Candida species are the most common causes of fungal infection in organ transplant recipients and cause a wide range of syndromes from minor and superficial cases to fatal ones. Nosocomial outbreaks of Candida species have been attributed to contaminated hands of hospital personnel. Esophageal candidiasis is a common finding in immunocompromised individuals and is often associated with oropharyngeal infection. Diagnosis is made by endoscopic evaluation, including biopsy. Since lesions related to herpetic and cytomegalovirus esophagitis, as well as the effects of radiation therapy and reflux, may have similar signs and symptoms on radiographs and even endoscopy, a careful diagnostic approach is necessary. It should be noted that candidal esophagitis requires systemic antifungal therapy and topical therapy is ineffective. Urinary tract candidiasis is also possible in organ transplant patients due to urinary tract instrumentation, diabetes, vulvovaginal infection, and the presence of a neurogenic bladder. The vast majority of urinary tract infections occur via the ascending route. Candidemia and disseminated candidal infection are most commonly due to infection of vascular access catheters, although enteric transmission can also occur in critically ill patients. Candida pneumonia via the tracheobronchial route is rare, whereas pulmonary invasion from bloodstream infection is well recognized. This is true even when sputum contains visible Candida species on microscopy and culture and even when blood cultures are positive.
Aspergillus species are widespread saprophytes in the environment, and the infectious form, conidia, enters the respiratory tract through inhalation and initiates the disease. After inhalation, these conidia can cause a variety of clinical syndromes that are grouped into four categories: hypersensitivity syndromes, colonization syndromes, semi-invasive aspergillosis, and invasive aspergillosis. Hospital-acquired exposures occur as patients move around the hospital for essential procedures. Therefore, outbreaks or isolated cases resulting from exposure in a contaminated operating room, radiology room, or while waiting in a waiting room for bronchoscopy or endomyocardial biopsy have been documented. Aspergillus fumigatus is responsible for about 90% of invasive disease cases, and Aspergillus flavus accounts for most of the remaining cases, especially those involving the paranasal sinuses. Aspergillus tereus, Aspergillus nidulans, and Aspergillus niger sometimes cause disease, and there is evidence that these unusual infections are increasing, particularly among lung transplant recipients. These unusual species tend to be more resistant to drugs. For example, Aspergillus tereus is resistant to amphotericin. The key feature of invasive aspergillosis, regardless of the site of entry, is its invasive behavior in the blood vessels. The three main features of invasive aspergillosis are hemorrhage, infarction, and metastasis.
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