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Jerome Ozkan, Mark D P Willcox, Jennifer Sandbach, Minas T Coroneo, Torsten Thomas; Bacterial contamination of intravitreal needles by the ocular surface microbiome. Invest. Ophthalmol. Vis. Sci. 2020;61(7):375.
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© ARVO (1962-2015); The Authors (2016-present)
A devastating complication of intravitreal (IVT) injection is exogenous endophthalmitis, caused by the inoculation of microorganisms into the vitreous cavity. Previous studies using conventional culturing-based methods have found up to 18% of IVT needles are contaminated with bacteria following injection, even after extensive sterilisation of the ocular surface. Our recent finding that bacteria are embedded in conjunctiva tissues led us to examine whether these could be transferred onto needles.
IVT needles were obtained from patients undergoing treatments for age-related macular degeneration, diabetic retinopathy and retinal vein occlusion. Needles were collected immediately after injection. A total of 20 needles (including two negative controls) were analysed by culturing on chocolate blood agar. In addition, 48 needles (including 8 negative controls) were analysed by extracting total DNA from needles and paired-end sequencing of the 16S rRNA gene on the MiSeq platform. Sequences were quality filtered using USEARCH, taxonomically classified using SILVA and contaminant filtered using DECONTAM software. Furthermore, five needles each were analysed by fluorescent in situ hybridisation (FISH) using the universal bacterial probe EUB338 and scanning electron microscopy (SEM) to directly visualise bacteria.
Using conventional culturing and the Vitek 2 system, three bacteria were isolated and identified from 5 of 18 needles (28%) - Kocuria kristinae (3 needles), Staphylococcus hominis and Sphingomonas paucimobilis (1 needle each). The negative control needles showed no bacterial growth. Following rigorous data filtering, bacterial community analysis using 16S rRNA gene sequencing showed the presence of predominantly Corynebacterium but also Pseudomonas, Acinetobacter, Sphingomonas, Staphylococcus, Bacillus and Kocuria on the needles. FISH showed cocci-shaped cells in a tetrad formation on the surface of a needle, while SEM images showed the presence of cocci-shaped bacteria (~ 2 micrometres) in pairs and irregular tetrads on another needle.
The study shows evidence for a large diversity of bacteria on IVT needles and visually confirmed their adherence. This microbial diversity was similar to that found on the ocular surface and embedded in conjunctival tissue. This suggests the risk of exogenous endophthalmitis remains even with extensive sterilization of the conjunctival surface.
This is a 2020 ARVO Annual Meeting abstract.
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