N-acetylcysteine Inhibits and Eradicates Candida albicans Biofilms

Current Microbiology, 2010

Candidosis has been attributed to C. albicans; however, infections caused by non-Candida albicans Candida (NCAC) species are increasingly being recognised. The ability of Candida to grow as a biofilm is an important feature that promotes both infection and persistence in the host. The biofilms' activity is significant since high activity might be associated with enhanced expression of putative virulence factors, whilst in contrast low activity has previously been suggested as a mechanism for resistance of biofilm cells to antimicrobials. The aim of this study was to determine the metabolic activity of in vitro biofilms formed by different clinical isolates of NCAC species. The in situ total metabolic activity of C. parapsilosis, C. tropicalis and C. glabrata biofilms was determined using 2,3-(2-methoxy-4-nitro-5sulphophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction assay, and the number of cultivable cells was also established by CFU (colony forming unit) counts. The biofilm structure was assessed by scanning electron microscopy (SEM). Results showed that total biofilm metabolic activity was species and strain dependent. C. glabrata exhibited the lowest biofilm metabolic activity despite having the highest number of biofilm cultivable cells. Similarly, the metabolic activity of resuspended C. glabrata biofilm and planktonic cells was lower than that of the other species. This study demonstrates the existence of intrinsic activity differences amongst NCAC species, which could have important implications in terms of species relative virulence. Furthermore, the absence of an obvious correlation, between cultivable cells number and total biofilm activity, raises the question about which parameter is the most appropriate for the in vitro assessment of biofilms and their potential clinical significance.

2020

Candida albicans is a fungal microorganism commonly found on the normal flora of the human body and the environment. An opportunistic pathogen causing local and systemic infection, this fungus is one of the leading causes of nosocomial infections through contamination of inserted medical devices. More alarming is Candida's growing multi drug resistance against an already limited antifungals for treatment of infections. Alcaligenes faecalis is a bacterium found in the soil and is a part of the normal flora of humans, but rarely causes disease. Currently, there is very little known about how microbes interact and there is increased interest in how we can exploit microbial relationships to better human health. The present study focused on the polymicrobial interactions between C. albicans and Alcaligenes faecalis. Previous research from our laboratory has shown that A. faecalis exerts an inhibitory effect on C. albicans. While considerable data suggests this inhibitory effect is significant in planktonic cultures, there is nothing known about how these interactions would work in biofilm growth. Therefore, we examined the interactions of Alcaligenes and Candida by attempting to inhibit Candida biofilm growth with Alcaligenes. This study may provide information on potential novel therapeutic methods and targets against C. albicans.

Introduction: The aims of this study were to evaluate the antibacterial and biofilm eradication efficacies of N-acetylcysteine (NAC) on Enterococcus faecalis. Methods: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of NAC on E. faecalis were determined. In addition, the ability of dentin powder to neutralize the antibacterial activity of NAC was examined. Calcium hydroxide, a commonly used intracanal medicament, was included as a comparison. The efficacy of NAC on E. faecalis biofilms was tested by exposure of 21-day old E. faecalis biofilms to NAC. Results: NAC was most bactericidal at pH 11 with MIC and MBC of 1.56 mg/mL and 12.5 mg/ mL, respectively. Although preincubation of calcium hydroxide with dentin powder abolished its antibacterial effects, NAC completely killed E. faecalis regardless of dentin powder preincubation. In addition, prolonged incubation of NAC with dentin powder (up to 3 weeks) did not significantly reduce its antibacterial activity on E. faecalis. Furthermore, NAC also effectively eradicated E. faecalis biofilms. Conclusions: NAC was bactericidal against both the planktonic and biofilm forms of E. faecalis. This antibacterial property of NAC was unaffected by the presence of dentin.

2001

A variety of manifestations of Candida albicans infections are associated with the formation of biofilms on the surface of biomaterials. Cells in biofilms display phenotypic traits that are dramatically different from their free-floating planktonic counterparts, such as increased resistance to anti-microbial agents and protection form host defenses. Here, we describe the characteristics of C. albicans biofilm development using a 96 well microtitre plate model, microscopic observations and a colorimetric method based on the use of a modified tetrazolium salt (2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide, XTT) to monitor metabolic activities of cells within the biofilm. C. albicans biofilm formation was characterized by initial adherence of yeast cells (0-2 h), followed by germination and micro-colony formation (2-4 h), filamentation (4-6 h), monolayer development (6-8 h), proliferation (8-24 h) and maturation (24-48 h). The XTT-reduction assay showed a linear relationship between cellular density of the biofilm and metabolic activity. Serum and saliva pre-conditioning films increased the initial attachment of C. albicans, but had minimal effect on subsequent biofilm formation. Scanning electron microscopy and confocal scanning laser microscopy were used to visualize C. albicans biofilms. Mature C. albicans biofilms consisted of a dense network of yeasts cells and hyphal elements embedded within exopolymeric material. C. albicans biofilms displayed a complex three dimensional structure which demonstrated spatial heterogeneity and a typical architecture showing microcolonies with ramifying water channels. Antifungal susceptibility testing demonstrated the increased resistance of sessile C. albicans cells against clinically used fluconazole and amphotericin B as compared to their planktonic counterparts.

Journal of Medical Microbiology, 2011

Candida albicans cells have the ability to form biofilms on biotic and abiotic surfaces, such as indwelling medical devices. C. albicans cells can interconvert between budded and hyphal growth forms, herein termed the budded-to-hyphal transition (BHT), which is important for the formation of mature biofilms. Previous work identified 23 small organic molecules that could inhibit the BHT but did not affect C. albicans cell viability or budded cell growth. These BHT inhibitors were proposed to inhibit multiple signalling pathways regulating the BHT, many of which also regulate biofilm formation. However, only three of the BHT inhibitors, buhytrinA, ETYA and CGP-37157, were capable of inhibiting in vitro biofilm formation of wild-type laboratory C. albicans strains. When clinical C. albicans isolates were examined for their ability to form biofilms, only 11 of the 28 clinical isolates tested (39 %) were capable of forming biofilms. Although buhytrinA, ETYA and CGP-37157 could inhibit the BHT of all 28 clinical isolates, they were only able to inhibit biofilm formation of a subset of these clinical isolates, with ETYA having 100 % efficacy. These data indicate that the biofilm-forming capability of laboratory and clinical isolates of C. albicans, as well as the efficacy of BHT inhibitors against these different isolates, can differ dramatically. These differences between laboratory and clinical isolates should be an important aspect to consider when examining potentially new antifungal therapeutics.

Journal of Antimicrobial Chemotherapy, 2013

Objectives: The aim of this study was to evaluate miltefosine and four synthetic compounds (TCAN26, TC19, TC106 and TC117) for their in vitro inhibitory activity against Candida albicans planktonic and biofilm cells and investigate whether these compounds are able to inhibit the biofilm formation and to reduce the viability of mature C. albicans biofilm cells.

Biofilm drug resistance may explain the persistence of many infections in the face of appropriate antimicrobial therapy. Sixty four isolates of planktonic Candida albicans revealed high incidence of resistance to azoles than polyenes antifungal agents. A semiquantitative assay was used to measure the metabolic activity of C. albicans biofilms treated with the antifungal agents and then determine the sessile minimum inhibitory concentration of the antifungal agents which caused 50 % inhibition of the formed biofilms (SMIC 50). There was dramatically increase in antifungal concentrations required to kill C. albicans isolates in the sessile forms compared to planktonic forms. Kinetics of biofilm formation showed that the biofilms were highly metabolically active after the first 12 hours. A severe drop in the finally formed biofilms was obtained by adding nystatin at a concentration equal to sub MIC of planktonic cells. On exposure of the biofilms during their formation to nystatin at a concentration equal to sub SMIC 50 of formed biofilm cells after 3 and 6 hours, there was a severe drop in the finally formed biofilms. Adding nystatin after 12 and 24 hours, the formed biofilms became more metabolically active. Scanning electron microscope (SEM) revealed that the fully mature biofilm was produced after incubation for up to 48 hour. Growing the biofilm from the beginning with nystatin at SMIC 50 resulted in a large reduction in cell numbers and in the thickness of the biofilm compared to the normal biofilm.

2019

The opportunistic human fungal pathogen Candida albicans rely on cell morphological transitions to develop biofilm and invade the host. In the current study, we developed new regulatory molecules, which inhibit the morphological transition of C. albicans from yeast-form cells to cells forming hyphae. These compounds, benzyl α-L-fucopyranoside and benzyl β-D-xylopyranoside, inhibit the morphological switching and adhesion of C. albicans to a polystyrene surface, resulting in a reduced biofilm formation. The addition of cAMP to cells treated with α-L-fucopyranoside restored the yeast-hyphae switch and the biofilm level to that of the untreated control. In the β-D-xylopyranoside treated cells, the biofilm level was only partially restored by the addition of cAMP, and these cells remained mainly as yeast-form cells.

Frontiers in Microbiology, 2021

In recent years, the demand for novel antifungal therapies has increased several- folds due to its potential to treat severe biofilm-associated infections. Biofilms are made by the sessile microorganisms attached to the abiotic or biotic surfaces, enclosed in a matrix of exopolymeric substances. This results in new phenotypic characteristics and intrinsic resistance from both host immune response and antimicrobial drugs. Candida albicans biofilm is a complex association of hyphal cells that are associated with both abiotic and animal tissues. It is an invasive fungal infection and acts as an important virulent factor. The challenges linked with biofilm-associated diseases have urged scientists to uncover the factors responsible for the formation and maturation of biofilm. Several strategies have been developed that could be adopted to eradicate biofilm-associated infections. This article presents an overview of the role of C. albicans biofilm in its pathogenicity, challenges it pose...

Eukaryotic Cell, 2013