Analysis of antibiotic resistance and genetic profile of conjunctival bacteria flora before and after cataract surgery

PURPOSE

To analyze antibiotic resistance and genetic profile of conjunctival bacteria flora before and after cataract surgery with the focus on coagulase-negative staphylococci (CNS) during cataract surgery and discuss the implications of this colonization as a potential risk of acquiring endophthalmitis.

METHODS

After approval of the institutional review board and informed consent from patients had been obtained, conjunctival swabs for culture from 59 patients undergoing cataract surgery were taken of the fellow eye at baseline (C0) and from the eye to be operated before (T0) and after (T1) irrigation with povine-iodine 5%, and at the end of surgery (T2). Genes responsible for virulence (mecA, ica and atlE) and antibiotic profile were determined; strain clonality of persistent colonizing Staphylococcus epidermidis strains was established by the Multi-locus sequence typing (MLST).

RESULTS

The frequency of CNS was significantly reduced in T1 (13.6%) from 81.4% in T0 and 86.4% in C0. The frequency of mecA, ica and atlE genes was 34.4%, 37.5% and 61.4%, 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 seven alleles of the S. epidermidis isolated previous to povine-iodine 5% disinfection and at the end of the surgery. CNS isolates from T1 or T2 corresponded to the same species, antibiotic and virulence profile as those isolates from C0 or T0.

CONCLUSION

Povidone-iodine 5% prophylaxis before surgery significantly reduced conjunctival contamination; in those that persisted, the source of contamination was mostly the patient's microbiota confirmed by the MLST system.