Analysis of Conjunctival Bacterial Flora among Patients Undergoing Multiple Intravitreal Injections for Diabetic Macular Oedema: A Cohort Study

Abstract

Introduction: Intravitreal Injections (IVI) are frequently used for the treatment of Diabetic Macular Oedema (DME). Serial IVI in these patients along with topical antibiotics as prophylaxis for infection has raised concern about the probable detrimental effect on conjunctival flora. However, the risk of postoperative endophthalmitis is higher in diabetics, especially with poor glycaemic control or in the presence of Chronic Kidney Disease (CKD) owing to poor immunity. Hence, preoperative conjunctival microbial growth has been studied in these patients to understand the need for antibiotic prophylaxis. Aim: To evaluate the preoperative conjunctival microbiological profile in diabetic patients treated with serial IVI (minimum of three) for DME and its association to their glycated haemoglobin (HbA1c) levels and the presence of associated CKD. Materials and Methods: This retrospective cohort study conducted in the Department of Ophthalmology at ESIC Medical College and Research Institute, Bengaluru, Karnataka, India, in May 2021. Total 92 eyes of 79 patients with type 2 diabetes mellitus who had received a minimum of three serial IVI of antiVascular Endothelial Growth Factor (anti-VEGF) injections for DME between May 2018 and January 2020 were included in the study. Conjunctival swabs for culture were taken from each eye before the injection and were evaluated for microbial growth. The association between microbial growth and HbA1c levels and/or CKD was analysed statistically using the Chi-square test. Results: The conjunctival cultures taken before IVI, were positive in 29.3% (27 of 92 eyes). Among them, Coagulase Negative Staphylococcus (CONS) bacteria were isolated in 15 of 27 eyes (55.5%) followed by Micrococci in 10 eyes (37%) and Diphtheroids in two eyes (7.4%). The average HbA1c among the eyes with positive growth was 7.23±1.31 as compared to 6.64±1.08 in eyes with no growth (p-value=0.1). There was a statistically significant association of culture positivity in patients with CKD and having HbA1c ≥7% (p-value=0.01) with CONS being the most common organism. Conclusion: A statistically significant association of conjunctival swab culture positivity in type 2 diabetics with DME requiring multiple IVI having uncontrolled diabetes HbA1c ≥7% and the presence of CKD was observed in the present study. Hence, the routine use of topical antibiotics as infection prophylaxis may be recommended in these patients as an additional precaution against endophthalmitis.