2008 OMIG, Abstract 10

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Role of Microbial Cell Wall Products in Culture Negative Contact lens Associated Keratitis
Darlene Miller, DHSc, E.C. Alfonso, MD
Bascom Palmer Eye Institutes, Miami, FL

Purpose: Microbial cell wall products (endotoxin , peptidoglycans/Lipotechoic acids (LTA), 1,3 glucan and chitin) can induce corneal inflammation and toxicity by activating Toll like receptors in corneal tissues. We evaluated the presence of microbial cell wall products in contaminated contact lens systems in culture negative contact lens (CTL) associated keratitis.
Methods:Culture and limulus lystate assays were used to detect the frequency and diversity of microbial cell wall products in 243 matched cornea and contact lens, cases and solution collected at our Institute between  2000-2007.
Results:Microbial cell wall products were present in contact lens systems in 80.2% (97/121) of culture negative CTL-associated keratitis.  LPS (endotoxins-gram negatives) were recovered in 75.3% of the cases, followed by 1,3 glucan (fungi), 10.3, peptidoglycan/LTA(-gram positives-2.1%), chitin (acanthamoeba-1.0%) and mixed products in 11.3% of cases.  Antibiotics use was more likely to be associated with culture negative/ contact lens positive cases.  Correlation between positive culture (122/243-50.2%) and contact lens systems was (213/243-88%) was 95% (116/122).  Predictive value of a positive contact lens for identification of corneal pathogen was only 54% (116/213).
Conclusions:  Microbial cell wall products may induce corneal toxicity/inflammation in the absence of microbial invasion. Detection of such products can play a role in the management of CTL associated keratitis.