Microbial keratitis in corneal grafts
Reviewed by Sofia Rokerya

The authors report a retrospective case series of 59 episodes of microbial keratitis identified in 41 eyes of 41 patients (39 penetrating keratoplasty (PKPs) and two deep anterior lamellar keratoplasty (DALKs)), from a total of 759 consecutive corneal grafts identified from a UK Cornea Transplantation database over a 17 year period (1997–2014). Overall incidence of microbial keratitis in corneal grafts was 41/759, 5.4% (39/685, 5.7% in PKP; 2/20, 10% in DALK; and 0/54, 0% in descemet stripping automated endothelial keratoplasty (DSAEK)). The most common indication for corneal transplantation in these eyes was for aphakic or pseudophakic bullous keratopathy); 30/41 (73.2%) developed a single episode of microbial keratitis (30 PKP) whilst 11/41 (26.8%) patients with microbial keratitis developed multiple (two or more) episodes of microbial keratitis in the same eye (nine PKPs and two DALKs). Overall, 35/59 (59.3%) episodes of microbial keratitis in 22 eyes occurred in failed grafts. A total of 15/59 (25.4%) episodes of microbial keratitis resulted in a persistent epithelial defect (PED) at one month from diagnosis of microbial graft keratitis. A total of 9/15 (60%) patients had clear grafts after a period of topical antimicrobial treatment with adjunctive bandage contact lens, 4/15 (26.7%) developed corneal scarring, and 1/15 (6.7%) subsequently developed a failed graft. One-third of the episodes of microbial keratitis (19/58, 32.8%) resulted in reduced BCVA post keratitis with a median loss of two Snellen lines (range 1-7). In all, 46/58 episodes (78.0%) of microbial keratitis required hospitalisation with a median stay of seven days (SD=6.2 days). Microbiology results were available for all 59 episodes. In all, 25/59 (42.4%) corneal scrapes reported no growth, 18/59 (30.5%) grew Gram-positive organisms, 11/59 (18.6%) grew Gram-negative organisms, and 5/59 (8.5%) fungi. Gram-positive organisms isolated were S. pneumoniae and S. aureus and the most frequently isolated Gram-negative species were Pseudomonas aeruginosa and Moraxella. The rate of microbial graft keratitis, 5.4%, provides the published statistic based on UK data and is comparable to the 1.8-7.6% previously reported in the developed world. Graft age was significantly associated with graft failure in microbial keratitis. The ongoing risk of microbial keratitis warrants providing patients with long-term open access to hospital eye services. 

Microbial keratitis in corneal grafts: predisposing factors and outcomes.
Okomkwa A, Siah AF, Hogg J, et al.
EYE
2018;32:775-81.