The interaction between piperacillin/tazobactam and assays for Aspergillus galactomannan and 1,3-beta-D-glucan in patients without risk factors for invasive fungal infections.

BACKGROUND: The aim of this study was to investigate the interaction between intravenous piperacillin/tazobactam treatment and Aspergillus galactomannan antigen (GM) and 1,3-beta-D: -glucan (BDG) test results in patients without known risk factors for invasive fungal infections (IFI). PATIENTS AND METHODS: Patients without known risk factors for IFI and who were to receive piperacillin/tazobactam monotherapy were considered eligible for the study. Serum samples were obtained both before and after antibiotic infusion on the first, third, seventh and tenth days of a piperacillin/tazobactam treatment course and 4 days after the last dose. GM was determined by Platelia Aspergillus ELISA (Bio-Rad Laboratories) and BDG was assayed using the Fungitell kit (Associates of Cape Cod, East Falmouth, MA) according to manufacturers' specifications.
RESULTS: A total of 135 serum samples were collected from 15 patients. When a cut-off level of >or=0.7 was used for GM positivity, there were no false positive results. When a cut-off level of >or=0.5 was used, six serum samples were positive. There were no statistically significant differences between the median GM indices or median BDG levels of the various sampling times. However, 24 of 135 serum samples were positive for BDG for a threshold of 80 pg/mL. After ruling out fungal infections and all known potential causes of false BDG positivity, environmental contamination remained a possible cause of BDG reactivity.
CONCLUSION: No significant interaction was observed between piperacillin/tazobactam administration and Aspergillus GM and BDG assays. Positive results for these tests should be evaluated cautiously in patients at high risk for IFI receiving piperacillin/tazobactam.