 10 μg/mL and the antimycotics caspofungin and amphotericin B, pointing to the potential of RsAFP2 as a novel antibiofilm compound. In addition, we characterized the solution structure of rRsAFP2 and compared it to that of RsAFP1, another defensin present in radish seeds. These peptides have similar amino acid sequences, except for two amino acids, but rRsAFP2 is more potent than RsAFP1 against planktonic and biofilm cultures. Interestingly, as in case of rRsAFP2, also RsAFP1 acts synergistically with caspofungin against C. albicans biofilms in a comparable low dose range as rRsAFP2. A structural comparison of both defensins via NMR analysis revealed that also rRsAFP2 adopts the typical cysteine-stabilized αβ-motif of plant defensins, however, no structural differences were found between these peptides that might result in their differential antifungal/antibiofilm potency. This further suggests that the conserved structure of RsAFP1 and rRsAFP2 bears the potential to synergize with antimycotics against C. albicans biofilms.
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Affiliation(s)
- Kim Vriens
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium
| | - Tanne L Cools
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium
| | - Peta J Harvey
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Annabel Braem
- Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium
| | - Jozef Vleugels
- Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, 3001 Heverlee, Belgium
| | - Barbara De Coninck
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium; Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Ghent, Belgium
| | - Bruno P A Cammue
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium; Department of Plant Systems Biology, VIB, Technologiepark 927, 9052 Ghent, Belgium.
| | - Karin Thevissen
- Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium
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161
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Pierce CG, Chaturvedi AK, Lazzell AL, Powell AT, Saville SP, McHardy SF, Lopez-Ribot JL. A Novel Small Molecule Inhibitor of Candida albicans Biofilm Formation, Filamentation and Virulence with Low Potential for the Development of Resistance. NPJ Biofilms Microbiomes 2015; 1. [PMID: 26691764 PMCID: PMC4681527 DOI: 10.1038/npjbiofilms.2015.12] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND/OBJECTIVES Candida albicans is the principal causative agent of candidiasis, the most common fungal infection in humans. Candidiasis represents the third-to-fourth most frequent nosocomial infection worldwide, as this normal commensal of humans causes opportunistic infections in an expanding population of immune- and medically-compromised patients. These infections are frequently associated with biofilm formation, which complicates treatment and contributes to unacceptably high mortality rates. METHODS To address the pressing need for new antifungals we have performed a high content screen of 20,000 small molecules in a chemical library (NOVACore™) to identify compounds that inhibit C. albicans biofilm formation, and conducted a series of follow-up studies to examine the in vitro and in vivo activity of the identified compounds. RESULTS The screen identified a novel series of diazaspiro-decane structural analogs which were largely represented among the bioactive compounds. Characterization of the leading compound from this series indicated that it inhibits processes associated with C. albicans virulence, most notably biofilm formation and filamentation, without having an effect on overall growth or eliciting resistance. This compound demonstrated in vivo activity in clinically-relevant murine models of both invasive and oral candidiasis and as such represents a promising lead for antifungal drug development. Furthermore, these results provide proof of concept for the implementation of anti-virulence approaches against C. albicans and other fungal infections that would be less likely to foster the emergence of resistance.
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Affiliation(s)
- Christopher G Pierce
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
| | - Ashok K Chaturvedi
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
| | - Anna L Lazzell
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
| | - Alexander T Powell
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
| | - Stephen P Saville
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
| | - Stanton F McHardy
- Department of Chemistry and Center for Innovation in Drug Discovery, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
| | - Jose L Lopez-Ribot
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, United States of America
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162
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Vriens K, Cools TL, Harvey PJ, Craik DJ, Spincemaille P, Cassiman D, Braem A, Vleugels J, Nibbering PH, Drijfhout JW, De Coninck B, Cammue BPA, Thevissen K. Synergistic Activity of the Plant Defensin HsAFP1 and Caspofungin against Candida albicans Biofilms and Planktonic Cultures. PLoS One 2015; 10:e0132701. [PMID: 26248029 PMCID: PMC4527839 DOI: 10.1371/journal.pone.0132701] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/17/2015] [Indexed: 12/11/2022] Open
Abstract
Plant defensins are small, cysteine-rich peptides with antifungal activity against a broad range of yeast and fungi. In this study we investigated the antibiofilm activity of a plant defensin from coral bells (Heuchera sanguinea), i.e. HsAFP1. To this end, HsAFP1 was heterologously produced using Pichia pastoris as a host. The recombinant peptide rHsAFP1 showed a similar antifungal activity against the plant pathogen Fusarium culmorum as native HsAFP1 purified from seeds. NMR analysis revealed that rHsAFP1 consists of an α-helix and a triple-stranded antiparallel β-sheet stabilised by four intramolecular disulfide bonds. We found that rHsAFP1 can inhibit growth of the human pathogen Candida albicans as well as prevent C. albicans biofilm formation with a BIC50 (i.e. the minimum rHsAFP1 concentration required to inhibit biofilm formation by 50% as compared to control treatment) of 11.00 ± 1.70 μM. As such, this is the first report of a plant defensin exhibiting inhibitory activity against fungal biofilms. We further analysed the potential of rHsAFP1 to increase the activity of the conventional antimycotics caspofungin and amphotericin B towards C. albicans. Synergistic effects were observed between rHsAFP1 and these compounds against both planktonic C. albicans cells and biofilms. Most notably, concentrations of rHsAFP1 as low as 0.53 μM resulted in a synergistic activity with caspofungin against pre-grown C. albicans biofilms. rHsAFP1 was found non-toxic towards human HepG2 cells up to 40 μM, thereby supporting the lack of a general cytotoxic activity as previously reported for HsAFP1. A structure-function study with 24-mer synthetic peptides spanning the entire HsAFP1 sequence revealed the importance of the γ-core and its adjacent regions for HsAFP1 antibiofilm activity. These findings point towards broad applications of rHsAFP1 and its derivatives in the field of antifungal and antibiofilm drug development.
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Affiliation(s)
- Kim Vriens
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Tanne L. Cools
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Peta J. Harvey
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - David J. Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Pieter Spincemaille
- Department of Hepatology, University Hospitals Leuven, Leuven, Belgium
- Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
| | - David Cassiman
- Department of Hepatology, University Hospitals Leuven, Leuven, Belgium
- Metabolic Center, University Hospitals Leuven, Leuven, Belgium
| | - Annabel Braem
- Department of Materials Engineering, KU Leuven, Leuven, Belgium
| | - Jozef Vleugels
- Department of Materials Engineering, KU Leuven, Leuven, Belgium
| | - Peter H. Nibbering
- Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Jan Wouter Drijfhout
- Department of Immunohematology and Bloodtransfusion, Leiden University Medical Center, Leiden, The Netherlands
| | - Barbara De Coninck
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
- Department of Plant Systems Biology, VIB, Ghent, Belgium
| | - Bruno P. A. Cammue
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
- Department of Plant Systems Biology, VIB, Ghent, Belgium
- * E-mail:
| | - Karin Thevissen
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
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163
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Abstract
The Candida albicans RHR2 gene, which specifies a glycerol biosynthetic enzyme, is required for biofilm formation in vitro and in vivo. Prior studies indicate that RHR2 is ultimately required for expression of adhesin genes, such as ALS1. In fact, RHR2 is unnecessary for biofilm formation when ALS1 is overexpressed from an RHR2-independent promoter. Here, we describe two additional biological processes that depend upon RHR2: invasion into an abiotic substrate and pathogenicity in an abdominal infection model. We report here that abiotic substrate invasion occurs concomitantly with biofilm formation, and a screen of transcription factor mutants indicates that biofilm and hyphal formation ability correlates with invasion ability. However, analysis presented here of the rhr2Δ/Δ mutant separates biofilm formation and invasion. We found that an rhr2Δ/Δ mutant forms a biofilm upon overexpression of the adhesin gene ALS1 or the transcription factor genes BRG1 or UME6. However, the biofilm-forming strains do not invade the substrate. These results indicate that RHR2 has an adhesin-independent role in substrate invasion, and mathematical modeling argues that RHR2 is required to generate turgor. Previous studies have shown that abdominal infection by C. albicans has two aspects: infection of abdominal organs and persistence in abscesses. We report here that an rhr2Δ/Δ mutant is defective in both of these infection phenotypes. We find here that overexpression of ALS1 in the mutant restores infection of organs, but does not improve persistence in abscesses. Therefore, RHR2 has an adhesin-independent role in abdominal infection, just as it does in substrate invasion. This report suggests that RHR2, through glycerol synthesis, coordinates adherence with host- or substrate-interaction activities that enable proliferation of the C. albicans population.
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164
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Abstract
Morphogenesis in fungi is often induced by extracellular factors and executed by fungal genetic factors. Cell surface changes and alterations of the microenvironment often accompany morphogenetic changes in fungi. In this review, we will first discuss the general traits of yeast and hyphal morphotypes and how morphogenesis affects development and adaptation by fungi to their native niches, including host niches. Then we will focus on the molecular machinery responsible for the two most fundamental growth forms, yeast and hyphae. Last, we will describe how fungi incorporate exogenous environmental and host signals together with genetic factors to determine their morphotype and how morphogenesis, in turn, shapes the fungal microenvironment.
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Affiliation(s)
- Xiaorong Lin
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258
| | - J Andrew Alspaugh
- Department of Medicine, Division of Infectious Diseases, Duke University Medical Center, Durham, North Carolina 27710
| | - Haoping Liu
- Department of Biological Chemistry, University of California, Irvine, California 92697
| | - Steven Harris
- Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, Nebraska 68588
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