Comparison of techniques for culturing corneal ulcers

Area of Science:

• Ophthalmology
• Microbiology
• Infectious Diseases

Background:

• Microbial keratitis is a serious eye infection requiring prompt diagnosis.
• Accurate laboratory culture is crucial for identifying causative organisms and guiding antimicrobial therapy.
• Standardized culturing techniques are essential for maximizing microbial yield from corneal ulcers.

Purpose of the Study:

• To compare the efficacy of a moistened calcium alginate swab versus a platinum spatula for culturing microbial keratitis.
• To determine which method provides superior organism retrieval for bacterial and fungal corneal ulcers.

Main Methods:

• Consecutive cases of presumed microbial keratitis underwent corneal culturing.
• Both a platinum spatula and a calcium alginate swab (moistened with trypticase soy broth) were used for inoculation.
• Agar plates were inoculated directly from the swab and spatula for comparative analysis of microbial growth.

Main Results:

• The moistened swab yielded significantly greater colony counts and more confluent growth in 77% of culture-proven ulcers.
• All culture-positive bacterial ulcers demonstrated growth with the swab method.
• The spatula was potentially superior for culturing filamentous bacteria (Actinomycetes-Streptomyces/Nocardia).

Conclusions:

• A calcium alginate swab moistened with trypticase soy broth is superior for retrieving organisms in bacterial keratitis.
• This enhanced retrieval facilitates accurate diagnosis and effective treatment strategies for microbial keratitis.
• Further investigation is warranted for optimizing techniques for specific etiologies like filamentous bacterial infections.