A Comparative Study of Mixed Microbial Biofilms of Aspergillus fumigatus, Scedosporium apiospermum and Lomentospora prolificans Formed with Pseudomonas aeruginosa

E. Manavathu, S. Wakade, J. Vazquez

Author address: 

Med. Coll. of Georgia/Augusta Univ., Augusta, GA

Abstract: 

Background: Aspergillus fumigatus (Af), Scedosporium apiospermum (Sa) and Lomentospora prolificans (Lp) are the most commonly isolated filamentous fungi from the airways of cystic fibrosis (CF) patients either alone or with Pseudomonas aeruginosa (Pa). In the CF airways Pa interacts with fungi to form polymicrobial (PM) biofilm highly tolerant/resistant to antimicrobial drugs. The primary objective of this study was to research the structure, development and antimicrobial susceptibility of Af-Pa, Sa-Pa and Lp-Pa PM biofilms. Methods: Pa PA01, 27853, MJK8, CF39wt, CF39s, Sa3634, Lp201214, Af43004 and Af43135 were used. Structure and development of PM biofilm were examined by SEM. Mixed microbial interaction was studied by coculture experiments and agar plate inhibition assays. Antimicrobial susceptibility was studied by exposing biofilms to various concentrations of the drug(s) individually and in combination. The effectiveness of the drug treatment was determined by CFU or MTT assays. Results: Pa formed PM biofilm with Af, Sa and Lp. The structure and development of Pa-Af, Pa-Sa and PaLp biofilms were similar. The Pa cells were firmly attached to the fungal hyphae by surface appendages exploiting the extracellular matrix (ECM). In mature PM biofilm the bacterial cells were fully encased or trapped in the ECM made up of bacterial and fungal cellular components. The interaction of Pa and Af cells in mixed microbial cultures resulted in the growth inhibition and death of Af cells. In contrast, Sa and Lp cells were tolerant to the killing effect of Pa in cocultures, although growth was substantially inhibited. The antimicrobial drug susceptibility of the fungal cells in PM and monomicrobial (MM) biofilms was similar. In contrast, the Pa cells in PM showed tolerance/resistance to cefepime and imipenem (0.5-1.5 logs CFU reduction at 64µg/ml) compared to that in MM biofilm (2-3 logs CFU reduction at 64µg/ml). The susceptibility to ciprofloxacin and tobramycin was similar (4-5 logs CFU reduction at 64 µg/ml) for both MM and PM biofilms. Conclusions: The structure, development and antimicrobial drug susceptibility of Pa-Af, Pa-Sa and Pa-Lp biofilms are similar. However, the interaction of Pa with Af leads to the death of the fungal cells, whereas the fungicidal effect of Pa against Sa and Lp was minimal.
2016

abstract No: 

SATURDAY-316

Full conference title: 

ASM Microbe 2016
    • ASM microbe 1st (2016)