Evaluation of Acanthamoeba spp. adherence in scleral contact lenses according to lens shape and amoeba pathogenicity

Abstract

Purpose : To investigate the adherence of Acanthamoeba spp. to the scleral contact lens (ScCL) surface according to lens shape, surface treatment, and strain pathogenicity.

Methods : Two strains of A. polyphaga (CDC:V062 and ATCC 30461) and one clinical isolate obtained from a severe Acanthamoeba keratitis, were inoculated onto five contact lenses: one first-generation silicone-hydrogel (Lotrafilcon B; adherence control) with Plasma surface treatment; two ScCL (fluorosilicone acrylate) one with a surface treatment composed of Plasma and the other by Plasma with Hydra-PEG; and two flat lenses (fluorosilicone acrylate) with the same surface treatment of the ScCL respectively. The total of trophozoites adhered to the lens surfaces (initial inoculum of 10⁵ trophozoites per lens) was assessed by inverted optical light microscopy after 90-minutes incubation. Possible alterations of the lenses surfaces were evaluated by scanning electron microscopy (SEM). Strain pathogenic profiles were performed by the kinetics of Acanthamoeba trophozoite growth and encystment. Clinical strain genotyping was evaluated by Sanger sequencing of 18S rRNA gene. For all statistical tests, a significance level of 5% was considered.

Results : The three isolates tested adhered more to the surface of the ScCL when compared to the flat lenses, independent of the lens surface treatment (p<0.001). The clinical isolate and the ATCC 30461 exhibited a superior pathogenicity profile when compared to the CDC:V062 and higher adherence (p<0.001) to ScCL and flat lens. Folds were observed on the surface of the lenses tested by SEM. Also, it was noticed that the isolates had a rounded and shrunken appearance on the surface of the flat lens and ScCL (figure 1) and an amoeboid and elongated appearance on the surface of the silicone-hydrogel lens (figure 2). All the Acanthamoeba isolates belonged to the T4 genotype.

Conclusions : The data suggest that the Acanthamoeba pathogenicity and lens shape surface interferes on amoeba adherence.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure 1. SEM of the clinical isolate (rounded trophozoite) adhered to the ScCL surface. Magnification x20,000.

 

Figure 2. SEM of the clinical isolate (amoeboid trophozoite) adhered to the silicone-hydrogel lens surface. Magnification x20,000.