# The Antimicrobial Efficacy of Amine-Containing Surfactants Against Cysts and Trophozoites of Acanthamoeba spp

## TL;DR

This study explores new surfactants that effectively kill Acanthamoeba, a cause of dangerous eye infections, potentially improving disinfectant solutions for contact lenses.

## Contribution

The study introduces amidopropyl quaternary trimethylammoniums (APTs) as more effective antimicrobial agents against Acanthamoeba cysts compared to existing compounds.

## Key findings

- EAPT and OAPT achieved greater log reductions of Acanthamoeba cysts at 25 µM within 24 hours.
- The enhanced efficacy is attributed to unsaturated alkyl chains and positive charge disrupting cell membranes.
- APTs show potential for improved disinfection in contact lens solutions and Acanthamoeba keratitis treatment.

## Abstract

Microbial keratitis, a vision-threatening infection commonly linked to contact lens use, poses a significant challenge, particularly when caused by Acanthamoeba species. Acanthamoeba keratitis (AK) is difficult to treat due to the organism’s ability to form resilient cysts, necessitating prolonged and complex therapeutic interventions. This study evaluated novel amidopropyl dimethylamines (APDs) and amidopropyl quaternary trimethylammoniums (APTs) for their antimicrobial efficacy against Acanthamoeba castellanii and Acanthamoeba polyphaga cysts. Minimum effective concentrations were determined, and time–kill assays assessed microbial inactivation over 24 h. The results indicated that certain APTs, particularly elaidamidopropyl trimethylammonium (EAPT) and oleamidopropyl trimethylammonium (OAPT), demonstrated superior cysticidal activity compared to the commercially used MAPD, achieving greater log reductions within 24 h (p < 0.0001) at a concentration of 25 µM. The enhanced efficacy of these compounds is potentially attributed to their unsaturated alkyl chains and positive charge, improving antimicrobial activity through the greater disruption of the Acanthamoeba cell membrane. These findings highlight the potential of APTs as alternative agents for incorporation into multipurpose lens disinfectants and AK treatment, offering improved disinfection efficacy. Further investigation is justified to optimise formulations for clinical and commercial applications.