CHICAGO—Zygomycosis, an invasive fungal infection with substantial morbidity and mortality, is increasing steadily in the United States among solid organ and stem cell transplant recipients, according to the largest prospective study looking at contemporary cases.


Researchers at the Centers for Disease Control and Prevention (CDC) in Atlanta analyzed data from the 25 academic TRANSNET (Transplant-Associated Infection Surveillance Network) centers. These centers monitor for invasive fungal infections among transplant recipients and identify proven and probable cases of such infections. TRANSNET has been screening patients since Octo-ber 2001. To date, more than 31,600 transplants have been screened and 31,150 person-years of follow-up have been conducted.

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From October 2001 through De-cember 2006, investigators identified 105 cases of proven and probable zygomycosis. The mean age of infected patients was 50 years (range 10-74 years); 60 (57%) were male. Rhizopus (52%) and Mucor (18%) were the most common fungal genera identified. Sinus or pulmonary infection was the most common clinical presentation, occurring in 80% of patients.


A total of 77 cases (73%) occurred among stem cell transplant patients and 28 cases (27%) occurred among solid organ transplant patients. The median time from transplantation to zygomycosis was 135 days among the stem cell transplant patients and 312 days among solid organ recipients. Nine of the 28 cases (32%) among the solid organ transplant patients occurred in kidney recipients.


Voriconazole was the most frequent antifungal agent given prior to infection for both stem cell pa-tients (53%) and solid organ transplant patients (21%). Among the stem cell transplant patients, 33 (43%) had active diabetes, 39 (51%) were neutropenic, and 59 (77%) were on steroids at the time zygomycosis developed. 


The 90-day crude mortality was 61%. The one-year cumulative incidence was 3.8 cases per 1,000 stem cell recipients and 0.6 cases per 1,000 solid organ transplant recipients. Among all transplant patients, the incidence increased from 0.04% to 0.21% during the course of the study. 


“These data are important because this study looks at patients over a five-year period and it doesn’t lend itself to some of the biases of retrospective studies,” said lead investigator Benjamin Park, MD, a medical epidemiologist at the CDC who presented his study findings here at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy.


“For nephrologists and urologists, there was some good news because the incidence rate among solid organ transplant patients was lower than what we found among bone marrow transplant patients,” Dr. Park told Renal & Urology News. “Nevertheless, because kidney transplants are so common they actually represented a lot of the disease.”


Importantly, he noted, these infections are occurring almost one year after transplantation. “This has led us to believe that these infections are occurring late and may be occurring outside the typical window that we think about these infections happening,” he said.


Many institutions give solid organ transplant recipients voriconazole as prophylaxis against aspergillus infections, Dr. Park said, adding that the medication could play a role in the recent increase in zygomycosis.


“Because voriconazole is not effective against zygomycosis, some people think these are breakthrough [aspergillus] infections because voriconazole is already on board,” Dr. Park said. “We think this is a very interesting hypothesis, but our study is not designed to answer that question, although our data are consistent with that.”