[Fluconazole-resistant Candida species from HIV infected patients with recurrent Candida stomatitis: cross resistance to itraconazole and ketoconazole]

In vitro anti-Malassezia activity of xanthorrhizol isolated from Curcuma xanthorrhiza Roxb

AIMS

This study aimed at investigating the anti-Malassezia activity of xanthorrhizol (XTZ) isolated from Curcuma xanthorrhiza Roxb. against Malassezia furfur ATCC 14521 and Malassezia pachydermatis ATCC 14522.

METHODS AND RESULTS

The in vitro susceptibility tests for XTZ were carried out in terms of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC), using broth microdilution method with endpoint after 48 h. Time-kill curves were determined at concentrations ranging from 0 to 25 microg ml(-1). The MIC values of XTZ against M. furfur and M. pachydermatis were 1.25 and 0.25 mug ml(-1), respectively. The MFC of XTZ was 5 microg ml(-1) for M. furfur and 2.5 microg ml(-1) for M. pachydermatis. Time-kill curves demonstrated that treatment with 25 microg ml(-1) of XTZ for 5 h was able to kill 100% of M. furfur, while 20 microg ml(-1) of XTZ for 15 min killed M. pachydermatis completely.

CONCLUSION

XTZ shows potential as an anti-Malassezia agent for inhibiting the growth of M. furfur ATCC 14521 and M. pachydermatis ATCC 14522 in vitro.

SIGNIFICANCE AND IMPACT OF THE STUDY

XTZ may be a useful alternative for treating Malassezia-associated diseases.

(B1) Candida and mycotic infections

Oral candidiasis (OC) is the most common mucosal manifestation of HIV infection. This workshop examined OC and other mycoses associated with HIV infection. Historically, blood CD4 cell numbers were the primary prognosticator for the development of OC. However, a study that statistically evaluated the predictive role of HIV viral load vs. CD4 cell counts revealed viral load to be a stronger predictor for OC. The role of biofilms and antifungal resistance in recalcitrant OC is unclear at present. In general, micro-organisms including yeasts in biofilms are more resistant to antifungals than their planktonic counterparts. When the remaining organisms are eliminated, the few resistant organisms may not be problematic, because they are present in low numbers. Unusual exotic mycoses in HIV-infected patients are more common in patients from the developing than the developed world. These infections may be recurrent and recalcitrant to therapy, be present in multiple and uncommon sites, increase with the progression of HIV disease, and may play a role similar to that of the more common mycoses. Typing and subtyping of yeasts are probably not critical to the clinical management of candidiasis caused by Candida albicans and non-albicans strains, including C. dubliniensis, because it is responsive to antifungal therapy. C. glabrata is probably the only exception. The presence of oral thrush in infants younger than 6 months of age is associated with an increased post-natal transmission risk of HIV infection. Thus, perinatal retroviral therapy should be combined with the treatment of oral thrush to prevent the post-natal acquisition of HIV.

Distribution of gentamicin from a Gentacoll sponge measured by in vivo microdialysis

Microdialysis has produced valuable information concerning the distribution of antibiotics in peripheral tissue. The aim of this study was to measure the local distribution of gentamicin in cancellous bone tissue after the application of a Gentacoll sponge. Two microdialysis catheters were inserted into the cancellous bone of 9 pigs. After calibration of the microdialysis, a Gentacoll sponge was implanted, either dry or wet, into the bone marrow of the tibia. Serum and microdialysates were obtained over a period of 6 h. Data presented are median (range). A rank sum test was performed for statistical analysis. The peak concentration was 120 mg/l (33-585) (wet group) and 178 mg/l (60-1294) (dry group) (p=0.31). The AUC6 of the catheters placed 1 cm away from the implant was 24,431 mg*min/l (5155-152,855) and the AUC6 of the catheter placed 2 cm away from the implant was 13,759 mg*min/l (6351-74,573) (p=0.25). The study showed that peak concentrations and AUC6 did not differ between the wet- and dry-application group; neither did the distance from the sponge to the catheter have a significant impact on the distribution of gentamicin. It seems that microdialysis is capable to measure concentrations of locally applied antibiotics.

Anti-Candida effects of estragole in combination with ketoconazole or amphotericin B

The anti-Candida effects of estragole combined with amphotericin B or ketoconazole, commonly used antifungal drugs for treatment of candidasis, were evaluated in this study. The fractional inhibitory concentration (FIC) indices of both estragole combined with ketoconazole against C. albicans and C. utilis calculated from the checkerboard microtiter assay were 0.28 and 0.50 respectively, indicating significant synergism. These drug combinations exhibited additive effects against C. tropicalis, with FIC index of 0.75. Consistent for the most part with the results from the checkerboard titer tests, the time-kill curves of the tested samples also indicated significant synergism or additive effect between ketoconazole and estragole against the Candida species evaluated. In contrast, amphotericin B showed antagonism in combination with estragole in most experiments of this study. Thus, we have shown the synergistic combination effects between estragole and ketoconazole, which may be effective combinations for the treatment of Candida infections.

Antifungal therapy--state of the art at the beginning of the 21st century

The most relevant information on the present state of the art of antifungal chemotherapy is reviewed in this chapter. For dermatomycoses a variety of topical antifungals are available, and safe and efficacious systemic treatment, especially with the fungicidal drug terbinafine, is possible. The duration of treatment can be drastically reduced. Substantial progress in the armamentarium of drugs for invasive fungal infections has been made, and a new class of antifungals, echinocandins, is now in clinical use. The following drugs in oral and/or intravenous formulations are available: the broad spectrum polyene amphotericin B with its new "clothes"; the sterol biosynthesis inhibitors fluconazole, itraconazole, and voriconazole; the glucan synthase inhibitor caspofungin; and the combination partner flucytosine. New therapy schedules have been studied; combination therapy has found a significant place in the treatment of severely compromised patients, and the field of prevention and empiric therapy is fast moving. Guidelines exist nowadays for the treatment of various fungal diseases and maintenance therapy. New approaches interfering with host defenses or pathogenicity of fungal cells are being investigated, and molecular biologists are looking for new targets studying the genomics of pathogenic fungi.

Susceptibility testing of fungi--current status and open questions

The increase of fungal infections and the improvement of therapeutical options demand reliable antifungal susceptibility testing. In vitro susceptibility testing of fungi--in contrast to bacteria--is not yet established as a routine method. The NCCIS (National Committee for Clinical Laboratory Standards) guidelines for susceptibility testing of yeasts (and proposed for hyphomycetes) are most important for standardization. Meanwhile, essential parts of this test procedure are accepted, but it should still be improved. The concept of using only one test medium for all drugs and test organisms is not realized so far. There are also some test situations that prevent the NCCLS standard from being applied. Based on our experience, this article describes the NCCLS methods and their modifications. It places emphasis on lipophilic drugs showing controversies despite standardization. Furthermore, the prediction of MICs on the clinical outcome is discussed. Since there are some pitfalls in testing antifungals, this should be done in experienced laboratories only. The MIC has to be regarded as only one, but an important, factor in the management of fungal diseases. Host-, drug-, and pathogen-specific data should be considered simultaneously.

Antifungal activity of the essential oil of Agastache rugosa Kuntze and its synergism with ketoconazole

AIMS

To evaluate the fungitoxic activity of the essential oil of Agastache rugosa alone and to determine its combination effect with ketoconazole against Blastoschizomyces capitatus.

METHODS AND RESULTS

The antifungal activities of the essential oil of A. rugosa and its main constituent estragole were investigated using the broth microdilution, disk diffusion methods and checkerboard microtitre assay. Both estragole and the essential oil exhibited strong activities against the tested fungi and showed synergism with ketoconazole against B. capitatus.

CONCLUSIONS

Both estragole and the essential oil of A. rugosa have significant growth-inhibiting activities against B. capitatus showing strong synergistic effect with ketoconazole.

SIGNIFICANCE AND IMPACT OF THE STUDY

The essential oil of A. rugosa, combined with ketoconazole, may be particularly useful against B. capitatus, a rare pathogenic fungus documented to cause severe and fatal mycoses in immunocompromised patients.

Frequency and clinical significance of bloodstream infections caused by C albicans strains with reduced susceptibility to fluconazole

Reduced susceptibility to fluconazole (RSF) is relatively common in non-albicans Candida isolates and in Candida albicans recovered from HIV-infected patients with relapsing Candida stomatitis or esophagitis. However, little clinical data on bloodstream infections caused by C. albicans with RSF is available. We analyzed 116 episodes of C. albicans fungemia detected over an 11-year period. Four patients (3.4%) had a blood isolate of C. albicans with RSF. Fluconazole MICs were 16 (3 SDD strains) and 128 microg/ml (1 resistant strain), respectively. Three of the patients were HIV (+) and the fourth was a liver transplant recipient. All of them had been previously treated with an azole compound. The liver recipient had breakthrough fungemia while being treated with 400 mg of preemptive fluconazole despite having an MIC of 16 microg/ml. Fluconazole clinical failure was documented in two of the remaining three cases. Only five other patients with C. albicans fungemia caused by fluconazole-resistant strains (>or=64 microg/ml) are described in the literature. Candida albicans fungemia produced by strains with RSF is still uncommon. It should be suspected in patients previously treated with azole agents or with breakthrough fungemia. In our experience, fluconazole remains a safe option for the treatment of most C. albicans fungemias, although surveillance seems advisable.

Resistance of Candida species to antifungal agents: molecular mechanisms and clinical consequences

Candida albicans and related species pathogenic for man become resistant to antifungal agents, in particular triazole compounds, by expression of efflux pumps that reduce drug accumulation, alteration of the structure or concentration of antifungal target proteins, and alteration of membrane sterol composition. The clinical consequences of antifungal resistance can be seen in treatment failures in patients and in changes in the prevalences of Candida species causing disease. These effects were seen unequivocally in HIV-infected patients with oropharyngeal candida infections, but their incidence has decreased dramatically with the introduction of highly active antiretroviral therapy. The evidence for similar emergence of antifungal-resistant yeast strains and species in other types of candida infections is confounded by non-standardised susceptibility testing methods and definitions of a resistant fungal isolate. Recent large-scale surveys of yeasts isolated from blood cultures, based on standardised methodology and resistance definitions, do not support the view that antifungal resistance in pathogenic yeasts constitutes a significant or growing therapeutic problem.

Treatment of fungal infections in neutropenic children

Fungal infections have emerged as one of the most significant complications of antineoplastic therapy and marrow transplantation in children. Morbidity and mortality associated with fungal infections are high. Recent trends indicate that the incidence and spectrum of fungal infections are increasing, partly because of the increase in the number of children receiving intensive chemotherapy and marrow transplantation, but also because of the successful management of bacterial and viral infections. Though many factors may contribute to risk for developing a fungal infection, prolonged neutropenia is the most important. Until recently, options for antifungal therapy were limited. Advances include less toxic formulations of amphotericin B and an expanding armamentarium of azoles as well as new antifungal compounds. This review addresses the therapeutic options available for treatment of fungal infections in immunocompromised children.