The sterility of eye drop content is a primary concern from manufacturing until opening, as well as during handling by end users, while microbial contamination of the dropper tip and cap are often disregarded. The contamination of these sites during drug administration represents a risk of microbial transmission and ocular infection. In this review, we aim to assess microbial contamination of the dropper tip and cap of in-use eye drops, the associated contributory factors, and the risk of infection. We conducted a literature search of the MEDLINE, PubMed, and Cochrane Central databases. A total of 31 out of 1503 studies were selected. All the studies conducted in different settings that documented microbiologically contaminated in-use eye drops were included. Our review showed that microbial contamination of the dropper tip and cap of in-use eye drops ranged from 7.7 to 100% of the total contaminated tested samples. Documented contributory factors were conflicting across the literature. Studies investigating the association between eye infection and microbial contamination of the dropper tip and cap were scarce. New technologies offer a promising potential for securing the long-term sterility of eye drop content, tips, and caps, which could benefit from more research and well-defined study protocols under real-life scenarios.

Culture remains the reference method for microbiological diagnosis of endophthalmitis, but its sensitivity is limited by small sample volumes, prior antibiotics, and fastidious organisms. This study evaluates the diagnostic contribution of 16S rRNA gene-targeted polymerase chain reaction (PCR) in improving bacterial identification in patients with endophthalmitis, compared to conventional culture. We conducted a retrospective cohort study including patients diagnosed with endophthalmitis and managed at Limoges University Hospital (France) from January 2018 to December 2024. Aqueous and/or vitreous samples were analyzed using both conventional culture and broad-range PCR targeting the bacterial 16S rRNA gene. The primary outcome was the global identification rate of pathogens by each method and their combination. Subgroup analyses considered the type of ocular sample. Seventy-one intraocular samples from 50 episodes were analyzed (41 aqueous humor, 30 vitreous). Culture allowed bacterial identification in 21.1% of cases (15/71), compared to 39.4% for PCR (28/71, p = 0.002). The approach combining culture and PCR reached 42.3% (30/71, p < 0.001). Notably, PCR was positive in 26.8% of culture-negative cases (15/56), providing additional identification. Vitreous samples yielded higher identification rates than aqueous samples for both cultures (36,7% vs. 9,8%) and PCR (56,7% vs. 26,8%). PCR targeting the 16S rRNA gene significantly increases the diagnostic and the microbiological yield of intraocular sampling in endophthalmitis, particularly in culture-negative cases and in vitreous specimens. These findings support the complementary role of PCR in the microbiological workup of endophthalmitis. The online version contains supplementary material available at 10.1186/s12348-026-00581-2.