Stefano Tais

Background/Objectives: Strongyloides stercoralis is a soil-transmitted helminth that can cause severe disease in immunocompromised individuals. In non-endemic clinical settings, recommended diagnostic strategies rely on serology alone or in combination with a sensitive fecal test, maximizing sensitivity to avoid missed infections. The S. stercoralis VirClia^® IgG monotest (Vircell, Spain) is a novel automated chemiluminescent immunoassay (CLIA) that detects IgG antibodies against the recombinant NIE and SsIR antigens. This study evaluated its diagnostic accuracy (sensitivity and specificity) in a non-endemic clinical setting. Methods: In this monocentric retrospective study, 245 serum samples from the Tropica Biobank of a referral centre for parasitic diseases in Italy were analyzed. Samples originated from individuals from Africa (n = 85), America (n = 31), Asia (n = 53), and Europe (n = 76). Diagnostic accuracy was estimated using Bayesian latent class analysis based on a model including five routinely used diagnostic tests. Results: The S. stercoralis VirClia^® IgG monotest showed a sensitivity of 95.0% (95% credible interval [CrI]: 90.1–98.2%) and a specificity of 90.8% (95% CrI: 85.1–96.0%) for the tested population. Conclusions: In immunocompetent individuals with a risk of previous exposure to S. stercoralis, the S. stercoralis VirClia^® IgG monotest showed high diagnostic accuracy. Its high sensitivity supports current recommendations favouring highly sensitive serological assays for screening and diagnosis in non-endemic clinical settings.

Background/Objectives: The diagnosis of infection with Strogyloides stercoralis, recently targeted for control by the World Health Organization, (WHO), is challenging. Specific coproparasitological methods (agar plate culture [APC], Baermann sedimentation), recommended by the WHO for public health use, are labor-intensive and require bulky disposable materials as well as experienced microscopists. We explored the sensitivity of an alternative stool culture method using recyclable glass beads, followed by microscopy and PCR in comparison to routine APC and PCR performed on uncultured stool. Methods: We conducted a diagnostic sensitivity study on samples from patients with positive serology for strongyloidiasis who submitted stool specimens to our laboratory between January 2023 and December 2025 for parasitological confirmation. Samples were processed by routine APC and PCR on fresh stool, as well as experimental culture on bead-based plates (BPC), PCR on APC- and BPC-cultured stool, and PCR on stool incubated directly in the collection container. Results: Twenty-six of 110 samples (23.6%) tested positive in at least one technique. Within this subset, the most sensitive techniques were the APC and PCR after APC (both 84.62%); PCR on fresh stool was the least sensitive (42.31%) (p = 0.002). The sensitivity of BPC (65.38%) was lower than that of APC, although not statistically significantly. Comparable sensitivity was observed between microscopy and PCR after APC or BPC. PCR after incubation in the container showed a sensitivity of 57.69%. Agreement ranged from 50 to 84.6%. Conclusions: Alternative culture methods with more field-friendly implementation features could be interesting alternatives to standard methods. Further studies evaluating their performance and applicability in public health and clinical contexts are warranted.

Background: Currently approved vaccines are highly effective in protecting against hospitalization and severe COVID-19 infections. How pre-existing immunity responds to new variants with mutated antigens is crucial information for elucidating the functional interplay between antibodies and B and T cell responses during infection with new SARS-CoV-2 variants. Methods: In this study, we monitored the dynamics and persistence of the immune response versus different SARS-CoV-2 variants of concern that emerged during the pandemic period (2021–2022) in a cohort of vaccinated healthcare workers, who experienced breakthrough infection in the Pre-Delta, Delta, and Omicron waves. We evaluated both the humoral and cell-mediated responses after infection. We also evaluated the anti-SARS-CoV-2 antibodies levels produced by infection in comparison with those produced after vaccination. Results: Our results highlighted that the immune response against the Delta VOC mainly involved an adaptive humoral and switched memory B cells component, even 3 months after the last vaccine dose, conversely showing a high percentage of depleted adaptive T cells. Omicron infections triggered a consistent production of non-vaccine-associated anti-N antibodies, probably to balance the spike epitope immune escape mechanisms. Conclusion: Our results suggest a direct dependence between the VOC and different humoral and B and T cell balances in the post-infection period, despite the administration of a different number of vaccine doses and the elapsed time since the last vaccination.

The differential diagnosis of hepatic cystic echinococcosis (CE) may be challenging. When imaging is insufficient, serology can be applied, but no consensus diagnostic algorithm exists. We evaluated the performances of nine serological tests commercialized in Europe for the diagnosis of “echinococcosis”. We performed a diagnostic accuracy study using a panel of sera from patients with hepatic CE (n = 45 “liquid” content stages, n = 25 “solid” content stages) and non-CE focal liver lesions (n = 54 with “liquid” content, n = 11 with “solid” content). The diagnosis and staging of CE were based on ultrasound (gold standard). Nine commercial seroassays (5 ELISA, 2 WB, 1 Chemiluminescence Immunoassay [CLIA] and 1 Immunochromatographic test [ICT]) were the index tests. Sensitivity (Se) ranged from 43 to 94% and from 31 to 87%, and specificity (Sp) from 68 to 100% and from 94 to 100%, when borderline results were considered positive or negative, respectively. Three seroassays (2 ELISA, 1 WB) were excluded from further analyses due to poor performances. When tests were combined, Sp was 98–100%. The best results were obtained using the WB-LDBIO alone (Se 83%) or as a third test after two non-WB tests (Se 67–86%). A validated WB or two non-WB tests, read with stringent criteria (borderline = negative and considered positive only if concordant positive), possibly confirmed by the WB, appear sensible approaches.

Chagas disease, a neglected protozoal disease endemic in Latin America, is also currently considered an emerging threat in nonendemic areas because of population movements. The detection of Trypanosoma cruzi DNA is increasingly being considered as important evidence to support Chagas disease diagnoses. However, further performance evaluation of molecular assays is useful for a standardization of strategy considering the whole process in routine diagnosis, especially for the different settings such as endemic and nonendemic countries. Seventy-five samples were collected from subjects screened for Chagas disease in Italy. The DNA was isolated from blood using automated extraction. We evaluated the performance of the commercial RealCycler^® CHAG kit (pmPCR) based on satellite DNA (SatDNA) and of an in-house real-time PCR (ihPCR) targeting Sat and kinetoplast (k) DNAs, using the concordance of two serology assays as a reference standard. The sensitivity of kDNA and SatDNA tests by ihPCR and SatDNA by pmPCR were 14.29% (95% confidence interval (CI) 6.38 to 26.22), 7.14% (95% CI 1.98 to 17.29), and 7.14% (95% CI 1.98 to 17.29), respectively. Specificity was 100% for all PCR assays and targets. Overall, our results suggest that the preferred approach for clinical laboratories is to combine the kDNA and SatDNA as targets in order to minimize false-negative results increasing sensitivity.

We analyzed the accuracy of Chagas Quick Test®, a rapid diagnostic test, for the diagnosis of chronic Chagas disease through a retrospective study on a cohort of 669 patients consecutively examined at a single reference center in Italy, during a 7-year period. We observed high concordance with serological reference standard but low accuracy for screening purposes (sensitivity/specificity: 82.8%/98.7%) at least in our nonendemic context.