The effect of chlorhexidine gluconate on the germ tube formation of Candida albicans and its relatedness to post-antifungal effect

published_or_final_versio

Impacts of PAFE on the relative CSH of Candida albicans

published_or_final_versio

Differential Actions of Chlorhexidine on the Cell Wall of Bacillus subtilis and Escherichia coli

Chlorhexidine is a chlorinated phenolic disinfectant used commonly in mouthwash for its action against bacteria. However, a comparative study of the action of chlorhexidine on the cell morphology of Gram-positive and Gram-negative bacteria is lacking. In this study, the actions of chlorhexidine on the cell morphology were identified with the aids of electron microscopy. After exposure to chlorhexidine, numerous spots of indentation on the cell wall were found in both Bacillus subtilis and Escherichia coli. The number of indentation spots increased with time of incubation and increasing chlorhexidine concentration. Interestingly, the dented spots found in B. subtilis appeared mainly at the hemispherical caps of the cells, while in E. coli the dented spots were found all over the cells. After being exposed to chlorhexidine for a prolonged period, leakage of cellular contents and subsequent ghost cells were observed, especially from B subtilis. By using 2-D gel/MS-MS analysis, five proteins related to purine nucleoside interconversion and metabolism were preferentially induced in the cell wall of E. coli, while three proteins related to stress response and four others in amino acid biosynthesis were up-regulated in the cell wall materials of B. subtilis. The localized morphological damages together with the biochemical and protein analysis of the chlorhexidine-treated cells suggest that chlorhexidine may act on the differentially distributed lipids in the cell membranes/wall of B. subtilis and E. coli

Author Correction:Single human B cell-derived monoclonal anti-Candida antibodies enhance phagocytosis and protect against disseminated candidiasis

We thank the BBSRC, SULSA BioSKAPE and Pfizer Inc. for funding for a studentship for F.M.R. and the Wellcome Trust (086827, 075470, 099215, 099197 and 101873) and a Wellcome Trust ISSF award (105625), MRC CiC (MC_PC_14114) and MRC Centre for Medical Mycology and University of Aberdeen for funding and a Wellcome Trust Strategic Award (097377) and a Wellcome Trust grant 099197MA to T.F. and FCT Investigator IF/00033/2012 and PTDC/QUI-QUI/112537/2009 to A.S.P. We thank Ian Broadbent, Angus McDonald and Ron Gladue for constructive discussions; Chris Boston and Amanda Fitzgerald for advice on antibody expression and purification; Ed Lavallie and Wayne Stochaj for design and expression of the recombinant Hyr1; Louise Walker for high-pressure freezing of samples for TEM analysis; Jeanette Wagener for endotoxin testing of mAbs for in vivo experiments; Yan Liu of the Glycosciences laboratory for insight in the analysis with N-glycan array; Rebecca Hall and Mark Gresnigt for providing fungal strains; Andrew Limper and Theodore J. Kottom for providing Pneumocystis infected lung tissue extracts; David Williams for C. albicans mannoprotein; Christopher Thornton for A. fumigatus mannoprotein; Katie J. Doores for mAb PGT 128; and Gordon Brown for the murine Fc-Dectin-1. We are grateful to Lucinda Wight, Debbie Wilkinson and Kevin MacKenzie in the Microscopy and Histology Core Facility (Aberdeen University) and Raif Yuecel in the Iain Fraser Cytometry Centre (Aberdeen University) for their expert help with microscopy and cytometry experiments. We are also grateful to the staff at the University of Aberdeen Medical Research Facility for assistance with in vivo experiments and members of the Glycosciences Laboratory for their support of the Carbohydrate Microarray Facility. 18 January 2019 - Author Correction: Single human B cell-derived monoclonal anti-Candida antibodies enhance phagocytosis and protect against disseminated candidiasis F. M. Rudkin, I. Raziunaite, H. Workman, S. Essono, R. Belmonte, D. M. MacCallum, E. M. Johnson, L. Silva, A. S. Palma, T. Feizi, A. Jensen, L. P. Erwig & N. A. R. Gow Nature Communicationsvolume 10, Article number: 394 (2019)Peer reviewedPublisher PD

Impact of brief, sequential exposure to fluconazole and amphotericin B on the cell surface hydrophobicity of oral Candida albicans isolates obtained from HIV infected patients

Cell surface hydrophobicity (CSH) status influences the virulence of Candida albicans isolates and is inextricably involved in candidal adhesion to mucosal and solid surfaces. As the concentration of antimycotic agents reach sub-therapeutic levels at dosage intervals in the oral cavity, the impact of fluconazole and amphotericin B on the CSH of oral C. albicans isolates obtained from Human Immunodeficiency Virus (HIV) infected patients, should be of clinical relevance. Hence, we evaluated using an aqueous-hydrocarbon assay, the CSH of 1,1 isolates of C. albicans following limited (1 hour), sequential (10 days) exposure of the isolates to sub-therapeutic concentrations of fluconazole and amphotericin B. Next, we analyzed the growth curves (computerized turbidometric measurement) of these isolates following such repeated exposure to the antifungals. The reduction in CSH following exposure to fluconazole and amphotericin B was 6.15% (p < 0.05 for 18.18% of the isolates) and 22.80% (p < 0.05 for 54.54% of the isolates), respectively. Analysis of growth curves indicated that the drugs were able to produce a significant fungistatic effect on two of the 11 isolates compared with the controls. Taken together, these data elucidate further pharmacodynamic mechanisms by which antimycotics may operate in vivo in modulating candidal virulence.link_to_subscribed_fulltex

The in vitro post-antifungal effect of nystatin on Candida species of oral origin

The post-antifungal effect (PAFE) is defined as the suppression of growth that persists following limited exposure of yeasts to antimycotics and subsequent removal of the drug. Although limited data are available on the PAFE of nystatin on oral isolates of C. albicans, there is no information on non-albicans Candida species. As nystatin is the commonest antifungal agent prescribed in dentistry, the main aim of this investigation was to measure the PAFE of oral isolates of Candida belonging to six different species (five isolates each of C. albicans, C. tropicalis, C. krusei, C. parapsilosis, C. glabrata and C. guilliermondii) following limited exposure (1 h) to nystatin. The yeasts were examined for the presence of the PAFE after 1 h exposure to the minimum inhibitory concentration (MIC) of nystatin. The PAFE was determined as the difference in time (h) required for the growth of the drug-free control and the drug-exposed test cultures to increase to the 0.05 absorbance level following removal of the antifungal agent. The mean duration of nystatin-elicited PAFE was lowest for C. albicans (6.85 h) and greatest for C. parapsilosis (15.17 h), while C. krusei (11.58 h), C. tropicalis (12.73 h), C. glabrata (8.51 h), and C. guilliermondii (8.68 h) elicited intermediate values. These findings clarify another intriguing possibility for the persistent, chronic recurrence of oral C. albicans infections despite apparently adequate antifungal drug regimens. The significant variations in nystatin-induced PAFE amongst non-albicans species may also have clinical implications, in terms of nystatin regimens used in the management of these fungal infections.link_to_subscribed_fulltex

The effect of limited exposure to antifungal agents on the germ tube formation of oral Candida albicans

Candidal adherence has been implicated as the first step in the pathogenesis of oral candidosis, and germ tube formation by Candida albicans has been attributed as a co-factor that promotes adherence. Oral candidosis is treated with polyenes and the azole group of antifungal agents. As the intraoral concentrations of antifungals fluctuate considerably due to the dynamics of the oral cavity, we investigated the effect of short exposure to sub-lethal concentrations of antifungals on the germ tube formation of Candida albicans. After determining the minimum inhibitory concentration (MIC) of the antifungal agents, ten oral isolates of Candida albicans were exposed to sub-lethal concentrations of nystatin (6xMIC), amphotericin B (8xMIC), 5-fluorocytosine (8xMIC), ketoconazole (4xMIC) and fluconazole (4xMIC), for 1 h. Following removal of the antifungal agent and subsequent incubation in a germ tube-inducing medium, the germ tube formation of these isolates was quantified. When compared with the controls, exposure to nystatin and amphotericin B almost completely inhibited germ tube formation of all the isolates (mean percentage reduction of 97.68 and 97.52%, respectively; P<0.0001), while ketoconazole suppressed this activity to a lesser degree (30.84%; P=0.0174). However, 5-fluorocytosine- and fluconazole-mediated germ tube suppression was minimal (12.63 and 15.93%, respectively; P=0.3255 and P=0.3791). In clinical terms, these findings indicate that short exposure to sub-therapeutic levels of commonly prescribed antifungals may modulate candidal germ tube formation, and thereby the clearance of the organisms from the oral cavity.link_to_subscribed_fulltex