Morphologic and Molecular Characterization of Isospora belli Oocysts from Patients in Thailand

Abstract

To investigate the extent of genetic heterogeneity in the genus Isospora infecting patients in Thailand, a total of 38 fecal samples containing Isospora oocysts from human immunodeficiency virus/acquired immunodeficiency syndrome patients (n = 30), corticosteroid-treated patients (n = 3) and immunocompetent individuals (n = 5) were recruited for analysis. Remarkable variation in the maximum width and length of oocysts both within and between isolates was observed. However, the average length-width ratio of oocysts was within the range for I. belli (> 1.2). Ex vivo sporogonic development of freshly passed oocysts in feces from three of these isolates was observed longitudinally, showing that 27% of these oocysts underwent complete sporulation. Interestingly, 95% of sporulated oocysts contained two sporocysts in an oocyst with four sporozoites in each sporocyst, and Caryospora-like oocysts, characterized by eight sporozoites enclosed by a single sporocyst, were also detected (5%). The small subunit ribosomal RNA (rRNA), 5.8S rRNA, internal transcribed spacer 1 (ITS-1), and ITS-2 were highly conserved, indicating that there were no cryptic species or extensive strain variation.

Polymorphisms in the 18S rDNA gene of Cystoisospora belli and clinical features of cystoisosporosis in HIV-infected patients

“…These results are distinct from those reported in the literature who demonstrated no significant intraspecific variations in SSU rDNA-encoding regions of the 38 C. belli isolates (Jongwutiwes et al 2007), and between strain CI1 present in GenBank and the isolate from a patient with chronic cystoisosporosis (Franzen et al 2000). These divergences might be related to differences in the distribution of C. belli genotypes between geographically distinct regions.…”

Molecular characterization of Cystoisospora belli and unizoite tissue cyst in patients with Acquired Immunodeficiency Syndrome

“…Nested PCR amplification of a fragment of the 18S Samarasinghe et al (2008) rRNA gene produced the expected 396 bp amplicon in all samples and sequences of the 8 cases were identical to those previously reported for C. belli. Identity was 100% for previously reported sequences for C. belli, with the exception of 1 case described by Jongwutiwes et al (2007) of an immunocompetent patient with multiple relapses. 2).…”

“…Identity was 100% for previously reported sequences for C. belli, with the exception of 1 case described by Jongwutiwes et al (2007) of an immunocompetent patient with multiple relapses. GenBank Accession numbers and species are detailed in Table 3. identical size when digested with Alu I. Sequences of the 8 isolates examined were identical between them, but differed from the isolates reported by Jongwutiwes et al (2007) and Samarasinghe et al (2008) (GenBank Accession nos. The DNA fragment generated from the nested PCR for the ITS-1 contained 440 bp.…”

Molecular Identification of Biliary Isospora Belli

“…To definitively identify the pathogen, polymerase chain reaction (PCR) amplification of the rRNA gene was performed as previously described. 3 The nest PCR product was sequenced by a 3130 Genetic Analyzer (Applied Biosystems) and was compared to those searched from the GenBank database (http://www.ncbi.nlm.nih.gov/BLAST/BLAST.cgi). IB infection was identified by the PCR method.…”