In Vitro Evaluation of the Virulence Attributes of Oropharyngeal Candida Species Isolated from People Living with Human Immunodeficiency Virus with Oropharyngeal Candidiasis on Antiretroviral Therapy

Background

Oropharyngeal Candida species are part commensal microflora in the the oral cavity of health individuals. Commensal Candida species can become opportunist and transition to pathogenic causes of oropharyngeal candidiasis (OPC) in individuals with impaired immunity through ecological cues and expression of virulence factors. Limited studies have evaluated virulence attributes of oropharyngeal Candida species among people living with human immunodeficiency virus (PLHIV) with OPC on antiretroviral therapy (ART) in Uganda.

Objective

Evaluation of the Virulence Attributes of Oropharyngeal Candida Species Isolated from People Living with Human Immunodeficiency Virus with Oropharyngeal Candidiasis on Antiretroviral Therapy.

Methods

Thirty-five (35) Candida isolates from PLHIV with OPC on ART were retrieved from sample repository and evaluated for phospholipase activity using the egg yolk agar method, proteinase activity using the bovine serum albumin agar method, hemolysin activity using the blood agar plate method, esterase activity using the Tween 80 opacity test medium method, coagulase activity using the classical tube method and biofilm formation using the microtiter plate assay method in vitro.

Results

Phospholipase and proteinase activities were detected in 33/35 (94.3%) and 31/35 (88.6%) of the strains, respectively. Up to 25/35 (71.4%) of the strains exhibited biofilm formation while esterase activity was demonstrated in 23/35 (65.7%) of the strains. Fewer isolates 21/35 (60%) of the strains produced hemolysin and coagulase production was the least virulence activity detected in 18/35 (51.4%).

Conclusion

Phospholipase and proteinase activities were the strongest virulence attributes of oropharyngeal Candida species.

Genotypes and virulence-related activities of Candida albicans derived from oral cavity of patients in Hokkaido

OBJECTIVE

This study aimed to elucidate the difference in virulence of Candida albicans derived from oral candidiasis and non-oral candidiasis patients, and its genotype differences in Hokkaido to obtain a clue of a platform to develop new approaches for diagnosis and treatment.

DESIGN

C. albicans strains were collected from patients who visited the Hokkaido University Hospital Dental Center. Each strain was examined to i) identify the Candida albicans genotype by PCR, ii) measure the strain's extracellular secretory enzyme activity, iii) determine the strain's ability to induce the production of interleukin-8, and iv) determine the strain's ability to induce cell death.

RESULTS

Certain virulence-related protease activities and cytotoxicity were higher in strains derived from patients with oral candidiasis compared with strains derived from patients without oral candidiasis. This is the first report on genotypes and the virulence-related activities, such as some protease secretion, IL-8 induction and cytotoxicity of C. albicans in Hokkaido.

CONCLUSIONS

The virulence-related activities of the fungal strain may influence the pathogenesis of oral candidiasis, such as production of secreted aspartyl protease and cytotoxicity. In addition, C. albicans genotype C may be important for pathogenicity in Hokkaido, because the ratio of genotype C was increased in strains derived from oral candidiasis patients.

Influence of oral biofilm index, caries experience, and laboratory markers of disease progression on the oral carriage of Candida in HIV-infected and non-infected children: a cross-sectional study

The present study aimed to compare the oral Candida rate between infected and uninfected children with the human immunodeficiency virus (HIV), as well as analyze the association between Candida spp. and predisposing factors of colonization, like oral biofilm index, caries experience, and laboratory markers of AIDS progression. A cross-sectional study was employed. Candida species were identified and quantified from saliva samples of 50 HIV-infected and 50 uninfected children. Biofilm index and decayed, missing, and filled teeth (dmft/DMFT) indices were assessed by oral clinical examinations. Additionally, CD4+ T lymphocyte count and viral load were obtained from medical records of the HIV-infected children. Candida species were cultured from 74% of the HIV-infected children and 46% of uninfected ones (p = 0.0076). Candida albicans and Candida parapsilosis were the most frequently isolated species in both studied groups. The isolation of Candida species was significantly higher in HIV-infected children with CD4 ≤ 15% (p = 0.0146); it had influence of mature oral biofilm and the caries index (dmft + DMFT ≥ 8) (p < 0.05) and was associated with the plasma viral load. The present data show that the HIV infection, oral biofilm index, caries experience, and laboratory markers of AIDS progression exert an influence on the prevalence of oral Candida in children.

Increased diversity, fungal burden, and virulence of oral Candida spp. in patients undergoing anti-tuberculosis treatment

Some studies have demonstrated a high prevalence of Candida species in patients with tuberculosis (TB). This is most likely due to long-term antimicrobial therapy. To date, no longitudinal studies addressed the effects of anti-TB treatment on the fungal burden and virulence of Candida spp. This study investigated the prevalence and virulence of Candida spp. in the oral cavity of 30 TB patients at different stages of treatment through a cohort study. These results were compared with those of 60 systemically healthy individuals in a cross-sectional study. Oral rinse samples from TB patients were collected before 45 and after 120 days of treatment. In the control group, the biological samples were collected only once. Candida spp. were identified by restriction fragment length polymorphism (RFLP) assays, and the following virulence factors were studied: phospholipase C and proteinase production, as well as Candida spp. biofilm and hyphae formation. The clinical diagnosis of TB and its treatment time were associated with the greater fungal burden (p < 0.0001), presence of non-albicans Candida (NAC) species (p = 0.0003), and increased virulence factors when compared with the Candida spp. isolated from systemically healthy individuals. The results showed that anti-TB treatment time was responsible for the increased fungal burden and isolation of NAC in TB patients (p = 0.0233). The increased prevalence, quantification, and virulence of Candida spp. isolated from the oral cavity of TB patients highlight the greater risk of oral lesions and cases of systemic dissemination in these patients.

Antibiofilm Efficacy of Luteolin Against Single and Dual Species of Candida albicans and Enterococcus faecalis

Candida albicans and Enterococcus faecalis biofilm-associated infections have been a huge challenge to the medical community. However, the efficacy of natural products against mixed biofilms of C. albicans and E. faecalis still remains largely unexploited. The aim of this study was to evaluate the efficacy of luteolin against planktonic cell growth, adhesion, and biofilm formation of C. albicans and E. faecalis in single and mixed cultures in vitro. The results showed that the minimum inhibitory concentrations of luteolin against planktonic cells of C. albicans, E. faecalis, and mixed cultures were 32 and 64 μg ml^–1, respectively. The results displayed that a remarkable variation in biofilm biomass, viability, structure, and composition of single and dual-species biofilms formed by mono- and dual-species biofilms of C. albicans and E. faecalis in the presence of luteolin was confirmed by mainly crystal violet staining assay (CVSA), optical microscope, field emission scanning electron microscope (FESEM), and confocal laser scanning microscope (CLSM). The tolerance of luteolin-treated single- and dual-species biofilms to antibiotics was found to obviously decrease, and the loss of biofilm matrix components (mainly polysaccharides and proteins) was revealed by CLSM. Moreover, luteolin was effective at inactivating biofilm cells, as well as destructing preformed biofilm structures by single and dual species by CVSA, FESEM, and CLSM. Collectively, these data indicate the potential of luteolin as a promising antibiofilm agent for the therapeutic management of biofilm-related infections induced by single and dual species of C. albicans and E. faecalis.

Evaluation of the antifungal photodynamic activity of Thymophylla pentachaeta extracts against Candida albicans and its virulence factors

BACKGROUND

Candida albicans is one of the most common causative of opportunistic infections. Treatment of candidiasis is challenging considering the few antifungal drugs available and the increase in resistance. Antimicrobial photodynamic therapy (aPDT) is a recently developed therapeutic option that combines a non-toxic photosensitizer (PS) and light to kill the microbial pathogens. Targeting virulence, defined as the ability of a pathogen to cause overt disease, represents another attractive target for the development of novel antifungal agents. Thymophylla pentachaeta (DC.) Small var. belenidium (DC.) is an endemic plant from Argentina in which the presence of thiophenes, biologically active compounds whose antifungal activity is enhanced by irradiation with Ultraviolet A (UVA), have been already described.

PURPOSE

The purpose of this study was to evaluate the photodynamic antifungal activity of hexane (Hex), dichloromethane (DCM), ethyl acetate (EtOAc) and methanol (MeOH) extracts from T. pentachaeta var. belenidium and their inhibitory effects on C. albicans virulence factors as well as biofilm formation and eradication.

STUDY DESIGN/METHODS

Antifungal photodynamic activity of Hex, DCM, EtOAc and MeOH extracts from different parts of the plant were assessed with the microbroth dilution, bioautography and the time-kill assays, under light and darkness conditions. The capacities of the most active extracts of inhibiting Candida virulence factors (adherence to epithelial cells, germ tube and pseudomycelium formation and hydrolytic enzyme secretion) were assessed. In addition, the activity against biofilm formation and eradication has been investigated by reaction with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) that quantifies living cells in these structures.

RESULTS

Hex and DCM extracts from T. pentachaeta roots exhibited high photodynamic antifungal activity against C. albicans [Minimal fungicide concentrations (MFCs)= 7.8 µg/ml] under UVA light irradiation. Chemical analysis of active extracts (Hex and DCM from roots) revealed the presence of photoactive thiophenes. Both extracts generate reactive oxygen species through type I and II mechanisms. These extracts, at sub-inhibitory concentrations, under light conditions decreased the adherence of C. albicans to Buccal Epithelial Cells (BEC), inhibited germ tube formation and reduced esterase production. Finally, they demonstrated activity against preformed biofilms submitted to irradiation (MFCs= 3.91 µg/ml and 15.63 µg/ml for Hex and DCM extracts, respectively).

CONCLUSION

Taking together, results demonstrated the strong photodynamic effects of T. pentachaeta root extracts under UVA irradiation, making them valuable alternatives to the already established antifungal drugs against C. albicans.

Are Candida albicans isolates from the oral cavity of HIV-infected patients more virulent than from non-HIV-infected patients? Systematic review and meta-analysis

Candida albicans is the main causative agent of oral lesions in HIV-infected patients and its oral colonization is a potential source of systemic dissemination. Although the high prevalence of lesions in HIV patients can be explained by the immunosuppressive condition, several studies have reported that natural selection can make C. albicans more virulent in this group of patients. Comparisons of the activity of exoenzymes (phospholipase, proteinase and hemolysin) in C. albicans isolated from HIV-infected and uninfected patients have yielded conflicting results. This study aimed, through a systematic review and meta-analysis, to answer the question: "Is the hydrolytic enzymatic activity of C. albicans, isolated from the oral cavity, different in individuals infected and not infected with HIV?" The question was addressed using the PECO framework: P (Population): children and adults, E (Exposure): HIV infection, C (Comparator): non-HIV-infected patients; O (Outcomes): exoenzymes activity i.e. phospholipase, proteinase and hemolysin. We conducted a systematic search on Pubmed, Embase, Scopus, Livivo, Lilacs, Web of Science, and Science Direct databases, and Google Scholar. The MAStARI tool was used to evaluate the risk of bias in the selected studies. From 2259 studies, 19 were included in this review and 11 comprised the meta-analysis. The activity of phospholipase (M-H = 0.15; Z = 2,76; p = 0.0006) and hemolysin exoenzymes (M-H = 0.07; z = 1,94; p = 0.05) was higher in C. albicans isolated from the oral cavity of HIV-infected patients, whereas the levels of protease activity were not different compared with non-HIV-infected individuals. This study showed a higher phospholipase and hemolysin activity in C. albicans isolates from the oral cavity of HIV-infected patients.

Anticandidal activity of bioinspired ZnO NPs: effect on growth, cell morphology and key virulence attributes of Candida species

The pathogenicity of Candida species in human is dependent on a variety of virulence factor such as adhesion factors, germ tube and hyphal formation, secretion of hydrolytic phospholipases and proteinases and drug resistance biofilm. ZnO NPs have been synthesized by using leaf extract of Crinum latifolium and were characterized by UV-Vis spectrophotometer, FTIR, SEM, EDX and TEM. In this study for the first time, potent inhibitory effects of ZnO NPs on principal virulence factors of Candida albicans and non-albicans such as germ tube formation, secretion of hydrolytic phospholipases and proteinases and biofilm formation has been investigated. ZnO NPs remarkably reduced the germ tube formation of C. albicans at 1 (86.4%), 0.5 (75.0%), 0.25 (61.4%), 0.125 (34.1%) and 0.062 mg/ml (11.4%). ZnO NPs significantly lowered the phospholipase and proteinase secretion by 58.8 and 95.2% at 0.25 mg/ml, respectively. CSLM results showed that ZnO NPs suppressed biofilm formation up to 85% at 0.25 mg/ml. SEM and TEM micrograph showed that ZnO NPs penetrated inside the cell and causes extensive damaged in cell wall and cell membrane. Inhibition of Candida growth and various virulent factors by ZnO NPs provides an insight towards their therapeutic application for the treatment of Candida-associated infections.

Curcumin-mediated anti-microbial photodynamic therapy against Candida dubliniensis biofilms

The purpose of this study was to evaluate the effectiveness of anti-microbial photodynamic therapy (aPDT) mediated by curcumin (Cur) associated with LED light against biofilms of Candida dubliniensis, and further, investigate cellular uptake and drug penetration through the biofilms under confocal laser scanning microscopy (CLSM). Four C. dubliniensis strains were tested: three clinical isolates from HIV-positive patients and one reference strain (CBS 7987). Biofilms were treated with three Cur concentrations (20.0, 30.0, and 40.0 μM). All samples were incubated in the dark for 20 min and exposed to a 5.28 J/cm² of LED light fluence. Additional samples of each strain were treated either with Cur or LED light only. Control samples had neither Cur nor light. After aPDT, results were read using the XTT salt reduction method. The data were statistically analyzed by two-way ANOVA followed by Games-Howell post-hoc test (α = 0.05). Confocal laser scanning microscopy was used to verify both the uptake of Cur by yeast cells and its penetration through the biofilm. The results showed that aPDT promoted significant reduction on the metabolism of the biofilm-organized cells of C. dubliniensis. Further, while Cur was rapidly taken up by C. dubliniensis cells, a longer time interval was required to allow Cur penetration into biofilm cells. Based on these results, aPDT associating LED and Cur presents promising potential on fungal control of biofilms of C. dubliniensis.

Oral mycoses and other opportunistic infections in HIV: therapy and emerging problems - a workshop report

Oral mycoses and other opportunistic infections are recognized features of HIV infection even after four decades of the epidemic. The therapeutic options, challenges of therapy, and evolving patterns of opportunistic infections were evaluated by the workshop. It was observed that high Candida counts and infection are still more prevalent in HIV-positive individuals even in the era of antiretroviral therapy. Furthermore, one or more non-Candida albicans are present in some HIV-positive individuals. While Candida species are more virulent in HIV infection, similar virulence may be present in other states of immunosuppression. Consequently, the interplay between host factors and virulence ultimately determines the clinical outcomes. Adverse clinical outcomes such as candidemia and other deep fungal infections are on the increase in HIV infection. Disseminated histoplasmosis and penicilliosis have been reported, especially with low CD4 counts. Even with advances in antifungal therapy, mortality and morbidity from deep fungal infections have not changed significantly. In addition, long-term exposure to common antifungal drugs such as fluconazole has led to the development of antifungal resistance in 6% to 36%. Development of new antifungal therapeutic agents and the use of alternative therapies may offer breakthrough. In addition, effective strategies to enhance the host immune status are being explored.

Prevalence, virulence factors and antifungal susceptibility of Candida spp. isolated from bloodstream infections in a tertiary care hospital in Brazil

Candida spp. are responsible for 80% of all systemic fungal infections and are associated with high mortality rates. This study characterised 79 bloodstream isolates of C. albicans, C. glabrata, C. orthopsilosis, C. parapsilosis and C. tropicalis from patients in a Brazilian hospital. The susceptibility to amphotericin B, caspofungin, fluconazole and voriconazole was determined; virulence factor production was assessed based on haemolysin, phospholipase and proteinase activities, and the patients' clinical characteristics were analysed. C. albicans was the predominant species (44%), followed by C. glabrata (19%), C. tropicalis (19%), C. parapsilosis (14%) and C. orthopsilosis (4%). The candidemia incidence was 1.52 per 1000 admissions, and the crude mortality rate was 52%. One C. albicans isolate was resistant to fluconazole and voriconazole. Moreover, 20.2%, 2.5% and 3.8% of the isolates exhibited dose-dependent susceptibility to fluconazole, voriconazole and caspofungin, respectively. In conclusion, although the C. glabrata incidence was higher than that usually described in Brazil, its increase was previously observed in studies conducted worldwide. Furthermore, the azole resistance of the C. albicans isolate could be due to previous exposure to these antifungals. These results highlight the importance of epidemiological studies and will facilitate an improved understanding of candidemia in the studied hospital.

Candida species from oral cavity of HIV-infected children exhibit reduced virulence factors in the HAART era

This study aimed to assess, in vitro, the biofilm viability and the phospholipase and protease production of Candida spp. from the saliva of HIV infected children and healthy controls, and to correlate the results with the use of medical data. A total of 79 isolates were analyzed: 48 Candida albicans isolates (33/15) and 20 Candida parapsilosis sensu lato complex isolates (12/8) (from HIV/control patients, respectively), and 8 Candida krusei, 1 Candida tropicalis, 1 Candida dubliniensis and 1 Candida guilliermondii from HIV patients. The XTT (2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-Carboxanilide) reduction assay analyzed the biofilm viability. Phospholipase and protease assays were performed using the egg yolk and Bovine Serum Albumin agar plate methods, respectively. All isolates were able to form biofilm with cell viability. Quantitatively, Candida isolates from both groups presented a similar ability to form biofilm (p > 0.05). The biofilm viability activity was higher in C. albicans isolates than in non-albicans Candida isolates (p < 0.05) for both groups. Phospholipase activity was detected in 32 isolates (40.5%) and it was significantly higher in the HIV group (p = 0.006). Protease activity was detected in 66 isolates (84.8%) and most of them were relatively/very strong producers. No statistical association with medical data was found in the HIV group. Although Candida spp. isolates from HIV-positive children presented higher phospholipase production, in vitro they exhibited reduced virulence factors compared to isolates from healthy individuals. This finding may enlighten the role played by immunosuppression in the modulation of Candida virulence attributes.

Candida virulence and ethanol-derived acetaldehyde production in oral cancer and non-cancer subjects

OBJECTIVES

To compare biofilm-forming ability, hydrolytic enzymes and ethanol-derived acetaldehyde production of oral Candida isolated from the patients with oral cancer and matched non-oral cancer.

MATERIAL AND METHODS

Fungal biofilms were grown in RPMI-1640 medium, and biofilm mass and biofilm activity were assessed using crystal violet staining and XTT salt reduction assays, respectively. Phospholipase, proteinase, and esterase production were measured using agar plate method, while fungal acetaldehyde production was assessed via gas chromatography.

RESULTS

Candida isolated from patients with oral cancer demonstrated significantly higher biofilm mass (P = 0.031), biofilm metabolic activity (P < 0.001), phospholipase (P = 0.002), and proteinase (P = 0.0159) activity than isolates from patients with non-oral cancer. High ethanol-derived acetaldehyde-producing Candida were more prevalent in patients with oral cancer than non-oral cancer (P = 0.01). In univariate regression analysis, high biofilm mass (P = 0.03) and biofilm metabolic activity (P < 0.001), high phospholipase (P = 0.003), and acetaldehyde production ability (0.01) were significant risk factors for oral cancer; while in the multivariate regression analysis, high biofilm activity (0.01) and phospholipase (P = 0.01) were significantly positive influencing factors on oral cancer.

CONCLUSION

These data suggest a significant positive association between the ability of Candida isolates to form biofilms, to produce hydrolytic enzymes, and to metabolize alcohol to acetaldehyde with their ability to promote oral cancer development.

Molecular mechanisms associated with Fluconazole resistance in clinical Candida albicans isolates from India

Resistance to azole antifungals is a significant problem in Candida albicans. An understanding of resistance at molecular level is essential for the development of strategies to tackle resistance and rationale design of newer antifungals and target-based molecular approaches. This study presents the first evaluation of molecular mechanisms associated with fluconazole resistance in clinical C.albicans isolates from India. Target site (ERG11) alterations were determined by DNA sequencing, whereas real-time PCRs were performed to quantify target and efflux pump genes (CDR1, CDR2, MDR1) in 87 [Fluconazole susceptible (n = 30), susceptible-dose dependent (n = 30) and resistant (n = 27)] C.albicans isolates. Cross-resistance to fluconazole, ketoconazole and itraconazole was observed in 74.1% isolates. Six amino acid substitutions were identified, including 4 (E116D, F145L, E226D, I437V) previously reported ones and 2 (P406L, Q474H) new ones. CDR1 over-expression was seen in 77.7% resistant isolates. CDR2 was exclusively expressed with CDR1 and their concomitant over-expression was associated with azole cross-resistance. MDR1 and ERG11 over-expression did not seem to be associated with resistance. Our results show that drug efflux mediated by Adenosine-5'-triphosphate (ATP)-binding cassette transporters, especially CDR1 is the predominant mechanism of fluconazole resistance and azole cross-resistance in C. albicans and indicate the need for research directed towards developing strategies to tackle efflux mediated resistance to salvage azoles.

Occurrence of oral Candida colonization and its risk factors among patients with malignancies in China

OBJECTIVES

Oral colonization of Candida could lead to later development of oropharyngeal candidiasis or candidemia among the immunocompromised patients. This study aims to describe the occurrence and risk factors of oral Candida colonization in patients with malignancies.

MATERIALS AND METHODS

From October 2012 to March 2013, 78 patients with pulmonary cancer (group I), 101 patients with gastrointestinal tract tumor (group II), 79 patients with hematopoietic system malignant tumor (group III), and 101 healthy controls were consecutively recruited in a hospital in Beijing, China. The oral rinse samples were taken and Candida species were identified; the enzymes activities were tested.

RESULTS

In total, 110 and 27 Candida strains were isolated from 91 patients and 26 controls, respectively. The oral colonization rate with Candida albicans in group III (12.7 %) was significant lower than that in group I (30.8 %), group II (33.7 %), and control group (25.7 %). The oral colonization rates with non-albicans Candida species in group I, group II, and group III were 15.4, 10.9, and 12.7 %, respectively, while only one non-albicans Candida strain was identified in control group. The non-albicans Candida species exhibited a lower virulence than C. albicans. Age was an independent risk factor for Candida colonization in patients with pulmonary cancer and digestive tract malignant tumor, "Teeth brush <1 time/day" was an independent risk factor for Candida colonization in patients with hematopoietic system tumor.

CONCLUSIONS

The differences of risk factors for oral Candida colonization in patients with different cancers require different strategies for the prevention and control of Candida infection.

CLINICAL RELEVANCE

Old aged patients with pulmonary cancer and digestive tract malignant tumor are high-risk population for Candida colonization. Increasing frequency of teeth brush might be helpful for preventing Candida colonization.

Fresh Garlic Extract Enhances the Antimicrobial Activities of Antibiotics on Resistant Strains in Vitro

Background:

Infections caused by strains with multi-drug resistance are difficult to treat with standard antibiotics. Garlic is a powerful remedy to protect against infections of many bacteria, fungi and viruses. However, little is known about the potentials of fresh garlic extract (FGE) to improve the sensitivity of multi-drug resistant strains to antibiotics.

Objectives:

In this study, we used the disk diffusion method to investigate the antimicrobial activities of FGE and the combination of antibiotics with FGE, on methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Candida albicans, to evaluate the interactions between antibiotics and FGE.

Materials and Methods:

Clinical isolates were isolated from clinical specimens obtained from the inpatients at the First Affiliated Hospital of Xi’an Jiaotong University Health Science Center. The isolates consisted of MRSA, (n = 30), C. albicans (n = 30) and P. aeruginosa (n = 30). Quality control for CLSI (Clinical and Laboratory Standards Institute) disk diffusion was performed using S. aureus ATCC®25923, C. albicans ATCC®90028 and P. aeruginosa ATCC®27853. The 93 microorganisms were divided into four groups in a factorial design: control (deionized water), FGE, antibiotics without FGE, and antibiotics with FGE. Next, antibacterial activity was evaluated by measuring the diameter of inhibition zones according to performance standards for antimicrobial susceptibility testing of the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS).

Results:

Fresh garlic extract displayed evident inhibition properties against C. albicans and MRSA, yet weak inhibition properties against P. aeruginosa. Additionally, FGE showed the potential to improve the effect of antibiotics on antibiotic resistant pathogens. The synergism of fluconazole and itraconazole with FGE on C. albicans yielded larger sized inhibition zones compared with fluconazole and itraconazole without FGE (P < 0.01). The factorial analysis represents intense positive interaction effects (P < 0.01). The synergism of cefotaxime and ceftriaxone with FGE on P. aeruginosa yielded larger sized inhibition zones than cefotaxime and ceftriaxone without FGE (P < 0.01). The factorial analysis represents intense positive interaction effects (P < 0.01).

Conclusions:

The results suggest that FGE can improve the antibiotic sensitivity of these pathogens to some antibiotics.

Sub-inhibitory concentrations of antifungals suppress hemolysin activity of oral Candida albicans and Candida tropicalis isolates from HIV-infected individuals

Secretion of hydrolytic enzymes such as hemolysin is considered an important virulence attribute of the opportunistic pathogenic fungus Candida. It is known that Candida spp. isolated from HIV-infected patients produce copious hemolysins. As common antifungal agents may perturb the production of extracellular enzymes, we evaluated the effect of three antifungals nystatin, amphotericin B and fluconazole on the hemolytic activity of Candida albicans and Candida tropicalis isolates from HIV-infected individuals. The impact of antimycotics on hemolytic activity was assessed by a previously described in vitro plate assay, after exposing ten isolates each of C. albicans and C. tropicalis recovered from HIV-infected individuals to sub-minimum inhibitory concentrations (sub-MIC) of nystatin, amphotericin B and fluconazole. All Candida isolates showed a significant reduction in hemolytic activity. The reduction was highest for amphotericin B-exposed C. albicans and C. tropicalis followed by nystatin and fluconazole. The effect of antimycotics was more pronounced on the hemolytic activity of C. tropicalis compared to that of C. albicans. Commonly used antifungal agents significantly suppress hemolysin activity of Candida species. This implies that the antifungals, in addition to their lethality, may modulate key virulence attributes of the yeast. The clinical relevance of this phenomenon in HIV disease and other similar pathologies remains to be determined.

Virulence of oral Candida isolated from HIV-positive women with oral candidiasis and asymptomatic carriers

OBJECTIVE

This study compared the virulence of oral Candida species isolated from human immunodeficiency virus (HIV)-positive women with and without oral candidiasis.

STUDY DESIGN

Candida species were isolated from 197 women, and their virulence attributes were measured.

RESULTS

Of the 197 women, 117 (59.4%) carried Candida. Of these, 15 (12.8%) had symptoms of oral candidiasis. Among highly active antiretroviral therapy (HAART)-naive patients, 33% were diagnosed with oral candidiasis, whereas 5.9% were asymptomatic carriers (P < .01). C. albicans was the predominant species, with higher virulence attributes than non-albicans Candida. Women diagnosed with oral candidiasis had higher levels of Candida (P = .02) than asymptomatic carriers. There was no difference in the CD4 counts and the virulence attributes of Candida from both the groups.

CONCLUSIONS

This study indicates that oral candidiasis is mainly caused by high counts of C. albicans and suggests the importance of therapies targeting Candida counts in the oral cavity even in patients on HAART to reduce the development of infections.

Novel Nystatin A₁ derivatives exhibiting low host cell toxicity and antifungal activity in an in vitro model of oral candidosis

Opportunistic oral infections caused by Candida albicans are frequent problems in immunocompromised patients. Management of such infections is limited due to the low number of antifungal drugs available, their relatively high toxicity and the emergence of antifungal resistance. Given these issues, our investigations have focused on novel derivatives of the antifungal antibiotic Nystatin A1, generated by modifications at the amino group of this molecule. The aims of this study were to evaluate the antifungal effectiveness and host cell toxicity of these new compounds using an in vitro model of oral candidosis based on a reconstituted human oral epithelium (RHOE). Initial studies employing broth microdilution, revealed that against planktonic C. albicans, Nystatin A1 had lower minimal inhibitory concentration than novel derivatives. However, Nystatin A1 was also markedly more toxic against human keratinocyte cells. Interestingly, using live/dead staining to assess C. albicans and tissue cell viability after RHOE infection, Nystatin A1 derivatives were more active against Candida with lower toxicity to epithelial cells than the parent drug. Lactate dehydrogenase activity released by the RHOE indicated a fourfold reduction in tissue damage when certain Nystatin derivatives were used compared with Nystatin A1. Furthermore, compared with Nystatin A1, colonisation of the oral epithelium by C. albicans was notably reduced by the new polyenes. In the absence of antifungal agents, confocal laser scanning microscopy showed that C. albicans extensively invaded the RHOE. However, the presence of the novel derivatives greatly reduced or totally prevented this fungal invasion.

Comparison of the hemolytic activity between C. albicans and non-albicans Candida species

The ability to produce enzymes, such as hemolysins, is an important virulence factor for the genus Candida.The objective of this study was to compare the hemolytic activity between C. albicansand non-albicans Candida species. Fifty strains of Candida species, isolated from the oral cavity of patients infected with HIV were studied. The isolates included the following species: C. albicans, C. dubliniensis, C. glabrata, C. tropicalis, C. krusei, C. parapsilosis, C. dubliniensis, C. norvegensis, C. lusitaniae, and C. guilliermondii. Hemolysin production was evaluated on Sabouraud dextrose agar containing chloramphenicol, blood, and glucose. A loop-full of pure Candidaculture was spot-inoculated onto plates and incubated at 37 ºC for 24 h in a 5% CO2 atmosphere. Hemolytic activity was defined as the formation of a translucent halo around the colonies. All C. albicansstrains that were studied produced hemolysins. Among the non-albicans Candidaspecies, 86% exhibited hemolytic activity. Only C. guilliermondiiand some C. parapsilosis isolates were negative for this enzyme. In conclusion, most non-albicans Candidaspecies had a similar ability to produce hemolysins when compared to C. albicans.

Smoking as a risk factor for oral candidiasis in HIV-infected adults

OBJECTIVE

We aimed to examine if smoking is an independent predictor of oral candidiasis (OC) among HIV-1 infected persons.

METHODS

The cross-sectional part of this study evaluated 631 adult dentate HIV-1 seropositive persons examined for OC from 1995-2000 at the University of North Carolina Hospitals in Chapel Hill, NC. In the second part, from the above sample, a total of 283 individuals who were free of HIV-associated oral diseases at baseline were followed up for 2 years to assess incident OC events. Data collected from medical record review, interview questionnaires, and clinical examinations were analyzed using chi-squared tests and t-tests. Logistic regression models were developed for prevalent OC employing the likelihood ratio test, whereas Poisson regression models were developed for assessing cumulative incidence of OC. These models included a variety of independent variables to adjust for confounding.

RESULTS

Thirteen percent of participants had OC only; 4.6% had OC with Oral Hairy Leukoplakia; and 69.7% had neither. Smoking was associated with OC in all models [prevalent OC - current smokers: logistic regression - Odd ratio (95% CI) = 2.5 (1.3, 4.8); Incident OC - current smokers: Poisson regression (main effects model) - Incidence rate ratio (95% CI) = 1.9 (1.1, 3.8)]. Other Poisson regression models suggested evidence for effect modification between CD4 cell count and incident OC by smoking.

CONCLUSION

Smoking is an independent risk factor for the development of OC in HIV-1 infected persons, and the risk of OC is modified by CD4 cell count which measures strength of the immune system.

Candida and candidiasis in HIV-infected patients: where commensalism, opportunistic behavior and frank pathogenicity lose their borders

In this era of efficacious antiretroviral therapy and consequent immune reconstitution, oropharyngeal and esophageal candidiasis (OPC and OEC) still remain two clinically relevant presentations in the global HIV setting. Both diseases are predominantly caused by Candida albicans, a polymorphic fungus which is a commensal microbe in the healthy individual but can become an aggressive pathogen in a debilitated host. Actually, C. albicans commensalism is not the result of a benign behavior of one of the many components of human microbiota, but rather the result of host's potent innate and adaptive immune responses that restrict the growth of a potentially dangerous microrganism on the epithelia. An important asset guarding against the fungus is the Th17 functional subset of T helper cells. The selective loss of these cells with the progression of HIV infection causes the decay of fungal containment on the oral epithelium and allows C. albicans to express its pathogenic potential. An important part of this potential is represented by mechanisms to evade host immunity and enhance inflammation and immunoactivation. In C. albicans, these mechanisms are mostly incorporated into and expressed by characteristic morphogenic transitions such as the yeast-to-hyphal growth and the white-to-opaque switch. In addition, HIV infection generates an 'environment' selecting for overexpression of the virulence potential by the fungus, particularly concerning the secreted aspartyl proteinases (Saps). These enzymes can degrade critical host defense components such as complement and epithelial defensive proteins such as histatin-5 and E-cadherin. It appears that part of this enhanced Candida virulence could be induced by the binding of the fungus to HIV and/or induced by HIV proteins such as GP160 and tat. Both OPC and OEC can be controlled by old and new antimycotics, but in the absence of host collaboration, anticandidal therapy may become ineffective in the long run. For these reasons, new therapeutics targeting virulence factors and specific immune interventions are being addressed. Among these new approaches, vaccination is a promising one. Two subunit vaccines based on antigens dominantly expressed by C. albicans in vivo, that is the Als3 adhesin and Sap2, have recently undergone phase 1 clinical trials. Overall, studies of Candida and candidiasis in the HIV-positive patient while certainly contributing to a more effective control of the microorganism may also provide useful information on HIV-host relationship itself that can assist the fight against the virus.