New diagnostic tool

Postoperative bacterial endophthalmitis requires prompt intervention. However, conventional microbiology techniques are time consuming and have low sensitivity. Brazilian researchers report that real-time polymerase chain reaction testing is useful in distinguishing between contamination and infection based on the cycle thresholds value. They evaluated 11 patients with infectious endophthalmitis, 12 control vitreous samples, and 50 control aqueous samples. Gram and culture identified 80 per cent and 75 per cent, respectively, of patients with infectious endophthalmitis. Real-time PCR assays were positive in 91 per cent of patients with a clinical diagnosis of endophthalmitis using aqueous samples, vitreous samples, or both. None of the 12 vitreous controls were positive by PCR. Two aqueous control samples were positive by real-time PCR. The cycle threshold cut-off value was 36 for universal PCR (sensitivity 93.8 per cent; specificity 100 per cent) and 38 for gram-specific PCR (sensitivity 93.8 per cent; specificity 100 per cent). Gram-positive microorganisms prevailed, and visual acuity varied according to the causative bacteria.

G Barreto Melo et al., JCRS, “Real-time polymerase chain reaction test to discriminate between contamination and intraocular infection after cataract surgery,†Volume 37, No. 7, 1244-1250.