Ocular Microbiology and Immunology Group
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2025 OMIG Abstract

Free-Living Amoebae in Contact Lens Cases-
Biological By-Passes for Non-Amebic Keratitis?

Darlene Miller¹, Jorge Maestre-Mesa¹, Alexander Alfonso¹, Maribel Hernandez¹, Beatriz Munoz¹,
Juan Carlos Navia², Heather Durkee², Jaime D. Martinez3, Eduardo C Alfonso³ Harry W. Flynn1-3,
Jean-Marie Parel², Guillermo Amescua1-3

¹Ocular Microbiology Laboratory, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Health Care System, Miami, Florida; 2Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Health Care System, Miami, Florida; ³Department of Ophthalmology, University of Miami Health Care System, Miami, Florida

Purpose: Free-living amoebae (FLA) in contact lens cases can serve as biological by-passes and transmission vehicles for nonamebic and mixed microbial corneal infections.

Methods: We used a combination of conventional culture (bacterial, fungal, amoebic) techniques, PCR (primer-specific), DFA, and metagenomics to confirm the presence of FLA in matched corneal/ctl pairs at our Institute (1987-2024) to determine a) prevalence of nonamebic pathogens as primary corneal pathogens in lens case harboring acanthamoeba (AC) and other free-living amoebae, b) highlight prevalence of mixed or coinfections among this group and to document the frequency and diversity of viral endosymbionts among Acanthamoeba hosts.

Results: 74 FLA (Acanthamoeba, n=67,90.54%, Hartmannella species n=4 (5.41%), FLA, NOS, n=2 (2.70%), and 1 (Valkampfia species (1.35%) were documented during the study. Nineteen patients, 14 corneal positive and 5 corneal negative (treated for bacterial infections) had non-amoebic pathogens as primary corneal pathogens recovered from amoebic-contaminated cases. Eight or 42.1% were detected only by molecular survey. Gram-negative organisms were the most common non-amoebic pathogens (7/14 patients, 50%- P. aeruginosa). Mixed infections were detected in 36 patients, 40 isolates. Co-pathogens included gram-positive (n=23, 57.5%, gram-negative (n=10, 25%, fungi (=410%) and HSV (n=3,7.5%). Viral endosymbionts were confirmed in 21 patients. These included Giant viruses (n=17, 80.95%, Mimiviridae (n=6-35%), Pandoraviridae (n=11-64.71%), Herpesviridae (n=8-38.10%, 6-75%-HSV, 2-HHV7-25%, Adenovirus C-(n=4-19.05%0 and HPV4 (n=2-6.45%).

Conclusions: Not always Acanthamoeba! Other Free-living amoebae are frequent inhabitants of contaminated lens cases. Molecular methods may complement culture in detecting amoebic or mixed infections in contact lens wearers. Viral endosymbionts are frequent members of contact lens FLA-associated communities, and along with bacteria and fungi, may modulate corneal pathology.