Investigating the activity of antibiotics at aerosolized concentrations against Burkholderia cepacia complex biofilms

S. Kennedy1,2, Y. Yau3, E. Caraher4, V. Waters1,2. 1Hospital for Sick Children,
Physiology and Experimental Medicine, Toronto, Canada; 2Hospital for Sick
Children, Infectious Diseases, Toronto, Canada; 3Hospital for Sick Children,
Microbiology, Toronto, Canada; 4Institute of Technology Tallaght, Centre of Host
Microbial Interactions, Dublin, Ireland



Objectives: Burkholderia cepacia complex (Bcc) causes chronic pulmonary infections
in patients with Cystic Fibrosis (CF). Bcc isolates are drug resistant and
grow as biofilms in vivo, thus protecting themselves from host defences. Currently,
there is no effective antimicrobial therapy for CF patients infected with Bcc. New
aerosolized antimicrobials can deliver very high intrapulmonary concentrations of
drug that may be able to overcome this antimicrobial resistance. The objective of
this study was to compare the activity of tobramycin at systemically achievable vs
aerosolized concentrations on Bcc biofilms cultured under continuous flow in the
novel microfluidic Bioflux system.
Methods: Biofilms of CF Burkholderia multivorans (tagged with gfp) were generated
for 24 hours and were treated with 8 and 1,000 mg/ml tobramycin for 24 hrs.
Results: Analysis of each channel demonstrated that biofilm biomass decreased in
comparison to the controls after treatment with tobramycin. However, while biomass
was decreased, confocal Z-stack images indicated that thickness of microcolonies
within treated biofilms (8 mg/ml, 33 mm; 1000 mg/ml, 41 mm) are similar to controls
(48 hr, 40 mm).
Conclusion: In conclusion, although tobramycin at concentrations achievable by
aerosolization does not eradicate Bcc biofilms in vitro, additional work is underway
to determine its effect on the viability of bacterial cells within this biofilm. Taken
together, this and future work will provide a greater understanding of how Bcc
biofilms can be eradicated in order to improve existing antibiotic therapies and
develop novel treatments, for patients with Cystic Fibrosis.