scholarly journals Diptera (Insecta: Pterygota) larvae as predators of Strongyloides stercoralis causing false negative stool cultures

IDCases ◽  
2022 ◽  
pp. e01387
Author(s):  
Pedro E. Fleitas ◽  
Ximena G. Acosta ◽  
Paola A. Vargas ◽  
Nicolas Caro ◽  
Alejandro J. Krolewiecki ◽  
...  
Keyword(s):  
False Negative ◽  
Strongyloides Stercoralis ◽  
Stool Cultures

scholarly journals Descriptive Investigation of Strongyloidiasis Infection and Characterization of Strongyloides stercoralis Using Morphological and Molecular-Based Methods

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Nayana Gunathilaka ◽  
Nilmini Chandrasena ◽  
Tharaka Wijerathna ◽  
Yoshito Fuji ◽  
Deepa Gunasekara ◽  
...  
Keyword(s):  
Gastrointestinal Symptoms ◽  
Strongyloides Stercoralis ◽  
Molecular Evidence ◽  
Pcr Assay ◽  
Its1 Region ◽  
Promising Tool ◽  
Hyperinfection Syndrome ◽  
Polymerase Chain ◽  
Stool Cultures

Strongyloidiasis is caused by the nematode Strongyloides stercoralis which has the unique ability to reproduce and complete its entire life cycle within the human host through its autoinfection cycle. Diagnosis of this infection is important because of its potential to cause fatal hyperinfection syndrome or disseminated infections in those with defective cellular immunity. Parasitological methods based on faecal microscopy and culture often fail to detect low-intensity infections. A multiplex polymerase chain reaction (PCR) assay was developed for the detection of S. stercoralis, Ascaris lumbricoides, and Enterobius vermicularis by designing primers specific for the ITS1 region of ribosomal DNA of S. stercoralis and A. lumbricoides and 18S region of rRNA of E. vermicularis. A 61-year-old patient presented with chronic gastrointestinal and respiratory symptoms and weight loss with a stool microscopy positive for helminth larvae. Stool cultures with the Harada–Mori technique yielded L3 larvae which were identified as S. stercoralis based on morphology. The multiplex PCR performed on DNA extracted from stool elicited the expected band at 129 bp on gel electrophoresis of the PCR yield providing molecular evidence of intestinal strongyloidiasis. The patient’s gastrointestinal symptoms improved with a six-day course of albendazole (400 mg twice daily). Negative posttreatment stool microscopy, culture, and PCR confirmed successful clearance of infection. Molecular-based PCR assay is a promising tool to diagnose and assess the therapeutic efficacy of anthelmintics in intestinal helminthiases such as strongyloidiasis.

scholarly journals Detection of six soil-transmitted helminths in human stool by qPCR- a systematic workflow

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0258039
Author(s):  
Kristy I. Azzopardi ◽  
Myra Hardy ◽  
Ciara Baker ◽  
Rhian Bonnici ◽  
Stacey Llewellyn ◽  
...  
Keyword(s):  
Potassium Dichromate ◽  
Mitochondrial Gene ◽  
False Negative ◽  
Strongyloides Stercoralis ◽  
Chain Reactions ◽  
Soil Transmitted Helminths ◽  
Multiplex Qpcr ◽  
Negative Results ◽  
False Negative Results ◽  
Multiple Species

Soil-transmitted helminths (STH) infect up to one-quarter of the global population, with a significant associated disease burden. The main human STH are: Ancylostoma spp. and Necator americanus (hookworms); Ascaris lumbricoides, Trichuris trichiura, and Strongyloides stercoralis. The aim of this study was to establish a scalable system for stool STH multiplex quantitative real-time polymerase chain reactions (qPCR). Stool samples collected in Fiji and preserved in potassium dichromate were transferred to Melbourne at ambient temperature. Samples were washed to remove potassium dichromate and DNA was extracted with the Mini-Beadbeater-24 and a column-based kit. A SYBR green qPCR to detect the vertebrate mitochondrial gene was used as a DNA extraction control. Samples were tested using a probe-based multiplex qPCR targeting A. lumbricoides, T. trichiura and S. stercoralis, and in a second multiplex reaction to detect hookworms to the species level (A. duodenale, A. ceylanicum, N. americanus). An internal amplification control in both multiplex assays was included to prevent false-negative results due to PCR inhibitors. Samples were homogenised for a single cycle of 40 seconds to release STH DNA and washed stool was stored for up to 15 weeks at -30°C without compromising DNA. Our multiplex qPCR detected multiple species of STH without reduced sensitivity compared to singleplex. qPCR data from 40 stools was validated against STH-positive stools determined by microscopy. We have developed and validated an efficient and staged system for detecting six clinically important STH affecting humans that could be easily implemented without advanced automation in any qPCR-capable laboratory.

scholarly journals Is Gastric Involvement by Strongyloides stercoralis in an Immunocompetent Patient a Common Finding? A Case Report and Review of the Literature

2021 ◽  
Author(s):  
Irene Pecorella ◽  
Tom Richard Okello ◽  
Gaia Ciardi ◽  
David Martin Ogwang
Keyword(s):  
Inflammatory Cell ◽  
False Negative ◽  
Strongyloides Stercoralis ◽  
Duodenal Mucosa ◽  
Immunocompetent Patient ◽  
Common Finding ◽  
Inflammatory Cell Infiltrate ◽  
Microscopical Examination ◽  
Pubmed Search ◽  
Acute Inflammatory Cell

Abstract Purpose Gastric infection with Strongyloides stercoralis (SS) usually occurs in immunocompromised patients. The unexpected observation of this parasite in an otherwise healthy young lady who had undergone upper endoscopy and biopsy sampling of the gastro-duodenal mucosa, prompted us to review the literature to ascertain the conditions favouring gastric colonization by SS. Methods Pathology files of gastroduodenal biopsies received at St. Mary’s hospital, Northern Uganda, between 2007 and 2017 were reviewed. Pubmed search was performed under the headings “Strongyloides stercoralis”, “Gastric parasitosis”. Results Histology of the only gastroduodenal biopsy with SS infection showed parasite eggs, immature rhabditiform larvae, and numerous adult worms in gastric pits and rhabditiform larvae in interepithelial parasitic tunnels, causing reactive changes of the glandular epithelium. There was no significant acute inflammatory cell infiltrate surrounding the parasites. Literature review showed that gastric SS infection appears to be very uncommon and was, as expected, largely prevalent in immunodeficient individuals (84.2% of published cases). The rare gastric SS infection is a complication of systemic strongyloidiasis, either hyperinfective, or disseminated form. It is also commonly associated with duodenal infection at microscopical examination. Conclusion Involvement of gastric mucosa in the absence of duodenal strongyloidiasis appears to be quite rare and false-negative histopathological exams are reported if only the stomach is biopsied.

Stool Cultures Rarely Useful in Managing Diarrhea

2005 ◽  
Vol 39 (10) ◽  
pp. 25
Author(s):  
JANE SALODOF MACNEIL
Keyword(s):  
Stool Cultures

Clinically Meaningful Change

Methodology ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 97-105
Author(s):  
Rodrigo Ferrer ◽  
Antonio Pardo
Keyword(s):  
Effect Size ◽  
False Negative ◽  
False Negative Rate ◽  
Point Of View ◽  
Skewed Distribution ◽  
Effect Sizes ◽  
False Negatives ◽  
Large Size ◽  
Before And After ◽  
Post Test

Abstract. In a recent paper, Ferrer and Pardo (2014) tested several distribution-based methods designed to assess when test scores obtained before and after an intervention reflect a statistically reliable change. However, we still do not know how these methods perform from the point of view of false negatives. For this purpose, we have simulated change scenarios (different effect sizes in a pre-post-test design) with distributions of different shapes and with different sample sizes. For each simulated scenario, we generated 1,000 samples. In each sample, we recorded the false-negative rate of the five distribution-based methods with the best performance from the point of view of the false positives. Our results have revealed unacceptable rates of false negatives even with effects of very large size, starting from 31.8% in an optimistic scenario (effect size of 2.0 and a normal distribution) to 99.9% in the worst scenario (effect size of 0.2 and a highly skewed distribution). Therefore, our results suggest that the widely used distribution-based methods must be applied with caution in a clinical context, because they need huge effect sizes to detect a true change. However, we made some considerations regarding the effect size and the cut-off points commonly used which allow us to be more precise in our estimates.

Stool Cultures Rarely Useful in Managing Diarrhea

2005 ◽  
Vol 35 (19) ◽  
pp. 33
Author(s):  
JANE SALODOF MACNEIL
Keyword(s):  
Stool Cultures
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