Prophylaxis of fungal infections

Exposure of the yeast Candida albicans to the anti-neoplastic agent adriamycin increases the tolerance to amphotericin B

Cancer patients experience a high incidence of fungal infections due to their immuno-suppressed condition. This work has investigated the interaction of an anti-neoplastic agent, adriamycin (doxorubicin), with the yeast Candida albicans and examined whether this drug altered the susceptibility of the yeast to amphotericin B – an anti-fungal agent used for the treatment of systemic fungal infections in cancer patients. Exposure to adriamycin for 24 h increased the growth of C. albicans and increased the tolerance to amphotericin B by a small, but statistically significant, extent. Growth in adriamycin-supplemented medium suppressed the respiration rate of C. albicans, which resulted in a decrease in the ergosterol content of the fungal cell membrane. The tolerance to amphotericin B was lost after exposure to adriamycin for 48 h, which coincided with a restoration in the respiration rate and the ergosterol content of the fungal cell membrane. This work demonstrated that short-term exposure (24 h) to adriamycin increased the tolerance of C. albicans for amphotericin B, which may be mediated by a decrease in the ergosterol content as a result of an adriamycin-induced disruption of oxidative phosphorylation.

Current management of fungal infections

The management of superficial fungal infections differs significantly from the management of systemic fungal infections. Most superficial infections are treated with topical antifungal agents, the choice of agent being determined by the site and extent of the infection and by the causative organism, which is usually readily identifiable. One exception is onychomycosis, which usually requires treatment with systemically available antifungals; the accumulation of terbinafine and itraconazole in keratinous tissues makes them ideal agents for the treatment of onychomycosis. Oral candidiasis in immunocompromised patients also requires systemic treatment; oral fluconazole and itraconazole oral solution are highly effective in this setting. Systemic fungal infections are difficult to diagnose and are usually managed with prophylaxis or empirical therapy. Fluconazole and itraconazole are widely used in chemoprophylaxis because of their favourable oral bioavailability and safety profiles. In empirical therapy, lipid-associated formulations of amphotericin-B and intravenous itraconazole are safer than, and at least as effective as, conventional amphotericin-B (the former gold standard). The high acquisition costs of the lipid-associated formulations of amphotericin-B have limited their use.

Assessing risk factors for systemic fungal infections

The incidence of invasive fungal infection has increased in recent years. Most infections are caused by Candida albicans and Aspergillus spp. but the emergence of other fungal infections is changing the spectrum of disease. Immunosuppression and breakdown of anatomical barriers such as the skin are the major risk factors for fungal infections. Health care workers encounter at-risk patients in various settings, including AIDS clinics and intensive care, transplantation and oncology units. Patients with prolonged and deep neutropenia (haematological malignancy patients) are most at risk and are therefore most likely to receive prophylactic therapy. Practical measures can be taken to avoid exposing the patient to fungi (air filtration, regular hand washing, avoiding plants and flowers) and antifungal agents can be administered to prevent systemic fungal infection. Most fungal infections have non-specific symptoms; this makes recognition of the signs and symptoms of the disease important but also makes diagnosis difficult and empirical treatment necessary. Some antifungal agents have limitations but new formulations will improve therapy and play a key role in future antifungal strategies.

Preventing fungal infections in immunocompromised patients

The incidence of systemic fungal infections in immunosuppressed patients has increased in the past two decades (Fridkin and Jarvis, 1996). Bone marrow transplant recipients and patients with prolonged neutropenia are most at risk, particularly when environmental factors increase the presence of fungi and fungal spores. Preventive measures include air filtration, handwashing, exclusion of flowers and some foodstuffs and use of chemoprophylaxis. In April 1999, a meeting was held under the auspices of the European Group for Blood and Marrow Transplantation (UK) Nurses and Allied Professionals Group to discuss the role of nurses in the management of patients at risk of systemic fungal infection. Issues discussed included: the need for nurses to recognize risk factors for systemic fungal infection; the role of nurses in giving feedback to patients; and the use of antifungal agents and associated problems, such as non-compliance and side-effects.

A strategy for managing fungal infections in haematopoietic stem cell transplantation

As more indications continue to be found for allogeneic haematopoietic transplantation, more patients are at risk for invasive fungal infectious diseases (IFID), particularly candidiasis and aspergillosis. Risk factors for disease are becoming better defined and diagnostic methods have improved considerably. In addition, there is now international agreement that three elements form the basis for defining IFID (host factors, clinical evidence, and mycological results), that imaging is acceptable for diagnosing disease, and that indirect tests such as antigen detection are also adequate mycological proof of cause. There are also more drugs available and still more to come, offering the potential for selective prophylaxis as well as preemptive and specific therapy, as well as for flexible administration. Hence, all the elements are in place for designing and testing an effective and economically sound strategy for dealing with IFID.