Antibiotic Susceptibility And Epidemiology Of Infectious Keratitis: A 8-Year Study Of 211 Cases (2017–2024)

The purpose of this study was to identify the most common microorganisms responsible for infectious keratitis in our patient population. Additionally, we aimed to evaluate the antimicrobial resistance patterns in bacterial isolates from these patients, specifically assessing their resistance to fluoroquinolones, vancomycin/ceftazidime, and linezolid. Understanding these resistance patterns is crucial for guiding clinical decisions and developing effective treatment strategies for corneal infections.

We hypothesized that resistance to fluoroquinolones and vancomycin/ceftazidime has increased over time, which could have significant implications for the management of infectious keratitis.

This study was conducted at the Fundación de Oftalmología Médica de la Comunitat Valenciana, a specialized ophthalmology hospital in Valencia, Spain. Data were collected between May 2017 and October 2024.

A descriptive statistical analysis was performed using data obtained from the medical records of patients diagnosed with infectious keratitis at our hospital over the past eight years. We collected information on the causative microorganisms and, for bacterial cases, determined whether they were Gram-positive or Gram-negative. Additionally, we analyzed their susceptibility to fluoroquinolones, vancomycin/ceftazidime, and linezolid.

Subsequently, a logistic regression analysis was conducted to assess significant changes in susceptibility to fluoroquinolones, and vancomycin/ceftazidime over time.

A total of 211 microorganisms were isolated from 154 patients, of which 169 were bacteria.

Seventeen percent of bacterial isolates were resistant to fluoroquinolones; however, 50% of these remained susceptible to vancomycin/ceftazidime.
Eleven percent of bacterial isolates were resistant to vancomycin/ceftazidime, and 13% of these were susceptible to fluoroquinolones.
Eight percent of bacterial isolates were resistant to both fluoroquinolones and vancomycin/ceftazidime, but all remained susceptible to linezolid.

A logistic regression analysis comparing susceptibility to fluoroquinolones yielded a p-value of 0.311, while the same analysis for vancomycin/ceftazidime resulted in a p-value of <0.001.

Over the past eight years, in our geographical area, the most common microorganisms causing infectious keratitis were Gram-positive bacteria. Staphylococcus epidermidis and Pseudomonas aeruginosa were the most frequently identified species, with 41 cases each.

The logistic regression analysis for fluoroquinolone susceptibility yielded a p-value of 0.311, indicating no statistically significant difference over the past eight years. However, the logistic regression analysis for vancomycin and ceftazidime resulted in a p-value < 0.001, indicating a statistically significant decrease in bacterial susceptibility to these antibiotics over time.