Nitroimidazole-resistant Giardia intestinalis

Prevalence and genotypic characterization of nitroimidazole-resistant Giardia intestinalis 

INSTITUTIONS
Coordinator:
Centre de Recerca en Salut International de Barcelona (CRESIB), Hospital Clínic, Barcelona

Servei de Microbiologia, Hospital Clínic, Barcelona
Departamento de Microbiología, Facultad de Medicina. Universidad de Zaragoza.
Hospital Sant Joan de Déu, Esplugues de Llobregat.
Unitat de Medicina Tropical i Salut International, Drassanes. PROSICS Barcelona

Key-words: Giardia intestinalis, resistance, nitroimidazole

SUMMARY
Giardia intestinalis, one of the most common parasitic infections in travelers is generally treated with nitroimidazoles though treatment failure is recently a cause of concern. In these cases, nitroimidazole resistant strains or the possibility of reinfection should be both considered. Therefore, the genetic characterization of the parasite could be a high-quality tool to evaluate it.
This study is aimed to assess the prevalence of nitroimidazole-resistant Giardia intestinalis and the epidemiological risk factors of these patients as well as to differentiate between nitroimidazole-resistant Giardia infection and reinfection. 

STUDY DESCRIPTION
Research questions

  1. Which is the prevalence of nitroimidazole-resistant Giardia intestinalis imported from tropical countries?
  2. Which is the area of the world where most of these patients come from?
  3. Which is the treatment of choice for these travelers with resistant giardiasis?
  4. Can we ensure that a persistent infection is due to a nitroimidazole-resistant G. intestinalis and not due to a reinfection?

 Background
Giardia lamblia (Giardia intestinalis) is one of the most common parasitic infections in returning travelers1. Although a number of treatments have been used to treat this infection, nitroimidazoles appear to be the drug of choice2. Resistance of Giardia intestinalis to nitroimidazoles is a cause of concern.2-4, though there are few studies in the literature regarding this issue, particularly studies describing the mechanisms of resistance of G. intestinalis. This fact to some extent is due to the difficulty of growing the parasite in cultures in vitro5. The mechanism of resistance seems to be related to the activity of the enzyme pyruvate ferredoxin oxidoreductase (PFOR). However, to assess the expression of this enzyme is a complex process since the culture of the parasite is required.

In addition, we know that G. intestinalis infection can be provoked by mixed genotypes, and there is the possibility that antiparasitic treatment may select resistant strains6. Finally, in patients who fail to respond to the treatment, the possibility of a reinfection should be also considered, particularly in high endemic areas. In this sense, a reinfection case can be easily identified through the genetic characterization of the parasite7. Thus, the study of these nitroimidazole-resistant isolates and their comparison to the initial isolates should be done as a previous step, to assess whether we are facing a nitroimidazole-resistant giardiasis or a reinfection.

General Objectives and hypothesis
The general objective of this study is to estimate the prevalence of nitroimidazole-resistant Giardia intestinalis in travelers and migrants and to describe their epidemiological characteristics.    

Specific objectives

1. To determinate the proportion of nitroimidazole-resistant Giardia intestinalis in travelers and migrants

2. To determinate the risk factors related to nitroimidazole-resistant Giardia intestinalis in travelers and migrants, particularly the geographic area where these patients are coming from.

3. To differentiate between infection with nitroimidazole-resistant Giardia and reinfection, establishing clonal relationships between the parasites before and after treatment.

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