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. 2023 Aug 23;2(3):229-236.
doi: 10.1016/j.imj.2023.08.002. eCollection 2023 Sep.

A study implementing real-time PCR to identify Strongyloides species of third-stage larvae in human stool samples from Southern Vietnam

Le Duc Vinh  1 , Nguyen Kim Thach  2 , Huynh Hong Quang  3 , Do Nhu Binh  4 , Tran Thi Duc Hanh  5 , Nguyen Minh Toàn  6 , Nguyen Trung Tuyen  7 , Nguyen Thu Huong  6
Affiliations

A study implementing real-time PCR to identify Strongyloides species of third-stage larvae in human stool samples from Southern Vietnam

Le Duc Vinh et al. Infect Med (Beijing). .

Abstract

Background: Strongyloidiasis, a neglected disease caused by intestinal nematodes of the genus, is endemic to tropical and subtropical areas such as Vietnam. Morphological methods only identify the genus, while DNA-molecular techniques are susceptible in Strongyloides spp. detection. The study aims to determine the prevalence of dominant Strongyloides species among the population in Duc Hoa district, Long An, Vietnam.

Methods: A cross-sectional study used 1190 stool specimens collected from July 2017 to November 2018. All samples were transported within 2 h, stored at 2-8°C, and processed within 48 h for microscopy smear and culture at the Laboratory of Medical Parasitology, Pham Ngoc Thach University of Medicine (PNT). Then all positive samples with the above 2 methods were verified by real-time PCR technique. Real-time PCR amplification was conducted at the Laboratory of Molecular Biology, PNT.

Results: Direct microscopy and modified Harada-Mori culture detected Strongyloides spp. larvae in 79/1190 samples (6.6%). About 94.2% of the DNA samples were Strongyloides stercoralis, 2.9% were co-infections with Strongyloides ratti and S. stercoralis, and 2.9% were patients with S. ratti. The identity of 12/14 sequences was confirmed as S. stercoralis with a high level of similarity (91.3%-100%) and over 98% for S. ratti.

Conclusion: DNA-molecular techniques and sequence analysis are highly suitable for identifying Strongyloides species isolated from stool samples. It is remarkable evidence of the presence of zoonosis S. ratti disease in human, not just the known S. stercoralis. It is likely to result in a certain proportion of people being infected by this animal-borne infectious pathogen.

Keywords: DNA-molecular techniques; Strongyloides ratti; Strongyloides stercoralis; Strongyloidiasis.

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Figures

Image, graphical abstract
Graphical abstract
Fig 1
Fig. 1
The geographical distribution of the study site in Duc Hoa, Long An, Vietnam (study sites in red).
Fig 2
Fig. 2
Result of real-time PCR in identification of Strongyloides spp. (A) Sample No. 1 S. stercoralis; (B) Sample No. 25 co-infection of S. stercoralis–S. ratti; (C) Sample No. 54 S. ratti.
Fig 3
Fig. 3
Electrophoresis products of nested PCR on agarose gel 1.5%. M: scale of DNA 100 bp; C: Negative control (H2O); S: DNA sample of Strongyloides spp.
See this image and copyright information in PMC

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