Prevalence of microbial contamination in donor corneas

Postoperative infection is the most disastrous complication of penetrating keratoplasty (PK). Corneoscleral rim culture provided information regarding subsequent infections. Our aims were to identify the incidence of microbial contamination in donor corneas and to report the recovery of bacteria with two culture methods, i.e., conventional culture media after aerobic/anaerobic cotton swabs and blood culture media (Fastidious Antibiotic Neutralization [FAN]).

A total of 118 patients underwent PK. Corneoscleral rim cultures were performed using aerobic/anaerobic culture cotton swabs (Transystem™, COPAN, Italia) with subsequent convention media and blood culture media (FAN bottle, BD BACTEC™, USA). The results of the different methods were reported and analyzed.

Microorganisms were recovered from 24 in total 118 cases (20.3%, n = 118), 14 from blood culture media (FAN) (11.8%, n = 118), 9 from conventional culture media after aerobic/anaerobic cotton swabs (7.63%, n = 118), and 2 from fungus culture (1.69%, n = 118). The most commonly identified pathogen was coagulase-negative Staphylococcus (CoNS) (n = 13, 54.2%), and more isolates of CoNS and staphylococcus aureus were recovered from blood culture media (FAN) than those from conventional culture media after aerobic/anaerobic cotton swabs (13 vs. 4, P = 0.05). Conversely, more nonfermentative Gram-negative bacilli were recovered from conventional culture media after aerobic/anaerobic cotton swabs. None of the 24 cases with positive corneoscleral rim cultures reported ocular infection for the recipients in at least 6 months' follow-up.

The conventional culture media after aerobic/anaerobic cotton swabs and blood culture media (FAN) did not yield identical isolates of bacteria. The blood culture media (FAN) could further yield Gram-positive bacteria in addition to those recovered from convention media. It seemed adding gentamicin and streptomycin could achieve bacteriostatic effect instead of the bactericidal effect. The administration of postoperative antibiotic in the recipient was suggested.