Varying Susceptibility of Corneal and Environmental Strains of Acanthamoebae to Multipurpose Solutions using a Novel Method

Abstract

 

Abstract:

 

A novel method has been developed to compare Acanthamoeba strain differences by testing their susceptibility to multipurpose contact lens cleaning solutions (MPS). This method uses surface attached protozoa that mimic cells attached to a contact lens. In brief, acanthamoebae were grown on non nutrient agar plates with E. coli prey. Blocks of agar with cysts or trophs (ca. 50 cells) were cut out and transferred to MPS (ReNu, Complete, and Opti–free) for up to 24 h treatment. After neutralizing in Dey Engley Broth (Difco), blocks were washed in amoeba saline and reinoculated onto fresh prey bacteria. Postitve growth was indicative of survival.

 

Testing showed that the efficacy of the 3 MPS was different. ReNu was the most effective, followed by Opti–free while Complete was relatively ineffective. Not surprisingly, trophozoites were more susceptible than cysts. Overall strain differences are summarized in the table.

 

Findings for individual MPS complement previous work with other methods.This study has also identified that environmental strains vary in their sensitivity to disinfecting solutions. Overall, T3, T5 and T11 environmental isolates were more resistant than the T4 isolates from the cornea and beach. This resilience supports previous work on temperature tolerance, where T3 and T5 acanthamoebae survived up to 41 C. Investigators should consider the strain genotype and its source before embarking on sensitivity testing.

 

 

 

Keywords: Acanthamoeba • contact lens • pathobiology