Microbiology of corneal wounds after cataract surgery: biofilm formation and antibiotic resistance patterns

Abstract

Objective: To evaluate the bacterial flora of corneal wounds at the end of cataract surgery before intracameral antibiotic use and to determine agents to treat postoperative endophthalmitis, the potential for biofilm formation, and antibiotic resistance. Method: This cross-sectional clinical study included patients who underwent cataract surgery using the phacoemulsification technique without any complications. The hemifacial skin, periocular area, eyelids and eyelashes were washed with 10% povidone-iodine and the conjunctiva was washed with 5% povidone-iodine before cataract surgery. After uncomplicated surgery, a wipe sample was taken from the bulbar conjunctival surface, corneal surface, and wound rim before administering intracameral antibiotics. All samples were plated on blood agar, MRS agar, M17 agar, calcium-lactate agar, plate-count agar, and Sabouraud-dextrose agar. Biofilm formation was evaluated by microtitre plates and the Congo red-agar method. Antimicrobial resistance patterns of isolates were determined by the agar-disk diffusion method. Results: We recruited 50 patients and studied 55 eyes, obtaining 34 isolates from the cultures of 16 eyes. Isolated organisms were coagulase-negative staphylococci (CoNS) (35.3%), Bacillus cereus (29.4%) and Pseudomonas spp. (5.9%). We obtained isolates from 64% of diabetic cases and 20% of non-diabetic cases, (p= 0.002). It was observed that 21 out of 34 isolates produced a weakly positive biofilm, 8 were moderately positive, three were strongly positive, and two isolates were biofilm negative. Of the CoNS strains four of the 11 were resistance to four or more antibiotics. Conclusion: Microorganisms that remained at the end of cataract surgery had the capacity to produce biofilm and had high antibiotic resistance. Appropriate preoperative disinfection is very important and adequate disinfection and suitable antibiotics should be kept in mind for avoiding endophthalmitis, especially for diabetic patients. Biofilm is one of the major factors affecting the virulence of bacteria, and further studies into prevention of biofilm formation are required in this area.