Chapter 192. Candida and Aspergillus

1. When should a positive urine culture for Candida species be treated?

2. When should invasive candidiasis be suspected? How is it diagnosed and treated?

3. What is the clinical significance of a positive sputum culture for Aspergillus species?

4. How useful are antigen detection tests for the diagnosis of infection with Candida and Aspergillus species?

Mucocutaneous infection with Candida species is common in the hospital setting, due to the high prevalence of diabetes and the use of broad-spectrum antibiotics. Invasive infections with Candida species were once rare, but have become much more common in hospitalized patients, particularly among those with compromised immunity, antibiotic exposure, and central venous catheters. The increased prevalence of Aspergillus infections in the hospital is almost wholly due to neutropenia from chemotherapy and the use of high-dose glucocorticoids and other immunosuppressive agents in patients with organ and bone marrow transplants and rheumatological diseases.

Epidemiology

Candida species are normal flora of the oropharynx, bowel, and vagina. Candida overgrowth of these surfaces may arise in the setting of broad spectrum antibiotics, diabetes mellitus, or HIV infection, resulting in oral thrush, Candida esophagitis, and vaginal candidiasis. High estrogen states, such as pregnancy or oral contraceptive use, are an additional risk factor for vaginal yeast infection. Candida skin infections are often seen in moist, macerated intertrigenous folds, such as in the groin, perineum (diaper rash), pannus, axillae, and breasts.

While superficial candidiasis is common in both ambulatory and hospitalized patients, candidemia and disseminated candidiasis are usually seen in health care settings. Risk factors include critical illness, intensive antibiotic exposure, intraabdominal surgery, hemodialysis, central venous catheters, parenteral nutrition, intravenous drug use, and neutropenia.

Does This Patient Have Candida Infection?

Mucocutaneous Candida (Cutaneous, Thrush, Esophagitis, Vaginitis)

The diagnosis of mucocutaneous Candida infections is usually made clinically. Cutaneous candidiasis has a typical distribution in intertrigenous areas, with central erythema and maceration, surrounded by a collar of scale (Figure 192-1). Beyond this, there may be papular and pustular satellite lesions. Oral thrush (Figure 192-2) presents with painless white plaques on the mucous membranes and tongue that are easily scraped off. Fissures of the angles of the mouth (cheilitis) may also be present. Budding yeasts, hyphae, and pseudohyphae of Candida can be seen on microscopy when scrapings of skin or oral lesions are mixed with a drop of 10% potassium hydroxide, which digests host cells but not fungi.