Genetic and phenotypic traits of staphylococcus epidermidis strains causing post‐cataract endophthalmitis compared to commensal conjunctival flora

Abstract

PurposeThe aim of this study was to evaluate the virulence and antibiotic resistance traits of S. epidermidis strains causing post‐cataract endophthalmitis compared to those of the normal conjunctival flora in non‐infected control patients.MethodsThis prospective study included 22 patients (22 eyes) with acute post‐cataract endophthalmitis and 72 uninfected control patients (72 eyes). Antibiotic susceptibilities were evaluated using the Vitek II® automated system. These strains were then tested for the presence of eight virulence genes (icaA, icaB, icaC, icaD, atlE, aap, and capA), the insertion sequence IS256, and the mecA gene coding for methicillin‐resistance.ResultsCulture of 72 conjunctival samples collected from 41 patients allowed isolation of 43 S. epidermidis strains. The strains from the endophthalmitis group patients displayed higher prevalence rates for aap, atlE and mecA genes carriage compared to those of the control group (77% vs. 42%, p = 0.007; 100% vs. 79%, p = 0.02; and 54% vs. 11%, p < 0.001, respectively) and more frequently harbored simultaneously the mecA and icaA genes (13%) compared to the control group (2.3%, p = 0.01). They were also significantly more resistant than control strains to methicillin, fluoroquinolones, and the aminoglycosides.ConclusionsA higher capacity of adhesion to intraocular lens and formation of biofilms, and a higher resistance to antibiotics were found in S. epidermidis strains causing post‐cataract endophthalmitis compared to those of the normal conjunctival flora. The selection of such strains in endophthalmitis patients could be related to their specific virulence traits and/or their resistance to antibiotics used for prophylaxis of endophthalmitis.