A 56-year-old man hospitalized in the intensive care unit is being evaluated for fever. He was admitted 8 days ago with respiratory failure and has had a complicated hospital course, including mechanical ventilation, central venous line placement, and broad-spectrum antibiotic therapy. The patient has a history of HIV and a hematologic malignancy. His last chemotherapy session was 2 weeks ago. Chest x-ray does not reveal a new infiltrate, and urine cultures are negative for infection. Blood cultures grow pseudohyphae-producing yeast species with an ability to form germ tubes. Which of the following most likely directly contributed to the development of fungemia in this patient?

Question

A 56-year-old man hospitalized in the intensive care unit is being evaluated for fever.  He was admitted 8 days ago with respiratory failure and has had a complicated hospital course, including mechanical ventilation, central venous line placement, and broad-spectrum antibiotic therapy.  The patient has a history of HIV and a hematologic malignancy.  His last chemotherapy session was 2 weeks ago.  Chest x-ray does not reveal a new infiltrate, and urine cultures are negative for infection.  Blood cultures grow pseudohyphae-producing yeast species with an ability to form germ tubes.  Which of the following most likely directly contributed to the development of fungemia in this patient?

Quizplus · Accepted Answer

This patient with HIV likely has candidemia, a disseminated form of Candida infection. Candida exists as a single-celled budding yeast with pseudohyphae (C albicans also exhibits "germ tubes," hyphal structures formed when the organism is grown in a specific nutritionally rich serum). Candida is a component of normal human skin and mucous membrane flora and is an opportunistic pathogen (does not cause disseminated infection in healthy people). Host defense is provided by 2 immune system components with distinct functions: The interplay of these 2 components can be seen in patients with HIV. These patients frequently have superficial Candida infections given their low T-cell counts, but they do not typically suffer from disseminated candidiasis as a result of HIV itself. If they also have neutropenia, there is a risk for both localized and disseminated candidiasis. (Choice A) Deficiency of complement components C1, C2, and C4 leads to increased susceptibility to infections and systemic lupus erythematosus-like disease. Low levels of C5, C6, C7, C8, and C9 predispose individuals to infections with Neisseria gonorrhea and N meningitidis. (Choice B) Hypogammaglobulinemia predisposes patients to bacterial infections. Neither superficial nor systemic candidiasis is associated with low gammaglobulin levels. (Choice C) Low eosinophil counts are not associated with fungal infections. (Choice E) This patient's HIV increases the risk of superficial Candida infections. However, fungemia is a disseminated rather than a localized (superficial) infection. Educational objective: Local defense against Candida is performed by T cells, whereas systemic infection is prevented by neutrophils. For this reason, localized candidiasis is common in patients who have HIV, but neutropenic individuals are more likely to have the systemic form of the disease. __________ References: Innate versus adaptive immunity in Candida albicans infection. (http://www.ncbi.nlm.nih.gov/pubmed/15061774)

A 56-Year-Old Man Hospitalized in the Intensive Care Unit Is