The incidence of post-cataract surgery endophthalmitis varies considerably in the medical literature. An incidence of 1.11 per 1,000 surgeries in the USA has been reported [6], 0.48 per 1,000 surgeries in Sweeden [7], 1.4 per 1,000 surgeries in Canada [8], and 0.49 per 1,000 surgeries in Brazil [9]. Visual outcome after endophthalmitis is generally poor; half the patients of the Endophthalmitis Vitrectomy Study achieved a visual acuity of 20/40 or better by 9 months after treatment [10].
Microorganisms from the ocular and periocular surface may enter the anterior chamber during phacoemulsification, with reported rates of anterior chamber contamination as high as 21 % [11]. In the Endophthalmitis Vitrectomy Study, 70 % of microbiological isolates contained coagulase-negative micrococci [12]. The isolates involved are usually normal flora of the surface of the eye and surrounding mucosa, such as S. epidermidis, which are generally not highly virulent. S. epidermidis has been isolated from 70 % of normal eyes [13].
Biofilm is a microbially derived sessile community characterized by cells that are irreversibly attached to a substratum or interface or to each other, and are embedded in a matrix of extracellular polymeric substances that they have produced exhibiting an altered phenotype with respect to growth rate and gene transcription [14]. Formation of S. epidermidis biofilm is one of the most important virulence factors. Strains isolated from septic patients and prosthetic infections have the ica genes which mediate biofilm formation, and the mecA gene which is related to methicillin resistance. However, saprophytic isolates usually do not have these markers of virulence [15, 16].
This in vitro study shows that ketorolac reduces the formation of biofilm by 47.6 % on all the strains tested. The mechanism by which ketorolac decreased biofilm production was not addressed in this study, and further research is needed for elucidation. The concentration of ketorolac used in our experiment is equivalent to approximately 0.5 % ketorolac, the formulation present in commercially available products. Nonsteroidal anti-inflammatory drugs (NSAIDs) like salicylic acid and ketorolac can prevent adhesion and bacterial colonization of contact lenses [3]. Salicylic acid inhibited the production of teichoic acid, slime-associated proteins, and polysaccharide/adhesin production by S. epidermidis [17]. The adherence of bacteria to intraocular lenses (IOLs) during implantation and colonization of IOLs appears to have a role in the pathogenesis of postoperative endophthalmitis [18, 19]. Herein is the importance for reducing biofilm production.
Most ophthalmic medications contain benzalkonium chloride as preservative. It has been shown that the presence of benzalkonium chloride at the minimal inhibitory is able to inhibit biofilm formation. However, it was able to induce biofilm development for the S. epidermidis at sub-MIC [20].
The failure of antibiotic treatment of biofilm-associated infections has led to a search for additive measures to eradicate bacteria within biofilms. Our findings support the hypothesis that the use of ketorolac in the perioperative period of cataract surgery may decrease the virulence of S. epidermidis, the most common microorganism involved in post-cataract endophthalmitis. Further studies are needed to prove this effect in vivo.