Pathogenesis, microbiological and clinical aspects of oral candidiasis (candidosis)

Evaluation of drug susceptibility test for Efinaconazole compared with conventional antifungal agents

BACKGROUND

Superficial fungal infections are one of the most common and burdensome skin problems affecting quality of life in patients. Various conventional antifungal agents have been used to treat fungal infections; however, various problems have been reported including drug interaction, drug resistance and low effectiveness. Efinaconazole is a novel antifungal agent, which has proven to be particularly effective against onychomycosis compared with conventional antifungal agents. However, the antifungal efficacy of Efinaconazole for specific strains has not been analysed.

OBJECTIVE

We conducted an in-vitro study to measure the antifungal activity of Efinaconazole against strains of Trichophyton rubrum, Trichophyton mentagrophytes and Candida albicans compared with widely-used antifungal drugs.

METHODS

We obtained strains of T. rubrum, T. mentagrophytes and C. albicans isolated from patients with onychomycosis and tinea pedis. The minimal inhibitory concentration (MIC) for various strains of fungal species was evaluated for the antifungal susceptibility test.

RESULTS

Efinaconazole showed a low MIC against almost strains of dermatophytes and C albicans and also presented low resistance, indicating high potency of efinaconazole for treatment of superficial fungal infections.

CONCLUSION

Efinaconazole could be a comparable alternative to replace existing conventional agents.

Adjuvant antifungal therapy using tissue tolerable plasma on oral mucosa and removable dentures in oral candidiasis patients: a randomised double-blinded split-mouth pilot study

Extended use of antimycotics in oral candidiasis therapy gives rise to problems related to fungal drug resistance. The aim of this pilot study was to investigate the efficacy of tissue tolerable plasma (TTP) in denture stomatitis patients. It was hypothesised that (I): erythema and (IIa): complaint remission would be accelerated and (IIb): colony forming unit (CFU) reduction would be improved. The halves of the upper jaws of eight patients were randomly assigned to control (nystatin, chlorhexidine and placebo treatment) and test sides (nystatin, chlorhexidine and TTP administered six times each 7 days). The patients and the investigators, who were different from the therapists, were both blinded. Compared to the control sides, the erythema surface was reduced significantly more extensively on the test sides between 2 and 6 weeks of antifungal therapy (P ≤ 0.05). Visual analogue scale values and the frequency of moderate or heavy growth of Candida post-treatment did not differ significantly between both sides (P > 0.05). The primary hypothesis was confirmed, which may be interpreted as an accelerated remission. As drug therapy is usually limited to the time in which signs of infection are present, TTP might help reducing antifungal use. Even though the secondary hypotheses were not confirmed, persistence of Candida might be only colonisation.

Candida concentrations determined following concentrated oral rinse culture reflect clinical oral signs

BACKGROUND

Oral candidiasis is an infection caused by a yeast-like fungus called Candida. Various methods can be used to isolate Candida from the oral cavity. However, it is difficult to correctly and satisfactorily diagnose oral candidiasis because currently no microbiological or laboratory standards based on samples from the oral cavity are available. The aim of this study is to establish a reliable laboratory test for diagnosing oral candidiasis.

METHODS

Oral swab, rinse and concentrated rinse samples were obtained from 200 consecutive outpatients (103 male patients and 97 female patients; mean age, 47.2 years; age range, 9-89 years). Candida colonies from cultured samples were enumerated to compare the sensitivities and specificities of the above sampling methods, and the associations between Candida detection or concentration and the clinical oral signs were examined.

RESULTS

The mean colony numbers were 263 ± 590 CFU/swab for the swab method, 2894 ± 6705 CFU/100 μL for the rinse method, and 9245 ± 19,030 CFU/100 μL for the concentrated rinse method. The median numbers were 23 CFU/swab for the swab method, 56 CFU/100 μL for the rinse method, and 485 CFU/100 μL for the concentrated rinse method. Candida was detected in the oral cavity of 33.5 % and 52.0 % of the outpatients by the swab method and concentrated rinse, respectively. Candida concentrations determined by the concentrated rinse were closely related to the severity of the clinical oral signs. The positive predictive values of residual root, redness of the oral mucosa, denture, glossalgia, dry mouth, and taste disorder were useful predictors of oral candidiasis.

CONCLUSIONS

Concentrated rinse sampling is suitable for evaluating oral candidiasis, and Candida concentrations examined using this method strongly associated with the oral signs associated with Candida infection.

Clinical and microbiological diagnosis of oral candidiasis

Introduction: Candidiasis or oral candidiasis is the most frequent mucocutaneous mycosis of the oral cavity. It is produced by the genus Candida, which is found in the oral cavity of 53% of the general population as a common commensal organism. One hundred and fifty species have been isolated in the oral cavity, and 80% of the isolates correspond to Candida albicans, which can colonize the oral cavity alone or in combination with other species. Transformation from commensal organism to pathogen depends on the intervention of different predisposing factors that modify the microenvironment of the oral cavity and favor the appearance of opportunistic infection. The present study offers a literature review on the diagnosis of oral candidiasis, with the purpose of establishing when complementary microbiological techniques for the diagnosis of oral candidiasis should be used, and which techniques are most commonly employed in routine clinical practice in order to establish a definitive diagnosis. Materials and methods: A Medline-PubMed, Scopus and Cochrane search was made covering the last 10 years. Results: The diagnosis of oral candidiasis is fundamentally clinical. Microbiological techniques are used when the clinical diagnosis needs to be confirmed, for establishing a differential diagnosis with other diseases, and in cases characterized by resistance to antifungal drugs. Biopsies in turn are indicated in patients with hyperplastic candidiasis. Staining (10% KOH) and culture (Sabouraud dextrose agar) are the methods most commonly used for diagnosing primary candidiasis. Identification of the individual species of Candida is usually carried out with CHROMagar Candida®. For the diagnosis of invasive candidiasis, and in cases requiring differentiation between C. albicans and C. dubliniensis, use is made of immunological and genetic techniques such as ELISA and PCR.

Key words:Clinical, oral candidiasis, microbiology.

Wild-type Drosophila melanogaster as a model host to analyze nitrogen source dependent virulence of Candida albicans

The fungal pathogen Candida albicans is a common cause of opportunistic infections in humans. We report that wild-type Drosophila melanogaster (OrR) flies are susceptible to virulent C. albicans infections and have established experimental conditions that enable OrR flies to serve as model hosts for studying C. albicans virulence. After injection into the thorax, wild-type C. albicans cells disseminate and invade tissues throughout the fly, leading to lethality. Similar to results obtained monitoring systemic infections in mice, well-characterized cph1Δ efg1Δ and csh3Δ fungal mutants exhibit attenuated virulence in flies. Using the OrR fly host model, we assessed the virulence of C. albicans strains individually lacking functional components of the SPS sensing pathway. In response to extracellular amino acids, the plasma membrane localized SPS-sensor (Ssy1, Ptr3, and Ssy5) activates two transcription factors (Stp1 and Stp2) to differentially control two distinct modes of nitrogen acquisition (host protein catabolism and amino acid uptake, respectively). Our results indicate that a functional SPS-sensor and Stp1 controlled genes required for host protein catabolism and utilization, including the major secreted aspartyl protease SAP2, are required to establish virulent infections. By contrast, Stp2, which activates genes required for amino acid uptake, is dispensable for virulence. These results indicate that nutrient availability within infected hosts directly influences C. albicans virulence.

Candida albicans Csy1p is a nutrient sensor important for activation of amino acid uptake and hyphal morphogenesis

Candida albicans is an important human pathogen that displays a remarkable ability to detect changes in its environment and to respond appropriately by changing its cell morphology and physiology. Serum- and amino acid-based media are known to induce filamentous growth in this organism. However, the mechanism by which amino acids induce filamentation is not yet known. Here, we describe the identification and characterization of the primary amino acid sensor of C. albicans, Csy1. We show that Csy1p plays an important role in amino acid sensing and filamentation. Loss of Csy1p results in a lack of amino acid-mediated activation of amino acid transport and a lack of induction of transcription of specific amino acid permease genes. Furthermore, a csy1Delta/csy1Delta strain, lacking Csy1p, is defective in filamentation and displays altered colony morphology in serum- and amino acid-based media. These data provide the first evidence that C. albicans utilizes the amino acid sensor Csy1p to probe its environment, coordinate its nutritional requirements, and determine its morphological state.

Effect of orally administered bovine lactoferrin on the immune response in the oral candidiasis murine model

Therapeutic activity against oral candidiasis of orally administered bovine lactoferrin (LF), a multifunctional milk protein, was shown in a previous report using an immunosuppressed murine model. In the present study, the influence of orally administered LF on immune responses relevant to this therapeutic effect was examined. Because mice were immunosuppressed with prednisolone 1 day before and 3 days after the infection with Candida, the numbers of peripheral blood leukocytes (PBL) and cervical lymph node (CLN) cells were reduced. LF feeding prevented the reduction in the numbers of PBL on day 1 and CLN cells on days 1, 5 and 6 in the Candida-infected mice. The number of CLN cells of individual mice on days 5 and 6 was inversely correlated with the Candida c.f.u. in the oral cavity. Increased production of IFN-gamma and TNF-alpha by CLN cells stimulated with heat-killed Candida albicans on day 6 was observed in LF-treated mice compared with non-treated mice. Concanavalin A (ConA)-stimulated CLN cells from LF-treated mice also showed a significant increase in the production of IFN-gamma and IL12 on day 5 and a tendency for increased production of IFN-gamma and TNF-alpha on day 6. The levels of cytokine production by ConA-stimulated CLN cells on day 6 were inversely correlated with the Candida c.f.u. in the oral cavity. In conclusion, the alleviation of oral candidiasis by LF feeding in this model may correlate with the enhancement of the number of leukocytes and their cytokine responses in regional lymph nodes against Candida infection.

Oral lactoferrin treatment of experimental oral candidiasis in mice

We assessed the potential of lactoferrin (LF), a multifunctional milk protein, for treatment of oral candidiasis with immunosuppressed mice, which have local symptoms characteristic of oral thrush. Oral administration of bovine LF in drinking water starting 1 day before the infection significantly reduced the number of Candida albicans in the oral cavity and the score of lesions on the tongue on day 7 after the inoculation. The symptomatic effect of LF was confirmed by macroscopic and microscopic observations of the tongue's surface. Similar effects were also observed upon administration of LF pepsin hydrolysate, but not lactoferricin B, an antimicrobial peptide of LF. The anticandidal activity of LF was evident on administration either in drinking water or by intragastric intubation with a stomach tube. These results suggest that the effect of LF in this oral candidiasis model is not due to direct antifungal action. In conclusion, LF could have potential as a food component supporting antifungal drug treatment.