BackgroundTick-borne diseases (TBDs) represent an increasing public health threat globally. Climate change has facilitated tick range expansion and extended active seasons, contributing to rising TBD incidence rates. In Switzerland, TBDs represent a major health concern. This study aims to characterise patterns in spatio-temporal distribution of tick-borne pathogens (TBPs) in ticks removed from humans across Switzerland, examine associations between tick developmental stages and TBP infection prevalence, and analyse co-infection patterns amongst different TBPs.Methods We employed the "Tick Prevention" citizen science app to collect spatial and temporal data on tick bite incidents and to obtain tick specimens for pathogen screening throughout Switzerland during 2018-2020. Specimens underwent DNA extraction for TBP detection. Quantitative PCR targeted different TBPs at genus and species levels. Data analysis examined TBP infection prevalence in submitted ticks across geographic regions, seasons, and tick developmental stages, including co-infection patterns in ticks.ResultsOf 1056 tick specimens, 352 (33.3%) tested positive for at least one TBP, with Borrelia spp. (16.3%) and Rickettsia spp. (12.69%) showing higher infection prevalence than other TBPs, including Neoehrlichia mikurensis (5%), Anaplasma phagocytophilum (1.8%), Chlamydiales (1.8%), and Babesia spp. (1.7%). Co-infections occurred in 59 specimens (5.6%), predominantly dual infections (5.2%), with Borrelia spp. and N. mikurensis representing the most common co-infection pattern. Among 58 larvae, 898 nymphs, and 96 adult ticks examined, tick infection prevalence increased with developmental stage, rising from larvae (18.9%) to nymphs (32.6%) to adults (48.9%), consistent with pathogen acquisition through successive blood meals during tick development. Spatially, TBPs were detected across 70 of 76 Swiss administrative regions, with most TBPs displaying uniform distribution. Temporally, tick-human encounters peaked during May-June (59.7% of announced events), with TBP detection rates remaining steady (28-37%) across the tick-active months from April to September. One-third of examined ticks harboured at least one TBP, with weighted models indicating infection prevalence in submitted ticks could reach 45% in certain Swiss Plateau regions.ConclusionThese findings emphasise the importance of continued tick and TBP surveillance programmes to inform public health interventions and prevention.

Syndromic multiplex panels enable rapid cerebrospinal fluid (CSF) diagnosis of meningitis and encephalitis, but clinically relevant inter-platform discordance persists, and its analytical basis remains incompletely understood. In this retrospective multicenter study, 182 residual CSF specimens from 182 patients at 4 Swiss tertiary-care centers and 10 external quality assessment samples were tested centrally by the QIAstat-Dx Meningitis/Encephalitis panel and compared with routine BioFire FilmArray results. Discordant results were adjudicated using pathogen-specific quantitative laboratory-developed tests (LDTs) calibrated to external standards, and enterovirus-positive specimens underwent molecular typing. Among 182 clinical CSF specimens, concordance was 87.9% across shared targets. Complete agreement was observed for herpes simplex virus type 2, Haemophilus influenzae, Neisseria meningitidis, Streptococcus agalactiae, and Cryptococcus neoformans/gattii. Across the remaining shared targets, positive percent agreement ranged from 50% to 93% and negative percent agreement from 98% to 100%. Enterovirus showed the greatest discordance, with 86% positive percent agreement and 10 FilmArray-only detections. LDT testing confirmed low-level enterovirus positivity in four discordant specimens (100‒700 copies/mL), and discordant viral detections clustered at lower target burden than concordant positives (P < 0.001). Molecular typing identified enterovirus species A, B, and C in both concordant and FilmArray-only positive specimens. In conclusion, FilmArray and QIAstat-Dx showed high agreement for CSF pathogen detection. Residual discordance was largely confined to low-burden viral detections, particularly enterovirus, and was more consistent with near-threshold target abundance than with a major type-restricted detection gap. These findings support routine syndromic CSF testing and emphasize interpretation of borderline positives in conjunction with confirmatory LDT testing and clinical context.IMPORTANCESyndromic cerebrospinal fluid panels are increasingly used as first-line tests for suspected central nervous system infection, yet aggregate agreement metrics can obscure clinically relevant differences near the limit of detection. In this multicenter comparison, most discordance clustered in low-burden enterovirus-positive cerebrospinal fluid (CSF) specimens and showed no clear segregation by enterovirus type, indicating that disagreement largely arose from near-threshold detection rather than a major gap in assay inclusivity. The broader implication is that performance comparisons of syndromic panels should move beyond overall agreement and specifically address how platforms handle borderline-positive results. This matters clinically because low-level viral detections can alter post-test probability, antimicrobial stewardship, CSF resampling, and follow-up microbiologic workup. More generally, the data support laboratory-integrated diagnostic strategies that combine multiplex screening with quantitative adjudication, molecular characterization, and interpretation of semiquantitative signals to strengthen the analytical and clinical utility of syndromic testing for central nervous system infections.

Since late 2020, the emergence of variants of concern (VOCs) of SARS-CoV-2 has been of concern to public health, researchers and policymakers. Mutations in the SARS-CoV-2 genome-for which clear evidence is available indicating a significant impact on transmissibility, severity and/or immunity-illustrate the importance of genomic surveillance and monitoring the evolution and geographic spread of novel lineages. Lineage B.1.619 was first detected in Switzerland in January 2021, in international travellers returning from Cameroon. This lineage was subsequently also detected in Rwanda, Belgium, Cameroon, France, and many other countries and is characterised by spike protein amino acid mutations N440K and E484K in the receptor binding domain, which are associated with immune escape and higher infectiousness. In this study, we perform a phylogeographic analysis to track the geographic origin and subsequent dispersal of SARS-CoV-2 lineage B.1.619. We employ a recently developed travel history-aware phylogeographic model, enabling us to incorporate genomic sequences with associated travel information. We estimate that B.1.619 most likely originated in Cameroon, in November 2020. We estimate the influence of the number of air-traffic passengers on the dispersal of B.1.619 but find no significant effect, illustrative of the complex dispersal patterns of SARS-CoV-2 lineages. Finally, we examine the metadata associated with infected Belgian patients and report a wide range of symptoms and medical interventions.

Bacteria of the Borrelia burgdorferi sensu lato (sl) species complex can cause Lyme borreliosis (LB) in humans. PCR plays an important role in the diagnosis of many infectious diseases but it is used auxiliary in LB diagnostics. Here, we re-analysed a previously published real-time PCR targeting the multicopy gene of the large subunit of phage terminase (terL) in Borrelia. We analysed cultured material of Borrelia burgdorferi sl species, serum and clinical tissue samples of LB patients. PCR conditions were as previously described by Shan et al. 2021 but we also investigated PCR modifications. PCR on cultured specimens showed that whilst all samples of B. burgdorferi sensu stricto (ss) gave a positive result, not all isolates of Borrelia species causing LB in Europe (i.e. B. afzelii, B. garinii) were detected by the terL PCR. Only slight differences in Ct values were detected between PCR runs using the original ZEN/IFBQ double quencher probe compared to other double quencher probes or single quencher probes. Contrary to the hypothesis expressed by the authors of the original paper that the PCR could detect phage DNA in serum, our data show that the terL PCR was negative on all tested serum samples of individuals diagnosed with proven LB. Furthermore, using patient's tissue samples not all infections with B. afzelii or B. garinii were detected, similar to the results obtained with cultured material or serial DNA dilutions of Borrelia species. We conclude, that the terL PCR in its current form is unsuitable for LB diagnosis in Europe.

Background During the COVID-19 pandemic, non-pharmaceutical interventions (NPIs) such as social distancing, lockdowns and enhanced hygiene led to a decrease in respiratory pathogens. However, as NPIs were relaxed, a resurgence in several respiratory pathogens was observed including one local Chlamydia pneumoniae outbreak in Switzerland, prompting the need for a better understanding of C. pneumoniae epidemiology. Aim To assess temporal and geographical variations in C. pneumoniae detection before, during and after the COVID-19 pandemic. Methods Data on C. pneumoniae PCR detection ratios (number of positive tests/ total number of tests) across pre-pandemic (2018–2019), pandemic (2020–2022) and post-pandemic (2023) periods were collected via a global survey disseminated through various professional networks. Results C. pneumoniae detection ratios were analysed across 28 sites (27 in Europe, one in Taiwan) in 2023 (Dataset A, n = 172,223 tests) and 20 sites from 2018 to 2023 (Dataset B, n = 693,106 tests). Twenty-seven sites were laboratories (hospital or clinical) and one a surveillance system (Denmark). A significant decrease in detection ratios was observed during the pandemic period (from 1.05% to 0.23%, p < 0.001). In 2023, detection ratios increased to 0.28% (p < 0.002). Notable regional variations were found, with statistically significant increases in detection ratios at six sites located in Switzerland and Slovenia, where ratios ranged from 0.52% to 3.25%. Discussion The study highlights how NPIs influenced C. pneumoniae epidemiology, with reduced detection during the pandemic and partial resurgence afterwards. Regional variations suggest differing NPI impacts and underscore the need for continued surveillance.

Lyme borreliosis (LB), caused by Borrelia burgdorferi sensu lato (Bbsl), is a significant public health concern in Switzerland. Reliable data on seroprevalence and incidence are needed to better understand disease burden and inform prevention strategies. This study aimed to estimate the seroprevalence of Bbsl-specific antibodies and the incidence of symptomatic LB infections in the Swiss adult population.We analyzed Bbsl-specific IgG antibodies in 2,194 residual plasma samples from blood donors (aged 18–75 years) collected at seven Swiss Red Cross donation centers between September and December 2022. Samples were tested using the Liaison® Borrelia IgG VlsE chemiluminescence immunoassay and confirmed with the SeraSpot Anti-Borrelia-10 IgG assay according to National Reference Laboratory interpretative criteria.The overall seroprevalence was 6.1%, with higher prevalence in males (8.2%) than in females (2.9%) and regional variation ranging from 1.6% in Genève to 8.8% in Bern. Based on seroprevalence data, the estimated incidence of symptomatic Bbsl infections was 224 cases per 100,000 population per year (PPY). This estimate, although 1.3 times higher, is similar to the incidence derived from the Sentinella surveillance network. Using Sentinella data, clinically diagnosed erythema migrans was the most common manifestation (150 cases per 100,000 PPY), while disseminated forms, confirmed by clinical and laboratory criteria, occurred less frequently (1.0–8.5 cases per 100,000 PPY).Our findings provide critical insights into the burden of LB in Switzerland, highlight its public health relevance, and reinforce the importance of preventive measures. Future research should focus on longitudinal monitoring and harmonized methodologies to facilitate cross-country comparisons.

BACKGROUND:Laboratory diagnosis of Lyme borreliosis (LB) is used in a variety of clinical settings where a range of other diagnoses may be considered. Therefore, it is essential that diagnostic accuracy studies and literature reviews consider information from different types of studies and choices of sample groups. The quality of patient selection is important to minimize the risk of misclassification. This narrative review was inspired by systematic reviews where nearly all studies on the diagnostic accuracy for LB tests were determined as biased and having low quality based solely on study design considerations-not the clinical relevance. OBJECTIVES:To propose flexible design and interpretation of studies used to assess diagnostic accuracy in clinical microbiology. SOURCES:Criteria for rating the quality of studies were discussed among the ESCMID study group for LB ESGBOR (The ESCMID study group for Lyme borreliosis). The literature was searched for similar methodological discussions. CONTENT:Knowledge of antibody reactivity in the background population across various clinical patient groups with and without infection should consider variations in clinical presentation and duration of disease. Case-control studies are the most frequently used design and were judged particularly instrumental in assessing serologic testing. However, clinical and epidemiological studies not specifically intended for diagnostic accuracy may also contribute estimates of sensitivity and specificity. Systematic reviews should focus on the application of the diagnostic assay for the individual patient in various clinical settings, rather than seeking an unbiased average. Different LB sample groups and controls for test panels are discussed. IMPLICATIONS:Case-control (two-gate design) studies, case series, and seroprevalence studies representing the range of LB in different populations are necessary to assess the diagnostic accuracy of serological tests for LB. A broader range of studies should be considered for inclusion in systematic reviews of diagnostic accuracy.

Tick-borne encephalitis virus (TBEV) infection can manifest as disease of variable severity, ranging from subclinical infection to severe disease with neurological involvement and potentially fatal outcome. Although TBE is recognized as a major public health problem in Europe, the true burden of disease is potentially underestimated. Here, we investigated TBEV-specific antibody prevalence, infection incidence, and seroreversion and antibody decline rates in a prospective Swiss healthcare worker (HCW) cohort. We screened serum samples from 1444 HCWs between June and October 2020, and from a subset again between August and September 2021, using a TBEV envelope (E) protein IgG ELISA. Positive samples underwent further analysis with a TBEV non-structural protein 1 (NS1) IgG ELISA, and seroconversions in unvaccinated individuals were confirmed by seroneutralization testing. Questionnaire data were used to determine vaccination status and risk factors. TBEV E protein-specific IgG prevalence was 72.1% (95% CI 68.2–75.7%) in TBEV-vaccinated and 6% (95% CI 4.4–7.8%) in unvaccinated individuals. The estimated annual incidence of infection was 735/100,000. Age was the only factor significantly associated with seroprevalence. The seroreversion rate in unvaccinated individuals was 30.3% within one year, which is almost ten times higher than in vaccinated individuals (3.4%, annual decline rate 8.0%). NS1-specific IgG antibodies were six times more common in vaccinated than unvaccinated HCWs. In conclusion, undetected TBEV infections are common, and infection incidence is much higher than reported clinical cases. Individuals with abortive infections have high antibody decline and seroreversion rates. Whether lifelong protection is conferred and by which immune subsets remain unclear.

Systematic review and meta-analysis on shortening antibiotic therapy for Lyme borreliosis (LB) patients. Data sources: Medline, Google, and Google Scholar (queried from January 2022-February 2024), following the PRISMA method and the Cochrane Handbook. Eligibility criteria: Randomized clinical trials, comparative studies; clear definitions of LB, duration of antibiotics and outcome; follow-up ≥ 6–12 months. Meta-analysis included studies that examined three outcomes: treatment failure; residual symptoms; adverse events. Intervention: Short vs. extended antibiotic therapy for erythema migrans (≤ 10 days vs. > 10 days) and disseminated LB (≤ 21 days vs. > 21 days). Assessment of risk of bias. Independently, using the Cochrane Tools. of data synthesis. Estimation of treatment effects based on a fixed-effect model (Mantel–Haenszel or Peto method), with odds ratio (OR) and 95

BACKGROUND:A surge of cases of Corynebacterium diphtheriae infection was observed in reception centers for migrants in Europe beginning in the summer of 2022. Most of the cases were cutaneous, although some respiratory cases as well as one death were reported. A pan-European consortium was created to assess the clinical, epidemiologic, and microbiologic features of this outbreak. METHODS:We assessed cases of toxigenic C. diphtheriae infection that were reported in 10 European countries from January through November 2022. Data regarding countries of origin and transit routes were obtained from interviews with the patients. Whole-genome sequencing and antimicrobial-susceptibility testing were performed on bacterial isolates that were obtained from the patients. The phylogenetic relationships of the isolates and their antimicrobial-resistance genes were evaluated. RESULTS:A total of 363 toxigenic C. diphtheriae isolates were identified among 362 patients during the study period. Clinical data were available for 346 patients (95.6%): 268 (77.5%) had cutaneous diphtheria, 53 (15.3%) had respiratory diphtheria (11 [3.2%] had a pseudomembrane), and 9 (2.6%) had both respiratory and cutaneous symptoms. Four major genetic clusters were identified, which indicated the multiclonal nature of the outbreak. The ermX gene (which codes for erythromycin resistance) and the pbp2m and blaOXA-2 genes (which code for beta-lactam resistance) were detected in a subgroup of isolates. Isolates that carried ermX were resistant to erythromycin, and isolates that carried pbp2m were resistant to penicillin but were susceptible to amoxicillin. On the basis of the genomic variation within the four genetic clusters, their most recent common ancestors were estimated to have existed between 2017 and 2020. CONCLUSIONS:The distribution of each genetic cluster of C. diphtheriae isolates across multiple countries in Europe showed repeated cross-border spread. The large number of C. diphtheriae infections among migrants is a cause for concern, particularly given that antimicrobial-resistance phenotypes threaten the efficacy of first-line treatments. (Funded by the Bavarian State Ministry of Health, Care, and Prevention and others.).

In the last 10 years, an increase in tularemia cases has been observed in both humans and animals in Switzerland. In these, infection with Francisella tularensis, the causative agent of the zoonotic disease tularemia, can occur through arthropod vectors or contact to infected animals or exposure to contaminated environmental sources. Currently, we are only able to postulate potential aetiologies: (i) behavioral changes of humans with more exposure to endemic habitats of infected arthropod vectors; (ii) an increased rate of tularemia infected ticks; (iii) increasing number and geographical regions of tick biotopes; (iv) increasing and/or more diverse reservoir populations; (v) increasing presence of bacteria in the environment; (vi) raised awareness and increased testing among physicians; (vii) improved laboratory techniques including molecular testing. To approach these questions, a one-health strategy is necessary. A functioning collaboration between public health, human medicine, and diagnostic and veterinary units for the control of tularemia must be established. Furthermore, the public should be included within citizen-supported-science-projects.

Tick‐borne encephalitis (TBE) virus is the most prevalent tick‐transmitted orthoflavivirus in Europe. Due to the nonspecific nature of its symptoms, TBE is primarily diagnosed by ELISA‐based detection of specific antibodies in the patient serum. However, cross‐reactivity between orthoflaviviruses complicates the diagnosis. Specificity issues may be mitigated by serum neutralization assays (SNT), although the handling of clinically relevant orthoflaviviruses requires biosafety level (BSL) 3 conditions and they have highly divergent viral kinetics and cell tropisms. In the present study, we established a reporter virus particle (RVP)‐based SNT in which the infectivity is measured by luminescence and that can be performed under BSL‐2 conditions. The RVP‐based SNT for TBEV exhibited a highly significant correlation with the traditional virus‐based SNT (R2 = 0.8637, p < 0.0001). The RVP‐based assay demonstrated a sensitivity of 92.3% (95% CI: 79.7%–97.4%) and specificity of 100% (95% CI: 81.6%–100%). We also tested the cross‐reactivity of serum samples in RVP‐based assays against other orthoflaviviruses (yellow fever virus, dengue virus type 2, Zika virus, West Nile virus and Japanese encephalitis virus). Interestingly, all serum samples which had tested TBEV‐positive by ELISA but negative by RVP‐based SNT were reactive for antibodies against other orthoflaviviruses. Thus, the RVP‐based seroneutralization assay provides an added value in clinical diagnostics as well as in epidemiological studies.

Objectives: Bacteroides fragilis is the most frequent cause of anaerobic bacteraemia. Although recent data suggest a rise in antimicrobial resistance (AMR) of this and other anaerobic bacteria, surveillance remains limited due to a lack of both data availability and comparability. However, a newly introduced standardised method for antimicrobial susceptibility testing (AST) of anaerobic bacteria has made larger scale surveillance possible for the first time. The aim of this study was to investigate phenotypic AMR of Bacteroides fragilis isolates from bacteraemia across Europe in 2022. Methods: In a multicentre approach, clinical microbiology laboratories in Europe were invited to contribute results of AST for Bacteroides fragilis blood culture isolates (including only the first isolate per patient and year). AST of a selection of four antibiotics was performed locally by participating laboratories in a prospective or retrospective manner, using the new EUCAST disc diffusion method on fastidious anaerobe agar (FAA-HB). Results: A total of 16 European countries reported antimicrobial susceptibilities in 449 unique isolates of Bacteroides fragilis from blood cultures in 2022. Clindamycin demonstrated the highest resistance rates (20.9%, range 0- 63.6%), followed by piperacillin-tazobactam (11.1%, 0-54.5%), meropenem (13.4%, 0- 45.5%), and metronidazole (1.8%, 0-20.0%), all with wide variation between countries. Conclusion: Considering that the mean resistance rates across Europe were higher than expected for three of the four anti-anaerobic antibiotics under surveillance, both local AST of clinically relevant isolates of Bacteroides fragilis and continued surveillance on an international level is warranted. (c) 2024 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

BACKGROUND AND OBJECTIVES:The diagnosis of neurosyphilis (NS) lacks a true 'gold standard', making the diagnosis challenging while consequences of a misdiagnosis are potentially severe. The aim of this study was to evaluate the diagnostic performance of measuring an antibody index (AI) for the intrathecal synthesis of specific anti-Treponema pallidum (T. pallidum) IgG for the diagnosis of NS. METHODS:Specific anti-T. pallidum IgG were measured simultaneously in paired cerebrospinal fluid (CSF)-serum samples collected retrospectively and prospectively between 2007 and 2022, from patients suspected of NS, in Switzerland. An AI was calculated to account for blood-brain barrier integrity. Area under the receiver operating characteristic curve, sensitivity/specificity and positive/negative predictive values of AI test were estimated. Two NS definitions were used: NS1 included patients with NS suspicion presenting with neurological symptoms and/or acute neurosensory signs, and positive T. Pallidum Hemagglutinations Assay (TPHA)/T. pallidum particle agglutination assay (TPPA) serology and CSF-TPHA/TPPA ≥320, and either CSF-leucocytes >5 cells/mm3 and/or CSF-protein >0.45 g/L and/or a reactive CSF-venereal disease research laboratory (VDRL)/rapid plasma reagin (RPR) test. NS2 included patients with suspected NS presenting with acute ocular and/or otologic symptoms, and positive TPHA/TPPA serology, and a favourable response to NS treatment. Controls were patients diagnosed with any other central nervous system (CNS) pathologies and with positive TPHA/TPPA serology. RESULTS:The study included 71 NS (43 NS1 and 28 NS2) and 110 controls. With a threshold of ≥1.7, sensitivity and specificity of the specific AI test were 90.7% (CI 77.7 to 97.4) and 100% (CI 96.7 to 100.0), respectively, for NS1 and 14.3% (CI 4 to 32.7) and 100% (CI 96.7 to 100.0) for NS2. In patients suspected of NS with a CNS involvement (NS1 group), NS could be confirmed by the positivity of this specific AI. CONCLUSIONS:Measurement of an intrathecal synthesis index of specific anti-T. pallidum IgG in patients with CSF inflammatory signs appears to be a valuable diagnostic test. However, in otic or ocular syphilis, presenting few CSF abnormalities, AI is not sufficient alone to confirm NS diagnosis. TRIAL REGISTRATION:Swiss Association of Research Ethics Committees number 2019-00232.

In the last 10 years, an increase in tularemia cases has been observed in both humans and animals in Switzerland. In these, infection with Francisella tularensis, the causative agent of the zoonotic disease tularemia, can occur through arthropod vectors or contact to infected animals or exposure to contaminated environmental sources. Currently, we are only able to postulate potential aetiologies: (i) behavioral changes of humans with more exposure to endemic habitats of infected arthropod vectors; (ii) an increased rate of tularemia infected ticks; (iii) increasing number and geographical regions of tick biotopes; (iv) increasing and/or more diverse reservoir populations; (v) increasing presence of bacteria in the environment; (vi) raised awareness and increased testing among physicians; (vii) improved laboratory techniques including molecular testing. To approach these questions, a one-health strategy is necessary. A functioning collaboration between public health, human medicine, and diagnostic and veterinary units for the control of tularemia must be established. Furthermore, the public should be included within citizen-supported-science-projects.

In the last 10 years, an increase in tularemia cases has been observed in both humans and animals in Switzerland. In these, infection with Francisella tularensis, the causative agent of the zoonotic disease tularemia, can occur through arthropod vectors or contact to infected animals or exposure to contaminated environmental sources. Currently, we are only able to postulate potential aetiologies: (i) behavioral changes of humans with more exposure to endemic habitats of infected arthropod vectors; (ii) an increased rate of tularemia infected ticks; (iii) increasing number and geographical regions of tick biotopes; (iv) increasing and/or more diverse reservoir populations; (v) increasing presence of bacteria in the environment; (vi) raised awareness and increased testing among physicians; (vii) improved laboratory techniques including molecular testing. To approach these questions, a one-health strategy is necessary. A functioning collaboration between public health, human medicine, and diagnostic and veterinary units for the control of tularemia must be established. Furthermore, the public should be included within citizen-supported-science-projects.

Vaccine-induced protection against tick-borne encephalitis virus (TBEV) is mediated by antibodies to the viral particle/envelope protein. The detection of non-structural protein 1 (NS1) specific antibodies has been suggested as a marker indicative of natural infections. However, recent work has shown that TBEV vaccines contain traces of NS1, and immunization of mice induced low amounts of NS1-specific antibodies. In this study, we investigated if vaccination induces TBEV NS1-specific antibodies in humans. Healthy army members (n = 898) were asked to fill in a questionnaire relating to flavivirus vaccination or infection, and blood samples were collected. In addition, samples of 71 suspected acute TBE cases were included. All samples were screened for the presence of TBEV NS1-specific IgG antibodies using an in-house developed ELISA. Antibodies were quantified as percent positivity in reference to a positive control. For qualitative evaluation, cut-off for positivity was defined based on the mean OD of the lower 95% of the vaccinated individuals + 3 SD. We found significantly higher NS1-specific IgG antibody titers (i.e., quantitative evaluation) in individuals having received 2, 3, or 4 or more vaccine doses than in non-vaccinated individuals. Similarly, the percentage of individuals with a positive test result (i.e., qualitative evaluation) was higher in individuals vaccinated against tick-borne encephalitis than in unvaccinated study participants. Although NS1-specific IgG titers remained at a relatively low level when compared to TBE patients, a clear distinction was not always possible. Establishing a clear cut-off point in detection systems is critical for NS1-specific antibodies to serve as a marker for distinguishing the immune response after vaccination and infection.

OBJECTIVES:Serological tests for syphilis detect mainly total Ig, IgM or IgG antibodies. We aimed to evaluate the specific IgA response in syphilis patients according to disease stage.METHODS:A serum IgA-enzyme immunoassay was developed using commercially available microplates coated with recombinant treponemal antigens and an anti-IgA-conjugate. To define a cut-off, we used 91 syphilis positive and 136 negative sera previously defined by the rapid plasma reagin and the Treponema pallidum particle agglutination results. Then we determined the intra- and inter-assay precisions, diagnostic sensitivity according to the clinical stage (in 66, 55 and 42 sera from primary, secondary and latent syphilis patients, respectively) and specificity (in 211 sera from people with conditions different to syphilis). IgA values were further measured in 71 sera from patients with previously treated syphilis.RESULTS:The newly developed IgA-enzyme immunoassay showed a good discrimination between negative and positive samples with intra- and inter-assay variation coefficients <20%. The sensitivity was 80.3% (95% CI, 70.0-90.6), 100.0% (95% CI, 99.1-100.0) and 95.2% (95% CI, 87.6-100.0) in primary, secondary and latent syphilis, respectively, and the specificity was 98.1% (95% CI, 96.0-100.0). Further, IgA values were negative in 61.3% (38/62) of patients with previously treated syphilis.DISCUSSION:Our findings suggest serum IgA as a sensitive and specific marker of syphilis and its detection could be used as a screening assay for active infection. Further evaluation is needed in prospective longitudinal field studies.