Pseudomonas aeruginosaas a Cause of 1,3‐β‐d‐Glucan Assay Reactivity

Figure 1. The 1,3-b-d-glucan reactivity of different bacteria and other strains. The reactivity of several bacterial culture supernatants was tested with the Fungitell assay (Associates of Cape Cod) in accordance with the manufacturer's instructions. Bacteria, including those isolated from cultures of blood from immunocompromised patients and those isolated from human gut, were cultured in human serum from healthy donors supplemented with glucose (100 mmol/L) for 72 h at 120 rpm and 37؇C. All isolates were tested at least twice in duplicate. Bacterial strains are clinical isolates from the Radboud University Nijmegen Medical Center collection. In addition, Pseudomonas aeruginosa American Type Culture Collection 10145 was tested. Alcaligenes faecalis was used as a positive control, and culture medium was used as a negative control.stein, et al. Relationship between procedures and health insurance for critically ill patients with Pneumocystis carinii pneumonia. Pseudomonas aeruginosa as a Cause of 1,3-b-d-Glucan Assay Reactivity To the Editor—The fungal component 1,3-b-d-glucan is increasingly used to diagnose invasive fungal infection in im-munocompromised patients [1]. Some studies showed false-positive results (i.e., positive findings not related to invasive fungal infection) in bacteremic patients, which were not related to known causes of reactivity, such as 1,3-b-d-glucan in fungal-derived antibiotics [1–4]. We also observed 1,3-b-d-glucan reactivity in tests (Fungitell; Associates of Cape Cod) of plasma samples obtained from bacteremic patients. For 2 (22%) of 9 he-matology patients with Pseudomonas bac-teremia and 1 (20%) of 5 patients with Streptococcus pneumoniae bacteremia, 1,3-b-d-glucan reactivity (i.e., the 1,3-b-d-glucan level of the plasma samples is higher than the cutoff value of 80 pg/mL) was found in plasma that was obtained on the same day that the blood culture specimen was taken. All known causes of 1,3-b-d-glucan reactivity were ruled out in these patients, including the presence of invasive fungal disease or treatment with glucan-containing antibiotics. We then determined 1,3-b-d-glucan reactivity of different bacteria, including those that are commonly isolated from the blood of immunocompromised patients (figure 1). No reactivity was observed for most of the clinical isolates tested. However , in addition to Alcaligenes faecalis and S. pneumoniae, which are known to produce 1,3-b-d-glucan [2], we found that Pseudomonas aeruginosa also showed 1,3-b-d-glucan reactivity. The reactivity in the supernatant of all 7 P. aeruginosa cultures increased during growth and decreased after treatment with 1,3-b-d-glucanase, demonstrating the specificity of the reaction. Although a recent study showed the presence of osmoregulated periplas-mic 1,2-b-glucan and 1,6-b-glucan in P. aeruginosa [5], …