Pathogen interactions in the pathogenesis of endophthalmitis

Abstract Endophthalmitis is an often blinding complication of penetrating globe injury, and an unfortunate consequence of common ocular surgeries, which requires immediate intervention. Although penetrating injuries are more likely to be associated with infectious complications, because of the number of ocular surgeries performed, postoperative endophthalmitis is its most common form. Given the challenge of maintaining a sterile field in ocular surgery, the fact that many surgeries are sutureless leaving a potential portal of entry, and the reported rates of bacterial contamination of irrigation fluid, it is perhaps surprising that the rate of infection in most centers is between 1 and 3 per 1000 surgeries. Although postoperative endophthalmitis rates are low, they appear to be increasing in the US and potentially elsewhere. This may relate to increased age of patient at the time of surgical intervention, increased rates of underlying illness, especially adult‐onset diabetes, and other factors. The development of new knowledge in several key areas is setting the stage for new and better strategies for infection treatment and prevention. It is now appreciated that the immune privilege of the posterior segment creates a highly permissive environment for the growth of microbes of even low virulence, such as coagulase negative staphylococci – a leading cause of postoperative endophthalmitis. The widespread use of antibiotic has selected for resistant strains of these and other organisms with increased virulence, including the ability to form tenacious and antibiotic refractory biofilms. We are beginning to understand the molecular basis for immune privilege in the posterior segment as it relates to the ability of innate immunity to contend with infecting microbes. We are also beginning to understand basic principles of the physiology of bacterial biofilms. The posterior capsule represents an important anatomical barrier to endophthalmitis, but many cases occur without known intraoperative breach. Studies now are attempting to identify bacterial properties, such as the production of tissue‐destructive proteases, that promote translocation of the microbes through an intact capsule and into the posterior segment. The contribution of innate immune privilege of the posterior segment, microbial virulence, and biofilm formation to endophthalmitis will be presented.