Bacterial and fungal pathogen profiling in infective keratitis: a multimodal diagnostic approach

Infective keratitis is a serious ocular condition where early and accurate identification of the causative organisms is crucial for effective treatment. However, traditional diagnostic methods such as microbial culture often have low sensitivity, particularly in microbial culture-negative cases.

This study aimed to assess and compare the performance of conventional methods (microbial culture and smear microscopy) with molecular methods (PCR) for detecting bacterial and fungal pathogens in patients with infective keratitis in North India.

A total of 109 patients with clinically diagnosed infective keratitis and 30 healthy controls were enrolled between January 2023 and January 2024. Diagnostic methods included slit-lamp examination, microbial culture, 10% KOH wet mount, Gram staining, and polymerase chain reaction (PCR). The sensitivity and specificity of each method were evaluated.

Microbial culture showed a sensitivity of 14.68% and specificity of 90%, with Aspergillus and Staphylococcus species being the most commonly isolated organisms. Smear microscopy showed better sensitivity (72.47%). PCR achieved the highest sensitivity (84.4%) and detected pathogens in 86 out of 120 culture-negative cases. PCR identified 57 fungal and 48 bacterial infections, including 10 cases of mixed infections. 10% KOH smear detected fungi in 55 samples, and Gram stain identified bacteria in 23 samples.

PCR significantly improved pathogen detection, especially in culture-negative and polymicrobial cases. The findings support the integration of molecular diagnostics with conventional methods for more accurate and timely diagnosis of infective keratitis.