Nancy L. Stitt, RN, BSN

Disclosures

April 03, 2003

Fungal Infection

Significant changes have occurred in the epidemiology of fungal infections during the past decade; however, Candida spp and Aspergillus spp remain the most common fungal pathogens. These epidemiologic changes resulted from many innovations during recent years.[36] First, the goal of current immunosuppression has led to the use of novel immunosuppressive drugs, which are anticipated to modify the epidemiology of fungal infections following SOT. Second, improvements in surgical techniques, the requirement of fewer blood transfusions, the decrease in surgical operative time, and the early use of endoscopic diagnostic and therapeutic interventions may have diminished the incidence of fungal infections. Third, the use of antimicrobial prophylaxis may also have altered the natural course of fungal infections following SOT. Collectively, these factors are presumed to be contributing to the decrease in the overall incidence of fungal infection, an apparent "relative" increase in Aspergillus spp infection, an increase in other mold infection, an increase in non-albicans Candida spp infection, and the occurrence of fungal infection at a later period (ie, after 3 months).

Candida Infections

Fungal infections in transplant recipients are most frequently caused by Candida spp. C albicans and C tropicalis are the 2 most common species responsible for serious infection. The clinical syndromes of candidosis range from minimal mucosal colonization with mild infection to serious invasive infection such as candidemia (Candida in the blood with or without visceral involvement) and disseminated candidosis (several deep-seated organs or an organ and the blood are infected).

C albicans

In normal sterile fluids such as blood and cerebrospinal fluid, Candida growth is indicative of infection, but in specimens such as sputum, bronchial secretions, and urine that during collection pass through sites normally colonized with Candida, growth alone is not diagnostic of infection. Fungi favor a warm, moist environment with an acid pH (4.0-5.0). Therefore, primary sites of Candida growth are the mouth and vagina. The invasive potential of C albicans depends, however, on the number of colonies and host resistance. Patients receiving immunosuppressive agents and/or broad-spectrum antibiotics, those with diabetes, patients with iron deficiency anemia, and hypothyroid individuals are more susceptible to invasion of adventitia by C albicans.

The hospital environment is particularly favorable to the growth of C albicans in the immunosuppressed patient. Feeding tubes, nasogastric tubes, IV and central venous catheters, surgical drains, and urinary catheters have all been shown to support the growth of C albicans. Other important risk factors are malnutrition, surgical procedures, and length of hospitalization.

Oral candidiasis.There is an increased risk for the development of oral candidosis in the immunosuppressed transplant recipient. Oral candidosis can contribute to nutritional deficiencies because of the associated pain and can lead to esophageal candidosis and fungemia. Oral candidosis, commonly referred to as thrush, presents as single or multiple wet, white lesions scattered over the tongue and oropharyngeal mucous membranes. The throat, tongue, and gums become red and sore.

Thrush can be avoided in many cases, except when severe neutropenia exists, by application of a topical antifungal agent. Patients receiving broad-spectrum antibiotics, hyperalimentation, or immunosuppressive agents on a long-term basis should receive an oral-topical antifungal agent as a prophylactic measure. Frequent assessment of the oral cavity is an important component of the nursing care of the transplant recipient.

Esophageal candidiasis. Candida esophagitis occurs in conjunction with oral candidiasis. Prolonged use of nasogastric or feeding tubes can lead to colonization of the esophagus with Candida. Invasion of the esophageal mucosa is associated with retrosternal chest pain, dysphagia, nausea, and vomiting. Irregular mucosal ulcerations can be seen on endoscopy. Candida esophagitis is associated with broad-spectrum antibiotic therapy and prolonged nasogastric intubation. Untreated, Candida esophagitis can lead to esophageal bleeding, perforation, and dissemination of Candida through the circulation to other organs, and death. Candida esophagitis can be prevented with prophylactic oral antifungal agents, but may necessitate systemic treatment.

Vulvovaginal candidiasis. Vulvovaginal candidiasis is most often caused by C albicans. Itching is the most common symptom of vulvovaginal candidosis. Other signs and symptoms include a white, malodorous discharge and irritation. Pain is usually not a symptom unless vaginal adventitia is involved. Inspection of the vulvovaginal, perineal, perirectal, and anal areas for erythema, edema, and excoriations in immunosuppressed patients is an important component of the nursing assessment of transplant recipients.

Disseminated candidiasis. Candida species are normally present in the bowel, so it is not surprising that the GI tract is usually the source of disseminated candidosis. Under favorable conditions, Candida can penetrate through the gut mucosa and reach the muscles, kidneys, brain, lungs, liver, and pancreas through hematogenous spread, and can result in multi-organ dysfunction or failure. Signs and symptoms include persistent fever while the patient is receiving antibiotic therapy, negative blood culture results in the febrile patient, and pain in the eye or visual loss. Skin assessment is of utmost importance, because skin lesions may be the first sign of systemic infection, particularly Candida and Cryptococcus infections, and may appear weeks before CNS involvement.

Aspergillus

Aspergillus species are ubiquitous in the earth, dust, and air. Aspergillus infections are acquired by airborne transmission to the upper respiratory tract, and outbreaks have been reported when patients pass through or near a hospital construction site. The most pathogenic species are A fumigatus, A flavus, A niger, and A terreus. The 2 most common sites for dissemination in immunosuppressed hosts are the pulmonary system and the CNS. Pulmonary sequelae include hemorrhagic bronchopneumonia, pulmonary infection with abscess, and infarction of the pulmonary arteries. In the brain, cortical disease characterized by solitary or multiple abscesses is common.

Cryptococcus

Cryptococcus neoformans is an encapsulated yeast found in the soil, pigeon feces, and the skin of some fresh fruits and vegetables. Although the main portal of entry is the respiratory tract, Cryptococcus pneumonia is rare. Cryptococcus fungemia with seeding to the CNS is, however, common.

Coccidioides

Coccidioides immitus is a soil-borne fungus found in the deserts and cultivated areas of the North American southwest, Central America, and central South America. Infections occur after inhalation of the fungus. Dissemination occurs to the CNS, joints, liver, and skin.

Histoplasmosis

Histoplasma capsulatum infection is most common in the United States along the Mississippi River valleys. It is also common in river valleys of South America. The mild form of histoplasmosis presents as an influenza-like syndrome, but in immunosuppressed patients dissemination can occur to the lungs, liver, spleen, CNS, and lymph nodes. Aspergillus, Cryptococcus, Coccidioides, and Histoplasma infections can originate in the hospital setting, but are more likely to be acquired from the external environment, such as when patients are directly exposed to large amounts of dry soil or dust, or bird excrement.

Treatment of Fungal Infection

Amphotericin was the gold standard for treatment of fungal infection for 30 years. Recently, newer agents have been developed and are also used for prophylaxis in order to reduce the incidence of fungal infection following SOT. There is no widely accepted consensus with regard to a specific regimen, but factors taken into consideration include the presence of risk factors, drug toxicity profiles, and drug interactions with immunosuppressive agents. The most commonly used antifungal agent is fluconazole. Very limited data are available regarding the use of newer drugs such as voriconazole and caspofungin.

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