Pseudomonas aeruginosa infections and improper storage conditions influence the performance of 1,3-β-d-glucan in diagnosis of invasive fungal infections

Background

The association between 1,3-β-d-glucan (BDG) levels and infections caused by Pseudomonas aeruginosa or Streptococcus pneumoniae, and the stability of BDG under different storage conditions are unclear.

Methods

Strains of Pseudomonas aeruginosa and S. pneumoniae were grown in medium and human serum. The BDG concentrations in culture supernatants were measured. The specificity and stability of BDG were also evaluated.

Results

P. aeruginosa produced high levels of BDG in Luria–Bertani medium (>4 × 10⁴ pg/mL) and human serum (527.0 pg/mL), whereas S. pneumoniae produced low levels of BDG in THY medium (175.6 pg/mL) and human serum (78.3 pg/mL). The BDG produced by these two bacteria was specifically degraded by 1,3-β-d-glucanase. BDG was degraded when stored at different temperatures, decreasing by 22.5% and 9.3% at −20°C and −70°C, respectively, for 63 days; by 30.7% at 4°C for 12 days; and by 12.6% and 22.0% at 37°C for 6 and 12 h.

Conclusion

BDG false-positivity must be considered in patients with bacteremia caused by P. aeruginosa when diagnosing invasive fungal infection. Human serum samples for the BDG test in medical facilities should be tested as soon as possible or stored at low temperatures before testing.