Repeat Intraocular Sampling and Microbiological Testing in Infectious Endophthalmitis: A 27-Year Prospective...

Endophthalmitis requiring multiple ocular tissue sampling for microbiological testing is uncommon and has not been previously studied. This study aims to analyse cases with at least two ocular tissue samplings and testing of different ocular samples against culture yields.

A 27-year prospective observational study using data from the Victorian Endophthalmitis Registry, managed through the REDCap data platform. The study included 314 patients (317 eyes) who underwent at least two aqueous or vitreous specimen collections. The primary outcome measures included microbiological culture results from repeat and multiple intraocular samples and identification of isolated microorganisms.

The overall initial culture positivity rate was 75.7%, while the culture positivity rate at the second intervention was 34.7%. First vitreous taps had the highest culture yield (72.6%) among different sample types. Notably, 19.5% of eyes with initial negative vitreous cultures had subsequent positive results. Further analysis showed that 24.4% of eyes with initial negative vitreous cultures had corresponding positive aqueous cultures. Additionally, 12.2% of eyes with negative initial vitreous taps yielded positive cultures from vitreous biopsies or washings from vitrectomy. Staphylococcus and Streptococcus species were the main pathogens isolated (40.4% and 31.3% of cases respectively).

Our study demonstrated the trends and utility of repeated and different ocular tissue sampling in challenging endophthalmitis. Aqueous taps are most useful at the first biopsy, beyond which it has little diagnostic value. A second sampling can be valuable in patients who are initially culture-negative. Surgical specimens contribute meaningfully to the overall culture yield and enhance cumulative culture positivity.