Pseudomonas aeruginosa (Pa) inhibition of Aspergillus fumigatus (Af) is dependent on the source , phenotype and growth conditions of the bacterium

Ref ID: 19524

Author:

JA Ferreira1,2,3*, H Nazik4, JC Penner2, KV Clemons2,3, RB Moss3, N Banaei3, DA Stevens2,3

Author address:

1School of Medicine, Faculdade da Saúde e Ecologia Humana, Vespasiano, Brazil
2California Institute for Medical Research, San Jose, USA
3Stanford University School of Medicine, Stanford University, Stanford, USA
4Department of Medical Microbiology

Full conference title:

6th Advances Against Aspergillosis 2014

Abstract:

Purpose:
Co-colonization by Pa and Af in airways of cystic fibrosis (CF) patients is associated with worse
clinical outcomes. Our objective was to study in vitro the action of Pa on Af metabolism and the
ability of Af to establish a biofilm (AfBF).
Methods:
One Af strain (10AF), and 26 clinical Pa isolates (16 non-CF isolates (nonCF), 5 CF mucoid variant
(CFMuc), 5 CF non-mucoid (CFNMuc)) were studied. Biofilms were developed on polystyrene disks
in RPMI +10% fetal bovine serum in 12-well plates. Starting with 3×105 conidia, AfBF occurred
in 16 h. 3×107 live Pa cellsorspent culture filtrate (SCF) from Pa grown under planktonic (PK) or
biofilm (BF) conditions, or fresh medium (controls), were added to conidia initially, and after 16 h
fresh medium was substituted for 24 h further incubation. Af metabolic activity was quantified by
the XTT assay. Statistical differences were evaluated using one-way analysis of variance (ANOVA)
followed by a Tukey post-hoc test; statistical significance was considered p 8804;0.05.
Results:
All Pa isolates inhibited the metabolism of Af and AfBF development (p<0.001). CFMuc and CFNMuc isolates were more inhibitory than nonCF (p<0.001), and CFNMuc isolates were more inhibitory than CFMuc isolates (p<0.01). SCF from Pa cultures alone, from all 3 Pa types, grown under either PK or BF conditions, were inhibitory to the Af (p<0.001, all 6 comparisons). SCF from PK nonCF was less inhibitory (p<0.001) than that from either CFNMuc or CFMuc isolates; the 2 CF types were not significantly different. SCF from nonCF Pa grown as BF was not different than that from CFMuc isolates, but SCF from CFNMuc isolates was significantly more inhibitory than those from nonCF or CFMuc (p<0.001). Furthermore, SCF from all 3 types of Pa grown as BF appeared more inhibitory than SCF from Pa grown in PK conditions. Serial dilution experiments of intact media with distilled water indicated the inhibition noted with SCF was not due merely to the effect of prior exhaustion of SCF, but due to inhibitory substances for Af produced by Pa. Conclusions: Pa isolates were inhibitory to Af, though isolates from CF patients are more inhibitory, and nonmucoid CF isolates are most inhibitory. The inhibition, and the differences between Pa isolates, appear the result of soluble inhibitory substances, produced to a greater level when Pa was grown under biofilm conditions. Thus, direct microbial contact was not required. Since the development of mucoid Pa is a late development in CF airways, an hypothesis is that this development is less inhibitory to Af, allowing the formation of Af biofilm in the airways, explaining why Af establishment in airways usually occurs later in CF disease following conversion of environmental non-mucoid to non-mucoid Pa phenotypes in situ, to mucoid types.

Abstract Number: 51

Conference Year: 2014

Link to conference website: http://www.AAA2014.org

New link: NULL

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