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Jaime A. Castellanos, Darlene Miller, Eduardo C. Alfonso; Impact of AsaSite on Mature Pseudomona Biofilms. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1490.
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We compared the impact (MIC-Minimal inhibitory concentrations) of AzaSite, Azithromycin, ciprofloxacin, levofloxacin and tobramycin to disrupt mature Pseudomonas aeruginosa biofilms.
MICs of 12 day biofilms of Pseudomonas aeruginosa ( 3 reference strains PA01, 27853, 19142 (mucoid) 1 from contact lens associated infections, #9966) developed on plastic pegs in a 96 well microtiter plate (MBEC plates) and planktonic strains were determined and compared for AzaSite, Azithromycin, Ciprofloxacin, Levofloxacin and Tobramycin. MIC values (ug/ml) ranged from 0.3-16 ug/ml for all antibiotics. AzaSite concentrations ranged from 0.007-4 ug/ml. OD readings (560nm, 600 nm) were used to determine MICs, biofilm maturity and inhibition. Biofilms were grown and evaluated in triplicate.
MICs (ug/ml) for planktonic strains were: ciprofloxacin (0.5, 1,1,1), levofloxacin (0.5), tobramycin (0.5, 1, 1, 1), azithromycin (>16) and for AzaSite (0.5,0.5, 1, 1). MICs for strains in biofilm for the fluoroquinolones, azithromycin and tobramycin exceeded 16 ug/ml with no measurable reduction (OD readings were equal to or exceeding the OD reading of the growth control). The difference between planktonic vs biofilm strains ranged from 16-32 fold. AzaSite reduction of mature biofilms was strain specific. Reference strains: There was a 39-54% (average 51%,) reduction in biofilm formation for the ATCC 27853 strain MIC50 = > 4 ug/ml, vs a 2.7 fold increase in biofilm growth for strain PA01. CTL strains: Reduction in biofilm for strain 9966 ranged from 0.07-34% (average 22%), but a 1.3-1.5 fold increase in biofilm formation for strain 19142.
Pseudomonas aeruginosa strains in biofilm are refractory to commonly used ocular antibiotics. Azasite in combination may aid in disrupting the biofilm to allow other ocular antibiotics to be more effective.
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