Long term analysis of microbiological isolates and antibiotic susceptibilities in acute-onset postoperative endophthalmitis: a UK multicentre study

OBJECTIVES: To review the trend of microbial isolates for postoperative endophthalmitis (POE) in the United Kingdom (UK) and determine the sensitivity to current empirical intravitreal antibiotic treatment. METHODS: We conducted a long term multicentre consecutive case review of POE across 3 geographically distant tertiary eye centres in the UK: Sunderland Eye Infirmary (2000-2022), Oxford Eye Hospital (2016-2022), and Southampton General Hospital (2016-2022). Data on the microbial samples taken and results including sensitivities to antibiotics agents given were collected. Poisson regression was used to analyse microbial trends and outcomes were considered statistically significant at a level of p < 0.05. RESULTS: 179 consecutive eyes of 177 patients with POE met our inclusion criteria. The most common primary procedure was phacoemulsification and IOL insertion followed by intravitreal injections. 104 (58.1%) were culture positive and most were Grampositive bacteria (85, 81.7%). The microbial trend consistently showed Staphylococcus epidermidis and unspecified coagulasenegative Staphylococci to be the most prevalent pathogens. Poisson regression showed no statistically significant change in any of the bacterial isolates over our study period. Antibiotic sensitivity data was available for 74% of the culture positive samples (77/ 104). All Gram-positive bacteria (68/68, 100%) and most (8/9, 88.9%) Gram-negative bacteria were sensitive to the empirical antibiotics (Vancomycin and Ceftazidime/Amikacin) given at presentation. CONCLUSIONS: Most of the bacterial isolates causing POE in the UK are Gram-positive bacteria, and the trend has remained stable over more than two decades. Current empirical treatment with intravitreal Vancomycin and Ceftazidime/Amikacin provides effective broad coverage for the vast majority of cases.