Identification of Candida dubliniensis among oral yeast isolates from an Italian population of human immunodeficiency virus‐infected (HIV+) subjects

Candida dubliniensis, an emerging oral pathogen, phenotypically resembles Candida albicans so closely that it is easily misidentified as such. The aim of the present study was to evaluate the usefulness of two phenotypic methods, growth at 45°C and 2,3,5‐triphenyltetrazolium chloride (TTC) reduction, for confirming presumptive identification of C. dubliniensis and C. albicans by colony color on CHROMagar Candida (CAC) medium. A combination of these methods was used to establish the prevalence of oral C. dubliniensis in an Italian population of 45 human immunodeficiency virus (HIV)‐infected subjects. Twenty‐two samples (48.9%) were positive for yeasts on CAC medium producing a total of 37 fungal isolates. The colony color and 45°C growth ability test correctly identified all C. dubliniensis and C. albicans isolates (5/37, 13.5%, and 16/37, 43.2%, respectively), while assessment of TTC reduction misidentified one C. albicans isolate. The isolation rate of C. dubliniensis was 11.1% (5/45 patients). All of the C. dubliniensis isolates were highly susceptible to fluconazole (MIC = 0.5 µg/ml). The combination of CAC medium screening with growth at 45°C and TTC reduction tests may represent a simple, reliable and inexpensive identification protocol for C. dubliniensis.     

Inhibition of Candida albicans by the peroxidase/SCN−/H2O2 system

Effects of the salivary peroxidase (SPO) system on the growth, glucose uptake and metabolic activities of oral bacteria are well documented but the effects on oral fungi are virtually unknown. Therefore, the viability of Candida albicans (ATCC 28366) exposed to the peroxidase/SCN^?/H₂O₂: system was studied in sterilized saliva, in phosphate-buffered saline (PBS) and in potassium chloride. The growth of C. albicans in glucose-supplemented saliva was faster at pH 5.5 than at pH 7. The addition of the complete SPO (or lactoperoxidase) system to either sterilized saliva, KC1 (50 μM) or PBS at pH 5.5 inhibited dose-dependently the viability of C. albicans in KC1, but no inhibition was found in PBS or saliva. Maximal inhibition was achieved in 2 h and with > 320 μM of peroxidase-generated HOSCN/OSCN^?. However, physiological salivary concentrations of phosphate (> 1.0 μM) and PBS blocked the antifungal effect of HOSCN/OSCN^?. The relative proportions of SCN^? and H₂O₂: were critical to the antifungal effects. With 0.2 mM KSCN, a complete loss of viability was achieved, though the HOSCN/OSCN^? concentrations did not exceed 100 μM. It is concluded that C. albicans is sensitive to HOSCN/OSCN^? but salivary concentrations of phosphate block the antifungal effect of the peroxidase systems.     

Analysis of the strain relatedness of oral Candida albicans in patients with diabetes mellitus using polymerase chain reaction‐fingerprinting

To increase our understanding of Candida pathogenicity, the identification of those strains most frequently associated with infections is of paramount importance. Polymerase chain reaction (PCR)‐based methods are extremely effective in differentiating and determining reproducibility, they require minimum starting material and are rapid and simple to perform. In this study, the genetic relatedness of Candida albicans was assessed for two geographically different patient groups (London, UK and Parma, Italy) affected by diabetes mellitus. C. albicans samples from the oral cavities of non‐diabetic healthy subjects were also examined by PCR fingerprinting to evaluate the possible genetic differences among endogenous strains in individuals with and without diabetes mellitus. PCR fingerprinting, with subsequent phylogenetic analysis of C. albicans isolates from the diabetic patients from London and Italy and from the non‐diabetic subjects, revealed that there were significant differences (P < 0.0001) between C. albicans isolates indicative of the distinct ecological niches that occur in the oral cavities of these patient cohorts. The most diverse group comprised the isolates from the diabetic patients in the UK, possibly reflecting the antifungal treatment that these patients had received. Further studies that include isolates from patient cohorts with systemic diseases other than diabetes mellitus, and from more diverse geographic localities are required to explain the relatedness of C. albicans isolates in the mouth.     

Oral Candida isolates in patients undergoing radiotherapy for head and neck cancer: prevalence, azole susceptibility profiles and response to antifungal treatment

Oral pseudomembranous candidiasis and mucositis were assessed in 39 patients receiving a total dose of 39-70 Gy radiotherapy for head and neck cancer. Mucositis was scored using the Radiation Therapy Oncology Group criteria, and oral candidiasis was diagnosed on the basis of clinical evaluation and quantitative laboratory findings. Radiation-induced mucositis was observed in 9/39 patients. Only 3/39 patients discontinued radiotherapy due to acute severe mucosal effects. Candidiasis (colony-forming units 35 to > or = 60/lesion) associated with mucositis was diagnosed in 30/39 patients: the most frequent aetiology of the infection was Candida albicans (n = 23), followed by Candida glabrata (n = 3), Candida krusei (n = 2), Candida tropicalis (n = 1) and Candida kefyr (n = 1). Patients with confirmed oral pseudomembranous candidiasis were treated with either fluconazole 200 mg/day or itraconazole 200 mg/day for 2 weeks. Clinical improvement and concomitant negative Candida cultures (mycologic cure) were the criteria determining a response to antifungal treatment. Etest revealed very low voriconazole MICs (0.004-0.125 microg/ml) for all isolates, and fluconazole resistance for eight C. albicans strains (MIC > 64 microg/ml) and for the C. krusei isolates (MIC > 32 microg/ml). The same strains showed itraconazole susceptibility dose dependence (MIC 0.5 microg/ml). Despite the itraconazole susceptible dose dependent MIC readings, all patients with oral pseudomembranous candidiasis caused by these strains responded to antifungal treatment with 200 mg/day itraconazole. Oral mycologic surveillance of patients undergoing radiotherapy for head and neck malignancies and susceptibility testing of isolates may be indicated in cases with mucositis-associated confirmed oral pseudomembranous candidiasis to ensure prompt administration of targeted antifungal treatment. On the basis of the low MIC values found, clinical evaluation of voriconazole is indicated for management of oral pseudomembranous candidiasis refractory to other azoles.     

Distribution and hydrolytic enzyme characteristics of Candida albicans strains isolated from diabetic patients and their non‐diabetic consorts

Introduction: The aim of this study was to investigate the oral colonization profile of Candida albicans strains isolated from diabetic patients and their non‐diabetic consorts. In addition hydrolytic enzyme activity of these isolates was analysed. Methods: The genetic diversity of C. albicans oral isolates from 52 couples was established using isoenzyme marker and cluster analysis. Hydrolytic enzyme characteristics, namely secreted aspartyl proteinases (SAPs) and phospholipases (PLs) were also analysed. Results: Simultaneous colonization by C. albicans was observed in the consorts of 12 couples (23.1%). Patterns of monoclonal and polyclonal oral colonization by C. albicans strains were identified and the coexistence of identical or highly related strains was observed in both members of eight couples. The genetic diversity observed in the total yeast population revealed four large, genetically distinct groups (A to D) and the coexistence of strains in couples or consorts conjugally unrelated. SAP and PL activity was observed in the majority of C. albicans isolates without any association to particular strain, strain clusters (highly related isolates), or clinical characteristics of the consorts (diabetic, non‐diabetic, and gender). Conclusion: Possible sources of transmission and oral propagation of groups (clusters) of strains of C. albicans can occur between diabetic and non‐diabetic consorts. A conjugal genotypic identity exists in most C. albicans‐positive couples, that is, both consorts share identical or highly related strains; however, this identity is not couple‐specific as seen by the coexistence of clusters in couples and unrelated consorts.     

Ceragenin CSA‐13 exhibits antimicrobial activity against cariogenic and periodontopathic bacteria

Introduction: Ceragenin CSA‐13 is a bile‐acid‐based mimic of endogenous antimicrobial peptides and shares a mechanism of action with many of these antimicrobial agents. Because CSA‐13 is not peptide based, it is not a substrate for the proteases that are found in the oral cavity, which are capable of degrading antimicrobial peptides. Furthermore, the simplicity of the ceragenins makes them easier to prepare and purify than antimicrobial peptides. In this study, we examined the antimicrobial activities of CSA‐13 against oral pathogens and found that this compound was bactericidal against all of the strains tested. Methods: The strains used were isolates of Streptococcus mutans and Porphyromonas species. Minimum inhibitory concentrations (MIC) were determined using agar dilution methods. In susceptibility testing, viable counts were determined after incubation with CSA‐13. Results: CSA‐13 was potent against all 23 strains tested with MICs of 1–8 μg/ml for S. mutans and 1–16 μg/ml for 24 strains of the genus Porphyromonas. The MIC₅₀ was 2 and the MIC₉₀ was 8 μg/ml for S. mutans. MIC ranges for protease‐positive P. gingivalis and P. cangingivaliswere 2–16 μg/ml, and 1–2 μg/ml for protease‐negative P. circumdentaria. CSA‐13 interacted with lipopolysaccharide‐sensitized erythrocytes at a concentration of 5.0–20.0 μg/ml. Conclusion: CSA‐13 displays broad‐spectrum activity against cariogenic and periodontopathic bacteria. CSA‐13 was effective against protease‐positive Porphyromonas. It was shown to bind to erythrocytes coated with lipopolysaccharide and lipoteichoic acid from diverse bacterial strains. These results suggest that CSA‐13 may be useful for the prevention and treatment of oral microbial diseases.     

Correction to: Synergistic effect of thymoquinone and nystatin in the treatment of oral candidiasis; an in vitro study

The effectiveness of antifungal agents may be insufficient against resistant strains in some cases of oral candidiasis. The aim of this study was to evaluate the antifungal effect of thymoquinone against Candida albicans, Candida tropicalis, Candida glabrata and Candida krusei strains and the synergistic antifungal activity of these strains in combination with nystatin. To evaluate in vitro antifungal activity and interactions between thymoquinone and nystatin, substances were tested against Candida albicans ATCC 10,231, C. tropicalis ATCC 750, C.krusei ATCC 6258 and C. glabrata ATCC 2001 standard strains both individually and combinationally via microdilution method. MIC and ΣFIC index value were analysed. The Kruskal Wallis test and Bonferroni test were used for statistical evaluations. Statistical significance was set at p < 0.05. A statistically significant difference was observed between the mean ranks of all Candida species and doses of thymoquinone, nystatin, and the combination thymoquinone-nystatin (p < 0.05). MIC values for thymoquinone were determined as 15 μg/mL for C. albicans, C. tropicalis and C. krusei while it was 30 μg/mL for C. glabrata. Moreover, MIC for nystatin was found as 1.875 μg/mL for C. albicans, C. tropicalis and C. krusei, whereas it was 7.5 μg/mL in C. glabrata. Interaction assays and ΣFIC index value revealed that, TQ and nystatin have a synergistic effect against to all strains. Thymoquinone was found to have antifungal activity on Candida species and synergistic effect when combined with nystatin.

     

Clonal identity of Candida albicans in the oral cavity and the gastrointestinal tract of pre‐school children

The clonal relationship between oral and fecal Candida albicans isolated from children of pre‐school age was examined using RAPD analysis. Significantly higher levels of C. albicans were found in saliva, dental plaque, carious specimens and stools of 56 patients with severe caries as compared to 52 healthy control subjects. The highest prevalence was found in carious specimens and a strong correlation was observed between its presence in saliva, dental plaque, carious specimen and feces. RAPD analysis of isolates from 23 patients with simultaneous oral and fecal C. albicans revealed clonal counterparts present in both oral and stool samples in 15 cases; five patients harbored closely related strains; and three patients harbored unrelated strains. Our results demonstrate a strong correlation between oral and gastrointestinal C. albicans colonization. We assume that carious teeth may constitute an ecologic niche for C. albicans potentially responsible for recurrent oral and non‐oral candidiasis.     

Diversity,frequency and antifungal resistance of Candida species in patients with type 2 diabetes mellitus

Objective: To determine number, species of Candida and Candida resistance to antifungal therapy according to the metabolic control state and the associated salivary changes in patients with type 2 diabetes mellitus (DM2).

Materials and methods: Samples of non-stimulated saliva were collected from 52 patients with DM2. Salivary pH was measured and cultured on Sabouraud glucose agar and the values of CFU/ml were calculated. The species were presumptively identified using CHROMagar Candida^® plates, and identification was confirmed by polymerase chain reaction (PCR). C. albicans isolates were cultured on SGA tetracycline agar with nystatin and fluconazole diffusion disks to measure susceptibility.

Results: Sixty six percent of the yeasts isolated were Candida albicans, followed by C. glabrata (20.7%). In patients with decompensated DM2, there was an inverse association between HbA1c value and salivary pH. At higher levels of salivary acidification, a greater diversity and quantity of yeasts of the genus Candida were observed. With nystatin, higher inhibition was observed at lower pH.

Conclusions: The antifungal therapies could be more effective if it consider, qualitative salivary characteristics as pH, that could determine the susceptibility of species of Candida to at least to nystatin, which is the most used antifungal for treatment to oral candidiasis in patients with DM2.     

Prevalence and antifungal resistance profile of Candida spp. oral isolates from patients with type 1 and 2 diabetes mellitus

Objective

The goal of the study was to measure the prevalence of Candida spp. in the oral cavity of patients with diabetes types 1 and 2 when compared to healthy individuals and to study antifungal resistance profile of the isolates.

Design

There were 162 subjects in the study: diabetes type 1 (n = 39); control group 1 (n = 50): healthy individuals matched in gender, age, and oral conditions to diabetes type 1 patients; diabetes type 2 (n = 37); control group 2 (n = 36) who were matched to each patient of the diabetes type 2 group. Stimulated saliva was collected and isolates were identified with phenotypic tests. The presence of C. dubliniensis was determined by multiplex PCR.

Results

There were no statistically significant differences in Candida spp. frequency between the diabetes 1 group and its control (p = 0.443) nor between the diabetes 2 group and its control (p = 0.429). C. albicans was the most frequently isolated yeast in all groups. In the diabetes groups, C. stellatoidea, C. parapsilosis, C. tropicalis, C. lipolytica, C. glabrata, and C. krusei were also identified. Additionally, in control groups, C. kefyr was also detected. None of the isolates were resistant to amphotericin B and flucytosine. A low percentage of the isolates were resistant to ketoconazole.

Conclusions

No differences were detected in colonization of Candida spp. oral isolates from type 1 and type 2 diabetes when compared to matched controls. The antifungal resistance of Candida spp. isolates for ketoconazole from type 1 diabetes patients was significantly higher than that of its matched control.     

Heterogeneity in antifungal susceptibility of clones of Candida albicans isolated on single and sequential visits from a HIV-infected southern Chinese cohort

The increased frequency and severity of candidal infections in human immunodeficiency virus (HIV)-infected individuals has prompted the wide use of antifungals, such as amphotericin B, ketoconazole, and fluconazole, resulting in the emergence of drug-resistant strains of Candida albicans. To study this phenomenon in an ethnic Chinese cohort, we isolated multiple colonies of Candida from the oral cavities of 16 HIV-infected patients on single and subsequent sequential visits over a period of 12 months. Ten of the 16 patients had sporadic episodes of oropharyngeal candidiasis (Group A), while the remainder were asymptomatic with respect to this condition (Group B). Oral rinses were collected and immediately processed in the laboratory for the isolation of C. albicans in a standard manner. A total of 433 C. albicans isolates were tested for their susceptibility to amphotericin B, ketoconazole and fluconazole by an agar diffusion method using the commercially available E-test. All tested isolates demonstrated variable susceptibility to amphotericin B, ketoconazole and fluconazole. The minimum inhibitory concentration (MIC) of the isolates for amphotericin B, ketoconazole and fluconazole ranged from <0.002-1.5 microg/ml, <0.002-4.0 microg/ml and <0.016-32 microg/ml, respectively. Sequential isolates of a few patients demonstrated variable susceptibility to all the antifungals, and no discernible MIC pattern emerged either in group A or B over time. Interestingly, significant variation in antifungal susceptibility was also noted in isolates obtained from the same patient on a single visit. Sequential yeast isolates in 9 of 16 patients (56%) demonstrated significant differences in MIC within and between visits for both amphotericin B and ketoconazole, while a lower percentage--44%(7/16)--exhibited this trait for fluconazole. Our study demonstrates the diversity in antifungal susceptibility in either commensal or "infective" oral strains of C. albicans in HIV disease, and shows the need for vigilance for the emergence of resistant strains, and for frequent antifungal susceptibility studies.     

Oral candidosis in relation to oral immunity

Symptomatic oral infection with Candida albicans is characterized by invasion of the oral epithelium by virulent hyphae that cause tissue damage releasing the inflammatory mediators that initiate and sustain local inflammation. Candida albicans triggers pattern‐recognition receptors of keratinocytes, macrophages, monocytes and dendritic cells, stimulating the production of IL‐1β, IL‐6 and IL‐23. These cytokines induce the differentiation of Th17 cells and the generation of IL‐17‐ and/or IL‐22‐mediated antifungal protective immuno‐inflammatory responses in infected mucosa. Some immune cells including NKT cells, γδ T cells and lymphoid cells that are innate to the oral mucosa have the capacity to produce large quantities of IL‐17 in response to C. albicans, sufficient to mediate effective protective immunity against C. albicans. On the other hand, molecular structures of commensal C. albicans blastoconidia, although detected by pattern‐recognition receptors, are avirulent, do not invade the oral epithelium, do not elicit inflammatory responses in a healthy host, but induce regulatory immune responses that maintain tissue tolerance to the commensal fungi. The type, specificity and sensitivity of the protective immune response towards C. albicans is determined by the outcome of the integrated interactions between the intracellular signalling pathways of specific combinations of activated pattern‐recognition receptors (TLR2, TLR4, Dectin‐1 and Dectin‐2). IL‐17‐mediated protective immune response is essential for oral mucosal immunity to C. albicans infection.     

Impact of brief exposure to antifungal agents on the post-antifungal effect and hemolysin activity of oral Candida albicans

Post-antifungal effect (PAFE) of Candida and its production of hemolysin are determinants of candidal pathogenicity. Candida albicans is the foremost aetiological agent of oral candidosis, which can be treated with polyene, azole, and echinocandin antifungals. However, once administered, the intraoral concentrations of these drugs tend to be subtherapeutic and transient due to the diluent effect of saliva and cleansing effect of the oral musculature. Hence, intra-orally, Candida may undergo a brief exposure to antifungal drugs.

Objective

Therefore, the PAFE and hemolysin production of oral C. albicans isolates following brief exposure to sublethal concentrations of the foregoing antifungals were evaluated.

Material and Methods

A total of 50 C. albicans oral isolates obtained from smokers, diabetics, asthmatics using steroid inhalers, partial denture wearers and healthy individuals were exposed to sublethal concentrations of nystatin, amphotericin B, caspofungin, ketoconazole and fluconazole for 60 min. Thereafter, the drugs were removed and the PAFE and hemolysin production were determined by previously described turbidometric and plate assays, respectively.

Results

Nystatin, amphotericin B, caspofungin and ketoconazole induced mean PAFE (hours) of 2.2, 2.18, 2.2 and 0.62, respectively. Fluconazole failed to produce a PAFE. Hemolysin production of these isolates was suppressed with a percentage reduction of 12.27, 13.47, 13.33, 8.53 and 4.93 following exposure to nystatin, amphotericin B, caspofungin, ketoconazole and fluconazole, respectively.

Conclusions

Brief exposure to sublethal concentrations of antifungal drugs appears to exert an antifungal effect by interfering with the growth as well as hemolysin production of C. albicans.     

Correlation between enzyme production,germ tube formation and susceptibility to fluconazole in Candida species isolated from patients with denture‐related stomatitis and control individuals

Introduction: Phospholipase and proteinase secretion in yeasts of the genus Candida has been described as a relevant virulence factor. Also, germ tube formation by Candida albicans is associated with its invasive capacity and is considered an important pathogenic mechanism. Methods: To link the production of hydrolytic enzymes with the capacity to produce infection, 232 clinical isolates of yeasts from the oral cavity of 140 individuals wearing removable maxillary protheses were studied. The sample was composed of 70 patients with denture‐related stomatitis (DRS) and 70 individuals with normal palatal mucosa. For strains identified as C. albicans, the correlation between germ tube formation and their capacity to cause infection was studied and the presence of Candida dubliniensis was investigated. Susceptibility to fluconazole was evaluated. Results: Candida albicans was the only species producing phospholipase and germ tube. We observed a higher level of production of phospholipase in cases of infection compared with commensals. Significant differences between the two groups of C. albicans isolates were observed as to germ tube production. Only, Candida glabrata showed lower susceptibility to fluconazole. Conclusion: The results reinforced the idea that C. albicans is the most frequent and can be the most pathogenic yeast in oral candidosis. However, the strains isolated from DRS patients and healthy individuals showed the same virulence factors. It seems that several virulence attributes are involved in the infective process but no single factor contributes to Candida virulence. Candida dubliniensis was absent in the oral cavity of individuals with and without DRS.     

Use of antifungal agents for oral candidiasis: results of a national survey

Abstract: Background: Candida albicans is an opportunistic agent that colonizes the oral mucosa. Objectives: To determine the attitude of Spanish dentists toward the oral treatment of candidiasis. Method: Between May and November 2006, a questionnaire was circulated to a random selection of 1134 dentists obtained from the General Dental Council’s main list. The survey consisted of a block of socio‐demographic items followed by another block related to the diagnosis and treatment of oral candidiasis. Replies to the questionnaire were received from 840 (74%) dentists. Results: 50.4% of respondents were men, and 48.1% were female with a mean age of 38 and 12.2 years of professional experience. Miconazole was the most popular choice of antifungal agent prescribed (59.3%), followed by nystatin (57.7%) for topical use. Systemic antifungal agents were used by 30.20% of dentists, with a strong association between their use and the number of years in practice, gender and professional qualifications (P < 0.005). Conclusion: Most Spanish dentists make clinical diagnosis and treat oral infections by C. albicans themselves with topical drugs (miconazole and nystatin) as a first choice. Systemic treatments are more commonly chosen by male dentists with long professional experience, especially by stomatologists.     

Genetic diversity and exoenzyme activities of Candida albicans and Candida dubliniensis isolated from the oral cavity of Brazilian periodontal patients

Objective

Mucosal surfaces are the primary oral reservoirs of Candida species, but these species can also be found in subgingival biofilm. The present study investigated the genetic diversity and production of exoenzymes of C. albicans and C. dubliniensis isolated from the oral cavity of systemically healthy patients with periodontitis.

Design

Fifty-three patients were analysed. Samples were collected from three oral cavity sites (periodontal pocket, gingival sulci and oral mucosa), plated and, after isolation, suspect strains of C. albicans and C. dubliniensis were identified by PCR. The genetic diversity of the isolates was evaluated by RAPD and the activities of the secreted aspartyl proteinases and phospholipases were evaluated by the agar plate method.

Results

Twenty-one patients showed positive results for Candida spp. There were no statistically significant differences between genders, or between sites. C. albicans was the most frequently found specie, while C. dubliniensis was isolated from the periodontal pocket of only one patient. Sixteen genotypes were detected among the C. albicans isolates, and one among the C. dubliniensis isolates. The similarity coefficient (S_SM) values among the C. albicans genotypes ranged from 0.684 to 1.0 with an average of 0.905 ± 0.074. All isolates produced high levels of Saps and most of them produced high levels of phospholipases. No relationship was found between the genotypes and the pattern of enzymatic production. There was no association between specific genotypes and their site of isolation.

Conclusions

The results of the present study suggest that genetically homogeneous strains of C. albicans are present in the oral cavity of patients with periodontitis and that these strains are capable of producing high levels of exoenzyme.     

Stable azole drug resistance associated with a substrain of Candida albicans from an HIV-infected patient

Oral candidiasis is one of the earliest and most frequent complications of a failing immune system in HIV-infected individuals. For several years, oral candidiasis has been treated effectively with azole drugs, the one most frequently used is fluconazole. Unfortunately, extensive use of the drug for treatment and prophylaxis has led to treatment failure in an increasing number of patients. In most of these cases, strains of C. albicans isolated from the infection are less susceptible to fluconazole. The development of azole resistance in strains of C. albicans has been studied biochemically and more recently with molecular techniques. One excellent example of the development of azole resistance in C. albicans has been documented in a series of 17 C. albicans isolates from a single patient over a 2-year period. During this time, the patient experienced 14 episodes of oral candidiasis and was treated with increasing doses of fluconazole. Molecular and biochemical analyses confirms that the isolates are the same strain of C. albicans and that the resistance in these isolates is stable over 600 generations, suggesting that the changes in this strain are genetic in nature. In addition, the development of resistance is correlated with the identification of a substrain or variant of the original strain, as identified by restriction fragment length polymorphism (RFLP) analysis with the moderately repetitive probe, Ca3. The analysis of this series of isolates demonstrates that azole drug resistance is associated with several small genetic changes, each of which contributes to the overall resistance of the strain. Clearly, continual use of azole drugs by a patient can select for genetic changes that render oral candidiasis refractory to treatment.     

致病性口腔白色念珠菌耐药株和药物敏感株的ITS基因型比较

目的:探讨致病性口腔念珠菌ITS1-ITS2区域进化中变异的序列是否与接受放化疗相关,是否与菌株对抗真菌药物的敏感性相关.方法:收集两组(头颈部肿瘤放化疗患者合并念珠菌感染组和单纯口腔念珠菌感染组)临床菌株,依据NCCLS的M27-A2标准方案测定两组菌株对四种抗真菌药物的最低抑菌浓度;提取菌株的DNA,PCR扩增ITS1-ITS2区域,比较两组ITS1-ITS2序列的差异并比较药物敏感株和耐药株该区域核苷酸碱基序列的差异.结果:全部菌株对5-氟胞嘧啶敏感,92.1%对两性霉素B敏感,放化疗组和单纯白念感染组对氟康唑的耐药比例分别为26.7%和8.7%,对伊曲康唑的耐药比例分别为40%和13%;菌株ITS1-ITS2序列的差异与分组和药物敏感性无明显相关.结论:致病性口腔念珠菌ITS1-ITS2区域进化中变异的序列与是否接受放化疗无明显相关,与菌株对抗真菌药物的敏感性无明显相关.     

Effect of chitosan nanoparticles on the inhibition of Candida spp. biofilm on denture base surface

ObjectivesChitosan nanoparticles (ChNPs) have antifungal effects, however there is a lack of information about the effects of ChNPs against Candida biofilm on denture base surface. This study investigated the ChNPs effect against C. albicans biofilm adhesion and formation, and against Candida spp. biofilm on heat-cured acrylic resin.DesignThe ChNPs were synthetized (3800 μg/mL) and characterized by infra-red spectrophotometry and transmission electron microscopy. The minimum inhibitory/fungicidal concentrations (MIC/MFC) against Candida spp. were determined. The time-kill assay and changes on C. albicans micromorphology were evaluated. The % inhibition of ChNPs on C. albicans biofilm formation and reduction were investigated using 1 min and 8 h exposure. Candida biofilm was developed on resin surfaces and ChNPs were applied every 8 h for 5 days. After, fungal cells were counted (CFU/mL) and the surface roughness (Ra) and vickers microhardness (HV) of resin were analysed. For all experiments, sodium hypochlorite (NaOCl) was used as control. Data were analyzed by ANOVA, Tukey and paired t-tests (α = 0.05).ResultsThe MIC_80% of ChNPs was 30.1 μg/mL. ChNPs at 4 MIC showed complete inhibition in the time-kill assays. Blastoconidia cells were predominant after ChNPs application. The % inhibition ChNPs on C. albicans was proportional to its concentration, regardless of the exposure time. ChNPs decreased the CFU/mL of Candida spp. and showed lower alteration of HV and Ra values of resin surface compared to NaOCl.ConclusionsThe ChNPs inhibited C. albicans biofilm, reduced Candida biofilm on resin and caused small changes in roughness and hardness of acrylic resin surface.     

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.