A Tale of Two Biofilms: A Comparative Study of the Characteristics and Antifungal Drug Susceptibilities of Submerged and Surface Biofilms of Aspergillus fumigatus

Ref ID: 18678

Author:

E. K. Manavathu, Ph. D. – Research Scientist, D. L. Vager, M. S. – Med. Lab. Technologist, J. A. Vazquez, M. D. – Senior Staff;

Author address:

Henry Ford Hosp., Detroit, MI.

Full conference title:

52nd Annual ICAAC

Date: 9 September 2014

Abstract:

Background: A. fumigatus (Af) produces submerged (SUB) and surface (SUR) biofilms in vitro and in clinical settings. Airway infections due to Af in cystic fibrosis patients produce SUB-like biofilm whereas the multicellular Af mycelial growth in pulmonary cavities known as a “œfungus ball” is similar to SUR biofilm. The Af fungus ball is resistant to antifungal drug therapy and often requires surgical intervention for the resolution of the infection. The primary objective of this study was to examine the effects of antifungals against SUB and SUR biofilms of Af using an in vitro model. Methods: SUB and SUR biofilms of Af were formed in 12-well tissue culture plates in SD broth (1 x 106 conidia/ml) for 24 h – 72 h. The SUB and SUR biofilms were washed and the dry weight was determined. The hydrophobic interaction was determined by a crystal violet dye binding assay. For drug susceptibility studies, biofilms were exposed to voriconazole (VCZ) and posaconazole (PCZ) at 35 ºC for 24 h, washed, homogenized, diluted and 0.01 ml aliquots were plated on SD agar for CFU assay. The CFUs obtained for drug-treated group were compared with those obtained for the drug-free control. Results: The SUB biofilm reached maximum growth in 24 h, whereas the SUR biofilm grew to the maximum level in 60 h. The SUR biofilm was highly hydrophobic and bound < 10% of crystal violet dye, compared to the SUB biofilm. SUR biofilm showed no susceptibility to VCZ (CFUs for the control and the drug treated groups were 2 x 106 ± 0 CFU/ml and 1.66 x 106 ± 1.44 x 105 CFU/ml, respectively, p = 0.057) and PCZ (CFU for the control and the drug-treated groups were 2.70 x 106 ± 1.31 x 106 CFU/ml and 2.73 x 106 ± 9.08 x 105 CFU/ml, respectively, p = 0.9603). The SUB biofilm was inhibited ~ 95% (8776;1.5 logs CFU reduction) at a drug concentration of 64 µg/ml. Conclusions: Af is a highly versatile opportunistic fungus capable of producing SUB and SUR biofilms. The SUR biofilm is highly resistant to antifungal drugs such as VCZ and PCZ perhaps due to the presence of hydrophobin molecules on the surface.

Abstract Number: M-987

Conference Poster: y

Conference Year: 2012

Link to conference website: NULL

New link: NULL

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