Subtype analysis of Blastocystis isolates using SSU rRNA-DNA sequencing in rural and urban population in southern Turkey

Blastocystis colonization and associations with population parameters in Thai adults

BACKGROUND

Blastocystis is a unicellular eukaryote commonly found in the intestinal tract of humans and other animals. The prevalence of Blastocystis has been investigated in both developed and developing countries, yet its occurrence and distribution in rural locations has been less studied. Herein, we aimed to examine the distribution of Blastocystis colonization in Thai adults representing background populations along a rural/peri-urban gradient, as well as associations between colonization and personal characteristics.

METHODOLOGY

A total of 238 participants were recruited from rural and peri-urban areas situated in three provinces. The presence of Blastocystis in feces was evaluated using PCR and qPCR. Information on gender, age, region (province), rural/peri-urban location, and body mass index (BMI) was collected.

PRINCIPAL FINDINGS

The overall rate of Blastocystis carriage was 67.2%. Univariate analysis revealed significant associations between Blastocystis carriage and region (p<0.05), location (p<0.001) and age group (p<0.05). Logistic regression analysis revealed that rural/peri-urban location and BMI were significantly associated with Blastocystis carriage. Nine subtypes (ST1-ST7, ST10 and ST23) were identified with ST3, ST7 and ST1 as the most abundant ones, in this order. The greatest diversity of subtypes, in terms of numbers, was found in the middle aged group (nine subtypes), while the least diversity was found in the young adult and obese (three subtypes each) groups.

CONCLUSIONS

This study increases the understanding of the epidemiology of Blastocystis colonization and its association with population parameters and characteristics in middle-income countries.

Subtype Distribution of Blastocystis spp. in Patients with Gastrointestinal Symptoms in Northern Spain

Limited molecular data exist on the prevalence and subtype distribution of Blastocystis spp., the most prevalent parasite in human and animal feces worldwide. A total of 44 different subtypes (STs) of Blastocystis are currently recognized based on the sequence of the small subunit ribosomal RNA (SSU-rRNA) gene. This is a molecular study of Blastocystis spp. in hospitalized patients with gastrointestinal symptoms in northern Spain. We analyzed 173 Blastocystis-positive patients with gastrointestinal symptoms by using nested PCR for molecular detection, subtype identification, phylogenetic analyses, and genetic diversity assessment. ST2 (34.1%) and ST3 (34.7%) predominated, followed by ST1 (15.6%) and ST4 (15.6%). Mixed infections with different subtypes were observed in some patients. Sequence analysis revealed for the first time in European humans the allele 88 (a variant of ST1). In other cases, alleles commonly found in animal samples were detected (allele 9 in ST2, allele 34 in ST3, and allele 42 in ST4). Phylogenetic analysis showed high variability in ST1 and ST2, suggesting a polyphyletic origin, while both ST3 and ST4 exhibited higher genetic homogeneity, indicating a possible monophyletic origin and recent transmission to humans. These data confirm Blastocystis spp. subtype diversity and may help in understanding the evolutionary processes and potential zoonotic transmission of this parasite.

Frequency, spatial distribution, and genetic diversity of Blastocystis among referred individuals to a clinical laboratory: First report of subtype 9 in Brazil

The enteric protist Blastocystis has a worldwide distribution, however its prevalence in the human population is still underestimated, especially in developing countries where proper diagnosis is not performed in the routine of clinical laboratories. In this study, we aimed to assess the frequency, genetic diversity, and spatial distribution of Blastocystis isolates detected in fecal samples referred to a clinical laboratory for routine examination in inner São Paulo State, Brazil. A total of 348 leftover stool samples available for disposal from female and male individuals with age ranging from 3 months to 88 years were analyzed by both microscopic examination and PCR/sequencing of the SSU rRNA gene. The overall frequency of Blastocystis sp. was 31% (108/348), including 20.1% (70/348) and 31% (108/348) by microscopic examination and PCR/sequencing, respectively. Significant association was found only between Blastocystis infection and age, since the highest rate of positive samples was detected among 5-9 years old individuals (p < 0.0001). In addition, spatial distribution revealed a wide distribution of the positive samples, however they were densely concentrated in more populated areas. Seven subtypes were identified, namely ST1 (40.7%), ST2 (9.2%), ST3 (45.3%), ST4 (0.9%), ST6 (1.8%), ST7 (0.9%) and ST9 (0.9%). The intra-subtype analysis revealed a total of 25 different alleles previously reported. Here, the findings lead us to highlight the following aspects: (1) the identification of a ST9 isolate is a relevant finding since it is considered a very rare subtype in human infections as well as this is the first report in Brazil; (2) the high frequency of Blastocystis in fecal samples submitted for examination in a clinical laboratory points to the need to consider its search in routine parasitological examinations, (3) the spatial distribution of Blastocystis infection was not homogeneous but concentrated in more populated areas where the access for population to diagnostic services in healthcare is likely to be easier and, (4) the genetic variability of Blastocystis isolates suggests exposure of inhabitants living in inner municipalities to different sources of contamination involving anthroponotic and zoonotic transmission pathways.

Molecular prevalence of Blastocystis sp. and subtype diversity in fecal samples collected from cattle in dairy farms in Turkey

Close contact with infected animals is one of the main risk factors for zoonotic transmission of enteric protozoan parasite Blastocystis and thus, several animal species are being screened for the detection of the zoonotic subtypes. For this purpose, 22 fecal samples were collected from healthy cattle aged > 2 months and 39 fecal samples were also collected from cattle (aged <2 months) which are treated with TMP-SMX due to diarrhea. Later, Blastocystis sp. and subtypes were investigated by a PCR targeting the SSU rRNA gene and subsequently by sequencing. Among the 22 fecal samples collected from healthy cattle, Blastocystis was detected in 12 of them with a prevalence rate of 54.5 %. Among Blastocystis-positive samples, five different subtypes (ST3, ST5, ST10, ST12, and ST13) were detected. The predominant subtype was ST10 (allele 152) with a prevalence rate of 50 % (6/12). In the other group treated with TMP-SMX due to diarrhea, Blastocystis was detected in only one (2.56 %;1/39) fecal sample and its subtype was ST1 (allele 2). High prevalence of Blastocystis as well as predominance of ST10 (allele 152) were detected in healthy cattle. The identification of zoonotic ST1, ST3, ST5 and ST12 subtypes among the detected subtypes with a high prevalence (46.1 %; 6/13) showed the importance of cattle as a source for transmission of Blastocystis to humans. It was observed that the efficiency of TMP-SMX on the clearance of Blastocystis in cattle was very strong. Moreover, to our knowledge, this is the first study detecting Blastocystis ST13 subtype in the cattle.

Investigation of neglected protists Blastocystis sp. and Dientamoeba fragilis in immunocompetent and immunodeficient diarrheal patients using both conventional and molecular methods

Introduction

The clinical significance of Blastocystis sp. and Dientamoeba fragilis in patients with gastrointestinal symptoms is a controversial issue. Since the pathogenicity of these protists has not been fully elucidated, testing for these organisms is not routinely pursued by most laboratories and clinicians. Thus, the prevalence of these organisms and the subtypes of Blastocystis sp. in human patients in Turkey are not well characterized. This study aimed to determine the prevalence of Blastocystis sp. and D. fragilis in the diarrheic stool samples of immunodeficient and immunocompetent patients using conventional and molecular methods and to identify Blastocystis sp. subtypes using next generation sequencing.

Material and methods

Individual stool specimens were collected from 245 immunodeficient and 193 immunocompetent diarrheic patients between March 2017 and December 2019 at the Gazi University Training and Research Hospital in Ankara, Turkey. Samples were screened for Blastocystis sp. and D. fragilis by conventional and molecular methods. Molecular detection of both protists was achieved by separate qPCRs targeting a partial fragment of the SSU rRNA gene. Next generation sequencing was used to identify Blastocystis sp. subtypes.

Results

The prevalence of Blastocystis sp. and D. fragilis was 16.7% and 11.9%, respectively as measured by qPCR. The prevalence of Blastocystis sp. and D. fragilis was lower in immunodeficient patients (12.7% and 10.6%, respectively) compared to immunocompetent patients (21.8% and 13.5%, respectively). Five Blastocystis sp. subtypes were identified and the following subtype distribution was observed: ST3 54.4% (n = 37), ST2 16.2% (n = 11), ST1 4.4% (n = 3), ST6 2.9% (n = 2), ST4 1.5% (n = 1), ST2/ST3 11.8% (n = 8) and ST1/ST3 8.8% (n = 6). There was no statistically significant difference in the distribution of Blastocystis sp. subtypes between immunocompetent and immunodeficient patients.

Conclusion and recommendation

Our findings demonstrated that Blastocystis sp. and D. fragilis are commonly present in immunocompetent and immunodeficient patients with diarrhea. This study is the first to use next generation sequencing to address the presence of Blastocystis sp. mixed subtypes and intra-subtype variability in clinical samples in Turkey.

Blastocystis sp. and Dientamoeba fragilis are single-cell parasites of the human intestine which are common worldwide and reported in cases with gastrointestinal symptoms. However, the role of Blastocystis sp. and D. fragilis in patients with gastrointestinal symptoms is still controversial because their presence is not always associated with symptoms. As some intestinal parasitic infections can cause severe illness in immunocompromised individuals careful consideration of intestinal protist infection is warranted. However, testing for Blastocystis sp. and D. fragilis is not routinely carried out by most laboratories and clinicians. Therefore, this study aimed to determine the prevalence of Blastocystis sp. and D. fragilis in immunocompetent and immunosuppressed patients with diarrhea by conventional and molecular methods. Both Blastocystis sp. and D. fragilis were detected more frequently by quantitative polymerase chain reaction than by conventional methods. Next generation sequencing was used to characterize the diversity and frequency of Blastocystis sp. subtypes and mixed subtypes in patients in Turkey. Five Blastocystis sp. subtypes (ST1, ST2, ST3, ST4 and ST6) were detected. ST3 was the most frequent subtype in both immunocompetent and immunosuppressed patients. Mono-infections were more common than mixed subtype infections. Our findings showed that Blastocystis sp. and D. fragilis are commonly present in immunocompetent and immunodeficient patients with diarrhea.

The Coexistence of Blastocystis spp. in Humans, Animals and Environmental Sources from 2010-2021 in Asia

Blastocystis spp. are controversial unicellular protists that inhabit the gastrointestinal tract of humans and a wide range of animals worldwide. This review provides an overview of the prevalence and distribution of Blastocystis spp. and their subtypes throughout Asia. Research articles reporting on the presence of Blastocystis spp. in locations within Asia, between 1 January 2010, and 10 May 2021, were obtained from Scopus, PubMed, and Google Scholar. In 427 articles, the prevalence of Blastocystis spp. in 31 countries within the last decade was revealed. Isolates were found in humans, various mammals, birds, reptiles, insects, water sources, vegetables, and ambient air. Prevalence of Blastocystis spp. varied widely across host categories. Subtypes identified throughout Asia were STs 1-14, and ST18-22 (novel subtypes). ST1, ST2, ST3, ST4 were the most frequently isolated in humans; ST5 in pigs; ST10 and ST14 in goats, sheep, and cattle; and ST6 and ST7 in chickens. ST1 and ST3 were most common in water samples. ST1, ST2, ST3, ST4, ST5 and ST6 were shared by humans, animals, and water sources. There is a growing interest in the study of Blastocystis spp. and their subtypes in Asia. Due to the isolation of Blastocystis spp. from biotic and abiotic sources in Asia, the application of the One Health (OH) approach to the study of Blastocystis spp. is proposed for improved perception of this organism.

Prevalence, Molecular Characterization and Risk Factors of Blastocystis sp. from Farmed Pigs in Yunnan Province, Southwestern China

PURPOSE

Blastocystis is an enteral eukaryote that omnipresent existence in animals and humans global. The objective of the current study investigated the frequency and subtypes to evaluate risk factors for Blastocystis infection in pigs in southwestern China.

MATERIALS AND METHODS

The 866 fecal samples were collected from farmed pigs in Yunnan province, which were determined by the molecular method of the nested PCR and phylogenetic analysis established on the small subunit rDNA (SSU rDNA) gene fragment.

RESULTS

A total of 433 specimens were detected Blastocystis positive, and the prevalence of is 50.0% (433/866). The significant differences in prevalence were also observed in pigs from regions (P < 0.01, df = 8, χ² = 29.17) and age groups (P < 0.01, df = 2, χ² = 66.6). Older pigs had more Blastocystis infection than younger ones. Moreover, three zoonotic subtypes were identified by DNA sequence analysis, included ST1 (7.39%, 32/433), ST3 (4.39%, 19/433) and ST5 (88.22%, 382/433).

CONCLUSIONS

The results suggested a high prevalence and diversified subtypes in farmed pigs in Yunnan province, southwestern China, which indicated pigs are most likely to potential reservoirs and zoonotic transmission of Blastocystis for human infection. To our knowledge, the study is the first large-scale systematic statement of Blastocystis colonization in Yunnan province, Southwestern China, which contributed to the in-depth study of genetic characteristics and prevention, control and treatment of Blastocystis in pigs in Yunnan province and other regions.

Relative Frequency of Blastocystis Subtypes 1, 2, and 3 in Urban and Periurban Human Populations of Arequipa, Peru

Blastocystis is one of the most common protozoa found in the human gut and are genetically diverse and widely distributed around the world. Nonspecific and inconsistent symptoms have been associated with this protozoon; thus, its clinical importance remains controversial. Our aim was to estimate the relative frequency of Blastocystis subtypes 1, 2, and 3, which are the predominant subtypes reported in South America, based on conserved regions of SSU rDNA sequences and determine the factors associated with them. A total of 116 Blastocystis-positive stool samples were processed using conventional PCR with Blastocystis-specific primers. We identified subtype 1 (10.3%), subtype 2 (7.8%), subtype 3 (25.0%), and mixed subtype infections (8.7%). However, we could not identify any Blastocystis subtypes in 48.3% of the samples; therefore, it is likely that other subtypes were present in the area. No association was found between any gastrointestinal symptom and single or mixed Blastocystis subtypes. We found a statistically significant association between Blastocystis subtype 2 and irritable bowel syndrome (OR = 17.8, 95% CI = 1.5-408.4, p = 0.039); however, the number of samples with IBS was small (n= 4). There was no association between the Blastocystis subtypes and any epidemiological variable studied. In rural populations, we only identified subtype 1, while in urban and periurban populations, we identified subtypes 1, 2, and 3.

A Study on the Prevalence and Subtype Diversity of the Intestinal Protist Blastocystis sp. in a Gut-Healthy Human Population in the Czech Republic

Blastocystis sp. is a common intestinal protist colonizing the human intestine the prevalence of which varies across non-industrialized and industrialized countries. Its role in the human gut ecosystem remains unclear due to persisting gaps in knowledge of epidemiology and factors affecting gut colonization. Here, we aimed to expand the knowledge of the epidemiology of Blastocystis sp. in the gut-healthy humans in one of the industrialized European countries, including the distribution of its subtypes, the correlation between its occurrence and several factors such as lifestyle, contact with animals, age, and sex. A total of 288 stool samples were obtained from asymptomatic individuals over the entire age-range and 136 samples from animals with which the volunteers were in frequent contact. All samples were examined in parallel by PCR and xenic in vitro culture. Blastocystis sp. was detected in samples from both human and non-human hosts. In humans, the overall prevalence was 24% and eight subtypes were found; in animals, the prevalence was 10%, and only five subtypes were detected. A higher incidence of Blastocystis sp. was observed in individuals (i) traveling outside Europe, (ii) in frequent contact with livestock, and (iii) over 50 years of age. We found no effect on gender on Blastocystis sp. colonization.

Summary

This study provides data on the prevalence and diversity of the gut protist Blastocystis sp. and its subtypes in a gut-healthy human population with emphasis on several factors such as contact with animals, lifestyle, age, and gender.

Assessment of the subtypes and the zoonotic risk of Blastocystis sp. of experimental macaques in Yunnan province, southwestern China

Blastocystis is an enteral eukaryote with an omnipresent existence in animals and humans globally. Animals have been proposed to be a major reservoir for the transmission of Blastocystis to individuals due to their high prevalence and large amount of zoonotic subtypes. However, limited data on Blastocystis infection in experimental macaques in China exists. The objective of the current study was to investigate the frequency and subtypes of Blastocystis infection in macaques in southwestern China. A total of 505 fecal samples were collected from experimental macaques in Yunnan province and were analyzed by nested PCR and phylogenetic analyses on the basis of small subunit rRNA (SSU rRNA) gene fragments. A total of 235 specimens were positive for Blastocystis sp., and the prevalence of Blastocystis sp. was 46.5% (235/505). Significant differences in prevalence were also observed among the various species of macaques (P < 0.0133, df = 2, χ² = 8.64) and the different feed types (P < 0.0093, df = 1, χ² = 6.77). Moreover, three zoonotic subtypes, ST1, ST3, and ST5, were identified by DNA sequence analysis. There were mainly single subtype infections with some mixed subtype infections, and the predominant subtype was ST3. The results suggested a high prevalence and diversified subtypes in macaques in Yunnan province, southwestern China. Macaques are likely to be potential reservoirs capable of zoonotic transmission of Blastocystis sp. to humans. To our knowledge, this study is the first large-scale systematic analysis of Blastocystis sp. colonization in Yunnan province in the subtropics of China; these results contribute to the in-depth study of genetic characteristics and the prevention, control, and treatment of Blastocystis sp. in macaques in Yunnan province and other regions.

First genotyping of Blastocystis in yaks from Qinghai Province, northwestern China

Background

Blastocystis is a common protist that can infect domestic and wild animals worldwide. Yak (Bos grunniens), an ancient species which can survive in alpine regions, has supplied necessities to local residents in plateau areas for generations. However, the infections with Blastocystis in yaks has been ignored for a long time. In the present study, the infections and genotypes of Blastocystis spp. in domestic yaks from Qinghai Province (northwestern China) were explored.

Results

Of 1027 faecal samples collected from yaks in seven regions of Qinghai Province, northwestern China, the total prevalence of Blastocystis was 27.07% (278/1027) targeting the small subunit ribosome rRNA (SSU rRNA) gene. This protist was detected in yaks within each examined age group, geographical origin and season. Significant difference in prevalence was found in yaks from different geographical origins. The highest prevalence (48.94%) was observed in animals from Haixi county. Sequence analysis revealed three animal-specific subtypes (ST10, ST12 and ST14) of Blastocystis spp. in these yaks, with ST10 being the predominant subtype widely distributed in all investigated regions, seasons and age groups. Interestingly, this is the first report about subtype ST12 infecting yaks.

Conclusions

To our knowledge, this is the first systematic report on Blastocystis prevalence in yaks from China, and the findings provide fundamental data for establishing effective control measures for this protist in yaks as well as other animals in China.

Determination the Subtypes of Blastocystis sp. and Evaluate the Effect of These Subtypes on Pathogenicity

PURPOSE

The present study aimed to determine the frequency of subtypes of Blastocystis sp. in the immunosuppressed individuals, in patients with chronic urticaria, and in patients with GIS complaints to investigate the difference of Blastocystis sp. subtype distribution between patient and control groups.

METHODS

A total of 345 stool samples were collected from the patients and samples were studied by native-Lugol, trichrome staining, and Jones medium culture method. Positively detected samples were subjected to PCR to determine the subtypes.

RESULTS

This is the first study of nine subtypes of Blastocystis sp. investigated in our country and the most frequently found subtype was ST3, and then, the other subtypes were ST1, ST2, ST5, and ST6, respectively. Mix subtype was detected in the 11.6% and no subtype was detected in the 17.4% of the samples. The ST5 was detected first time in the control group and ST6, which is reported limitedly in our country, was found in patients with GIS complaints. ST1 and ST2 were found higher in the patient group.

CONCLUSION

This study confirmed that the subtype (ST) differences are an important factor affecting the pathogenesis of Blastocystis sp.

Blastocystis subtypes detected in long-tailed macaques in Thailand-Further evidence of cryptic host specificity

Blastocystis is an enteric parasitic protist with a widespread distribution in a variety of human and non-human hosts and supposedly a source of zoonotic transmission. This study aimed to determine the frequency and distribution of Blastocystis subtypes in free-ranging Macaca fascicularis (long-tailed macaques, LTMs) in Thailand. A total of 628 faecal samples were collected from free-ranging LTMs inhabiting fourteen tourist attraction sites in Thailand. Fresh faecal samples were individually cultured in Jones' medium, and Blastocystis-positive samples were subtyped using nuclear small subunit ribosomal DNA (SSU rDNA) sequencing. Two hundred and sixty-three (41.87%) samples were positive by culture, and 197 and 154 were successfully SSU rDNA-amplified and sequenced, respectively. Three subtypes (ST1, ST2, and ST3) comprising 19 alleles were observed. ST3 was the most common subtype detected (36.55%), followed by ST2 and ST1 (24.37% and 17.26%, respectively). Some subtype alleles not previously observed were identified. A couple of strains appeared similar to those found in humans as evidenced by SSU rDNA allelic profiles, while further evidence of cryptic host specificity emerged. This study provides the first data on Blastocystis subtypes in non-human primates in Thailand and confirms the trend observed in other Old-World countries with regard to the colonization rate and subtype distribution.

Genetic diversity analysis of Blastocystis subtypes from both symptomatic and asymptomatic subjects using a barcoding region from the 18S rRNA gene

Blastocystis is the most prevalent protozoa found in human stool samples. This study aimed to evaluate genetic diversity among Blastocystis subtypes isolated from both symptomatic and asymptomatic subjects as well as the potential correlation between subtypes and symptoms. A total of 55 Blastocystis-positive isolates were included in this study. A barcoding region of the small subunit rDNA was amplified and genetically assessed using MEGA6 and DnaSP regarding the presence of symptoms. BLAST analyses revealed the presence of 5 different subtypes (ST1, ST2, ST3, ST6 and ST7) among the samples. ST3 was the most prevalent subtype (25/55, 45%) while only one ST7 isolate was detected. Moreover, alleles 4 and 86 for ST1; alleles 9, 11 and 12 for ST2; alleles 31, 34, 36, 37 and 52 for ST3; allele 122 for ST6 and allele 137 for ST7 were detected. No statistically significant association was found between gender and symptoms with certain subtypes. Analysis of the intra-subtype variability in both symptomatic and asymptomatic subjects revealed highest similarity among ST1 isolates while lowest similarity was seen among ST3 isolates. Neutrality indices, Tajima's D and Fu's Fs, were negative but only statistically significant for ST3. Furthermore, highest values of Hd, π and S were observed among ST1, ST2 and ST3 isolated from symptomatic patients indicating high level of diversity among isolates obtained from these subjects. In addition, inter-subtype analysis showed the highest similarity between ST1 and ST2 isolates and the lowest similarity between ST2 and ST7 isolates. This is the first study revealing the presence of both ST6 and ST7 isolates in human from Iran. Phylogenetic analysis did not suggest any significant correlation between clinical manifestations and certain subtypes although genetic analysis showed highest value of diversity and significant neutrality indices among ST3 isolates obtained from symptomatic patients.

First report of Blastocystis infections in cattle in China

Blastocystis is one of the most common intestinal protists of humans and can also infect a variety of other mammals and birds. Blastocystis infections and subtype distribution in cattle have been documented, while nothing is known about those in China. Herein, a total of 526 dairy cattle from northeast China were sampled and investigated for the prevalence and genetic characteristics of Blastocystis and the potential role of bovine animals in zoonotic transmission of Blastocystis. The parasite was identified in 54 (10.3%) fecal specimens by nested PCR and DNA sequencing of the small subunit ribosomal RNA gene. Sequence analysis enabled identification of four Blastocystis subtypes (STs). Among those, subtype ST10 (75.9%, 41/54) has the highest frequency, followed by ST14 (18.5%, 10/54), ST4 (3.7%, 2/54), and ST5 (1.9%, 1/54). High prevalence and widespread distribution of ST10 and ST14 in cattle observed herein, together with analysis of their host distribution patterns in earlier studies, indicated some host-adapted potential in the two subtypes. The identification of human-pathogenic subtypes ST4 and ST5 might imply a potential zoonotic risk of cattle origin. This is the first study exploring the prevalence and genetic characteristics of Blastocystis in cattle in China. The host range of subtype ST4 was extended. The findings of this study should be helpful for a better understanding of the epidemiology and public health potential of Blastocystis.