OBJECTIVE To analyze the etiological characteristics of infectious keratitis in patients with type 2 diabetes and investigate the association of nuclear factor erythroid 2-related factor 2 mRNA (Nrf2 mRNA) and heme oxygenase-1 mRNA (HO-1 mRNA) in tear fluid with disease severity and prognosis.

METHODS A total of 63 patients with type 2 diabetes and infectious keratitis admitted to Xinxiang Central Hospital from Jan. 2020 to Jun. 2024 were enrolled. The pathogenic bacteria characteristics of the patients were analyzed. Patients were divided into mild (n=32), moderate (n=21) and severe (n=10) groups based on disease severity. The expression levels of Nrf2 mRNA and HO-1 mRNA were compared among the groups, and their correlation with disease severity was analyzed by Spearman′s correlation coefficient. According to treatment outcomes, patients were classified into a good prognosis group (n=51) and a poor prognosis group (n=12). The expression levels of Nrf2 mRNA and HO-1 mRNA were compared between the two groups, and receiver operating characteristic (ROC) curves were plotted to evaluate their predictive value for poor prognosis.

RESULTS A total of 71 pathogenic bacteria were isolated, including 38 gram-positive bacteria (53.52%), predominantly Staphylococcus epidermidis, 21 gram-negative bacteria (29.58%), mainly Pseudomonas aeruginosa and 12 fungi (16.90%), primarily Aspergillus spp. The expression levels of Nrf2 mRNA and HO-1 mRNA followed the trend: severe group < moderate group < mild group (P < 0.05), and both were negatively correlated with disease severity (P < 0.05). The poor prognosis group exhibited lower expression of Nrf2 mRNA and HO-1 mRNA than the good prognosis group (both P < 0.05). ROC curve analysis showed that the areas under the curve (AUC) for the expression of Nrf2 mRNA, HO-1 mRNA and their combined detection were 0.879, 0.900 and 0.953, respectively, with combined detection outperforming single detection (P < 0.05).

CONCLUSIONS Gram-positive bacteria are the predominant pathogenic bacteria in type 2 diabetes-related infectious keratitis. The expression of the Nrf2/HO-1 signaling pathway is associated with disease severity and prognosis.