Microbiological etiology of endogenous and exogenous postprocedural endophthalmitis: a 5-year German federal state...

To investigate the microbiological etiology of endogenous and exogenous postprocedural infectious endophthalmitis in patients referred to two tertiary eye care centers in the German federal state of Saarland over a five-year period (2019-2023).

We retrospectively analyzed all cases of endophthalmitis treated at two ophthalmological centers in southwest Germany between January 1, 2019, and December 31, 2023. Included were only those cases for which vitreous aspirate specimens were subjected to microbiological analysis. Cases of exogenous endophthalmitis secondary to other ocular or periocular infections (e.g., microbial keratitis) or trauma were excluded. Microbiological pathogen identification was performed using Gram stain microscopy, conventional bacterial and fungal cultures, as well as broad-range bacterial and fungal polymerase chain reaction (PCR), followed by sequencing in PCR-positive samples.

A total of 126 endophthalmitis vitreous aspirate samples from 126 patients with a mean age of 73.3 ± 11.4 years were included. The majority of endophthalmitis cases occurred after intravitreal injection (55.6%), followed by previous cataract surgery (23.8%), pars plana vitrectomy (5.6%), and glaucoma surgery (4.8%). Only 7.9% of all cases were endogenous. Overall, pathogens were identified in 58.7% (n = 74) of all cases, with culture yielding a higher detection rate compared to PCR (53.2% versus 43.5%). Staphylococcus epidermidis was most commonly detected (n = 43; 58.1%), followed by Staphylococcus aureus (n = 7; 9.5%) and Enterococcus faecalis (n = 5; 6.8%). Postinjection and postcataract endophthalmitis tended to be associated with positive bacterial culture results, whereas endogenous endophthalmitis was more frequently associated with negative bacterial culture results (p = 0.06). Fungal endophthalmitis was detected in three samples, of which the endogenous cases were caused by Candida albicans (n = 2). Bacterial multidrug resistance was rare, with only a single detected methicillin-resistant S. aureus strain. All Gram-positive bacteria were susceptible to vancomycin.

Our results confirm S. epidermidis to be the most common endophthalmitis-causing pathogen. No single microbiological diagnostic technique would have identified all cases of infection, thus calling for combined approaches that include culture and molecular testing.