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2008 OMIG, Abstract 19

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Endosymbionts as co-pathogens in Acanthamoeba keratitis
Lovieno1,2, D. Miller1, D. Ledee1, N. Mandal1, E. Alfonso1
1Bascom Palmer Eye Institute, University of Miami – Miller Scool of Medicine, Miami, FL; 2Ophthalmology Department, University Campus Bio-medico, Rome, Italy

Purpose: To determine the presence of bacterial endosymbionts in isolates obtained from patients with Acanthamoeba ketatitis (AK) and their possible contribution in the pathogenesis of the disease.
Methods: Clinical isolates recovered from cornea, contact lenses and contact lens cases (n=38) and environmental sources (n=12) were evaluated for the presence of microbial endosymbionts using PCR, sequencing techniques, fluorescence in situ hybridization (FISH) and electron microscopy.  Pathogenicity of clinical isolates of Acanthamoeba bearing different endosymbionts was determined by analyzing the sytopathic effect (CPE) on human corneal epithelial cells.
Results: Four different species of bacterial endosymbionts were detected in 28/38 (74%) clinical and 6/12 (50%) environmental Acanthamoeba isolates by PCR, FISH and electron microscopy.  Pseudomonas species were detected in 18/50 (36%), Legionella species other than pneumophilia in 7/50 (14%), Mycobacterium other than tuberculosis in 15/50 (30%) and Chlamydia trachomatis in 1/50 (2%).  7/50 (14%) of the isolates had more than one endosymbiont. 
CPE on corneal epithelial cells was significantly higher for Acanthamoebas hosting endosymbionts compared to isolates without endosymbionts (p<0.05). Interstingly, corneal pathogenic endosymbionts such as Pseudomonas and Mycobacterium  enhanced Acanthamoeba CPE significantly more than Legionella (p<0.05).
Conclusions: 74% of our clinical isolates showed one or more bacterial endosymbionts.  The presence of ocular pathogens such as Pseudomonas and Mycobacterium as endomsymbionts enhances the corneal pathogenicity of Acanthamoeba isolates.  This might have clinical relevance for the management and treatment af Acanthamoeba keratitis.


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