Vitreous cultures in suspected endophthalmitis. Biopsy or vitrectomy?

BACKGROUND: Isolation of bacteria from vitreous biopsy often guides therapy in suspected endophthalmitis. Therapeutic vitrectomy provides an additional source of culture material. The authors compared the ability of these two techniques to isolate organisms from patients with acute endophthalmitis.

METHODS: In a large ophthalmic microbiology laboratory during a 4-year period, the authors analyzed 206 microbial culture results from patients with suspected endophthalmitis.

RESULTS: Two hundred six cases were evaluated. While cultures of vitreous biopsy specimens obtained using a needle and syringe were positive in 91 (53.8%) of 169 patients, culturing the contents of the vitrectomy cassettes produced positive cultures in 29 (74.8%) of 39 patients. Both techniques were performed on 23 patients. Vitreous biopsy allowed isolation of the causative organism in 43% of these patients, whereas vitrectomy was 76% successful. Both comparisons were significant at the P < 0.01 level. No positive vitreous biopsy cultures had associated negative vitrectomy cultures.

CONCLUSION: Culturing the contents of the vitrectomy cassette significantly increases the likelihood of obtaining a positive culture compared with merely culturing a vitreous biopsy.