Abstract
Purpose :
To determine the causative organisms, antimicrobial susceptibility patterns, and demographic differences of microbial keratitis (MK) infections at a Midwestern tertiary eye center.
Methods :
MK patients were identified in the University of Michigan electronic health record from August 2012 to February 2021. Laboratory tests (culture, stain, smear, polymerase chain reaction, antibody, antigen) from 7 days before to 90 days after MK diagnosis were identified and classified as lab-positive (any positive result) or lab-negative. Lab-positive infections were categorized as bacterial (gram-positive, gram-negative, acid-fast bacilli [AFB]), fungal, viral, Acanthamoeba, or polymicrobial. Antimicrobial susceptibilities were obtained. Patient demographics were compared between lab-positive and negative cases and between MK organism types using t-, Kruskal-Wallis, Chi-square, or Fisher exact tests.
Results :
Of 2990 MK patients, 966 (32.3%) had labs performed, of which 517 (53.5%) were positive (289 females; 442 White, 45 Black, 9 Asian, 11 other races). Infections were bacterial in 72.7% (n=376) of patients, fungal in 6.6% (n=34), viral in 2.1% (n=11), Acanthamoeba in 0.8% (n=4), and polymicrobial in 17.8% (n=92). Of the bacterial infections, 72.1% (n=271) were gram-positive with coagulase-negative Staphylococcus (CoNS; 28.7%) and Staphylococcus aureus (S. aureus; 25.5%) as the most common pathogens. Bacteria were gram-negative in 26.1% (n=98) of cases, with Pseudomonas aeruginosa as the predominant pathogen (46.3%), and AFB in 1.9% (n=7). Methicillin-resistance occurred in 37% of S. aureus and 71% of CoNS; 100% were susceptible to vancomycin. Lab-positive patients were significantly older than lab-negative patients (mean ± standard deviation, 57.5 ± 20.5 years vs. 54.3 ± 20.3, p=0.015). White patients represented a larger percentage of bacterial, fungal, or polymicrobial infections than viral infections (87.0%, 97.1%, 88.9% vs 45.5%, all p<0.05). Black patients represented a larger percentage of viral infections than bacterial, fungal, or polymicrobial infections (45.5% vs 9.0%, 2.9%, 6.7%, all p<0.05).
Conclusions :
Bacterial keratitis accounted for most MK cases. Gram-positive bacteria were the most common isolates, followed by gram-negative. CoNS and S. aureus were universally susceptible to vancomycin. Patients with positive labs were significantly older. There were significant differences between MK types with respect to race.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.