Bacteria on the ocular surface are implicated in post-op endophthalmitis, even though, in many cases, the vitreous tap is culture-negative. Researchers recently found a large diversity of bacteria—similar to that seen on the ocular surface and in conjunctival tissue—on intravitreal needles and visually confirmed their adherence.

A team obtained intravitreal needles immediately after injection from patients undergoing treatment, predominantly for AMD. They analyzed needles with three different techniques: 18 needles with chocolate blood agar, 40 needles by gene sequencing and nine needles by either fluorescent in situ hybridisation (FISH) or scanning electron microscopy (SEM).

Using culturing, the investigators identified three bacteria from five of the 18 needles (28%)—Kocuria kristinae, Staphylococcus hominis and Sphingomonas paucimobilis. They noted that the negative control needles showed no growth.

They observed predominantly Corynebacterium but also Pseudomonas, Acinetobacter, Sphingomonas, Staphylococcus and Bacillus through 16S rRNA gene sequencing. They added that cocci-shaped cells in a tetrad formation were seen using FISH, while SEM showed cocci-shaped bacteria in pairs and irregular tetrads.

“This suggests the risk of exogenous endophthalmitis remains even with sterilization of the conjunctival surface,” the study authors concluded in their paper.