Infectious Keratitis Management: 10-Year Update

Abstract

Infectious keratitis (IK), including bacterial, fungal, parasitic, and viral etiologies, continues to represent a significant cause of ocular morbidity in the United States and around the world. Corneal scraping for smears and cultures remains the gold standard in diagnosing IK; however, molecular diagnoses, including metagenomic deep sequencing (MDS), are promising emerging diagnostic tools. Despite recent interest in procedural treatment such as riboflavin photoactivated chromophore corneal collagen cross-linking (PACK-CXL) and Rose Bengal photodynamic antimicrobial therapy (RB-PDAT), medical treatment advances have remained stagnant. Methods: This review highlights IK pathogens obtained from corneal cultures at Bascom Palmer Eye Institute (BPEI) from 2011 to 2021 and provides the current BPEI algorithms for initial management of IK or as a referred clinically worsening patient. The roles of corticosteroid therapy, PACK-CXL, and RB-PDAT for IK are also summarized. Results: A total of 9326 corneal cultures were performed at BPEI between 2011 and 2021, and only 3609 (38.7%) had a positive organism identified, of which bacteria were the most common (83.4%). Fortified vancomycin and tobramycin are recommended as first-line medical therapy for IK patients based on culture sensitivity data for the top Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria. PACK-CXL and RB-PDAT may benefit IK patients with corneal melting and fungal IK, respectively. Conclusions: Drug holidays, minimizing contamination, and optimizing sample order are crucial to maximizing corneal culture positivity. PACK-CXL and RB-PDAT are promising procedural advancements for IK therapy.

Keywords: antimicrobial therapy; corneal ulcer; infectious keratitis.

Figure 1

Corneal culture supplies. (A) #69 mini-blades for corneal scrapings. (B) Two microbiology slides, one for Gram stain (bacteria) and another for potassium hydroxide (KOH) stain (fungi). (C) Blood agar (top left, most bacteria), chocolate agar (top right, most bacteria, including fastidious respiratory bacteria, and most fungi), potato flake agar (bottom left, fungi), and non-nutrient agar (bottom right, acanthamoeba) plates. (D) Löwenstein–Jensen medium (left, mycobacteria), thioglycolate broth (middle, aerobic versus anaerobic microbes), and universal transport medium with flocked swab (right, viruses and chlamydia).

Figure 2

Algorithm for a new infectious keratitis (IK) patient. CL = contact lens; HSV/VZV = herpes simplex virus/varicella zoster virus; RB-PDAT = Rose Bengal photodynamic antimicrobial therapy; ROS = review of systems; TPKP = therapeutic penetrating keratoplasty.

Figure 3

Algorithm for a referred clinically worsening infectious keratitis (IK) patient. HSV/VZV = herpes simplex virus/varicella zoster virus; MDS = metagenomic deep sequencing; RB-PDAT = Rose Bengal photodynamic antimicrobial therapy; TPKP = therapeutic penetrating keratoplasty.