<![CDATA[Bacillus thuringiensis (Bt) is widely used as a microbial agent in bioinsecticide formulations and is generally regarded as safe for non-target organisms. However, clinical reports of corneal ulceration following ocular exposure to Bt-based products have raised concerns regarding its potential toxicity to the eye. This study aimed to evaluate corneal epithelial integrity, histopathological changes, neutrophil infiltration, and the expression of inflammatory and oxidative stress markers, including tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA), in Wistar rats following topical exposure to Bt bioinsecticide. A post-test-only control group design was applied using 24 male Wistar rats divided into one control and three treatment groups receiving Bt concentrations of 8 g/L, 10 g/L, and 12 g/L. Corneal epithelial defects were assessed using fluorescein staining, while histological examination and semi-quantitative measurements of neutrophils were performed on enucleated eyes. TNF-α levels were measured using ELISA, and MDA levels were determined via the thiobarbituric acid (TBA) assay. There was epithelial desquamation, increased epithelial thickness, and higher neutrophil infiltration in the treatment groups compared to controls, although these parameters did not reach statistical significance. Notably, TNF-α levels demonstrated a significant increase in the 10 g/L treatment group (p = 0.023), indicating activation of local inflammatory pathways. MDA levels showed a non-significant upward trend. Topical exposure to Bt can elicit corneal inflammatory responses even in the absence of clear structural damage, highlighting the need for caution regarding ocular contact with Bt-based bioinsecticides]]>
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