Incidence and microbiologic characteristics of positive intraocular cultures and clinical endophthalmitis following retained intraocular foreign bodies

Purpose To evaluate the incidence of clinical endophthalmitis following penetrating ocular injury with retained intraocular foreign bodies (IOFBs) and to characterize the microbiologic spectrum and antimicrobial susceptibility patterns of recovered organisms. Methods A retrospective review was performed on 91 consecutive eyes undergoing surgical removal of retained IOFBs at a tertiary care center during two study periods. Microbiologic specimens were collected preoperatively or during the initial surgical procedure at the treating surgeon’s discretion. Injury characteristics, microbiologic isolates, and in vitro antimicrobial susceptibilities were analyzed, and clinical outcomes were reviewed. Results Intraocular cultures were obtained in 42 eyes, of which 28 (67%) yielded positive growth. Despite frequent culture positivity, clinical endophthalmitis developed in only 4 of 91 eyes (4%). All cases of infection occurred in eyes in which IOFB removal was performed more than 24 h after injury. Metallic foreign bodies were identified in the majority of cases (75%), and penetrating projectile injuries accounted for most mechanisms of injury (90%); all four endophthalmitis cases involved metallic foreign bodies despite the absence of high-risk organic material. Gram-positive organisms predominated, with coagulase-negative Staphylococcus identified most often. All four eyes with clinical endophthalmitis yielded gram-positive organisms, most commonly Bacillus cereus ; the only gram-negative isolate from an infected eye ( Enterobacter cloacae ) was polymicrobial with Bacillus cereus. All gram-positive isolates tested were susceptible to vancomycin, and all gram-negative isolates tested were susceptible to ceftazidime. Conclusions Microbiologic culture positivity following IOFB injury was common, whereas clinically apparent endophthalmitis was uncommon. Although all four cases of endophthalmitis occurred following IOFB removal more than 24 h after injury, incomplete timing data precluded comparison of infection rates by removal timing. These findings remain consistent with the importance of prompt IOFB removal and empiric antimicrobial therapy. Empiric coverage with vancomycin and ceftazidime demonstrated reliable in vitro activity against isolates in this cohort.