Effect of inoculum size on the induction of endophthalmitis in aphakic rabbit eyes

Abstract

A reproducible animal model is necessary to examine the use of antimicrobial agents for prophylaxis and treatment of bacterial endophthalmitis. We determined the minimum inoculum size of S. aureus and P. aeruginosa that consistently produced endophthalmitis when injected into aphakic rabbit eyes immediately following surgery. Both anterior chamber and intravitreal injections were examined. For S. aureus, an intravitreal inoculum of 19.3 +/- 7.5 CFU and an anterior chamber inoculum of 50.5 +/- 4.0 CFU were required. For P. aeruginosa, an intravitreal inoculum of 5.5 +/- 2.6 CFU and an anterior chamber inoculum of 97.5 +/- 10.7 CFU consistently produced a fulminant infection. Lower inocula of both bacteria produced endophthalmitis in both locations, but the effect was inconsistent.

Incidence of postoperative endophthalmitis from 1990 to 2009 using povidone–iodine but no intracameral antibiotics at a single academic institution

“…25,26 Because a certain number of bacteria must be inoculated to overcome host defense mechanisms and to cause postoperative endophthalmitis, a preoperative reduction in the conjunctival bacterial load should help to prevent infection. 27 The aims of infection prophylaxis are to reduce the preoperative conjunctival bacterial load and to limit the growth of bacteria after intraocular inoculation in the perioperative period. Other factors in the development of postoperative endophthalmitis include surgical complications, contaminated surgical instruments, an unclean environment, and suboptimum wound integrity.…”

Corneal interface contamination during laser in situ keratomileusis

“…They include the load of inoculated microorganisms and the virulence of the organism. 14,15 The ability of the tissue to clear organisms is another factor. For example, the anterior chamber may clear small numbers of bacteria without overt signs of infection.…”

Perioperative Prophylaxis for Postcataract Extraction Endophthalmitis

“…The aphakic rabbit model study revealed 51 ± 4 colony-forming units of S. aureus were required to induce PCE when injected into the anterior chamber, whereas 19 ± 8 colony-forming units were needed when injected into vitreous. 55 …”