Patterns of Human Oral Yeast Species Distribution on Hainan Island in China

Infections by yeast strains of the genus Candida are among the most prevalent fungal infections of humans. These yeasts are common residents of the oral mucosa and other body surfaces. Since most yeast infections are due to endogenous strains and that species of Candida differ in virulence properties and in intrinsic susceptibilities to antifungal drugs, understanding the human commensal yeast flora can help designing effective treatment and prevention strategies against yeast infections. Here, we report the patterns of yeast species distributions in the oral cavities of 1,799 people from Hainan Island in southern China. Based on sequence information at the fungal barcode locus ITS regions, 368 of the 415 obtained oral yeast strains were identified as belonging to 26 yeast species, while the remaining 47 strains all showed significant sequence divergence to the currently described species. The four most common yeast species were C. albicans (42 %), C. tropicalis (20 %), C. glabrata (5.5 %), and C. parapsilosis (4.1 %) and 10 of the 26 yeast species were represented by only one strain each. Our analyses identified that the gender of hosts and ethnical background showed no contribution to oral yeast species distributions. However, the health status, place of birth, current residency, and the age of hosts all showed significant contributions to the distributions of the four dominant yeast species. We compared our results with those reported previously and discussed the potential mechanisms for the observed differences in oral yeast species distributions.     

Melanization and morphological effects on antifungal susceptibility of Penicillium marneffei

The biosynthesis of melanin has been linked with virulence in diverse pathogenic fungi. Penicillium marneffei, a dimorphic fungus, is capable of melanization in both mycelial and yeast phases, and the pigment may be produced during infection to protect the fungus from the host immune system. To investigate the impact of yeast morphological transformation on antifungal susceptibility, P. marneffei was cultured on various media including minimal medium, 1 % tryptone, brain heart infusion broth, and malt extract broth by using the standardized susceptibility protocol (the M27-A protocol, RPMI medium) for yeasts. We also investigated whether P. marneffei melanization affected its susceptibility to antifungal drugs by adding l-DOPA into culture broths. There were no differences in the minimum inhibitory concentrations of P. marneffei yeast cells previously grown in various culture broths with or without l-DOPA using the M27A protocol (into which no melanin substrate can be added due to a rapid colour change of the RPMI medium to black) for testing amphotericin B, clotrimazole, fluconazole, itraconazole and ketoconazole. However, both melanized and non-melanized P. marneffei displayed increased resistance to antifungal drugs when l-DOPA was added into a selected assay medium, 0.17 % yeast nitrogen base, 2 % glucose, and 1.5 % agar. Hence, active melanin formation appears to protect P. marneffei by enhancing its resistance to antifungal drugs.     

Epidemiology and Antifungal Susceptibilities of Yeasts Causing Vulvovaginitis in a Teaching Hospital

Vulvovaginal candidiasis is one of the most common mycosis. However, the information about antifungal susceptibilities of the yeasts causing this infection is scant. We studied 121 yeasts isolated from 118 patients with vulvovaginal candidiasis. The isolates were identified by phenotypic and molecular methods, including four phenotypic methods described to differentiate Candida albicans from C. dubliniensis. Antifungal susceptibility testing was performed according to CLSI documents M27A3 and M27S4 using the drugs available as treatment option in the hospital. Diabetes, any antibacterial and amoxicillin treatment were statistically linked with vulvovaginal candidiasis, while oral contraceptives were not considered a risk factor. Previous azole-based over-the-counter antifungal treatment was statistically associated with non-C.albicans yeasts infections. The most common isolated yeast species was C. albicans (85.2 %) followed by C. glabrata (5 %), Saccharomyces cerevisiae (3.3 %), and C. dubliniensis (2.5 %). Fluconazole- and itraconazole-reduced susceptibility was observed in ten and in only one C. albicans strains, respectively. All the C. glabrata isolates showed low fluconazole MICs. Clotrimazole showed excellent potency against all but seven isolates (three C. glabrata, two S. cerevisiae, one C. albicans and one Picchia anomala). Any of the strains showed nystatin reduced susceptibility. On the other hand, terbinafine was the less potent drug. Antifungal resistance is still a rare phenomenon supporting the use of azole antifungals as empirical treatment of vulvovaginal candidiasis.     

In Vitro susceptibility of 137 Candida sp. Isolates from HIV positive patients to several antifungal drugs

Oropharyngeal candidiasis caused by various species of Candida is one of the most common infections in HIV seropositive or AIDS patients. Drug resistance among these yeasts is an increasing problem. We studied the frequency of resistance profile to fluconazole, itraconazole, ketoconazole, amphotericin B and terbinafine of 137 isolates of Candida sp. From HIV positive or AIDS patients with oropharyngeal candidiasis at Instituto de Inmunología, U.C.V. and the Hospital “Jose Ignacio Baldó”, Caracas Venezuela, using the well diffusion susceptibility test (Magaldi et al.). We found that nearly 10% of C. albicans isolates were primarily fluconazole resistant, 45% of C. albicans isolates from patients with previous treatment were resistant to fluconazole, of which 93% showed cross-resistance to itraconazole, and even about 30% of C. tropicalis (n = 13) were resistant to fluconazole and/or itraconazole. To this respect, several recent reports have been described antifungal cross-resistance among azoles. Therefore, we consider that C. tropicalis should be added to the growing list of yeast in which antifungal drug resistance is common. This report could be useful for therapeutic aspect in AIDS patients with oral candidiasis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Yeast Oropharyngeal Colonization in Human Immunodeficiency Virus-Infected Patients in Central Taiwan

A prospective, cross-sectional study was conducted at a medical center in central Taiwan to understand the prevalence, associated factors, and microbiologic features for oropharyngeal yeast colonization in human immunodeficiency virus-infected outpatients. Oral yeast colonization was detected in 127 (45 %) patients, including 21 (16.5 %) colonized by more than one species. Of the 154 isolates, Candida albicans was the most common species (114, 74 %), followed by Candida dubliniensis (10, 6.5 %), Candida glabrata (10, 6.5 %), Candida tropicalis (7, 4.5 %), and 13 others. We found that receiving antituberculous drug (p = 0.046) or atazanavir (p = 0.045) was two predictors for patients colonized by non-C. albicans species (p = 0.005) and risking mixed yeast colonization (p = 0.009). Even though our data showed that clinical antifungal drugs remained effective in vitro against the colonizing yeasts, the increased mixed yeast colonization indicates a potential issue for controlling mixed infections in hospital settings.     

Yeasts isolated from nosocomial urinary infections: Antifungal susceptibility and biofilm production

BackgroundUrinary Candida infections in the hospital environment are frequent and need to be better understood.AimsTo compare the results of antifungal susceptibility profiles of yeasts isolated from patients with urinary infections obtained by broth microdilution method (BM) and by disk diffusion (DD), and also evaluate the capacity of these yeasts to form biofilms.MethodsOnly yeasts obtained from pure urine cultures with counts higher than 10⁵ colony-forming units per milliliter, without bacteria development, of symptomatic patients were included. The isolates were identified by classical methods and the antifungal susceptibility tests were performed with the following drugs: amphotericin B, ketoconazole, fluconazole, itraconazole, voriconazole and caspofungin. The biofilm studies were carried out in polystyrene microtitration plates.ResultsNinety-five yeasts isolates were analyzed, including 40 Candida albicans, 31 Candida glabrata, 24 Candida tropicalis. In general, the majority of the isolates were susceptible to the tested drugs but some resistance was observed, especially against fluconazole. Great variability in the antifungal susceptibility results was observed with the different tested drugs and a few discrepancies were observed between both methods. We suggest that in case of DD resistance this result should be confirmed by BM, the standard method. C. tropicalis isolates showed high biofilm production (91.7%) compared to C. albicans (82.5%) and C. glabrata (61.3%), with statistical significance (p = 0.0129).ConclusionsCandiduria in critical patients requires major attention and a better control. The different susceptibility results obtained in this study showed the need to identify yeasts up to the species level, especially in patients with urinary tract infection. The development of techniques of antifungal susceptibility tests can help the clinicians in the empiric treatment of candiduria.     

Antifungal Activity of Sodium Bicarbonate Against Fungal Agents Causing Superficial Infections

Although sodium bicarbonate—NaHCO₃ (SB) has many domestic and medical, traditional and empirical uses, only little scientific documentation of its activity is available. The aims of this study were to investigate the antifungal activity of SB on the three fungal groups (yeasts, dermatophytes and molds) responsible for human skin and nail infections. We first evaluated the in vitro antifungal activity of SB on 70 fungal strains isolated from skin and nail infections: 40 dermatophytes, 18 yeasts and 12 molds. A concentration of 10 g/L SB inhibited the growth of 80 % of all the fungal isolates tested on Sabouraud dextrose agar. The minimal inhibitory concentration 90 (MIC90) of SB measured on Sabouraud dextrose agar, Sabouraud dextrose broth and potato dextrose broth was 5 g/L for the yeasts, 20 g/L for the dermatophytes and 40 g/L for the molds. In a second step, we prospectively evaluated the ex vivo antifungal activity of SB on 24 infected (15 dermatophytes, 7 yeasts and 2 molds) clinical specimens (15 nails and 9 skin scrapings). The fungal growth was completely inhibited for 19 (79 %) specimens and reduced for 4 (17 %) specimens after 7 days of incubation on Sabouraud dextrose–chloramphenicol agar supplemented with 10 g/L of SB as compared to Sabouraud dextrose–chloramphenicol agar without SB. In conclusion, we documented the antifungal activity of SB on the most common agents of cutaneous fungal infection and onychomycosis, and we specified the effective concentrations for the different groups of pathogenic fungi. The mechanism of action of SB has yet to be explored.     

吸毒人群口腔念珠菌的药物敏感性分析

目的了解吸毒人群口腔念珠菌对常用抗真菌药物的敏感性,为临床治疗念珠菌病提供参考资料。方法采用美国CLSI推荐的微量稀释法测定75株念珠菌对4种常用抗真菌药物两性霉素B、5-氟胞嘧啶、氟康唑和酮康唑的药物敏感性。结果 75株吸毒人群口腔念珠菌对两性霉素B、5-氟胞嘧啶、氟康唑和酮康唑的耐药率分别为0%、4%、8%和13.3%(P0.01),对氟康唑和酮康唑的交叉耐药率为8%;非白念珠菌对氟康唑和酮康唑的耐药率高于白念珠菌(P0.05)。结论吸毒人群口腔念珠菌对两性霉素B和5-氟胞嘧啶的敏感性高于对氟康唑和酮康唑的敏感性。吸毒人群口腔念珠菌存在着对氟康唑、酮康唑和5-氟胞嘧啶的天然耐药株和对唑类药物的天然交叉耐药株,且非白念珠菌对氟康唑和酮康唑的耐药率及交叉耐药率高于白念珠菌。     

Assessment of Plant Lectin Antifungal Potential Against Yeasts of Major Importance in Medical Mycology

The search for new compounds with antifungal activity is accelerating due to rising yeast and fungal resistance to commonly prescribed drugs. Among the molecules being investigated, plant lectins can be highlighted. The present work shows the potential of six plant lectins which were tested in vitro against yeasts of medical importance, Candida albicans, Candida tropicalis, Candida parapsilosis, Cryptococcus gattii, Cryptococcus neoformans, Malassezia pachydermatis, Rhodotorula sp. and Trichosporon sp. Broth microdilution susceptibility testing was performed in accordance with standard protocols to evaluate antifungal activity. Minimum inhibitory concentration (MIC) was determined at 80 % yeast growth inhibition, whereas the minimum fungicidal concentration (MFC) was evaluated after making the subcultures of each dilution. Only C. parapsilosis growth was inhibited by the lectins tested. Abelmoschus esculentus lectin showed the highest MIC (0.97 μg ml^?1). Lectins from Canavalia brasiliensis, Mucuna pruriens and Clitoria fairchildiana presented the highest MFC at (3.90 μg ml^?1). These results encourage further studies with wider yeast strain selections, and open new perspectives for the development of pharmacological molecules.     

Susceptibility to antifungal agents of Candida sp. and biofilm formation

In recent years the increase in frequency of fungal infections with Candida sp. was noticed. These infections are connected with ability of Candida sp. to form biofilm on surfaces of biomaterials used in medicine. Furthermore fungal infections make serious therapeutic problems because ofbiofilm resistance to antifungal agents actually. The aim of the study was to evaluate the susceptibility to antifungal agents of Candida sp. and their ability to form biofilm on different biomaterials. 50 strains of Candida sp. isolated from patients of University Hospital No. 1 of dr A. Jurasz in Bydgoszcz were examined. API Candida (bioMérieux) tests were used to identify Candida sp. strains. The susceptibility of the yeast strains to antifungal agents was evaluated by ATB FUNGUS 2 INT (bioMérieux) tests. The susceptibility of examined strains to voriconazole, posaconazole, caspofungin and anidulafungin was assessed by means ofEtests (AB BIODISK) method employing drug concentrations from 0,002 to 32 microg/ml. All analysed strains were susceptible to amphotericin B and caspofungin. Biofilm formation on different biomaterials (silicon, latex, polychloride vinyl, polypropylene, nylon) was measured after 72 hour incubation at 37 degrees C. All examined yeasts formed biofilm on all analysed biomaterials. The highest number of strains formed biofilm on surface of polychloride vinyl: 23 (92,0%) by C. albicans strains and 24 (96,0%) Candida non-albicans strains. The lowest number of the strains formed biofilm on the surface of nylon: 12 (48,0%) of C. albicans strains and 9 (36,0%) of Candida non-albicans strains. The studied strains resistant to azoles and anidulafungin display stronger ability to form biofilm on surfaces of all analysed biomaterials.     

Melanin in the dimorphic fungal pathogen Paracoccidioides brasiliensis: effects on phagocytosis, intracellular resistance and drug susceptibility

The fungal pathogen Paracoccidioides brasiliensis produces a melanin-like pigment in the presence of l-DOPA in vitro. We investigated whether melanization affected yeast uptake by alveolar and peritoneal macrophages, the intracellular resistance of fungal cells and their susceptibility to antifungal drugs. The interactions of melanized and nonmelanized P. brasiliensis with murine primary macrophages and J774.16 and MH-S macrophage-like cell lines were investigated. Melanized yeast cells were poorly phagocytosed by the cells even in the presence of complement. Melanization caused significant interference with the binding of cell wall components to lectin receptors on macrophages. Melanized cells were also more resistant than nonmelanized cells to the antifungal activity of murine macrophages. No difference in the susceptibilities of melanized and nonmelanized P. brasiliensis to antifungal drugs was observed using the minimum inhibitory concentration (MIC) method. However killing assays showed that melanization significantly reduced fungal susceptibility to amphotericin B and also protected against ketoconazole, fluconazole, itraconazole and sulfamethoxazole. The present results indicate that fungal melanin protects P. brasiliensis from phagocytosis and increases its resistance to antifungal drugs.     

Update on the Genus <Emphasis Type="Italic">Trichosporon</Emphasis>

Trichosporon spp. are widely distributed in nature and can occasionally belong to the human microbiota. For many years, the unique species of the genus, Trichosporon beigelli, was only known as an environmental and saprophytic fungus occasionally found as the etiological agent of white piedra. However, case reports of invasive trichosporonosis have been frequently published and the genus is currently considered the second most common agent of yeasts disseminated infections. Based on molecular analysis, the taxon T. beigelli was replaced by several species and the taxonomy of the genus was progressively modified. Despite the reported increase of Trichosporon infections refractory to conventional antifungal drugs, there are only a few studies investigating in vitro susceptibility of Trichosporon spp. to new compounds. Difficulties on different species identification as well as the lack of standardized sensitivity tests in vitro, contribute to the limited information available on epidemiology, diagnosis and therapeutics of trichosporonosis.     

Candida albicans and Non-C. albicans Candida Species: Comparison of Biofilm Production and Metabolic Activity in Biofilms, and Putative Virulence Properties of Isolates from Hospital Environments and Infections

Candida albicans and, more recently, non-C. albicans Candida spp. are considered the most frequent fungi in hospitals. This study analyzed Candida spp. isolates and compared the frequency of different species, that is, C. albicans and non-C. albicans Candida spp., and the origins of isolates, that is, from hospital environments or infections. Yeast virulence factors were evaluated based on biofilm production and metabolic activity. Hemolysin production and the antifungal susceptibility profiles of isolates were also evaluated. Candida spp. were highly prevalent in samples collected from hospital environments, which may provide a reservoir for continuous infections with these yeasts. There were no differences in the biofilm productivity levels and metabolic activities of the environmental and clinical isolates, although the metabolic activities of non-C. albicans Candida spp. biofilms were greater than those of the C. albicans biofilms (p < 0.05). Clinical samples had higher hemolysin production (p < 0.05) and lower susceptibility to fluconazole (p < 0.05). Non-C. albicans Candida spp. predominated in samples collected from hospital environments and infections (p < 0.05). These species had a lower susceptibility to fluconazole and amphotericin B, and their biofilms had higher metabolic activities than those produced by C. albicans, which may explain the increased incidence of fungal infections with these yeasts during recent years.     

抗真菌药物增效剂的研究进展

近年来,真菌耐药发生率呈逐年上升趋势,真菌对氟康唑等氮唑类药物的耐药性最为严重,成为临床抗真菌治疗失败的原因之一.对于耐药真菌的治疗,往往采用加大剂量或联合用药的方法.此外,文献报道了一些植物提取物、小分子化合物能显著增强抗真菌药物对耐药真菌的敏感性,两个药物的协同作用有望成为治疗耐药真菌的新策略.该文结合近几年的研究报道,简要综述了抗真菌药物增效剂的研究进展.     

Eighteen new oleaginous yeast species

Of 1600 known species of yeasts, about 70 are known to be oleaginous, defined as being able to accumulate over 20 % intracellular lipids. These yeasts have value for fundamental and applied research. A survey of yeasts from the Phaff Yeast Culture Collection, University of California Davis was performed to identify additional oleaginous species within the Basidiomycota phylum. Fifty-nine strains belonging to 34 species were grown in lipid inducing media, and total cell mass, lipid yield and triacylglycerol profiles were determined. Thirty-two species accumulated at least 20 % lipid and 25 species accumulated over 40 % lipid by dry weight. Eighteen of these species were not previously reported to be oleaginous. Triacylglycerol profiles were suitable for biodiesel production. These results greatly expand the number of known oleaginous yeast species, and reveal the wealth of natural diversity of triacylglycerol profiles within wild-type oleaginous Basidiomycetes.     

Identificación presuntiva de Candida spp. y de otras levaduras de importancia clínica: utilidad de Brilliance Candida Agar

Fungal infections caused by yeasts have increased during the last decades and invasive forms represent a serious problem for human health. Candida albicans is the species most frequently isolated from clinical samples. However, other emerging yeast pathogens are increasingly responsible for mycotic infections, and some of them are resistant to some antifungal drugs. Consequently, it is necessary to have methods that can provide a rapid presumptive identification at species level.Numerous chromogenic agar media have been shown to be of value as diagnostic tools. We have compared a chromogenic medium, Brilliance Candida Agar, with CHROMagar Candida, the chromogenic medium most used in our country. A multicentre study was conducted in 16 Hospitals belonging to the Mycology Net of Buenos Aires City Government. A total of 240 yeast isolates were included in this research.The new chromogenic agar showed results very similar to those obtained with CHROMagar Candida.     

院内150例真菌感染及其耐药性分析

目的研究院内真菌感染的特点及耐药状况。方法对临床标本分离的真菌,用TAB Expression鉴定仪鉴定,E—test抗真菌药敏试纸条进行药敏试验。结果150株真菌共有14个种,以白色念珠菌为主．占45．3％。各种真菌对6种抗真菌药物均有不同程度的耐药。结论院内真菌感染呈上升趋势,并且产生一定的耐药株。     

Drug-induced apoptosis in yeast

In order to alter the impact of diseases on human society, drug development has been one of the most invested research fields. Nowadays, cancer and infectious diseases are leading targets for the design of effective drugs, in which the primary mechanism of action relies on the modulation of programmed cell death (PCD). Due to the high degree of conservation of basic cellular processes between yeast and higher eukaryotes, and to the existence of an ancestral PCD machinery in yeast, yeasts are an attractive tool for the study of affected pathways that give insights into the mode of action of both antitumour and antifungal drugs. Therefore, we covered some of the leading reports on drug-induced apoptosis in yeast, revealing that in common with mammalian cells, antitumour drugs induce apoptosis through reactive oxygen species (ROS) generation and altered mitochondrial functions. The evidence presented suggests that yeasts may be a powerful model for the screening/development of PCD-directed drugs, overcoming the problem of cellular specificity in the design of antitumour drugs, but also enabling the design of efficient antifungal drugs, targeted to fungal-specific apoptotic regulators that do not have major consequences for human cells.     

Candidemia by Species of the Candida parapsilosis Complex in Children’s Hospital: Prevalence, Biofilm Production and Antifungal Susceptibility

Opportunistic infections are an increasingly common problem in hospitals, and the yeast Candida parapsilosis has emerged as an important nosocomial pathogen. The aims of this study were to determine and compare (i) the prevalence rate among C. parapsilosis complex organisms isolated from blood in a public children’s hospital in São Paulo state, (ii) the ability of the complex C. parapsilosis species identified to produce biofilm and (iii) the antifungal susceptibility profiles. Forty-nine (49) specimens of isolated blood yeast were analyzed, previously identified as C. parapsilosis by conventional methods. After the molecular analysis, the isolates were characterized as C. parapsilosis sensu stricto (83.7 %), C. orthopsilosis (10.2 %) and C. metapsilosis (6.1 %). All species were able to form biofilm. The species with the highest biofilm production was C. parapsilosis sensu stricto, followed by C. orthopsilosis and further by C. metapsilosis. All of the strains have demonstrated similar susceptibility to fluconazole, caspofungin, voriconazole, cetoconazole and 5-flucytosine. Only one strain of C. parapsilosis was resistant to amphotericin B. Regarding itraconazole, 66.6 and 43.9 % isolates of C. metapsilosis and C. parapsilosis, respectively, have demonstrated to be susceptible dose-dependent, with one isolate of the latter species resistant to the drug. Candida parapsilosis sensu stricto has demonstrated to be the less susceptible, mainly to amphotericin B, caspofungin and “azoles” such as fluconazole. Therefore, C. metapsilosis and C. orthopsilosis are still involved in a restricted number of infections, but these data have become essential for there are very few studies of these species in Latin America.