In vitro biofilm formation and virulence of Paracoccidioides lutzii (LDR2) in a Galleria mellonella larval model

Abstract

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the thermodimorphic fungi Paracoccidioides brasiliensis and the newly identified species P. lutzii. This study investigated in vitro biofilm formation by P. lutzii (LDR2) and assessed its impact on Galleria mellonella larvae. Scanning electron microscopy (SEM) revealed that P. lutzii (LDR2) forms dense biofilms composed of a complex cellular network embedded in an extracellular matrix. Biofilm-associated infection significantly increased fungal virulence, resulting in higher larval mortality, reduced hemocyte density, and enhanced melanization. Moreover, infections with both biofilm and planktonic P. lutzii cells resulted in distinct nodule formations, as demonstrated by histological analysis. This study is also the first to present scanning electron microscopy (SEM) images of nodules induced by both planktonic and biofilm cells, as well as alterations in the fat body tissue of G. mellonella.

Keywords: Granulomas; Hemocytes; Melanization; Mycosis; Phagocytosis; Scanning electron microscopy.