A comprehensive analysis of viability assays for Giardia lamblia and Trichomonas vaginalis trophozoites: a systematic review

Abstract

Introduction: Giardia lamblia and Trichomonas vaginalis are flagellated protozoan parasites that often cause asymptomatic infections but may lead to gastrointestinal or genitourinary symptoms. Improved treatment options are needed due to emerging resistance. However, selecting an appropriate method for assessing the in vitro susceptibility of G. lamblia and T. vaginalis in the presence of potential therapeutic compounds remains challenging due to the variability in these methods. This study aimed to provide an overview of commonly employed methods for determining trophozoite viability in the presence of potential therapeutic compounds and to propose a standardized viability assay for susceptibility testing for G. lamblia and T. vaginalis.

Methodology: A systematic literature review was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) 2020 statement, using databases including MEDLINE, ScienceDirect, and Web of Science, with the following search equation: “in vitro” AND “method” AND (“susceptibility” OR “viability” OR “sensitivity”) AND (“giardia” OR “trichomonas”).

Results: The search identified 32 experimental studies with diverse viability assays. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, adherence inhibition assay, and [3H]-thymidine incorporation assay were prominent for G. lamblia. The trypan blue assay, motility assessment, and resazurin assay were frequently used for T. vaginalis. These findings underscore the diversity in viability assessment methods, highlighting the importance of standardizing viability assays to ensure accurate and reproducible results in drug susceptibility studies.

Conclusions: The fluorometric resazurin assay has emerged as a suitable choice for standardization in both parasites, offering cost-effectiveness, reliability, and ease of use.