Candida Infections

Introduction

• Eight species of Candida are regarded as clinically important pathogens in human disease: C. albicans, C. tropicalis, C. parapsilosis, C. krusei, C. stellatoidea, C. guilliermondii, C. lusitaniae, and C. glabrata.

Hematogenous Candidiasis

Hematogenous candidiasis describes the clinical circumstances in which hematogenous seeding to deep organs such as the eye, brain, heart, and kidney occurs.

• Candida is generally acquired via the gastrointestinal (GI) tract, although organisms may also enter the bloodstream via indwelling IV catheters. Immunosuppressed patients, including those with lymphoreticular or hematologic malignancies, diabetes, immunodeficiency diseases, or those receiving immunosuppressive therapy with high-dose corticosteroids, immunosuppressants, antineoplastic agents, or broadspectrum antimicrobial agents are at high risk for invasive fungal infections. Major risk factors include the use of central venous catheters, total parenteral nutrition, receipt of multiple antibiotics, extensive surgery and burns, renal failure and hemodialysis, mechanical ventilation, and prior fungal colonization.

Aspergillus Infections

\nOf more than 300 species of Aspergillus, three are most commonly pathogenic: A. fumigatus, A. flavus, and A. niger.

• Aspergillosis is generally acquired by inhalation of airborne conidia that are small enough (2.5–3 mm) to reach the alveoli or the paranasal sinuses.
• Superficial or locally invasive infections of the ear, skin, or appendages can often be managed with topical antifungal therapy.

Aspergilloma

In the nonimmunocompromised host, Aspergillus infections of the sinuses most commonly occur as saprophytic colonization (aspergillomas, or “fungus balls”) of previously abnormal sinus tissue. Treatment consists of removal of the aspergilloma. Therapy with glucocorticoids and surgery is generally successful.

Treatment

• Antifungal therapy should be instituted in any of the following conditions:

(1) persistent fever or progressive sinusitis unresponsive to antimicrobial therapy;

(2) an eschar over the nose, sinuses, or palate;

(3) the presence of characteristic radiographic findings, including wedge-shaped infarcts, nodular densities, or new cavitary lesions; or

(4) any clinical manifestation suggestive of orbital or cavernous sinus disease or an acute vascular event associated with fever. Isolation of Aspergillus spp. from nasal or respiratory tract secretions should be considered confirmatory evidence in any of the previously mentioned clinical settings.

• Voriconazole is the drug of choice for primary therapy of most patients with aspergillosis as it provided improved survival and fewer side effects.
• In patients who cannot tolerate voriconazole, amphotericin B can be used. Full doses (1–1.5 mg/kg/day) are generally recommended, with response measured by defervescence and radiographic clearing. The lipid-based formulations may be preferred as initial therapy in patients with marginal renal function or in patients receiving other nephrotoxic drugs. The optimal duration of treatment is unknown.
• Caspofungin is indicated for treatment of invasive aspergillosis in patients who are refractory to or intolerant of other therapies such as amphotericin B.
• The use of prophylactic antifungal therapy to prevent primary infection or reactivation of aspergillosis during subsequent courses of chemotherapy is controversial.