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Ben Wucher, Jordan Reed, Paul Dunman, Rachel Wozniak; Clinical keratitis isolates of Pseudomonas aeruginosa develop resistant biofilms. Invest. Ophthalmol. Vis. Sci. 2016;57(12):325.
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Pseudomonas aeruginosa is a leading cause of gram-negative keratitis, particularly in contact lens wearers and readily forms biofilms on biotic an abiotic surfaces, including contact lenses. Biofilms are thought to play a role in potentiating corneal infection, which has implications for treatment strategies in an era of increasing antibiotic resistance. We sought to demonstrate increased resistance of Pseudomonas clinical isolates to common ophthalmic antibiotics when grown in biofilms on synthetic surfaces, including contact lenses.
Seven keratitis P. aeruginosa strains were collected from the Flaum Eye Institute and compared to the laboratory strain PAO1. Phenotypic characteristics such as color, colony morphology and biofilm formation were noted. Virulence factors, exoS, exoY, exoU, exoT and pcrV were determined by PCR. Minimum inhibitory concentrations (MIC) to a panel of ophthalmic antibiotics were measured by determining colony-forming-units (CFUs) after a 24-hour treatment period for planktonic culture and biofilms. Biofilms were formed on multi-welled polystyrene plates and on Acuvue Oasis contact lenses.
There was noted phenotypic and genetic diversity among the clinical isolates indicating a non-clonal population. All isolates demonstrated a significant increase in resistance towards gentamycin, tobramycin, Neosporin (bacitracin/zinc/neomycin/polymixin), PolyTrim (trimethoprim/polymixin) and Vigamox (moxifloxacin) when grown as a biofilm on polystyrene plates or contact lenses compared to planktonic culture (p<0.001). Biofilms were particularly resistant to PolyTrim with an average 41-fold increase in MIC. Conversely, Vigamox had the smallest change in resistance with an average increase of 5-fold. Gentamycin, tobramycin and Neosporin demonstrated an increase in MIC ranging between 14-17 fold.
Pseudomonas aeruginosa is an important pathogen in keratitis, particularly in contact lens wearers. There was a significant, and in some instances, a dramatic increase in MIC for all tested ophthalmic antibiotics in clinical isolates grown as biofilms on both polystyrene plates and contact lenses. This has direct clinical significance when considering treatment strategies for acute keratitis as well as prevention in contact lens solutions and disinfectants.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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