Antimicrobial Monotherapy vs. Combination Therapy of Aspergillus fumigatus and Pseudomonas aeruginosa Biofilms

Ref ID: 18736

Author:

H. Zainah, MD (Doctor of Medicine) – Fellow, E. Manavathu, PhD – R. Scientist, D. Vager, BAS – RES, J. A. Vazquez, MD – Professor;

Author address:

Henry Ford Hosp., Detroit, MI.

Full conference title:

52nd Annual ICAAC

Date: 9 September 2014

Abstract:

Background: Aspergillus fumigatus (AF) frequently co-exists with Pseudomonas aeruginosa (PA) in the respiratory tract of cystic fibrosis patients. Both PA and AF are capable of producing biofilms in vivo. The objective of this study was to compare monotherapy vs combination therapy using posaconazole (PCZ) and different antimicrobials in both monomicrobial (MM) and polymicrobial (PM) biofilms. Methods: The MM biofilms of AF and PA were developed in 24-well culture plates in Sab dextrose (SD) broth at 35°C. PA was added to AF after 24 h to form PM biofilm. The MM biofilms were treated with PCZ or one of the following: tobramycin (TOB), cefepime (CEF), ciprofloxacin (CIP) or imipenem (IMP). The PM biofilms were treated with PCZ and either TOB, CEF, CIP or IMP. Biofilms were exposed (0-64 µg/ml) for 24 h. The efficacy was evaluated by colony forming unit (CFU) assay on selective SD agar. One-way and two-way ANOVA and t test were used. Results: Among the antibacterials used alone or in combination with PCZ in PM biofilm, TOB showed the best activity (6.5 logs CFU reduction, P = 0.7224), followed by CIP (3.5 logs CFU reduction, P=0.3594), CEF (1.5 logs reduction, P=0.1485) and IMP (1 vs. 1.5 logs CFU reduction, P=0.2808) at 32-64 µg/ml drug concentrations. This suggests that monotherapy is as effective as combination therapy. A comparison of the effects of the antibacterials on PA MM and PM biofilms showed that they are equally effective (TOB 3.5 vs. 6.5 logs CFU reduction, P=0.2347; CIP 4.5 vs. 3.5 logs CFU reduction, P=0.3293; CEF 1.5 logs CFU reduction, P=0.3677), except for IMP (2.6 vs. 1 logs CFU reduction, P=0.0409) where it showed a significant difference. Both mono- and combination therapies in AF PM biofilms showed similar susceptibilities (3.5 vs. 2.5 logs CFU reduction, P values 0.0915 – 0.9768). The CFU reduction in AF MM and PM biofilms by PCZ was 0.5 vs. 2.5 logs (P values 0.0184 – 0.0202). Conclusions: Our results showed that combination therapy was as effective as monotherapy in PA PM biofilm and in AF PM biofilm. Monotherapy against PA MM and PM biofilms was equally effective except for IMP where MM biofilm showed increased susceptibility. The increased susceptibility of AF PM biofilm to PCZ may be due to the reduced AF growth in PM biofilm.

Abstract Number: M-1716

Conference Poster: y

Conference Year: 2012

Link to conference website: NULL

New link: NULL

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