The effect of the new triazole, voriconazole (UK-109,496), on the interactions of Candida albicans and Candida krusei with endothelial cells

Semi-invasive pulmonary aspergillosis in an immunosuppressed patient: a case report

Background

The authors present the high-resolution computed tomography findings of an immunosuppressed patient with semi-invasive pulmonary aspergillosis.

Case presentation

The main finding consisted of irregular, thick-walled cavity in the right upper lobe and a mass with soft-tissue attenuation within it and thickening of adjacent pleura. Additional findings were bronchial wall thickening associated with a 'tree-in-bud' pattern. Following the clinical, laboratorial and imaging criteria, the diagnosis of semi-invasive pulmonary aspergillosis was defined and antifungical treatment was introduced.

Conclusion

The patient responded well to the treatment with improvement in his systemic symptoms and regression of the pulmonary lesions.

Voriconazole for serious fungal infections

Voriconazole is a new second generation triazole effective against a wide spectrum of fungal pathogens. A randomised, controlled trial has shown it to be superior to amphotericin B in invasive aspergillosis, and it is a potential alternative to amphotericin B in neutropenic sepsis and to fluconazole in oesophageal candidiasis. Early clinical reports and in vitro susceptibility data suggest that it may also be a valuable antifungal against fluconazole-resistant Candida species and certain emerging fungal pathogens, which cause infections that are often refractory to conventional therapies. There is limited evidence of azole cross-resistance of clinical importance. Voriconazole is available as intravenous and oral formulations and has excellent tissue penetration and a good safety profile, the main problems being transient visual impairment and hepatotoxicity in patients with liver disease. It is metabolised by cytochrome P-450 isoenzymes causing important drug interactions but, in contrast to amphotericin B, is safe in renal failure and rarely causes infusion-related reactions. This review outlines the pharmacology of voriconazole and focuses on its clinical applications and safety profile.

Candida: a causative agent of an emerging infection

Incidences of infections due to Candida have increased over the last 15-20 y. This increase in the incidence and the high associated mortality rate despite therapy has focused the attention on this disease and prompted investigators to undertake research aimed at understanding the pathogenesis of this disease as well as methods to treat it. This paper discusses recent developments in the Candida field and the impact they have on patient management.

Infections following hematopoietic stem cell transplantation

Numerous advances have been made in the management of infection in HSCT recipients. With increasing knowledge the authors are able to prevent several serious infections from occurring, and reduce the severity of infections once they occur. Despite these advances, several previously unrecognized pathogens have emerged and pose risks to this population. Ongoing surveillance and reporting of atypical infections are warranted. Transplant and infectious disease clinicians alike must be vigilant to the shifts in infectious syndromes as a consequence of various prophylaxis and preemptive strategies, and be ready to modify empiric strategies to meet the changing microbiologic milieu. As we increase our understanding of the HSCT process, and use the immune system rather than relying on high-dose chemotherapy, the authors are likely to reduce toxicities and improve patient outcomes.

Voriconazole: a new triazole antifungal

OBJECTIVE

To review the currently available information on the pharmacology, pharmacokinetics, efficacy, adverse effects, drug interactions, and dosage guidelines of voriconazole. Comparative data for voriconazole and other azole antifungal agents are described where available.

DATA SOURCES

A MEDLINE search restricted to English-language articles (1966 to September 1999) was conducted, and an extensive review of journals and meeting abstracts was performed. MeSH headings included itraconazole, fluconazole, voriconazole, UK-109,496, and amphotericin B.

DATA EXTRACTION

The data on pharmacokinetics, adverse effects, and drug interactions were obtained from open-label and controlled studies and case reports. Controlled studies and case reports were evaluated to demonstrate the efficacy of voriconazole in treatment of various fungal infections.

DATA SYNTHESIS

Voriconazole is a derivative of fluconazole that demonstrates enhanced in vitro activity against existent and emerging fungal pathogens. Limited data have revealed a favorable pharmacokinetic and safety profile for the agent. Moreover, select clinical trials and case studies of voriconazole suggest good in vivo efficacy against several fungal pathogens including Candida, Aspergillus, and Scedosporium.

CONCLUSIONS

Voriconazole has shown promise in the treatment of superficial and systemic mycoses. While several unresolved issues remain, voriconazole may be a viable therapeutic alternative for fluconazole-resistant mucocutaneous candidiasis and in cases of mild to moderate systemic mycoses requiring chronic treatment or that are refractory to currently available agents.

Germ tubes and proteinase activity contribute to virulence of Candida albicans in murine peritonitis

Peritonitis with Candida albicans is an important complication of bowel perforation and continuous ambulatory peritoneal dialysis. To define potential virulence factors, we investigated 50 strains of C. albicans in a murine peritonitis model. There was considerable variation in their virulence in this model when virulence was measured as release of organ-specific enzymes into the plasma of infected mice. Alanine aminotransferase (ALT) and alpha-amylase (AM) were used as parameters for damage of the liver and pancreas, respectively. The activities of ALT and AM in the plasma correlated with invasion into the organs measured in histologic sections and the median germ tube length induced with serum in vitro. When the activity of proteinases was inhibited in vivo with pepstatin A, there was a significant reduction of ALT and AM activities. This indicates that proteinases contributed to virulence in this model. Using strains of C. albicans with disruption of secreted aspartyl proteinase gene SAP1, SAP2, SAP3, or SAP4 through SAP6 (collectively referred to as SAP4-6), we showed that only a Deltasap4-6 triple mutant induced a significantly reduced activity of ALT in comparison to the reference strain. In contrast to the Deltasap1, Deltasap2, and Deltasap3 mutants, the ALT induced by the Deltasap4-6 mutant could not be further reduced by pepstatin A treatment, which indicates that Sap4-6 may contribute to virulence in this model.

Antifungal activity of voriconazole (UK-109,496), fluconazole and amphotericin B against hematogenous Candida krusei infection in neutropenic guinea pig model

Voriconazole (UK-109,496) is a new triazole with in vitro activity against a wide spectrum of fungi including yeasts intrinsically resistant to fluconazole such as Candida krusei. In this study the efficacy of voriconazole was compared to amphotericin B and fluconazole in a neutropenic guinea pig model of hematogenously disseminated C. krusei infection. In guinea pigs, neutropenia was established by using cyclophosphamide (intraperitoneally, i.p., 100 mg/kg on day 1 and 4), and dexamethasone (orally, 2 mg/kg/day, for 8 days). Neutropenic guinea pigs were infected with 0.5 ml of yeast cell suspension (1 x 10(8) CFU) intravenously. Challenged animals were treated with antifungals starting 1 h postinfection for 7 days. The animals were divided into five groups: untreated control, amphotericin B (1 mg/kg i.p. on alternate days), fluconazole (20 mg/kg orally twice daily), and voriconazole (two groups: 5 and 10 mg/kg orally twice daily) groups. Guinea pigs were sacrificed 1 day after the last treatment. Brain, liver, and kidneys were removed and weighed, tissues were homogenized and fungal burden determined by serial quantitative counts. Voriconazole at dosages of 5 or 10 mg/kg b.i.d. was shown to be significantly more efficacious than either amphotericin B or fluconazole in eradicating C. krusei from brain, liver and kidney tissue. These data indicate that voriconazole could be efficacious for the treatment of infections caused by fluconazole-resistant Candida, such as C. krusei.