Phenotypic and genotypic characterization of oral yeasts from Finland and the United States

A total of 4–22 isolates of oral yeasts per subjects from 48 yeast-positive Finnish and American subjects (25 females and 23 males) were phenotyped and genotyped to determine the frequency of simultaneous oral carriage of multiple yeast taxa. An oral sample from either periodontal pockets, oral mucosa or saliva was obtained. All subjects yielded Candida albicans and 3 subjects an additional yeast species ( Candida krusei, Candida glabrata or Saccharomyces cerevisiae ). The API 20C Aux kit distinguished 9 different carbohydrate assimilation profiles among the C. albicans isolates. Thirty-eight of 46 C. albicans biotype I isolates were categorized in a single numerical profile. PCR analysis, using a random primer OPA-03 and a repetitive primer (GACA)₄, detected 2 major genotypic groups among the C. albicans isolates; 44 subjects showing isolates with a "typical" PCR-profile and 4 subjects isolates with an "atypical" PCR-profile. The "atypical" PCR-profile was similar to that of Candida dubliniensis. All C. albicans isolates assimilated xylose, except 5, including the 4 with an "atypical" PCR-profile. No difference was found in distribution of oral yeast species, and of C. albicans phenotypes and genotypes between Finnish and American subjects. The present PCR method may offer a rapid and easy means of distinguishing oral Candida species.     

Oral yeast carriage in patients with advanced cancer

The aim of this study was to investigate oral yeast carriage amongst patients with advanced cancer. Oral rinse samples were obtained from 120 subjects. Yeasts were isolated using Sabouraud's dextrose agar and CHROMagar Candida, and were identified using a combination of the API 20 C AUX yeast identification system, species-specific PCR and 26S rDNA gene sequencing. Oral yeast carriage was present in 66% of subjects. The frequency of isolation of individual species was: Candida albicans, 46%; Candida glabrata, 18%; Candida dubliniensis, 5%; others, < 5%. The increasing isolation of non-Candida albicans species is clinically important, since these species are often more resistant to antifungal drugs. Oral yeast carriage was associated with denture wearing (P = 0.006), and low stimulated whole salivary flow rate (P = 0.009). Identification of these risk factors offers new strategies for the prevention of oral candidosis in this group of patients.     

Oral distribution of Candida species and presence of oral lesions in Brazilian leprosy patients under multidrug therapy

Objective:  The aim of this study was to evaluate the prevalence of Candida spp. and presence of oral lesions in Brazilian leprosy patients under multidrug therapy (MDT).
Methods:  Thirty-eight individuals (18 males and 20 females, median age 53 years) clinically and microbiologically diagnosed as leprosy (lepromatous variant), and under MDT for at least 45 days were studied. The control group constituted by 38 healthy individuals (median age 53.5), matched to the test group in relation to age, gender and oral conditions. Oral rinses were collected and the Candida identification was performed by phenotypic tests. The existence of Candida dubliniensis among the isolates was analyzed using a validated multiplex PCR assay. Twenty-nine leprosy patients were examined intra-orally for the presence of lesions. Data were analyzed by z- and Mann–Whitney tests (α = 5%).
Results:  Yeast carriage rate between leprosy patients (65.8%) and controls (47.4%) was similar ( P  = 0.099), and no significant difference between yeast counts was observed ( P  = 0.1004). Candida albicans was the most frequently isolated species in both groups. In the leprosy group, Candida tropicalis and Candida parapsilosis were also identified. In the control group, we additionally identified Candida tropicalis , Candida glabrata and Candida kefyr. Candida dubliniensis was not detected. No leprosy-related oral lesion was registered.
Conclusion:  Within the limits of the study, we concluded that Brazilian leprosy patients under MDT showed similar levels of carriage and Candida species distribution in relation to the controls.     

Carriage of Candida species in the oral cavity in diabetic patients: relationship to glycaemic control

To study the possible relationship between the quality of glycaemic control in diabetes mellitus and the carriage of Candida species, the Candidal carrier status of 412 diabetic patients was examined using an oral rinse technique and correlated with measurements of random blood glucose and total glycosylated haemoglobin. Candida was isolated in 210 diabetics (51%) with 13 patients (6%) carrying more than one species. The positive isolates were: Candida albicans (89%), Candida krusei (2.8%), Candida glabrata (2.8%), Candida tropicalis (6.2%), Candida stellatoidea (2.8%) and Candida parapsilosis (0.5%). No association was identified between carriage rates and the type of treatment of diabetes, or with the quality of glycaemic control. As in non-diabetic subjects, the carriage rates were higher in diabetic patients wearing dentures. Thus, the oral carriage of Candida in diabetic patients was independent of glycaemic control but in certain sub-groups the carriage rates were higher, and involved uncommon candidal species.     

Carriage of Candida species in the oral cavity in diabetic patients: relationship to glycaemic control

To study the possible relationship between the quality of glycaemic control in diabetes mellitus and the carriage of Candida species, the candidal carrier status of 412 diabetic patients was examined using an oral rinse technique and correlated with measurements of random blood glucose and total glycosylated haemoglobin. Candida was isolated in 210 diabetics (51%) with 13 patients (6%) carrying more than one species. The positive isolates were: Candida albicans (89%), Candida krusei (2.8%), Candida glabrata (2.8%), Candida tropicalis (6.2%), Candida stellatoidea (2.8%) and Candida parapsilosis (0.5%). No association was identified between carriage rates and the type of treatment of diabetes, or with the quality of glycaemic control. As in non-diabetic subjects, the carriage rates were higher in diabetic patients wearing dentures. Thus, the oral carriage of Candida in diabetic patients was independent of glycaemic control but in certain sub-groups the carriage rates were higher, and involved uncommon candidal species.     

Betel quid-associated oral lesions and oral Candida species in a female Cambodian cohort

BACKGROUND: Betel quid chewing (BQC) is still prevalent among elderly Cambodian women and is associated with a wide variety of oral mucosal lesions. BQC has also been associated with a reduced rate of dental caries and changes in the oral microbiological flora. METHODS: Since no studies were available on the impact of BQC on the oral carriage of Candida species, in this study oral swabs (Fungiquick, Hain Diagnostika, Germany) were taken from the tongue and palate of 48 Cambodian women with BQC habit (study group) and 13 control subjects without BQC habit (control group) to determine the spectrum of Candida species in these two groups. In addition, we investigated lesions of the oral mucosa likely to be associated with BQC habit in both study and control groups. RESULTS: The median duration of BQC was 10 years (range 10 months-30 years). The following oral lesions were found in the study group: betel chewer's mucosa (85.4%), oral leukoplakia (8.3%), leukoedema (37.5%) and oral lichen planus (4.2%). Oral candidiasis was seen neither in BQ-chewers nor in controls. Candida spp. were found in 70.8% of the cases (controls 69.2%). Whilst C. albicans was isolated from 27.1% of the study cohort, C. tropicalis was the second most common isolate. One control case was colonised by C. dubliniensis--the first report of this organism from a Cambodian population. There was no significant difference in the candidal carriage rate or the Candida species isolated between the study and the control group. CONCLUSIONS: Mycological findings from the present study do not indicate that BQC has a significant effect on oral colonisation by Candida species.     

化疗患者口腔白假丝酵母菌的分布及基因分组研究

目的研究以白假丝酵母菌（S.albicans）为代表的假丝酵母菌在化疗肿瘤患者口腔中的分布情况,并对检出的白假丝酵母菌进行基因分组。方法从390例接受化疗1年以上的肿瘤患者口腔中取样,采用颊黏膜拭子法,CHROMagar CandidaTM鉴定培养基初步鉴定,根据白假丝酵母菌25S rDNA基因多态性设计引物,根据PCR产物多态性进行基因分组。结果肿瘤患者口腔假丝酵母菌检出率为53.85％（210/390）,白假丝酵母菌的检出率为48.21％（188/390）,其余为光滑假丝酵母菌5.64%（22/390）;白假丝酵母菌基因分组A、B、C组均有检出,其中以B组为主,59.57%（112/188）。结论肿瘤患者口腔的假丝酵母菌以白假丝酵母菌为主,与健康人群的口腔白假丝酵母菌A组占有绝对多数的情况不同,B组白假丝酵母菌在化疗患者口腔中占主导地位。     

Prevalence of Candida species in Turkish children: relationship between dietary intake and carriage

In this study, the prevalence and intensity of Candida species were evaluated in 300 healthy Turkish children aged between 0 and 12 years. The candidal carriage in 26 children who were fed only with breast milk and 38 children who were fed with both breast milk and bottle milk or other fluids was also examined. Oral samples cultured for fungal growth and Candida species were identified using germ tube test, chlamydospore formation test and API 20C AUX system. The results demonstrated that the prevalence of oral candidal carriage in 300 healthy children was 26.3%. Candida albicans was the most frequently isolated yeast (84.8% of the isolates). The other yeasts were identified as Candida parapsilosis, Candida krusei, Candida kefyr, Candida famata, and Candida tropicalis. It was also observed that the frequency of carriage varied as a function of age. The prevalence of carriage in children who were fed with both breast milk and bottle milk or other fluids was 18.5%, while in children fed only with breast milk was 0%. This finding supports previously reported observations that there may be intrinsic differences in oral carriage of Candida species between different ages and populations and type of dietary intake may affect frequency of carriage.     

The in vitro proteolytic and saccharolytic activity of Candida species cultured in human saliva

The proteolytic and saccharolytic activity of 4 Candida species was investigated in batch cultures of pooled, human mixed saliva supplemented with glucose. All the Candida species investigated ( Candida albicans, Candida tropicalis, Candida glabrata and Candida krusei ) demonstrated a marked growth in saliva with a concomitant reduction in pH from about 7.5 to 3.3, within 72 h. Isotachophoretic analysis of the culture supernatant revealed the presence of a variety of acid anions of which pyruvate and acetate were the most abundant. Proteolysis of salivary components, evaluated by a biochemical assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was exhibited by all 4 Candida species, although there was inter-species variation. Despite the similarity in growth rates, C. tropicalis and C. krusei demonstrated greater proteolytic activity than C. albicans and C. glabrata. Neither candidal growth nor proteolysis was observed in glucose-free control saliva samples. In contrast, the degree of saccharolytic and proteolytic activity of a single isolate of C. albicans in glucose-supplemented parotid saliva appeared to be relatively weak compared with mixed saliva. As the oral cavity provides ideal low pH niches periodically supplemented with dietary carbohydrates, the acidic proteinases of Candida species may play a role in the pathogenesis of oral candidiasis.     

Oral Candida infection and colonization in solid organ transplant recipients

Introduction:  Oral Candida carriage and infection have been reported to be associated with a greater risk for systemic infection in transplant recipients; however, a systematic analysis of the oral Candida titers and species has not been previously conducted. The objectives of this study were to determine the prevalence of oropharyngeal candidiasis, the oral carrier status, Candida titers and species in this population.
Methods:  Ninety kidney and heart transplant subjects and 72 age-matched healthy controls were included. Swabs from the oral mucosa and a standardized amount of unstimulated saliva were plated on Chromagar™ Candida , and colony-forming units per millilitre were calculated. Initial speciation was based on colony color and was confirmed by standard germ tube, biotyping, or polymerase chain reaction assays.
Results:  Infection with C. albicans was detected in seven transplant subjects and none of the controls. The transplant group had significantly higher oral Candida titers than the control group. There were no statistically significant relationships between the dose or type of immunosuppressants and oral Candida titers or infection. A significantly higher percentage of transplant subjects were colonized by more than one species, compared with control subjects. The most frequent species combination in transplant subjects was C. albicans and C. glabrata . C. glabrata was isolated from 13.5% of transplant carriers and none of the controls.
Conclusions:  Increased oral Candida infection and carriage titers were found in the transplant population. Although the majority of transplant patients were colonized by C. albicans , C. glabrata appears to emerge as the second most prevalent species.     

In vitro antifungal effect of amine fluoride-stannous fluoride combination on oral Candida species

OBJECTIVE: The combination of amine fluoride and stannous fluoride (AmF/SnF2) was, by chance, found to be antifungal in a clinical trial. This study investigated its effect on pathogenic Candida species with the hypothesis that the antifungal action on different species is variable. MATERIALS AND METHODS: Growth inhibition effect of Meridol mouth rinse which contains 250 ppm AmF/SnF2 was evaluated on 43 reference and clinical strains of Candida albicans, C. dubliniensis, C. glabrata, C. guilliermondii, C. krusei, C. parapsilosis, and C. tropicalis. Meridol base solution without AmF/SnF2 was used as a negative control. RESULTS: Undiluted Meridolmouth rinse killed most study strains within a few minutes. In ascending order, C. parapsilosis, C. tropicalis, C. albicans, C. glabrata, C. krusei and C. dubliniensis showed higher resistance against AmF/SnF2 than C. guilliermondii. CONCLUSION: AmF/SnF2 could be used as a potent adjunct to antifungal therapy for oral yeasts. Although different Candida species demonstrated variable sensitivity the most prevalent oral yeast C. albicans appeared sensitive to the AmF/SnF2 combination.     

In vitro susceptibility of oral Candida to seven antifungal agents

The in vitro susceptibility of 618 Candida isolates to fluconazole, itraconazole, voriconazole, ketoconazole, miconazole, amphotericin B, and nystatin was determined. The isolates were obtained from 559 patients who had attended the UK dental hospital departments in Cardiff, Belfast, Glasgow or London. Antifungal susceptibility was assessed using a broth microdilution method following the National Committee for Clinical Laboratory Standards (NCCLS) M27-A guidelines. The majority of the test strains were C. albicans (n = 521) with few of these being resistant to fluconazole (0.3%). A low incidence of fluconazole resistance (0-6.8%) was similarly evident with all non albicans species (Candida glabrata, 5 of 59 resistant; Candida krusei, 0 of 7 resistant; Candida tropicalis, 0 of 13 resistant; Candida parapsilosis, 0 of 12 resistant; other Candida species, 0 of 6 resistant). Voriconazole, ketoconazole, and miconazole also revealed high activity against both C. albicans and non albicans isolates, and 23.7% of C. glabrata isolates were found to be resistant to itraconazole. There was little difference in the antifungal susceptibilities of Candida isolated from patients who had a history of previous antifungal therapy compared with those who had not received antifungal treatment. In summary, this surveillance study of antifungal susceptibility of oral candidal isolates in the UK, through the collaboration of four dental hospitals, demonstrates that oral Candida species have a high level of susceptibilities to a range of antifungal agents.     

Persistence of oral Candida albicans carriage in healthy Portuguese schoolchildren followed for 3 years

Little is known about carriage of Candida albicans, the predominant pathogenic yeast in oral infection, in children. We cultured buccal mucosal and gingival swabs from 150 Portuguese children to investigate the prevalence of C. albicans at baseline (before dental treatment), post-treatment, and 12, 24, and 36 months post-baseline. The children, aged 8 to 11 years at baseline, had no systemic disease or clinical symptoms of oral candidiasis. At each successive visit, respectively, 47, 32, 21, 27, and 28% of children were C. albicans positive, resulting in an almost 50% reduction in prevalence from baseline to post-treatment (P < 0.0005). Children who carried C. albicans at one visit had 3 to 20 times greater odds of carrying C. albicans at another visit. C. albicans was cultured from 12 children at all time-points and from 10 children at four time-points. Children with oral C. albicans frequently maintained carriage over time, even with regular dental care.     

Evaluation of the recurrence of denture stomatitis and Candida colonization in a small group of patients who received itraconazole

OBJECTIVES: The aim of the study was to determine the recurrence rate of denture stomatitis and persistence of Candida in 22 patients (5 male and 17 female, mean age 71 years) over a 3-year period. STUDY DESIGN: Denture hygiene practice, denture cleanliness, and the presence of palatal erythema were assessed for each patient at the start of the study (baseline). The oral cavity was sampled for yeasts by imprint culture and denture discs. Ten patients received a capsular form of itraconazole (100 mg twice daily for 15 days) and 12 patients were provided with 100 mg of itraconazole in the form of a mouthwash (10 mL twice daily), which was then swallowed. No further antifungal treatment was administered to any of the patients. Clinical and microbiological assessments were repeated for each patient at 6 months and 3 years after the original appointment. Yeasts were identified by colony color on CHROMagar Candida, germ-tube formation, and API-32C profiling. Selected isolates were then typed by inter-repeat polymerase chain reaction (IR PCR). RESULTS: Candida albicans was isolated at baseline from all patients either alone (12 patients) or in combination with another species (10 patients). Other yeast species recovered were C glabrata (5 patients), C tropicalis (1 patient), C guilliermondii (1 patient), C krusei (1 patient), C parapsilosis (1 patient), C kefyr (1 patient), and Saccharomyces cerevisiae (2 patients). Candida albicans and/or C glabrata were recovered from 11 of the 22 patients after 6 months or 3 years. A complete and consistent change of yeast species from baseline was observed in 6 patients after 6 months and at 3 years. The remaining 5 patients were yeast-free at the follow-up assessments. PCR fingerprinting of C albicans and C glabrata indicated strain persistence over 6 months in 10 patients and in 4 patients after 3 years. A switch in strain type occurred for 1 patient after 6 months and for 3 patients after 3 years. CONCLUSIONS: The recurrence of denture stomatitis in patients who maintained a high standard of denture cleanliness was low. Although itraconazole was beneficial in reducing the fungal load, there may be strain persistence or subsequent recolonization of the oral cavity by a broader range of potentially less sensitive yeast species.     

Prevalence of Candida species in necrotic pulp with chronic periapical processes

The aim of this study was to identify species of the genus Candida in mucosa of oral cavity and in single-rooted teeth with pulp necrosis with chronic endodontic periapical processes, with radiographic images 2+/-4 mm and without clinical symptomatology, in immunocompetent patients. The study included 82 immunocompetent patients of both sexes aged 18-70 years with a clinical dental diagnosis of septic pulp necrosis. Samples were taken from root canals with sterile # 25 paper points and from oral mucosa with a sterile swab. Seven different Candida species were identified (C. albicans, C. dubliniensis, C. guilliermondii, C. krusei, C. parapsilopsis, C. tropicalis and C. glabrata). All of them were present in oral mucosa, while two of them (C. parapsilopsis and C. glabrata) were not identified in the periapical zone of necrotic canals. Considering all the samples isolated from oral mucosa, there was a significantly greater frequency of C. albicans than there was in the periapical zone of necrotic canals.     

Implantation of Candida albicans and other Candida species in the oral cavity of rats

The carriage of five Candida species in the mouths of normal and siaioadenectomised rats was determined for periods up to 30 days after inoculation into the oral cavity. In both test and control animals. Candida albicans was the species recovered in greatest quantities at all periods, followed by C. parapsilosis and C. tropicalis. In contrast. C. gullliermondii and C. krusei were isolatable only in small numbers and only from the 1st up to the 5th day; they were not present thereafter. Sialoadenectomy favoured oral colonisation only by C. albicans ( P <0.05) and did not influence the carriage of the other species.     

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.     

Effect of saliva composition on growth of Candida albicans and Torulopsis glabrata

Candida albicans and Torulopsis glabrata are the most prevalent yeasts in humans. The majority harbor C. albicans in the oral cavity, but only a few develop oral candidiasis. We have sought a possible relationship between indigenous salivary constituents, including antimicrobial and nutritive factors, and the growth rate and/or viability of inoculated fungi in glucose-supplemented sterilized saliva. Stimulated whole saliva was collected from 30 healthy donors. Saliva samples were sterilized, supplemented with glucose and inoculated with C. albicans or T. glabrata . After incubation of the inoculates for 20 h, the number of viable cells were counted. All saliva samples were analyzed for different indigenous salivary components and Candida before as well as after sterilization. Besides a 4% reduction in calcium (Ca²⁺) and thiocyanate (SCN⁻) concentrations, sterilization did not affect the concentrations of saliva electrolytes, but the proteins were significantly reduced (19–85%). Indigenous candidal carriage ( n =19) correlated with neither the growth of inoculated fungi nor any of the analyzed components in saliva. The growth of C. albicans and T. glabrata was similar at pH 5 but, at pH 6, C. albicans had a remarkably slower growth rate than T. glabrata . Statistical analysis showed that the 5-h growth of C. albicans at pH 5 was associated with water and electrolyte secretion, whereas the growth after 20 h was associated with variations in protein-glycoprotein content. The growth of T. glabrata was not related to variations in the salivary variables analyzed.     

Susceptibility of oral Candida species to calcium hydroxide in vitro.

AIM: The susceptibility of common oral Candida species to saturated aqueous calcium hydroxide solution was studied. METHODOLOGY: The yeast species tested were C. albicans (16 strains). C. glabrata (three strains), C. guilliermondii (three strains), C. krusei (two strains), and C. tropicalis (two strains). At least one reference strain of each species was used; the others were clinical isolates either from persistent apical periodontitis or from marginal periodontitis. The susceptibility of Enterococcus faecalis (ATCC 29212) was studied for comparative purposes. Standardized inocula of the strains were incubated in aqueous calcium hydroxide solution, pH 12.4, for time-periods ranging from 5 min to 6 h. Volumes of 0.1 mL of the test suspension were cultured directly on Brucella blood agar and incubated in air at 37C. The plates were inspected for growth at 24 and 48 h and the colonies were counted. The time required to reduce the number of colony-forming units to less than 0.1% of the initial number was determined for each strain. RESULTS: The sensitivity of the C. albicans strains was generally low, with 16 h of incubation required to kill 99.9% of the colony-forming units. No differences in susceptibility between C. albicans strains isolated from root-canal infections and from periodontitis were found. Both strains of C. tropicalis were killed between 3 and 6 h of incubation, whilst strains of C. guilliermondii were killed after only 1020 min of incubation. All strains of C. glabrata survived 20 min, but not 1 h, of incubation, whilst 13 h were required to kill C. krusei. Compared with E. faecalis, all Candida spp. showed either equally high or higher resistance to aqueous calcium hydroxide. CONCLUSIONS: This study indicates that Candida spp. are resistant to calcium hydroxide in vitro, which may explain the isolation of yeasts from cases of persistent apical periodontitis.     

Asymptomatic oral Candida albicans carriage in HIV-infection: frequency and predisposing factors

Many studies have focused on the epidemiology and pathogenesis of oral candidiasis in HIV infection. Little is known on the incidence and predisposing factors of asymptomatic oral Candida carriage in this setting, obviously an important issue in view of prophylaxis. To address this question. 261 consecutive HIV-infected individuals without clinical evidence of candidiasis were investigated. C. albicans was isolated from cultured oral cavity swabs of 63 subjects (24%). Colonization was significantly more frequent in IV drug users. CDC groups IV. and in subjects with lymphocytopenia. CD4+ cell depletion, or elevated beta-2 microglobulin. These data further suggest that oral candidiasis occurs in HIV infection as a result of C. albicans overgrowth and raise the question of primary antifungal prophylaxis in subjects with low CD4 counts and asymptomatic oral Candida carriage.