Persistence of conjunctival colonization by coagulase-negative staphylococci in patients undergoing cataract surgery

Abstract

PurposeTo establish the conjunctival contamination source by coagulase-negative staphylococci (CNS) during cataract surgery and discuss the implications of this colonization as a potential risk of acquiring endophthalmitis.Methods Conjunctiva samples for culture from 59 patients undergoing cataract surgery were taken of the fellow eye at baseline (T1) and from the eye to be operated before (T0) and immediately after (T2) irrigation with povine-iodine IOP5%, and at the end of surgery (T3). Genes responsible for virulence (mecA, ica and atlE) and antibiotic profile were determined; strain clonality of persistent colonizing S. epidermidis strains was established by the Multi-locus sequence typing (MLST).Results The frequency of CNS was significantly reduced in T2 (13.6%) from 81.4% in T0 and 86.4% in T1. The frequency of mecA, ica and atlE genes was 35.9%, 41.7% and 67.2%, respectively; and methicillin phenotypic resistance was 35.4%. S. epidermidis was the most frequent species isolated in every time point. MLST revealed in 7 patients 100% coincidence of the 7 alleles of the S. epidermidis isolated previous to povine-iodine 5% disinfection and at the end of the surgery. CNS isolates from T2 or T3 corresponded to the same species, antibiotic and virulence profile as those isolates from T1 or T0.Conclusion Pre-surgical prophylactic scheme significantly reduced conjunctival contamination; in those that persisted, the source of contamination was mostly the patient's microbiota confirmed by the MLST system.