Molecular identification and subtypes distribution of Blastocystis sp. isolated from children and adolescent with cancer in Iran: evaluation of possible risk factors and clinical features

The associated risk of Blastocystis infection in cancer: A case control study

Background

Blastocystis is an anaerobic intestinal protozoan. Nine Blastocystis subtypes (STs) were detected in humans. A subtype-dependent association between Blastocystis and different cancer types has been debated in many studies. Thus, this study aims to assess the possible association between Blastocystis infection and cancer, especially colorectal cancer (CRC). We also screened the presence of gut fungi and their association with Blastocystis.

Methods

We used a case-control design; cancer patients and cancer-free (CF) participants. The cancer group was further sub-group into CRC group and cancers outside the gastrointestinal tract (COGT) group. Macroscopic and microscopic examinations were performed to identify intestinal parasites in participants' stool samples. Molecular and phylogenetic analyses were conducted to identify and subtype Blastocystis. Furthermore, gut fungi were investigated molecularly.

Results

104 stool samples were collected and matched between CF (n=52) and cancer patients (n=52); CRC (n=15) and COGT (n=37). As anticipated, Blastocystis prevalence was significantly higher among CRC patients (60%, P=0.002) and insignificant in COGT patients (32.4%, P=0.161) compared to CF group (17.3%). The most common subtypes were ST2 among cancer group and ST3 in the CF group.

Conclusion

Cancer patients have a higher risk of Blastocystis infection compared to CF individuals (OR=2.98, P=0.022). Increased risk of Blastocystis infection was associated with CRC patients (OR=5.66, P=0.009). Nevertheless, further studies are required to understand the underlying mechanisms of Blastocystis and cancer association.

Blastocystis sp. in Small Ruminants: A Universal Systematic Review and Meta-analysis

PURPOSE

The present review was done to evaluate the prevalence and subtype distribution of Blastocystis infection among small ruminants, at a global perspective.

METHODS

Systematic search was performed in PubMed, Scopus, Google Scholar, and Web of Science until 30th January 2022 and total estimates along with 95% confidence intervals (CIs) were computed using a random-effects model.

RESULTS

Ultimately, the required data were extracted from 25 papers including 19 datasets for each animal. Among 3125 sheep, the Blastocystis prevalence was 25.3% (95% CI 16.1-37.4%) (10 countries), being lower in comparison to that in 2869 examined goats [20.5% (95% CI 11-35.1%)] (12 countries). Regarding STs distribution, fourteen genetically diverse STs of Blastocystis (ST1-ST5, ST7, ST10, ST12, ST14, ST15, ST21, ST23, ST24, ST26) have been reported in sheep, and the highest pooled prevalence was related to ST10 [11 datasets, 57.8% (95% CI 43.7-70.8%)], followed by ST14 [8 datasets, 28.4% (95% CI 20.2-38.4%)], and ST7 [2 datasets, 21.1% (95% CI 4.5-60.3%)]. Compared to sheep, more STs (ST1, ST3-ST7, ST10, ST12, ST14, ST21, ST23-ST26, and ST32) were reported from goats, and the highest weighted frequency was related to ST10 [6 datasets, 45.1% (95% CI: 25.6-66.2%)], followed by ST7 [2 datasets, 40.4% (95% CI 30-51.7%)], and ST14 [4 datasets, 29% (95% CI 15.5-47.7%)]. Out of ten known zoonotic STs reported for Blastocystis (ST1-ST9, and ST12), 7 were isolated from sheep (ST1-ST5, ST7, and ST12) and 7 were reported from goats (ST1, ST3-ST7, ST12).

CONCLUSIONS

Overall, Blastocystis epidemiology in sheep and goats is yet to be elucidated and demands more comprehensive studies.

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.

Current global status, subtype distribution and zoonotic significance of Blastocystis in dogs and cats: a systematic review and meta-analysis

Background

Blastocystis is a common intestinal protozoa found in animal and human fecal samples, with over 1 billion individuals infected worldwide. Since domestication, dogs and cats have had a close bond with humans. However, their close proximity poses a potential health risk since they may harbor several zoonotic agents. A global estimate of Blastocystis infection and subtype (ST) distribution in dogs and cats would therefore be of great health importance to humans.

Methods

We performed a comprehensive systematic search of four English-language databases (PubMed, Scopus, Google Scholar, Web of Science) for relevant articles up to 8 November 2021. The random-effects model was used to make pooled estimates with confidence intervals (CIs).

Results

In total, we identified 49 publications that met our inclusion criteria and subsequently analyzed the 65 datasets in these articles, of which 23 and 42 datasets were on cats and dogs, respectively. Among the 2934 cats included in the 23 datasets, which involved 16 countries, the prevalence rate of Blastocystis infection was 9.3% (95% CI 5.3–15.9%). The prevalence of Blastocystis infection was slightly lower [7%, 95% CI 4.7–10.4%) among the 7946 dogs included in the 42 datasets, involving 23 countries. The sensitivity analysis showed that no remarkable variation in the estimates upon the stepwise removal of each dataset. Higher ST diversity was found among the examined dogs (ST1-8, ST10, ST23, ST24) than among cats (ST1-4, ST10, ST14). Among dogs, ST3 was the most frequent ST (41.3%), followed by ST2 (39.3%), ST1 (30.9%), ST4 (13.4%), ST8 (12.7%), ST10 (11%) and ST5 (8.1%). Also among dogs, each of ST6, ST7, ST23 and ST24 was observed in only one study. Of the ST found in the cats examined, ST4 (29.5%), followed by ST10 (22.5%), ST1 (19.8%) and ST3 (17.6%) were the most common. A single study also reported the presence of both ST2 and ST14 in cats. With respect to zoonotic Blastocystis STs (ST1–ST9 and ST12), eight were reported from dogs (ST1-ST8) and four were isolated from cats (ST1–ST4), showing the implication of dog and cats in zoonotic transmission.

Conclusions

Taken together, our results show that elucidation of the true epidemiology and ST distribution of Blastocystis in dogs and cats demands more comprehensive studies, particularly in the negelected regions of the world.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05351-2.

Are Blastocystis hominis and Cryptosporidium spp. playing a positive role in colorectal cancer risk? A systematic review and meta-analysis

Objective

Intestinal protozoa Blastocystis hominis and Cryptosporidium spp. are two influential factors in intestinal complications and malignancies. In present study, we estimated the pooled prevalence and odds ratio (OR) of the two parasites in colorectal cancer (CRC) patients and their possible association with the deadly disease.

Method

Our systematic search was conducted for published researches between January 1, 2000 and April 30, 2022 by using four international databases include Scopus, PubMed, and Web of Science as well as Google scholar search engine. The random- and fixed-effects models were used to estimate the pooled prevalence, OR, and 95% confidence interval (CI) by comprehensive meta-analysis (V2.2, Bio stat) software. Inclusion and exclusion criteria were applied.

Results

Thirteen papers (seven case–control and six cross-sectional studies) for B. hominis/CRC and six papers (two case–control and four cross-sectional studies) for Cryptosporidium spp./CRC were eligible to include in data synthesis. Pooled prevalence of B. hominis and Cryptosporidium spp. in CRC patients was calculated to be 26.8% (95% CI 19.4–35.7%) and 12.7% (95% CI 6.8–22.5%), respectively. Based on case–control studies, significant difference was found between case and controls in both protozoa (B. hominis OR 2.10; 95% CI 1.39–3.18% vs. Cryptosporidium spp. OR 5.06; 95% CI 1.8–13.6%). Considering the Blastocystis subtypes, ST1 (5/6; 83.33% studies) and ST3 (5/6; 83.33% studies) had the highest number of reports in CRC patients. Regarding the Cryptosporidium species, only C. parvum and C. hominis were reported.

Conclusion

Given the significant prevalence of both parasites in CRC patients and their statistically significant association, there is a need to pay more attention to these two intestinal parasites in under treatment patients.

An Association Between Blastocystis Subtypes and Colorectal Cancer Patients: A Significant Different Profile from Non-cancer Individuals

PURPOSE

Blastocystis is a common enteric human parasite of non-conclusive pathogenicity which may be determined by subtype (ST) variation. Colorectal cancer (CRC) is considered one of the primary causes of cancer mortality. Blastocystis ST7 has been shown to reduce beneficial intestinal microbiota and may exacerbate CRC. This study assessed the possible association between Blastocystis STs and CRC in comparison to non-cancer patients.

MATERIAL AND METHODS

A total of 200 fecal samples were obtained from CRC (100) and non-CRC (100) individuals attending Beni-Suef University Hospital, Egypt. Blastocystis was searched for in all samples using microscopy and culturing. Positive subculture samples were genetically sequenced and subtyped using conventional polymerase chain reaction (PCR). Blastocystis STs were determined by sequencing and a phylogenetic tree was created. Related patient characteristics and tumor stages were analyzed for association with presence of Blastocystis.

RESULTS

Blastocystis was identified in 52% and 42% of CRC and non-cancer individuals, respectively. ST1, 2, and 3 were isolated from both cancer and non-cancer individuals; however, for the first time, ST7 was only isolated from CRC stool samples with significant association. Associated patient characteristics were evaluated as predictors.

CONCLUSION

Blastocystosis is highly prevalent in CRC patients, predominantly in the latest CRC grades and stages. To the best of our knowledge, this is the first study to report the identification of Blastocystis ST7 in CRC patients. To determine whether certain STs of Blastocystis are associated with CRC would require further research, including the role played by gut microbiota.

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

Simple Summary

Blastocystis spp. are unicellular parasites that infect the gastrointestinal tract of humans and animals. Their occurrence in the environment had been detected in water sources, thus causing contamination. The presence of the parasites in humans, animals and environmental sources in Asia were reviewed according to countries in Asia, different categories of human and animal populations, and environmental sources including water samples, food and ambient air. The coexistence of the parasites poses a public health concern as the parasites are commonly found in most studies. Hence, there is a growing interest in the study of Blastocystis spp. Due to the isolation of Blastocystis spp. from living and non-living sources, a collaborative, multisectoral and transdisciplinary approach known as One Health is proposed for future study of Blastocystis spp. in order to achieve optimal health outcomes through the recognition of interconnection between people, animals and their shared environment.

Abstract

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.

Comparative molecular prevalence and subtypes distribution of Blastocystis sp. a potentially zoonotic infection isolated from symptomatic and asymptomatic patients in Iran: A systematic review and meta-analysis

PURPOSE

The present systematic review and meta-analysis was aimed to assess the weighted molecular prevalence of Blastocystis sp. in humans along with the comparative molecular prevalence and subtypes distribution of Blastocystis isolated from symptomatic and asymptomatic patients in Iran.

METHODS

International electronic databases including Medline/PubMed, ProQuest, Scopus, Embase, and Google Scholar were explored until 4th October 2020. Heterogeneity index was evaluated among studies using Cochran's Q test and I² index. Finally, 23 eligible studies were qualified to be included in this review.

RESULTS

The pooled molecular prevalence of Blastocystis sp. in Iran was reported 15.2% (95% CI 11.5-19.7). In addition, the molecular prevalence based on PCR-sequencing and STS primers was reported 12.5% (95% CI 8.6-17.7) and 19.8% (95% CI 13.1-28.8), respectively. Interestingly, there was a considerably higher prevalence among asymptomatic patients [25.1% (95% CI 20.8-30.0)] in comparison to symptomatic ones [21.0% (95% CI 15.9-27.2)]. In addition, the frequency of Blastocystis ST1, ST2, and ST3 from positive samples in symptomatic patients was 19.7%, 35.1%, and 47.4%, respectively. In addition, the prevalence of Blastocystis ST1, ST2, and ST3 from positive samples in asymptomatic patients was 27.1%, 26.8%, and 37.8%, respectively. The results obtained in Iran showed that Blastocystis is more common in asymptomatic patients compared to patients having clinical symptoms. Of note, ST3, as the most common subtype causing clinical symptoms, was the most prevalent reported subtype among both symptomatic and asymptomatic patients in the country.

CONCLUSIONS

Hence, the pathogenicity of the Blastocystis parasite is not subtype-specific and appears to be related to a variety of risk factors. Still the Blastocystis epidemiology is open to question and more large-scale studies should be performed on this aspect.

Investigation of Isolated Blastocystis Subtypes from Cancer Patients in Turkey

PURPOSE

It is not clear that Blastocystis remains without damage to the digestive tract or has a pathogenic effect in relation to subtypes in immunocompromised people, such as cancer patients. The present study aimed to investigate the frequency and subtype distribution of Blastocystis in cancer patients who were followed-up and treated in the Oncology clinic of Firat University Hospital and to determine the clinical signs of infected sufferers.

METHODS

201 patients aged ≥ 18 with a diagnosis of cancer were enrolled in this cross-sectional study. Patients' stool samples were examined between September 2017 and August 2019 by native-Lugol, trichrome staining. Microscopy-positive stool samples were subjected to DNA isolation and subtyped by Sequence Tagged Site (STS)-PCR analysis. The symptoms and demographic characteristics of the patients were also evaluated.

RESULTS

Totally, 29 (14.4%) samples were positive for Blastocystis after all methods. 15 (51.7%) out of 29 samples were successfully subtyped by the sequenced-tagged site(STS)-PCR, while 14 (48.3%) could not be typed. Three subtypes of Blastocystis were detected: ST3 (40%), ST2 (33%), ST1 (20%), and one mixed infections with ST1/ST2 (6%). There was no statistically significant difference in terms of clinical findings and demographic characteristics.

CONCLUSION

The outcomes of our study promote the idea that Blastocystis could be an asymptomatic and harmless commensal organism. However, more comprehensive molecular and clinical studies are needed to fully determine the pathogenicity and epidemiology of Blastocystis in cancer patients.

Global epidemiology of Giardia duodenalis infection in cancer patients: a systematic review and meta-analysis

Background

Application of chemotherapeutics in cancer patients may provide an immunosuppressive milieu, favourable for parasitic infections. Giardia duodenalis is an important zoonotic intestinal parasite responsible for diarrhoea in humans worldwide.

Methods

The present systematic review and meta-analysis was conducted to estimate the prevalence of G. duodenalis and respective odds ratios (ORs) in cancer patients around the globe. Four online databases—PubMed, Scopus, Web of Science and Google Scholar—were carefully explored for relevant literature without time limitation until 28 November 2020. Meta-analysis was done based on a random effects model to pool the estimations and define 95% confidence intervals (CIs).

Results

The overall weighted prevalence of G. duodenalis infection in cancer patients was calculated to be 6.9% (95% CI 0.5 to 9.3) globally, based on data from 32 studies. Although not statistically significant, eight case–control studies revealed that cancer patients were 1.24 times (95% CI 0.66 to 2.31; p=0.501) more exposed to G. duodenalis infection than healthy controls. Moreover, the prevalence of infection was not significantly associated with quantitative variables, including publication year (regression coefficient −0.0135, p=0.578), sample size (regression coefficient −0.0007, p=0.074) and human development index (regression coefficient −1.6263, p=0.419). Also, subgroup analysis of the pooled G. duodenalis infection was performed for publication year, World Health Organization regions, countries, continents, cancer types and country income.

Conclusions

Altogether, the epidemiology of G. duodenalis infection and its associated risk factors in immunocompromised individuals, especially cancer patients, is still open to question and deserves comprehensive investigations.

Comparative genotyping of Blastocystis infecting cattle and human in the south of Iran

BACKGROUND

Blastocystis is a unicellular protozoan and one of the most common parasites found in humans and many animals' intestinal tract. The present study aimed to compare the genotypes of Blastocystis infecting cattle and humans in the south of Iran.

METHODS

A total of 100 human stool samples and 75 cattle stool samples were microscopically examined for Blastocystis infection. DNA was extracted from thirty-eight microscopically positive samples (13 humans and 25 cattle). PCR was performed on positive samples targeting the Blastocystis-specific SSU rDNA gene. PCR products of eight humans and eleven cattle samples were sequenced and compared with available reference sequences in GenBank by BLAST queries. Genetic diversity was measured for Blastocystis subtypes in human and cattle, based on haplotype and nucleotide diversities.

RESULTS

The PCR detected Blastocystis in ten humans and twenty-four cattle samples. Blastocystis subtypes 1, 2, and 6 were found in humans whereas subtypes 5 and 10 were found in cattle. Subtype (ST) 2 was the most predominant subtypes in humans whereas, in cattle specimens, the ST5 was the most dominant subtype. Based on the Blastocystis sequences of SSU rDNA, 68 sites were polymorphic and 49 sites were parsimony informative, resulting in the identification of 15 haplotypes, 10 haplotypes in the cattle and 5 in humans. No haplotype was shared between cattle and human parasites.

CONCLUSION

Human-derived Blastocystis subtypes were different from cattle subtypes in southern Iran. Nevertheless, subtype 5 in cattle can be a risk factor for human infection.