Patients with corneal disease severe enough to prompt referral for surgery are likely to benefit significantly from a transplant procedure, but it comes with an elevated risk for long-term problems, particularly in those receiving full-thickness grafts. Researchers recently found that corneal transplant patients with preexisting ocular surface disease are more likely to contract microbial keratitis, with a graft infection risk of 4.77%. They noted that gram-positive species were the most common infective cultured organism.

Of the 1,508 grafts under analysis, the investigators reported 72 episodes of microbial keratitis in 66 eyes that had undergone keratoplasty procedures. Breaking this down even further, 93% of microbial keratitis episodes occurred in penetrating keratoplasty procedures, 6% in deep anterior lamellar keratoplasty procedures and none in endothelial keratoplasty procedures.

The team identified 79 organisms, 73% of which were gram-positive, 23% gram-negative and 4% fungi. With regard to gram-positive organisms, vancomycin and gentamicin showed 100% and 91% susceptibility, respectively. Ofloxacin had a resistance rate of almost 14%. In terms of gram-negative organisms, gentamicin and chloramphenicol showed 100% sensitivity, with cefuroxime showing 69%. Resistance rates were less than 15% in all tested gram-negative antimicrobials.

The study authors concluded that their findings may “aid clinicians in predicting possible causative organisms for microbial keratitis and aid antibiotic choice.”