• Christophe Chiquet, Max Maurin, Gilles Thuret, Yvonne Benito, Pierre-Loïc Cornut, Catherine Creuzot-Garcher, Frédéric Rouberol, André Pechinot, Gérard Lina, Jean-Paul Romanet, Alain Bron, François Vandenesch, and French Institutional Endophthalmitis Study (FRIENDS) group.
• Department of Ophthalmology, CHU de Grenoble, University Hospital, Université Joseph Fourier, Grenoble, France. cchiquet@chu-grenoble.fr
• Ophthalmology. 2009 Dec 1; 116 (12): 2437-41.e1.

PurposeThis study was designed to compare the diagnostic yield of microbiological analysis performed on diluted and undiluted vitreous samples from pars plana vitrectomy (PPV) in patients with acute postcataract endophthalmitis.DesignCohort study, evaluation of diagnostic test or technology.ParticipantsPatients with acute postcataract endophthalmitis (<6 weeks).MethodsUndiluted and diluted vitreous samples were taken from 34 consecutive patients at the beginning of PPV as part of the multicenter prospective study of the French Institutional Endophthalmitis Study (FRIENDS) group. Vitrectomy was performed after 1 (n = 12) or 2 (n = 22) intravitreous antibiotic injections. McNemar's nonparametric test was used to compare culture and polymerase chain reaction (PCR) results between diluted and undiluted samples.Main Outcome MeasuresRate of positivity of conventional culture (brain heart infusion broth) and eubacterial PCR tests from undiluted and diluted vitreous samples.ResultsThe microbiological analysis of both undiluted and diluted vitreous samples detected and identified a bacterial pathogen in 26 out of 34 cases (76.4%). The analysis of undiluted and diluted vitreous at the time of PPV, using eubacterial PCR and conventional culture, gave similar results (P = 0.99; McNemar test). However, eubacterial PCR was more sensitive than culture in detecting bacteria in vitreous at the time of PPV (76% vs 6%; P = 0.001; McNemar test). The difference in sensitivity between the 2 techniques was primarily associated with false-negative culture results for undiluted samples (2/3 of cases), mainly for coagulase-negative staphylococci.ConclusionsThe microbiological results obtained combining PCR and culture techniques were similar for diluted vitreous and undiluted vitreous analysis. When eubacterial PCR is available, sampling diluted vitreous, an easier procedure, may replace sampling undiluted vitreous.

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