Showing posts with label UAE. Show all posts
Showing posts with label UAE. Show all posts

Tuesday, December 1, 2015

This Month in Blastocystis Research (NOV 2015) - Persian Gulf Edition

Today is the first time an Airbus A380 will be landing in Copenhagen Airport, Denmark. Flying in from Dubai, it will mark the inauguration of a runway that was recently refurbished to enable accommodation of a plane of this size.

I therefore thought I'd make a tribute to this particular day by dedicating the "This Month in Blastocystis Research" post to studies on Blastocystis recently published by researchers based along the Persian Gulf. Three surveys on Blastocystis from this region recently made it to parasite/microbiology research journals. The studies are important since they represent examples of studies employing molecular tools for screening and molecular characterisation of parasite isolates identified in regions where such data are extremely scarce. Some of these data will enable us to better understand host specificity, differences in geographic distribution, clinical and public health significance, and transmission patterns.

 The first study was on Blastocystis in Qatar and published in Acta Tropica; it was already mentioned in my September blog entry.

I was lucky to be involved in the second study, which was a study carried out in Sharjah, United Arab Emirates, and designed by Ali ElBakri and colleagues. In this study, we screened a total of 133 samples from ex-pats living in Sharjah, subtyping the samples positive for Blastocystis using partial small subunit (SSU) ribosomal RNA gene sequencing. Fifty-nine (44.4%) samples were positive, of which 39 were successfully sequenced and subtyped. The ST distribution was as follows: ST3, 58.9% (23/39); ST1, 28.2% (11/39); and ST2, 7.6% (3/39). This study is the first to provide data on the prevalence of Blastocystis and the distribution of various STs in the UAE. As usual, ST4 was absent, while ST1, ST2, and ST3 were all common in this geographical region; a situation similar to most other regions outside of Europe.

The third study was from the city of Baghmalek in Southwestern Iran, and was published by Khoshnood and colleagues in Jundishapur Journal of Microbiology. This team used microscopy to identify Blastocystis in 1,410 stool samples from patients presumably suffering gastrointestinal symptoms. A very low prevalence was identified, about 3%. This low figure most likely reflects the use of microscopy, which is an extremely insensitive diagnostic method. From Blastocystis-positive samples, DNA was extracted and submitted to PCR and sequencing targeting the (SSU) ribosomal RNA gene. It says in the article that the subtypes identified in the study included "ST3, ST4, ST5, and ST7 with the most prevalent being ST4 (40.9%)", and the main conclusion is that, unlike the situation in other countries in the Middle East, ST4 was identified as the most prevalent subtype.

There are at least two conspicuous situations here: The first one pertains to the rather unusual subtype distribution reported, which appears quite dissimilar to the ones reported from neighbouring countries. The next one is even more odd and pertains to the fact that the sequences (AB915194 - AB915214) generated in the study, and from which the subtype data must have been inferred, do not BLAST to other nuclear ribosomal RNA genes in GenBank, of which there are thousands! In fact, AB915194 represents a protein-coding gene, translating into  

S P Y L L S I S T E E S Y T D S H Y Y G E C T T I A Q S I Y H Q S S K S V E A S I W D C V Y Met T L I Y E G V T D L T Y D E M K A S Y T D P V E T L T V L G K Y P G A D I S G I S L D L V F G Y I G R G I P V I S R I N D G R Y V L I V S Y N S E A V R Y Y D P V L D E Q V R K Q

... which is a Clostridium hypothetical protein with a peptidase domain! This may either reflect an error linked to the accession numbers, or it may reflect a situation where for some reason non-ribosomal DNA sequences were uploaded to GenBank. Given the appearance of the phylogeny included in the article, it could easily be suspected that the sequences produced and used were in fact non-Blastocystis DNA sequences, in which case the paper should be retracted. Before this mystery has been solved, the results of the Iranian study cannot be fully appreciated, and the relevance of citing the study appears very limited for now.

The last study highlights the importance of making sequence data publicly available; if these data had not been available for critical appraisal, the conclusions made in this article could easily have been accepted without any further ado!


Abu-Madi M, Aly M, Behnke JM, Clark CG, & Balkhy H (2015). The distribution of Blastocystis subtypes in isolates from Qatar. Parasites & Vectors, 8 PMID: 26384209

AbuOdeh R, Ezzedine S, Samie A, Stensvold CR, & ElBakri A (2015). Prevalence and subtype distribution of Blastocystis in healthy individuals in Sharjah, United Arab Emirates. Infection, Genetics and Evolution: Journal of Molecular Epidemiology and Evolutionary Genetics in Infectious Diseases PMID: 26611823 

Khoshnood S, Rafiei A, Saki J, & Alizadeh K (2015). Prevalence and Genotype Characterization of Blastocystis hominis Among the Baghmalek People in Southwestern Iran in 2013 - 2014. Jundishapur Journal of Microbiology, 8 (10) PMID: 26587213