Molecular characterization of intestinal protozoa in an oil wastewater treatment facility; risk for contamination of downstream farmlands.

Authors

Hanieh Mohammad-Rahimi, Saeid Andalib, Maryam Niyyati, Hamed Mirjalali

Published in

BMC microbiology. Jul 18, 2026. Epub Jul 18, 2026.

Abstract

Oil refinery (OR) facilities consume vast volumes of water during their processes, generating a large amount of wastewater (WW). The oil refinery wastewater (ORWW) contains toxic materials, and few microorganisms are believed to remain active in this environment.
Water samples were collected from an ORWW facility for nine months. After recording physical-chemical features, filtration and sedimentation were employed. DNA extraction was performed for all samples and the presence of targeted parasites was evaluated using real-time PCR. Genotype/subtype of positive samples was characterized using sequencing.
Real-time PCR showed that from 76 ORWW samples, targeted protozoa were identified in 26 (34.2%) samples. Accordingly, Blastocystis sp., Enterocytozoon bieneusi, and Giardia duodenalis were detected among 9.21% (7/76), 25.0% (19/76), and 2.63% (2/76) of samples, respectively. Enterocytozoon bieneusi was the most common detected species in samples followed by Blastocystis sp. and G. duodenalis. There was a statistically association between the presence of Blastocystis sp. and the type of wastewater treatment plants (WWTPs). Enterocytozoon bieneusi genotypes BEB6 (3/5; 60%), C (1/5; 20%), and an unknown genotype were detected among samples. Also, Blastocystis sp., ST1 (2/4; 50%), ST3 (1/4; 25%), uncultured uncharacterized stramenopile (1/4; 25%) and ST2 (1; 100%), were characterized in samples. Giardia duodenalis was the assemblage AII (1/2; 50%). Phylogenetic analysis showed that E. bieneusi genotypes were grouped within the groups 1 and 2, human-infecting genotypes. In addition, Blastocystis sp., subtypes were clustered within subtypes isolated from humans.
This is the first study investigating intestinal protozoa in a super harsh condition. Our findings signify the concern due to the distribution of potentially pathogenic parasites to downstream farmlands through industrial treated wastewaters which are used for irrigation.

PMID:
42471555
Bibliographic data and abstract were imported from PubMed on 19 Jul 2026.

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