Bacterial Identification Using PCR in Acute Endophthalmitis

Abstract

Abstract: : Purpose: To improve identification and speciation of bacteria involved in acute endophthalmitis, using polymerase chain reaction (PCR) technique. Methods: This prospective study (march 2004, 1 year) includes, in November 2004, 48 patients (mean age 67.6 years, 1.7–94), with endophthalmitis after cataract surgery (n = 37), strabismus surgery (n = 1), vitreo–retinal surgery (n=1), combined surgery (n=1, cataract and epiretinal membrane) or trauma (n=5). In emergency, an anterior chamber puncture (n= 32) and/or a vitreous puncture (n=18) was performed and associated with intravitreal injection of antibiotics. Aqueous humor and/or vitreous samples were collected: 100 microL for standard culture (Brain Heart Infusion) and 150 microL for PCR. In 23 patients (48%) a posterior vitrectomy was performed after the first intravitreal injection of antibiotics and vitreous samples were analysed using the same techniques. Results: After aqueous humor puncture (n=32), microbiological diagnosis is performed on 31% of the samples using cultures and on 38 % using PCR. In two cases, PCR was positive whereas cultures were negative and in one case, inversely. The association of PCR and cultures allows the identification of the bacteria in 40 % of the cases. After vitreous puncture (n=18), cultures were positive in 56% and PCR was positive in 69%. In two cases, PCR was positive whereas cultures were negative and in one case, inversely. The association of PCR and cultures allows the identification of the bacteria in 75% of the cases. For aqueous or vitreous samples, the correlation between both techniques is 100%. After vitrectomy (n = 23 eyes, n = 13 samples), the microbiological diagnosis was made in 15% using cultures and in 77% using PCR. The culture was negative in two cases with negative PCR. Considering aqueous humor and vitreous samples (puncture and vitrectomy), the infectious agent was identified in 75% of the cases. Conclusions: These results confirm that the use of PCR offers a great advantage compared to conventional microbiologic testing and demonstrates that the association of culture and PCR improves the identification of the causative pathogens in endophthalmitis. These preliminary results suggest that cultures and PCR performed on vitreous samples allow a higher rate of bacterial identification than on aqueous humor.

Keywords: endophthalmitis • inflammation • astroglia: optic nerve head