Exploring methodologies from isolation to excystation for Giardia lamblia: a systematic review

Introduction: Giardia lamblia is a flagellated protozoan and the etiological agent of giardiasis, a leading cause of epidemic and sporadic diarrhoea globally. The clinical significance and public health impact of giardiasis underscores the need for robust methodologies to investigate and manage this pathogen. This study systematically reviews the main methodologies described in the literature for studying the life cycle of G. lamblia, focusing on isolation, purification, axenization, excystation, and encystation processes. Methods: A systematic literature review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) statement. The search was performed in the MEDLINE, ScienceDirect, and Web of Science databases using the following search equation: “("axenization" OR "isolation" OR "excystation" OR "encystation" OR "purification") AND ("method") AND ("giardia")". Results: A total of 39 studies were included in the review, revealing 56 methods for isolation and purification, 7 methods for excystation, and 3 methods for axenization and encystation. Isolation and purification methods exhibited significant variability, often involving two phases: an initial separation using simple techniques such as filtration and centrifugation, followed by a purification phase using a density gradient for faecal samples and immunomagnetic separation for water samples or nucleic acid extraction. The effectiveness of these methods differed depending on the source and sample type, highlighting the need for standardized protocols to ensure consistent and reliable results. Conclusion: Methods for the isolation and purification of G. lamblia exhibit notable variability and lack uniformity compared with the more consistent methods that re used for other life cycle stages. These findings underscore the urgent need for the development of standardized methodologies to enhance the reproducibility and reliability of research outcomes in this field.