Biofilm formation and its effect on the management of culture-positive bacterial endophthalmitis

Purpose: To compare the clinicomicrobiological features and outcomes in patients with infectious endophthalmitis caused by biofilm-positive (BP) and biofilm-negative (BN) bacteria. Methods: This was a prospective, interventional, comparative, nonrandomized, consecutive case series. Culture-positive bacterial endophthalmitis cases from August 1, 2018 to July 31st 31, 2019 were included. All vitreous samples were tested for biofilm using crystal violet plate and XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) methods and classified as BN and BP. The antibiotic susceptibility of all organisms was determined. Anatomic and functional success was defined as intraocular pressure >5 mm Hg and final best-corrected vision ≥20/400, respectively, at last visit. Results: There were 50 eyes in the BN group and 33 eyes in the BP group. BN group eyes required 2.86 ± 1.45 surgical interventions, and BP group eyes needed surgical 6.36 ± 2.89 interventions, P < 0.0001, 95% Confidence Interval, CI: 2-4. Median follow-up was 6 and 5 months, respectively (P = 0.33). Final logMAR vision was a median of 1.2 and 1.9 respectively; P = 0.0005, 95% C.I.: 0.4-1.7. Functional success was achieved in 44% and 21.2% (P = 0.03, 95% C.I.: 1.86%-40.08%) and anatomic success was achieved in 68% and 42.42%, respectively (P = 0.02, 95% C.I.: 3.85%-45.47%). The antimicrobial resistance patterns between the two groups were comparable. Conclusion: Endophthalmitis caused by the biofilm-forming bacteria needs a greater number of surgical interventions. The anatomic and functional outcomes are poorer than non-biofilm-forming bacterial endophthalmitis. The increased virulence and poorer outcomes can be hypothesized to be due to the physical barrier effect of the biofilm on the antibiotics.