Laboratory diagnosis of endophthalmitis: Comparison of microbiology and molecular methods in the European Society of Cataract & Refractive Surgeons multicenter study and susceptibility testing

PURPOSE:To investigate and compare the use of molecular biology with the use of traditional Gram stain and organism culture for labotatory diagnosis of postoperative endophthalmitis. SETTING: Twenty-four ophthalmolgy units together with 9 microbiology laboratories and 2 European reference molecular biology laboratories. METHODS: A prospective randomized partially masked multicenter cataract surgery study recruited 16603 patients. This resulted in 29 cases of presumed postoperative endophthalmitis. Gram stain and culture were performed in the local laboratory according to agreed protocols. Samples of aqueous and/or vitreous were transported to the first referenced molecular biology laboratory (Regensburg, Germany) for polymerase chain reaction (PCR) testing, and an extracted aliquot of DNA was then referred to the second laboratory (Alicant, Spain) for PCR. RESULTS: Of the 29 who presented with presumed postoperative endophthalmitis, 20 were classified as proven infectiveendophthalmitis with positive Gram stain, culture, or PCR. Fourteen patients were cultuire-positive; all but 1 of these was also positive by PCR. Six patients were positive by PCR but negative by Gram stain or culture. Nine patients were negative by both microbiology and PCR testing. CONCLUSIONS: Use of molecular bilogy technique increased the laboratory rate of identifying the pathogen by 20%, confirming the technique is very useful for the endophthalmitis specimen. Samples of both aqeous and vireous should be collected and stored at -20 degrees C for PCR at the time of diagnostic taps