Prophylaxie des endophtalmies après chirurgie de cataracte

DNA extraction methods for panbacterial and panfungal PCR detection in intraocular fluids

PURPOSE

Three different methods of DNA extraction from intraocular fluids were compared with subsequent detection for bacterial and fungal DNA by universal PCR amplification.

MATERIAL AND METHODS

Three DNA extraction methods, from aqueous and vitreous humors, were evaluated to compare their relative efficiency. Bacterial (Gram positive and negative) and fungal strains were used in this study: Escherichia coli, Staphylococcus epidermidis and Candida albicans. The quality, quantification, and detection limit for DNA extraction and PCR amplification were analyzed. Validation procedures for 13 aqueous humor and 14 vitreous samples, from 20 patients with clinically suspected endophthalmitis were carried out.

RESULTS

The column-based extraction method was the most time-effective, achieving DNA detection limits ≥10(2) and 10(3 )CFU/100 µL for bacteria and fungi, respectively. PCR amplification detected 100 fg, 1 pg and 10 pg of genomic DNA of E. coli, S. epidermidis and C. albicans respectively. PCR detected 90.0% of the causative agents from 27 intraocular samples collected from 20 patients with clinically suspected endophthalmitis, while standard microbiological techniques could detect only 60.0%. The most frequently found organisms were Streptococcus spp. in 38.9% (n = 7) of patients and Staphylococcus spp. found in 22.2% (n = 4).

CONCLUSIONS

The column-based extraction method for very small inocula in small volume samples (50-100 µL) of aqueous and/or vitreous humors allowed PCR amplification in all samples with sufficient quality for subsequent sequencing and identification of the microorganism in the majority of them.

[Chronic postoperative endophthalmitis]

Chronic postoperative endophthalmitis designates delayed-onset postoperative endophthalmitis appearing more than two weeks after surgery, revealed by chronic intraocular inflammation with phases of inflammatory recurrence, which, at the beginning of the disease course, is partially sensitive to local corticosteroid treatment. It differs therefore from acute endophthalmitis in the immediate postoperative phase, from acute differed endophthalmitis after filtrating surgery, which appears years after the surgery, and from endogenous endophthalmitis. The most frequent presentation is granulomatous uveitis, often hypertonic, in an eye operated for cataract, presenting phases of recurrence sensitive to corticosteroid therapy but which recurs as soon as treatment is interrupted. Whitish condensations in plaques on the posterior capsule suggest the diagnosis and over several months the vitreous becomes inflamed. Ocular samples allow cytological analysis of an infectious process and bacteriological analysis in culture and with PCR. Treatment includes lavage of the sac with vancomycin and can be associated with posterior capsulectomy and intravitreal injections of antibiotics possibly associated with systemic antibiotic therapy. Treatment is prolonged because of the slow replication of the microorganisms involved. In approximately one-third of cases, the implant, the capsule, and the sac must be removed over 360° to permanently halt the intraocular infection. The diagnosis and specific treatment should be as early as possible since the aggressiveness of the treatment required is correlated with the time to management of the infection.

[Eye infections associated with ocular implants]

Postoperative endophthalmitis associated with intraocular lens implantation is one of the most severe complications of cataract surgery. The prevalence of endophthalmitis following these procedures reported in several multicenter studies over the last decades is 0.05% to 0.32%. Currently, general consensus measures are available to prevent this serious complication. Abiotic biofilm formation with adhesion of pathogens on the surface of intraocular devices is a novel theory that is little understood, but widely accepted to explain the pathophysiologic aspects of intraocular infection. Bacterial adhesion on intraocular lenses has been observed in clinical practice and investigated with several in vitro approaches in various experimental conditions. Improvements in the surgical techniques used in cataract surgery and the advent of new antimicrobial agents with a wider spectrum of action and better penetration in the eye, have resulted in significant advances in the prevention and treatment of intraocular implant-related infection.

[Fluoroquinolones in ophthalmology: indications and current use]

Fluoroquinolones are commonly used in ophthalmology, either for conjunctival infections or endophthalmitis. Use of these antibiotics requires good knowledge of the pharmacokinetic profile and adverse effects, and contraindications must be respected. Fluoroquinolones are useful in 2008 given their antibacterial spectrum, good ocular penetration, and the potential benefit of intravitreal injection.