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Padmanabhan Saraswathi, Thet Aung, Shuhaida Salleh, Roger Beuerman; An Experimental Model of Biofilm Formation in the Mouse Cornea. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5208.
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Microbial keratitis is a severe and visually challenging outcome of corneal infection with antibiotic resistance being reported more frequently. The existence of bacteria in a protected state, the “Biofilm” a heterogeneous bacterial population within a bio polymeric extracellular matrix, shields bacteria from innate immune defence and antibiotics. Direct evidence of bacterial biofilm associated with ocular tissues is lacking. This study is an attempt to develop evidence for biofilm formation in a mouse model
A corneal infection was created in a C57BL/6 wild type black mouse by the topical application of a bacterial suspension of 108 CFU/ml (Pseudomonas aeruginosa -ATCC 9027 and Staphylococcus aureus ATCC-29213). The progress of the infection was measured by monitoring corneal opacity through slit lamp examination. The infected eyes were enucleated in different time points of post infection, the cornea was excised and used for imaging biofilm formation. Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) were used for this study
SEM demonstrated adherence of Pseudomonas on the corneal epithelial layer at early post infection times. Protruding clusters of Pseudomonas fixed within a matrix, as seen in a static culture, indicated the presence of extra polymeric substances (EPS) at day three post infection. Similarly, groups of Staphylococci were seen on the corneal epithelium in the early time of post infection. Assembly of cells connected with each other by fibre like structures and aggregates of bacteria enclosed in thick coatings of matrix substances observed by SEM suggested biofilm formation. CLSM images further confirmed the presence of bacteria within the biofilm
These preliminary findings demonstrated that biofilm formation could develop on the corneal surface in an experimental mouse model of corneal infection. Use of this corneal biofilm model can provide new insights into the interaction of microbial communities on ocular pathophysiology and antibiotic resistance
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