Microbiological Culture and Universal Pcr Yield of Diluted or Undiluted Vitreous From Vitrectomy Are Comparable in Acute Postsurgery Endophthalmitis

Abstract

Purpose: : To compare the diagnostic yield of microbiological analysis performed on diluted and undiluted vitreous samples from pars plana vitrectomy in patients with acute postcataract surgery endophthalmitis.

Methods: : Undiluted and diluted vitreous samples were harvested in 34 patients at the beginning of the vitrectomy, among the 57 vitrectomized patients (out of 100 patients presenting with an acute postcataract surgery endophthalmitis) included in the multicentric prospective study FRIENDS (2004-2005). Vitrectomy was performed after one (n=12) or two (n=22) antibiotics intravitreal injections. Each vitreous sample was divided into two parts. The first one was analyzed using conventional culture (Brain Heart Infusion broth) and the second one using universal PCR. Results obtained from undiluted and diluted vitreous were compared for each patient.

Results: : Microbiological analysis of both undiluted and diluted vitreous allowed a bacterial identification in 28 out of 34 cases (82.3%). Microbiological diagnosis using undiluted vitreous and conventional culture was negative in 32 cases and positive in 2 cases. In one case, there was a discrepancy between undiluted (culture negative) and diluted vitreous (S. epidermidis).Analysis of both undiluted and diluted vitreous using universal PCR was positive in 28 cases and negative in 6/34 cases. There was a discrepancy between both samples in three cases. Two cases among these three cases were false negative results observed in the undiluted vitreous analysis while PCR performed on diluted vitreous identified a strain of Proteus vulgaris and S. epidermidis, respectively. For the third case, the false negative result originated from the diluted vitreous analysis and PCR carried out on undiluted vitreous found a S. epidermidis/capitis strain.

Conclusions: : Undiluted vitreous sampling at the beginning of the vitrectomy for endophthalmitis may lead to an increase of vitreoretinal tractions. Once the infusion is started, sampling of the vitreous is more easily performed and less dangerous. Microbiological results combining PCR and cultures showed that diluted vitreous analysis may replace analysis of undiluted vitreous.

Keywords: endophthalmitis • vitreous • bacterial disease