ABSTRACT
Microbiological investigations of vitreous fluid [VF] and aqueous humour [AH] samples have often failed to detect the infecting agent in infectious endophthalmitis, resulting in a clinical dilemma regarding therapy. So in this study we aim to assess the usefulness of polymerase chain reaction in the diagnosis of acute bacterial endophthalmitis. This study included forty intraocular samples [25 vitreous fluids [VF] from 25 cases of endophthalmitis and 15 samples; 7 VF and 8 AH as control from non infective patients during vitreous and cataract surgery respectively. The samples were processed for microbiological investigation [Gram stain and periodic acid schiff and culture for aerobic, anaerobic bacteria and fungi]. Nested PCR directed at the 16S rDNA using universal primers for eubacterial genome was done. The 25 cases were divided into four groups according to the initial ophthalmic procedure. PCR for eubacterial genome showed 100% correlation with 12 [48%] bacterial culture positive samples. Two samples were positive by both direct smear and PCR but negative culture. Eubacterial genome was detected in 5 [38.4%] of 13 bacterial culture negative samples. Among the 8 eubacterial PCR negative samples, one was positive for fungus infection. Only one of 15 control samples was positive for eubacterial genome. The sensitivity and specificity of PCR in relation to culture results were 100% and 93.75%. respectively. The most common organisms recovered from patients with culture proven endophthalmitis were Coagulase Negative Staphylococci [CoNS] [41.7%], S.aureus [16.7] S. viridans [16.7%], Pneumococci [8.3%], P. aeruginosa [8.3%] and E. coli [8.3%]. The most common factors predisposing to acute bacterial endophthalmitis were intraoperative complications, use of anti-metabolite [mitomycin C] and diabetes mellitus. PCR performed on aqueous humour [AH] and vitreous fluid [VF] is a reliable tool for the diagnosis of acute bacterial endophthalmitis particularly in smear and culture negative samples