Entamoeba histolytica DNA Detection in Serum from Patients with Suspected Amoebic Liver Abscess

Abstract

Amoebic liver abscess (ALA) is regularly seen in travelers or immigrants from tropical countries. The diagnosis relies on liver imaging that is not specific, and the detection of anti-Entamoeba histolytica antibodies, which cannot distinguish acute from former infection. We tested whether E. histolytica DNA detection in serum can improve the diagnosis of ALA. We retrospectively tested available serum samples from patients with ALA and non-ALA liver space-occupying lesions between 01/01/2010 and 11/30/2019. The quantitative PCR (qPCR) assay tested specifically amplifies a 99-bp fragment of the small-subunit rRNA gene of E. histolytica. We analyzed 76 samples (ALA=19; non-ALA=57) from 76 patients collected within 6 days before and after the anti-amoebic treatment. Serum qPCR was positive in 17 of 19 ALA patients and in none of the control patients (sensitivity and specificity were 89.5% and 100%, respectively). In parallel, the sensitivity and specificity of the anti-E. histolytica antibody detection were 100% and 89.5%, respectively. The two false-negative qPCR results may be explained by ongoing metronidazole treatment or a possible persistent seropositivity that is not caused by the current liver abscess. Additionally, out of 12 abscess pus aspirates (ALA=5; non-ALA=7) tested, 5 were qPCR positive and 7 were qPCR negative with concordant results on serum. This study demonstrates that cell-free circulating E. histolytica DNA can be detected in serum in ALA. This may assist in both positive diagnoses and treatment efficacy follow-up. The origin of this circulating DNA remains to be investigated.

Amebic liver abscess: An update

“…Recently, circulating Gal/GalNAc lectin of EH was detected in the serum of ALA patients with high sensitivity (96%) prior to anti-amebic therapy[ 63 ]. Also, PCR can detect circulating DNA of EH in the serum of ALA patients with 89.5% sensitivity and 100% specificity[ 64 ]. However, the expense is a barrier to their regular usage in the poorly resourced endemic nations.…”

Amebic liver abscess by Entamoeba histolytica

“…A number of diagnostic tools are available for diagnosis; if there is a suspicion of amebiasis, testing yield can be maximized through a combination of stool testing and serology[ 6 ]. Diagnosis relies on nonspecific liver imaging and on detecting anti- E. histolytica antibodies, which cannot be used to distinguish between acute and previous infections[ 5 , 21 ]. Therefore, diagnostics must focus primarily on detecting E. histolytica using PCR or enzyme-linked immunosorbent assay[ 1 ].…”

“…The results found that loop-mediated isothermal amplification had significantly greater sensitivity (88%) then reverse transcriptase PCR (64%) as well as outstanding specificity (100%)[ 44 ]. On the other hand, in ALAs, cell-free circulating E. histolytica DNA can be detected in serum in ALAs, which could prove beneficial for not only positive diagnosis but also the efficacy of follow-up treatments[ 21 ]. Additional innovative detecting methods have been developed for E. histolytica , and stool samples were analyzed using PCR-denaturing gradient gel electrophoresis in order to distinguish between pathogenic E. histolytica (pathogenic) and non-pathogenic Entamoeba dispar [ 45 ].…”

Evaluation of total immunoglobulin G and subclass antibodies in an enzyme-linked immunosorbent assay for serodiagnosis of human amebic liver abscess

“…In endemic settings, however, significant background measurements are produced; consequently, the original protocol’s cut-off may need to be adjusted for each individual situation ( Fotedar et al, 2007 ; Saidin, Othman & Noordin, 2019 ), particularly by including healthy volunteer samples in each area for baseline subtraction and evaluating a larger number of other infectious disease samples as preliminary data for describing awareness prior to clinical use. To discriminate between previous and present infections, the best specimens, like pus or serum, should be submitted to a molecular reference laboratory for identifying the infectious agent ( Zaman et al, 2000 ; Ghelfenstein-Ferreira et al, 2020 ). Nowadays, in developing countries with limited resources, where PCR is not routinely conducted in the clinical laboratory, positive antibody testing along with a patient’s clinical manifestations, risk history, other laboratory findings, and/or abdominal imaging are useful for diagnosis ( Fotedar et al, 2007 ; Saidin, Othman & Noordin, 2019 ).…”