Molecular and Phenotypic Characterization of Staphylococcus epidermidis Isolates from Healthy Conjunctiva and a Comparative Analysis with Isolates from Ocular Infection

Abstract

Staphylococcus epidermidis is a common commensal of healthy conjunctiva and it can cause endophthalmitis, however its presence in conjunctivitis, keratitis and blepharitis is unknown. Molecular genotyping of S. epidermidis from healthy conjunctiva could provide information about the origin of the strains that infect the eye. In this paper two collections of S. epidermidis were used: one from ocular infection (n = 62), and another from healthy conjunctiva (n = 45). All isolates were genotyped by pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec), detection of the genes icaA, icaD, IS256 and polymorphism type of agr locus. The phenotypic data included biofilm production and antibiotic resistance. The results displayed 61 PFGE types from 107 isolates and they were highly discriminatory. MLST analysis generated a total of 25 STs, of which 11 STs were distributed among the ocular infection isolates and lineage ST2 was the most frequent (48.4%), while 14 STs were present in the healthy conjunctiva isolates and lineage ST5 was the most abundant (24.4%). By means of a principal coordinates analysis (PCoA) and a discriminant analysis (DA) it was found that ocular infection isolates had as discriminant markers agr III or agr II, SCCmec V or SCCmec I, mecA gene, resistance to tobramycin, positive biofilm, and IS256+. In contrast to the healthy conjunctiva isolates, the discriminating markers were agr I, and resistance to chloramphenicol, ciprofloxacin, gatifloxacin and oxacillin. The discriminant biomarkers of ocular infection were examined in healthy conjunctiva isolates, and it was found that 3 healthy conjunctiva isolates [two with ST2 and another with ST9] (3/45, 6.66%) had similar genotypic and phenotypic characteristics to ocular infection isolates, therefore a small population from healthy conjunctiva could cause an ocular infection. These data suggest that the healthy conjunctiva isolates do not, in almost all cases, infect the eye due to their large genotypic and phenotypic difference with the ocular infection isolates.

Sustained release of levofloxacin from thermosensitive chitosan‐based hydrogel for the treatment of postoperative endophthalmitis

“…S. aureus is a leading cause of acute‐onset postoperative endophthalmitis which commonly occurs after cataract surgery . S. epidermidis can cause ocular infection including conjunctivitis, blepharitis, corneal ulcers, and endophthalmitis . After treatment of levofloxacin‐containing hydrogel, the results of antimicrobial activity showed a clear zone of inhibition against both S. aureus and S. epidermidis for at least 7 days (Figure ).…”

“…34 S. epidermidis can cause ocular infection including conjunctivitis, blepharitis, corneal ulcers, and endophthalmitis. 35 In vitro biocompatibility of the levofloxacin-containing hydrogel to corneal epithelial cells was evaluated by cell counting kit-8 at days 2 (n = 3, p > 0.05). The cells were cultured with normal medium (control group), hydrogel extraction (Gel) or with the 10 mg/mL of levofloxacinhydrogel extraction (Gel-Lev-10) throughout the culture period.…”

Non‐biofilm‐forming commensal Staphylococcus epidermidis isolates produce biofilm in the presence of trypsin

“…Together with Staphylococcus aureus , CoNS are the primary agents responsible for nosocomial infections and represent the most common source of infections associated with medical devices (Darouiche, ), causing a problem for the public health system. Molecular epidemiological studies reveal a sizeable genetic diversity among staphylococci (Conlan et al, ; Schoenfelder et al, ); in isolates from ocular infections (OI), prosthetic joint infections (PJI), and healthy skin (HS), there is no genetic association among them (Flores‐Páez et al, ; Ortega‐Peña et al, , in press). For the case of isolates from ocular infections (OI), biofilm formation is a discriminant biomarker compared to commensal isolates (Duggirala et al, ; Jain & Agarwal, ; Okee et al, ; Suzuki, Kawamura, Uno, Ohashi, & Ezaki, ); however, there is evidence that the number of isolates from prosthetic joint infections with biofilm formation capacity is similar to commensal isolates (Hellmark, Söderquist, Unemo, & Nilsdotter‐Augustinsson, ).…”

Emulsion of Chloramphenicol: an Overwhelming Approach for Ocular Delivery

“…It has been found that ocular infection isolates are not resistant to chloramphenicol so it has been recommended in treatment of ocular infections. 2 Chloramphenicol is a broad spectrum antibiotic effective against gram-positive, gram-negative, anaerobic bacteria, extracted from Streptomyces venezuelae. The mechanism of its action is based on inhibition of protein synthesis at prokaryotic ribosomal level by binding with 50S part of ribosomal subunit and thus preventing association of aminoacyl-tRNA to ribosome.…”