Recent case reports describe patients receiving piperacillin-tazobactam who were found to have circulating galactomannan detected by the double sandwich enzyme-linked immunosorbent assay (ELISA) system, leading to the false presumption of invasive aspergillosis. Since this property of piperacillin-tazobactam and galactomannan ELISA is not well understood, we investigated the in vitro, in vivo, and clinical properties of this interaction. Among the 12 reconstituted antibiotics representing four classes of antibacterial compounds that are commonly used in immunocompromised patients, piperacillin-tazobactam expressed a distinctively high level of galactomannan antigen in vitro (P ‫؍‬ 0.001). After intravenous infusion of piperacillin-tazobactam into rabbits, the serum galactomannan index (GMI) in vivo changed significantly (P ‫؍‬ 0.0007) from a preinfusion mean baseline value of 0.27 to a mean GMI of 0.83 by 30 min to slowly decline to a mean GMI of 0.44 24 h later. Repeated administration of piperacillin-tazobactam over 7 days resulted in accumulation of circulating galactomannan to a mean peak GMI of 1.31 and a nadir of 0.53. Further studies revealed that the antigen reached a steady state by the third day of administration of piperacillin-tazobactam. Twenty-six hospitalized patients with no evidence of invasive aspergillosis who were receiving antibiotics and ten healthy blood bank donors were studied for expression of circulating galactomannan. Patients (n ‫؍‬ 13) receiving piperacillin-tazobactam had significantly greater mean serum GMI values (0.74 ؎ 0.14) compared to patients (n ‫؍‬ 13) receiving other antibiotics (0.14 ؎ 0.08) and compared to healthy blood bank donors (0.14 ؎ 0.06) (P < 0.001). Five (38.5%) of thirteen patients receiving piperacillin-tazobactam had serum GMI values > 0.5 compared to none of thirteen subjects receiving other antibiotics (P ‫؍‬ 0.039) and to none of ten healthy blood bank donors (P ‫؍‬ 0.046). These data demonstrate that among antibiotics that are commonly used in immunocompromised patients, only piperacillin-tazobactam contains significant amounts of galactomannan antigen in vitro, that in animals receiving piperacillin-tazobactam circulating galactomannan antigen accumulates in vivo to significantly increased and sustained levels, and that some but not all patients receiving this antibiotic will demonstrate circulating galactomannan above the threshold considered positive for invasive aspergillosis by the recently licensed double sandwich ELISA.The recent development and introduction of the double sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of galactomannan antigenemia is an important advance in the nonculture diagnosis of invasive aspergillosis (3, 5-8, 14, 15). Depending on the patient population, several studies have demonstrated a sensitivity ranging from 50 to 95% and a specificity ranging from 87 to 99% for the diagnosis of invasive aspergillosis. However, recent clinical reports describing results of circulating galactomannan antigenemia in ...

The treatment, diagnosis and therapeutic monitoring of hematogenous Candida meningoencephalitis (HCME) are not well understood. We therefore studied the expression of (133)-␤-D-glucan (␤-glucan) in cerebrospinal fluid (CSF) and plasma in a nonneutropenic rabbit model of experimental HCME treated with micafungin and amphotericin B. Groups studied consisted of micafungin (0.5 to 32 mg/kg) and amphotericin B (1 mg/kg) treatment groups and the untreated controls (UC). Despite well-established infection in the cerebrum, cerebellum, choroid, vitreous humor (10 2 to 10 3 CFU/ml), spinal cord, and meninges (10 to 10 2 CFU/g), only 8.1% of UC CSF cultures were positive. By comparison, all 25 UC CSF samples tested for ␤-glucan were positive (755 to 7,750 pg/ml) (P < 0.001). The therapeutic response in CNS tissue was site dependent, with significant decreases of the fungal burden in the cerebrum and cerebellum starting at 8 mg/kg, in the meninges at 2 mg/kg, and in the vitreous humor at 4 mg/kg. A dosage of 24 mg/kg was required to achieve a significant effect in the spinal cord and choroid. Clearance of Candida albicans from blood cultures was not predictive of eradication of organisms from the CNS; conversely, ␤-glucan levels in CSF were predictive of the therapeutic response. A significant decrease of ␤-glucan concentrations in CSF, in comparison to that for UC, started at 0.5 mg/kg (P < 0.001). Levels of plasma ␤-glucan were lower than levels in simultaneously obtained CSF (P < 0.05). CSF ␤-glucan levels correlated in a dose-dependent pattern with therapeutic responses and with Candida infection in cerebral tissue (r ‫؍‬ 0.842). Micafungin demonstrated dose-dependent and site-dependent activity against HCME. CSF ␤-glucan may be a useful biomarker for detection and monitoring of therapeutic response in HCME.

Pulmonary infiltrates in neutropenic hosts with invasive pulmonary aspergillosis are caused by vascular invasion, hemorrhagic infarction, and tissue necrosis. Monitoring the dynamics of pulmonary infiltrates of invasive aspergillosis is an important tool for assessing response to antifungal therapy. We, therefore, introduced a multidimensional volumetric imaging (MDVI) method for analysis of the response of the volume of pulmonary infiltrates over time to antifungal therapy in experimental invasive pulmonary aspergillosis (IPA) in persistently neutropenic rabbits. We developed a semiautomatic method to measure the volume of lung lesions, which was implemented as an extension of the MEDx visualization and analysis software using ultrafast computerized tomography (UFCT). Volumetric infiltrate measures were compared with UFCT reading, histopathological resolution of lesions, microbiological clearance of Aspergillus fumigatus, and galactomannan index (GMI). We also studied the MDVI method for consistency and reproducibility in comparison to UFCT. Treatment groups consisted of deoxycholate amphotericin B (DAMB) at 0.5 or 1 mg/kg of body weight/day and untreated controls (UC). Therapeutic monitoring of pulmonary infiltrates using MDVI demonstrated a significant decrease in the infiltrate volume in DAMB-treated rabbits in comparison to UC (P < 0.001). Volumetric data by MDVI correlated with conventional CT pulmonary scores (r ‫؍‬ 0.83, P < 0.001). These results correlated with validated biological endpoints: pulmonary infarct scores (r ‫؍‬ 0.85, P < 0.001), lung weights (r ‫؍‬ 0.76, P < 0.01), residual fungal burden (r ‫؍‬ 0.65, P < 0.05), and GMI (r ‫؍‬ 0.78, P < 0.01). MDVI correlated with key biological markers, improved the objectivity of radiological assessment of therapeutic response to antifungal therapy, and warrants evaluation for monitoring therapeutic response in immunocompromised patients with invasive aspergillosis.

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