&lt;i&gt;Giardia intestinalis&lt;/i&gt; in Thailand: Identification of Genotypes

Anchalee Tungtrongchitr,Nitaya Indrawattana,Nitat Sookrung,Sukanya Kwangsi,Wanpen Chaicumpa,Jeerawan Ongrotchanakun

doi:10.3329/jhpn.v28i1.4522

Abstract

This study was undertaken to determine the genetic diversities of Giardia intestinalis isolated in Thailand. G. intestinalis cysts were collected from stool samples of 61 subjects residing in Bangkok or in rural communities of Thailand with and without gastrointestinal symptoms. All the cyst samples gave positive tpi amplicons (100% sensitivity), either of the 148- or the 81-bp tpi segments. Cyst assemblage identification of the 148- and 81-bp tpi gene segments by polymerase chain reaction showed that 8% of the cysts were assemblage A, 41% assemblage A and B combined, and 51% assemblage B. The prevalence of assemblage A was significantly lower than that of assemblage B and the mixed types. Restriction fragment length polymorphism (RFLP) of the 384-bp beta-giardin gene segment revealed that 12% and 88% of the assemblage A cysts were AI and AII respectively. RFLP, based on the 432-bp gdh gene segment, showed 45.5% of the assemblage B cysts to be BIII and 54.5% to be BIV. The AI sub-assemblage was less prevalent than the others. All subjects with AI and 50% of the subjects with BIII sub-assemblage cysts were symptomatic; 80% of symptomatic Bangkok residents were adults/elderly while 85% of the rural cases were children.

Highlights

Flagellated protozoa of the genus Giardia comprise several species and are ubiquitous
Infection in humans is caused by Giardia intestinalis, which is molecularly classified into seven genotypes, namely A-G [4,5]
The genomic DNA of the G. intestinalis cysts of all the subjects was extracted using a genomic DNA extraction-kit (SBS Gentech, China) according to the instructions of the manufacturer. These DNA preparations, together with the 11 oligonucleotide primer sequences presented in Table 2, were used for polymerase chain reaction (PCR) amplifications of the 292-bp ssrRNA [19], 753-bp and 384bp ß-giardin [19], 432-bp gdh [20], and 148-bp and 81-bp tpi segments which were specific for assemblage A and B respectively [21], under PCR conditions previously described [19,20,21] using pfu DNA polymerase (Fermebtus, Lithuania)

Summary

INTRODUCTION

Flagellated protozoa of the genus Giardia comprise several species and are ubiquitous. The parasite infects the intestinal tract of a wide range of vertebrate hosts belonging to different phyla, including avian, reptile, mammal, and human [1,2,3]. Infection in humans is caused by Giardia intestinalis (synonyms: G. lamblia, G. duodenalis), which is molecularly classified into seven genotypes (assemblages), namely A-G [4,5]. Giardia-associated infection is the most common intestinal infestation worldwide [7]. The worldwide incidence was estimated at 2.8x108. G. intestinalis is a common parasite in Thailand and in other developing countries [12,13,14,15,16]. Giardia genotypes in Thailand ertheless, this parasitic infestation did not receive much attention or concern so far. The data provide additional molecular information on human G. intestinalis isolates which was so far lacking from Thailand

MATERIALS AND METHODS

RESULTS

DISCUSSION