Incidence and significance of Aspergillus cultures following liver and kidney transplantation

Aspergillus infection is a rare but devastating complication following solid organ transplantation, with mortality rates that approach 100%. Aspergillus species (sp)* are also ubiquitous in our environment and may contaminate culture plates. To determine the significance of positive Aspergillus cultures, we analyzed all positive cultures from the liver and kidney transplant services at our center for the treatments used and clinical outcomes. Aspergillus sp. were cultured from 4.5% of liver and 2.2% of kidney transplant recipients. A. fumigatus was the most common isolate, followed by A. niger and A. flavus. The lung was the most common site of positive cultures. Body fluids (ascites, pleural fluid) were common sources of positive cultures but were never associated with clinical disease. Positive brain biopsies occurred in 10% of patients. Analysis of risk factors for significant infection revealed that cultures with >2 colonies or more than one site of infection were predictive of significant infection and portended a poor prognosis even with aggressive therapy. Two or fewer colonies from a single site likely represented contamination and may be followed with repeat cultures. The high mortality rate associated with Aspergillus sp. infections in transplant recipients highlights the need for better anti-fungal prophylaxis and treatment.