Blastocystis subtypes detected in humans and animals from Colombia

Blastocystis is a common enteric protist colonizing probably more than 1 billion people along with a large variety of non-human hosts. This protist has been linked to symptoms and diseases such as abdominal pain, constipation, diarrhea, flatulence and irritable bowel syndrome (IBS). Remarkable genetic diversity has been observed, leading to the subdivision of the genus into multiple subtypes (ST), some of which are exclusively found in non-human hosts. The aim of this study was to determine the distribution of Blastocystis STs in different Colombian hosts. We obtained fecal samples positive for Blastocystis by microscopy from 277 humans, 52 birds, and 117 mammals (25 cattle, 40 opossums, 40 dogs, 10 rats and 2 howler monkeys). The samples were submitted to DNA extraction, PCR and sequencing using primers targeting the small subunit rRNA gene, and ST identification was performed according to DNA barcoding. We observed the occurrence of ST1 (34%) and ST2 (23%) and lower proportions of STs 3 (11.4%), 4 (0.8%), 6 (19.8%) and 8 (10.5%). Domesticated mammals shared the same STs as those usually seen in humans (ST1, ST2, ST3), while birds and marsupials had STs, which are usually rare in humans (ST6, ST8). Further studies implementing high-resolution molecular markers are necessary to understand the phylodynamics of Blastocystis transmission and the role of this stramenopile in health and disease in Colombian populations, and to expand on the phylogeographic differences observed so far with a view to exploring and understanding host-parasite co-evolution.

Difference of hepatitis B virus genotype distribution in two groups of mexican patients with different risk factors. High prevalence of genotype H and G

BACKGROUND

Hepatitis B virus (HBV) has been classified in eight genotypes, from A to H (HBV/A to HBV/H). HBV genotypes were determined in two groups with different risk factors.

METHODS

Group I consisted of 42 patients with chronic and acute hepatitis and group II with 25 men who have sex with men (MSM). HBV genotypes were determined by DNA sequencing of the S-gene.

RESULTS

Both groups differed with respect to genotype distribution (p < 0.001). In group I, there were 31 (74%), 9 (21%) and 2 patients (5%) with HBV/H, HBV/D and HBV/A; respectively. In group II, HBV/H, HBV/A, and HBV/G were found in 13 (52%), 8 (32%) and 4 (16%) cases, respectively. By using an HBV/G-specific PCR, 3 more cases of HBV/G were identified in group II, rising to a total 28%. All HBV/G strains were present in coinfection with other HBV genotypes, 86% with HBV/H, and 14% with HBV/A.

CONCLUSIONS

HBV/H predominated in both groups. A high frequency of HBV/G was found in MSM, which was always coinfected with HBV/H or HBV/A. Significant differences in HBV genotype distribution were also found, since HBV/D was present only in patients with liver disease, whereas HBV/G was present only in MSM.

Genotypes and S-gene variability of Mexican hepatitis B virus strains

The genotypes and subtypes of 15 Mexican hepatitis B virus strains were determined by sequencing and phylogenetic analysis of the small S-gene. The most predominant strains were found to be divergent genotype/subtype F/adw4 strains (66.6%), followed by A/adw2 (20.0%), D/ayw3 (6.7%), and G/adw2 (6.7%). The S-genes of the Mexican genotype F strains and two Nicaraguan strains described previously formed a subcluster with more than 4% divergence from the other strains within this genotype. The Mexican strains within genotypes A and D showed the highest homology with strains from Europe and the United States. Ten amino acid substitutions not described previously were found in the S-genes of strains from nine chronic carriers, whereas the S gene in strains from six acute hepatitis B patients were highly conserved as compared to their respective genotypes. One genotype F strain from an HBsAg positive chronic carrier had a T to A mutation at position 647, forming a translational stop at codon 216. Two genotype F strains from HBsAg negative chronic carriers had a Val180 instead of an Ala found in the other genotype F strains. This study shows that a divergent genotype F predominates in Mexican strains analyzed, which presented amino acid substitutions not reported previously outside the a determinant.