Extracellular DNA release confers heterogeneity in Candida albicans biofilm formation

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Abstract

Background

Biofilm formation by Candida albicans has shown to be highly variable and is directly associated with pathogenicity and poor clinical outcomes in patients at risk. The aim of this study was to test the hypotheses that the extracellular DNA release by C. albicans is strain dependent and is associated with biofilm heterogeneity.

Results

Initially, biofilm formed by C. albicans high biofilm formers (HBF) or low biofilm formers (LBF) were treated with DNase to find whether eDNA play a role in their biofilm formation. Digestion of biofilm eDNA significantly reduced the HBF biofilm biomass by five fold compared to untreated controls. In addition, quantification of eDNA over the period of biofilm formation by SYBR green assay demonstrate a significantly higher level of 2 to 6 fold in HBF compared to LBF. Biochemical and transcriptional analyses showed that chitinase activity and mRNA levels of chitinase genes, a marker of autolysis, were upregulated in 24 h biofilm formation by HBF compared to LBF, indicating autolysis pathway possibly involved in causing variation. The biofilm biomass and eDNA release by single (∆cht2, ∆cht3) and double knockout ( ∆cht2/∆cht3) chitinase mutants were significantly less compared to their parental strain CA14, confirming the role of chitinases in eDNA release and biofilm formation. Correlation analysis found a positive correlation between chitinases and HWP1, suggesting eDNA may release during the hyphal growth. Finally, we showed a combinational treatment of biofilms with DNase or chitinase inhibitor (acetazolamide) plus amphotericin B significantly improved antifungal susceptibility by 2 to 8 fold.

Conclusions

Collectively, these data show that eDNA release by C. albicans clinical isolates is variable and is associated with differential biofilm formation. Digestion of biofilm eDNA by DNase may provide a novel therapeutic strategies to destabilise biofilm growth and improves antifungal sensitivity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-014-0303-6) contains supplementary material, which is available to authorized users.

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Most cited references 31

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Time to initiation of fluconazole therapy impacts mortality in patients with candidemia: a multi-institutional study.

Kevin W. Garey, Milind Rege, Manjunath Pai … (2006)

Inadequate antimicrobial treatment is an independent determinant of hospital mortality, and fungal bloodstream infections are among the types of infection with the highest rates of inappropriate initial treatment. Because of significant potential for reducing high mortality rates, we sought to assess the impact of delayed treatment across multiple study sites. The goals our analyses were to establish the frequency and duration of delayed antifungal treatment and to evaluate the relationship between treatment delay and mortality. We conducted a retrospective cohort study of patients with candidemia from 4 medical centers who were prescribed fluconazole. Time to initiation of fluconazole therapy was calculated by subtracting the date on which fluconazole therapy was initiated from the culture date of the first blood sample positive for yeast. A total of 230 patients (51% male; mean age +/- standard deviation, 56 +/- 17 years) were identified; 192 of these had not been given prior treatment with fluconazole. Patients most commonly had nonsurgical hospital admission (162 patients [70%]) with a central line catheter (193 [84%]), diabetes (68 [30%]), or cancer (54 [24%]). Candida species causing infection included Candida albicans (129 patients [56%]), Candida glabrata (38 [16%]), Candida parapsilosis (25 [11%]), or Candida tropicalis (15 [7%]). The number of days to the initiation of antifungal treatment was 0 (92 patients [40%]), 1 (38 [17%]), 2 (33 [14%]) or > or = 3 (29 [12%]). Mortality rates were lowest for patients who began therapy on day 0 (14 patients [15%]) followed by patients who began on day 1 (9 [24%]), day 2 (12 [37%]), or day > or = 3 (12 [41%]) (P = .0009 for trend). Multivariate logistic regression was used to calculate independent predictors of mortality, which include increased time until fluconazole initiation (odds ratio, 1.42; P < .05) and Acute Physiology and Chronic Health Evaluation II score (1-point increments; odds ratio, 1.13; P < .05). A delay in the initiation of fluconazole therapy in hospitalized patients with candidemia significantly impacted mortality. New methods to avoid delays in appropriate antifungal therapy, such as rapid diagnostic tests or identification of unique risk factors, are needed.

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A characterization of DNA release in Pseudomonas aeruginosa cultures and biofilms.

Marie Allesen-Holm, Kim Bundvig Barken, Liang Yang … (2006)

Pseudomonas aeruginosa produces extracellular DNA which functions as a cell-to-cell interconnecting matrix component in biofilms. Comparison of extracellular DNA and chromosomal DNA by the use of polymerase chain reaction and Southern analysis suggested that the extracellular DNA is similar to whole-genome DNA. Evidence that the extracellular DNA in P. aeruginosa biofilms and cultures is generated via lysis of a subpopulation of the bacteria was obtained through experiments where extracellular beta-galactosidase released from lacZ-containing P. aeruginosa strains was assessed. Experiments with the wild type and lasIrhlI, pqsA, pqsL and fliMpilA mutants indicated that the extracellular DNA is generated via a mechanism which is dependent on acyl homoserine lactone and Pseudomonas quinolone signalling, as well as on flagella and type IV pili. Microscopic investigation of flow chamber-grown wild-type P. aeruginosa biofilms stained with different DNA stains suggested that the extracellular DNA is located primarily in the stalks of mushroom-shaped multicellular structures, with a high concentration especially in the outer part of the stalks forming a border between the stalk-forming bacteria and the cap-forming bacteria. Biofilms formed by lasIrhlI, pqsA and fliMpilA mutants contained less extracellular DNA than biofilms formed by the wild type, and the mutant biofilms were more susceptible to treatment with sodium dodecyl sulphate than the wild-type biofilm.

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Impact of treatment strategy on outcomes in patients with candidemia and other forms of invasive candidiasis: a patient-level quantitative review of randomized trials.

D Andes, N Safdar, J Baddley … (2012)

Invasive candidiasis (IC) is an important healthcare-related infection, with increasing incidence and a crude mortality exceeding 50%. Numerous treatment options are available yet comparative studies have not identified optimal therapy. We conducted an individual patient-level quantitative review of randomized trials for treatment of IC and to assess the impact of host-, organism-, and treatment-related factors on mortality and clinical cure. Studies were identified by searching computerized databases and queries of experts in the field for randomized trials comparing the effect of ≥2 antifungals for treatment of IC. Univariate and multivariable analyses were performed to determine factors associated with patient outcomes. Data from 1915 patients were obtained from 7 trials. Overall mortality among patients in the entire data set was 31.4%, and the rate of treatment success was 67.4%. Logistic regression analysis for the aggregate data set identified increasing age (odds ratio [OR], 1.01; 95% confidence interval [CI], 1.00-1.02; P = .02), the Acute Physiology and Chronic Health Evaluation II score (OR, 1.11; 95% CI, 1.08-1.14; P = .0001), use of immunosuppressive therapy (OR, 1.69; 95% CI, 1.18-2.44; P = .001), and infection with Candida tropicalis (OR, 1.64; 95% CI, 1.11-2.39; P = .01) as predictors of mortality. Conversely, removal of a central venous catheter (CVC) (OR, 0.50; 95% CI, .35-.72; P = .0001) and treatment with an echinocandin antifungal (OR, 0.65; 95% CI, .45-.94; P = .02) were associated with decreased mortality. Similar findings were observed for the clinical success end point. Two treatment-related factors were associated with improved survival and greater clinical success: use of an echinocandin and removal of the CVC.

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Author and article information

Contributors

Ranjith Rajendran: Ranjith.Rajendran@glasgow.ac.uk

Leighann Sherry: leighann.sherry@glasgow.ac.uk

David F Lappin: David.Lappin@glasgow.ac.uk

Chris J Nile: Christopher.Nile@glasgow.ac.uk

Karen Smith: karen.smith@uws.ac.uk

Craig Williams: Craig.Williams@uws.ac.uk

Carol A Munro: c.a.munro@abdn.ac.uk

Gordon Ramage: gordon.ramage@glasgow.ac.uk

Journal

Journal ID (nlm-ta): BMC Microbiol

Journal ID (iso-abbrev): BMC Microbiol

Title: BMC Microbiology

Publisher: BioMed Central (London )

ISSN (Electronic): 1471-2180

Publication date (Electronic): 5 December 2014

Publication date PMC-release: 5 December 2014

Publication date Collection: 2014

Volume: 14

Issue: 1

Electronic Location Identifier: 303

Affiliations

[ ]Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, 378 Sauchiehall Street, Glasgow, G2 3JZ UK

[ ]Institute of Healthcare Associated Infection, School of Health, Nursing and Midwifery, University of the West of Scotland, Paisley, UK

[ ]Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, AB25 2ZD UK

Article

Publisher ID: 303

DOI: 10.1186/s12866-014-0303-6

PMC ID: 4262977

PubMed ID: 25476750

SO-VID: 30a35dea-9b53-4fd8-81d8-44da9650e761

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

History

Date received : 15 July 2014

Date accepted : 19 November 2014

Custom metadata

ScienceOpen disciplines: Microbiology & Virology

Keywords: candida albicans,biofilm,edna,chitinases

Data availability:

ScienceOpen disciplines: Microbiology & Virology

Keywords: candida albicans, biofilm, edna, chitinases

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Extracellular DNA release confers heterogeneity in Candida albicans biofilm formation

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Abstract

Background

Results

Conclusions

Electronic supplementary material

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Bacterial vaginosis and biofilm

Most cited references 31

Time to initiation of fluconazole therapy impacts mortality in patients with candidemia: a multi-institutional study.

A characterization of DNA release in Pseudomonas aeruginosa cultures and biofilms.

Impact of treatment strategy on outcomes in patients with candidemia and other forms of invasive candidiasis: a patient-level quantitative review of randomized trials.

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Cited by 23

Most referenced authors 452