Background: Legionnaires’ disease (LD) is most often described as caused by a single Legionella pneumophila (Lp) serogroup (SG), typically SG1. However, mixed infections involving multiple SGs or even different Legionella species can occur within a single host. Such cases remain underrecognized and pose challenges for diagnosis, clinical management, and outbreak investigation. Case presentation: A 61-year-old woman developed acute fever, malaise, and productive cough after visiting a wellness spa in France, with radiological findings consistent with a lower respiratory tract infection. The urinary antigen test (UAT) for Lp was negative, but respiratory multiplex PCR was weakly positive. Subsequent testing at the Belgian National Reference Centre (NRC) for Legionella revealed an unexpected discordance between an in-house SG1-specific PCR and culture-based findings. Further analysis identified co-infection with two distinct Lp strains, SG1 (sequence type, ST146) and SG10 (ST1267), using a combination of direct sequence-based typing (SBT) and culture with serogrouping of multiple colonies. The patient improved rapidly after treatment with oral levofloxacin. Conclusions: Mixed Lp SG infections are likely underrecognized in routine practice, as neither UAT, commercial molecular assays, nor characterization of a single cultured isolate may adequately capture within-host strain diversity. Comprehensive diagnostic approaches combining culture with analysis of multiple colonies and molecular tests are essential for accurate case detection and source attribution. Referral to NRCs is recommended when advanced typing methods are unavailable. This first reported Belgian case illustrates the potential implications for patient management and epidemiological investigations, underscoring the need for broader diagnostic strategies.

Prior to the COVID-19 pandemic, Bordetella pertussis strains not producing pertactin were globally increasing, especially in countries using the acellular pertussis vaccine. Subsequently, during the pandemic, global pertussis incidence dropped to extreme lows, likely due to non-pharmaceutical interventions (e.g., social distancing and face masks). During 2022-2024, many countries-including Belgium-saw a re-emergence of the disease. The newly circulating strains are mostly pertactin-expressing. Pertactin (Prn) antigen-expression testing was performed on 432 Belgian isolates collected in 2014-2023. Whole-genome sequencing for virulence typing and phylogenetic analysis was performed on 416 isolates. Before COVID-19, Prn-negative strains in Belgium went from making up less than 20% of circulating strains to being in the majority from 2017 to 2020. In 2022 and 2023, during the post-COVID re-emergence, all tested strains expressed pertactin. Further typing showed a variety of different mutations of the prn gene and/or its promoter region in the pre-pandemic Prn-negative strains. In phylogenetic analysis, these do not cluster together. Prn-positive B. pertussis strains have replaced Prn-negative ones in Belgium since the post-COVID-19 re-emergence. This could potentially be an effect of reduced population immunity, allowing some strains to spread rapidly with less selective pressure for pertactin deficiency. Further research and surveillance should be done to identify or refute other potential factors influencing pertactin expression. IMPORTANCE:During the COVID-19 pandemic, non-pharmaceutical intervention measures prevented the spread of other diseases, such as whooping cough (caused by Bordetella pertussis). Now that the use of anti-COVID measures has reduced, many countries have seen a return of infections with B. pertussis. Whereas pre-pandemic, a large part of these strains did not express pertactin, a component used in the pertussis vaccine, now most strains do. A large part of Belgian B. pertussis strains did not express pertactin before the COVID-19 pandemic. We found several different genetic mechanisms as the cause of this. During the pandemic, cases dropped to almost non-existent. Upon their return around 2023, strains showed less genetic diversity, and all expressed pertactin. Our findings illustrate how pertussis epidemiology can be unpredictable and change quickly. Genetic changes in the bacteria can have an effect on vaccine effectiveness and immunity; therefore, it is important to study these changes and maintain epidemiological surveillance.

Whole genome sequencing (WGS) marks a turning point for outbreak investigations for microorganisms related to public health matters, like Legionella pneumophila (Lp). Here, we evaluated the available Lp WGS typing tools for isolates of previously documented Belgian outbreaks, as well as small groups of related and non-related isolates. One reference strain and 77 clinical and environmental isolates were evaluated. Seven isolates belong to a Sequence Type (ST) 36 outbreak in 1999 and sixteen (ten clinical, two matching environmental and four non-related controls) belong to another ST1 outbreak in 1985–1987. The remaining isolates belong to small groups of related and non-related isolates of diverse ST’s. WGS was performed and data were analysed using whole genome (wg) and core genome (cg) multilocus sequence typing (MLST) with “Ridom SeqSphere + ” (cgMLST), “Applied Maths-Bionumerics” (wgMLST) and the 50 loci cgMLST (CDC/ESGLI_ESCMID). Results of the three tools were concordant with the traditional Sequence Based Typing (SBT). The known outbreaks and small clusters could be detected and clear discrimination of ST1 non-related isolates was obtained. In addition, the 50 loci cgMLST allowed to classify the isolates into subtypes because almost all the 50 genes could be called in all the analysed isolates, which was not achieved by the other tools. This is a big advantage in terms of standardisation and comparison between laboratories for future epidemiological investigations. WGS allowed to analyse a large volume of samples and generated more accurate conclusions for outbreak investigations compared to other typing methods due to its higher discriminatory power and throughput.

Bordetella pertussis is the causative pathogen of whooping cough or pertussis, a contagious respiratory disease. Aside from serodiagnosis, laboratory confirmation of pertussis is done through PCR, as B. pertussis is difficult to culture.The ELITe InGenius instrument (ELITechGroup, France) with accompanying Bordetella ELITe MGB Kit was evaluated against a laboratory-developed assay. Both assays combine two screening (IS481, IS1001) and two confirmation targets (recA, ptxA-Pr or IS1002) for optimal sensitivity and specificity.The company's stated claims on sensitivity and reproducibility were confirmed. Accuracy testing showed full concordance between both assays for the screening targets. Minor discrepancies were seen for the B. pertussis confirmation target. Some cross-reactivity with other Bordetella species was observed for the IS481-target, however, none of these were confirmed in the ptxA-Pr target. These results show the suitability of the Bordetella ELITe MGB Kit for the detection and differentiation of B. pertussis, B. parapertussis and B. holmesii.

It is generally accepted that microorganisms can colonize a non-pathological endometrium. However, in a clinical setting, endometrial samples are always collected by passing through the vaginal–cervical route. As such, the vaginal and cervical microbiomes can easily cross-contaminate endometrial samples, resulting in a biased representation of the endometrial microbiome. This makes it difficult to demonstrate that the endometrial microbiome is not merely a reflection of contamination originating from sampling. Therefore, we investigated to what extent the endometrial microbiome corresponds to that of the vagina, applying culturomics on paired vaginal and endometrial samples. Culturomics could give novel insights into the microbiome of the female genital tract, as it overcomes sequencing-related bias. Ten subfertile women undergoing diagnostic hysteroscopy and endometrial biopsy were included. An additional vaginal swab was taken from each participant right before hysteroscopy. Both endometrial biopsies and vaginal swabs were analyzed using our previously described WASPLab-assisted culturomics protocol. In total, 101 bacterial and two fungal species were identified among these 10 patients. Fifty-six species were found in endometrial biopsies and 90 were found in vaginal swabs. On average, 28 % of species were found in both the endometrial biopsy and vaginal swab of a given patient. Of the 56 species found in the endometrial biopsies, 13 were not found in the vaginal swabs. Of the 90 species found in vaginal swabs, 47 were not found in the endometrium. Our culturomics-based approach sheds a different light on the current understanding of the endometrial microbiome. The data suggest the potential existence of a unique endometrial microbiome that is not merely a presentation of cross-contamination derived from sampling. However, we cannot exclude cross-contamination completely. In addition, we observe that the microbiome of the vagina is richer in species than that of the endometrium, which contradicts the current sequence-based literature.

Quantification of EBV DNA is important in transplantation settings for the diagnosis of post-transplantation. We evaluated the performance of the AltoStar® EBV PCR Kit 1.5 on whole blood specimens: limit of detection, linearity, accuracy, and precision were determined using the WHO NIBSC 09/260 international standard. Results of 69 clinical samples were compared between the AltoStar® EBV PCR Kit 1.5 (altona Diagnostics) and the RealTime EBV assay (Abbott). The LoD of the AltoStar® Kit was 148 IU/mL and linearity was between 375 and 500000. A high concordance was found between nominal value of the NIBSC dilutions and the AltoStar EBV result. The total variation ranged from 2.2% to 9.6%. Out of 69 clinical samples tested, there was a high concordance between the 22 paired results within the overlapping linear ranges of both tests. The AltoStar® EBV assay is reliable and accurate for EBV viral load determination on whole blood samples.

This case report describes a 60-year-old female patient suffering from systemic sclerosis, for which she received immunomodulatory drugs. Her first SARS-CoV-2-positive nasopharyngeal sample was obtained in the emergency department, on 31 January 2022. Whole genome sequencing confirmed infection with Omicron BA.1.1. Her hospital stay was long and punctuated by many complications, including admission to the intensive care unit. At the beginning of April 2022, she started complaining of increased coughing, for which another SARS-CoV-2 RT-qPCR test was performed. The latter nasopharyngeal swab showed a strongly positive result. To support the theory of healthcare-associated reinfection, whole genome sequencing was performed and confirmed reinfection with Omicron BA.2. Since this patient was one of ten positive cases in this particular ward, a hospital outbreak investigation was performed. Whole genome sequencing data were available for five of these ten patients and showed a cluster of four patients with ≤2 small nucleotide polymorphisms difference.

BackgroundWorldwide, healthcare-associated SARS-CoV-2 infections are a major problem: they are associated with increased morbidity, mortality, and hospitalization costs. In-depth studies across the pandemic are crucial to understand and prevent transmission in hospital settings. The principal aims of this study were to characterise patients and validate ECDC definitions of healthcare-associated COVID-19 infections.MethodsWe set up a retrospective observational study spanning the first three waves of the COVID-19 pandemic in a Belgian university hospital: it describes the characteristics of COVID-19 patients admitted, with either healthcare- or community-associated infections. We performed a cluster analysis through epidemiological and viral genome analyses of the healthcare-associated infections, in order to validate the ECDC definitions of healthcare-associated COVID-19 infections.ResultsBetween week 10 of 2020 and week 22 of 2021, 168 patients were hospitalized with healthcare-associated COVID-19. The following factors were found more often in symptomatic healthcare- than in community-associated hospitalized patients: older age, increased frailty, smoking habits, and comorbidities. The genome-based cluster analyses showed that different viral lineages predominated in different timeframes. We observed a good correlation of epidemiological data with genome sequencing results in at least 12 different outbreaks in our hospital, thus validating the ECDC definitions. ConclusionsThis in-depth characterization sheds new light on the problem of healthcare-associated COVID-19 infections, in particular on patients’ characteristics, epidemiology, and cluster dynamics. Even though epidemiological evaluation of nosocomial infections is vital, management of nosocomial outbreaks can undoubtedly benefit from genome sequencing analyses to reinforce their strategy.

Background: Healthcare-associated SARS-CoV-2 infections need to be explored further. Our study is an analysis of hospital-acquired infections (HAIs) and ambulatory healthcare workers (aHCWs) with SARS-CoV-2 across the pandemic in a Belgian university hospital. Methods: We compared HAIs with community-associated infections (CAIs) to identify the factors associated with having an HAI. We then performed a genomic cluster analysis of HAIs and aHCWs. We used this alongside the European Centre for Disease Control (ECDC) case source classifications of an HAI. Results: Between March 2020 and March 2022, 269 patients had an HAI. A lower BMI, a worse frailty index, lower C-reactive protein (CRP), and a higher thrombocyte count as well as death and length of stay were significantly associated with having an HAI. Using those variables to predict HAIs versus CAIs, we obtained a positive predictive value (PPV) of 83.6% and a negative predictive value (NPV) of 82.2%; the area under the ROC was 0.89. Genomic cluster analyses and representations on epicurves and minimal spanning trees delivered further insights into HAI dynamics across different pandemic waves. The genomic data were also compared with the clinical ECDC definitions for HAIs; we found that 90.0% of the ‘definite’, 87.8% of the ‘probable’, and 70.3% of the ‘indeterminate’ HAIs belonged to one of the twenty-two COVID-19 genomic clusters we identified. Conclusions: We propose a novel prediction model for HAIs. In addition, we show that the management of nosocomial outbreaks will benefit from genome sequencing analyses.

An adequate SARS-CoV-2 genomic surveillance strategy has proven to be essential for countries to obtain a thorough understanding of the variants and lineages being imported and successfully established within their borders. During 2020, genomic surveillance in Belgium was not structurally implemented but performed by individual research laboratories that had to acquire the necessary funds themselves to perform this important task. At the start of 2021, a nationwide genomic surveillance consortium was established in Belgium to markedly increase the country's genomic sequencing efforts (both in terms of intensity and representativeness), to perform quality control among participating laboratories, and to enable coordination and collaboration of research projects and publications. We here discuss the genomic surveillance efforts in Belgium before and after the establishment of its genomic sequencing consortium, provide an overview of the specifics of the consortium, and explore more details regarding the scientific studies that have been published as a result of the increased number of Belgian SARS-CoV-2 genomes that have become available.

From early 2020, a high demand for SARS-CoV-2 tests was driven by several testing indications, including asymptomatic cases, resulting in the massive roll-out of PCR assays to combat the pandemic. Considering the dynamic of viral shedding during the course of infection, the demand to report cycle threshold (Ct) values rapidly emerged. As Ct values can be affected by a number of factors, we considered that harmonization of semi-quantitative PCR results across laboratories would avoid potential divergent interpretations, particularly in the absence of clinical or serological information. A proposal to harmonize reporting of test results was drafted by the National Reference Centre (NRC) UZ/KU Leuven, distinguishing four categories of positivity based on RNA copies/mL. Pre-quantified control material was shipped to 124 laboratories with instructions to setup a standard curve to define thresholds per assay. For each assay, the mean Ct value and corresponding standard deviation was calculated per target gene, for the three concentrations (107, 105 and 103 copies/mL) that determine the classification. The results of 17 assays are summarized. This harmonization effort allowed to ensure that all Belgian laboratories would report positive PCR results in the same semi-quantitative manner to clinicians and to the national database which feeds contact tracing interventions.

The microbiome of the reproductive tract has been associated with (sub)fertility and it has been suggested that dysbiosis reduces success rates and pregnancy outcomes. The endometrial microbiome is of particular interest given the potential impact on the embryo implantation. To date, all endometrial microbiome studies have applied a metagenomics approach. A sequencing-based technique, however, has its limitations, more specifically in adequately exploring low-biomass settings, such as intra-uterine/endometrial samples. In this proof-of-concept study, we demonstrate the applicability of culturomics, a high-throughput culturing approach, to investigate the endometrial microbiome. Ten subfertile women undergoing diagnostic hysteroscopy and endometrial biopsy, as part of their routine work-up at Brussels IVF, were included after their informed consent. Biopsies were used to culture microbiota for up to 30 days in multiple aerobic and anaerobic conditions. Subsequent WASPLab®-assisted culturomics enabled a standardized methodology. Matrix-assisted laser desorption/ionization–time of flight mass spectrometry (MALDI-TOF MS) or 16S rRNA sequencing was applied to identify all of bacterial and fungal isolates. Eighty-three bacterial and two fungal species were identified. The detected species were in concordance with previously published metagenomics-based endometrial microbiota analyses as 77 (91%) of them belonged to previously described genera. Nevertheless, highlighting the added value of culturomics to identify most isolates at the species level, 53 (62.4%) of the identified species were described in the endometrial microbiota for the first time. This study shows the applicability and added value of WASPLab®-assisted culturomics to investigate the low biomass endometrial microbiome at a species level.

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in the general population in the context of a relatively high immunity gained through the early waves of coronavirus disease 19 (COVID-19), and vaccination campaigns. Despite this context, a significant number of patients were hospitalized, and identifying the risk factors associated with severe disease in the Omicron era is critical for targeting further preventive, and curative interventions. We retrospectively analyzed the individual medical records of 1501 SARS-CoV-2 positive hospitalized patients between 13 December 2021, and 13 February 2022, in Belgium, of which 187 (12.5%) were infected with Delta, and 1036 (69.0%) with Omicron. Unvaccinated adults showed an increased risk of moderate/severe/critical/fatal COVID-19 (crude OR 1.54; 95% CI 1.09–2.16) compared to vaccinated patients, whether infected with Omicron or Delta. In adults infected with Omicron and moderate/severe/critical/fatal COVID-19 (n = 323), immunocompromised patients showed an increased risk of in-hospital mortality related to COVID-19 (adjusted OR 2.42; 95% CI 1.39–4.22), compared to non-immunocompromised patients. The upcoming impact of the pandemic will be defined by evolving viral variants, and the immune system status of the population. The observations support that, in the context of an intrinsically less virulent variant, vaccination and underlying patient immunity remain the main drivers of severe disease.

Background Hydroxychloroquine and chloroquine have been used for hospitalized coronavirus disease 2019 patients because of their antiviral and anti-inflammatory function. However, little research has been published on the impact of the immunomodulatory effect of (hydroxy)chloroquine on humoral immunity. Case presentation We report a case of symptomatic severe acute respiratory syndrome coronavirus 2 reinfection, diagnosed 141 days after the first episode, in a 56-year-old man of Black African origin treated with hydroxychloroquine for lupus erythematosus. No anti-severe acute respiratory syndrome coronavirus 2 IgG antibodies could be detected 127 days after the initial episode of coronavirus disease 2019. Conclusions The treatment with hydroxychloroquine probably explains the decreased immune response with negative serology and subsequent reinfection in our patient. As humoral immunity is crucial to fight a severe acute respiratory syndrome coronavirus 2 infection, the use of (hydroxy)chloroquine is likely to have a detrimental effect on the spread of the virus. This case emphasizes that more needs to be learned about the role of antibodies in protecting against severe acute respiratory syndrome coronavirus 2 (re)infection and the role of (hydroxy)chloroquine on humoral immunity.

Background/aims SARS-CoV-2 is highly contagious. More evidence concerning extrapulmonary transmission routes such as the eyes is urgently needed. Although the humoral immune response is important in the viral containment, the local response in tears has not yet been studied. The aim of our study was twofold: to assess the prevalence of both SARS-CoV-2 RNA and antibodies in tear fluid. Methods In a first series, nasopharyngeal sampling and tear sampling by Schirmer test strips were performed in 26 acutely ill patients with COVID-19 to assess the presence of SARS-CoV-2 RNA by reverse transcription PCR. In a second series, IgG and IgA responses to SARS-CoV-2 spike protein in serum and tear fluid of convalescent individuals (n=22) were compared with control individuals (n=15) by ELISA. Results SARS-CoV-2 RNA was detected in tears of 7/26 (26.9%) patients with COVID-19. None of them had ocular symptoms. Convalescent individuals displayed a significant higher ratio of IgG (p<0.0001) and IgA (p=0.0068) in tears compared with control individuals. A sensitivity of 77.3% and specificity of 93.3% was observed for IgG, and 59.1% and 100% for IgA. Conclusions Our results demonstrate the presence of SARS-CoV-2 RNA and a local IgG and IgA immune response in tear fluid. These data confirm the possibility of SARS-CoV-2 transmission through tear fluid and the importance of the eye as a first defence against SARS-CoV-2, indicating the potential of tears as a non-invasive surrogate for serum in monitoring the host immune response.

In Western Europe, the incidence of both respiratory and cutaneous diphtheria, caused by toxin-producing Corynebacterium diphtheriae, Corynebacterium ulcerans or Corynebacterium pseudotuberculosis, has been low over the past few decades thanks to the use of an effective vaccine and a high level of vaccination coverage. However, the disease has still not been eradicated and continues to occur in all of Europe. In order to prevent sequelae or a fatal outcome, diphtheria antitoxin (DAT) should be administered to suspected diphtheria patients as soon as possible, but economic factors and issues concerning regulations have led to poor availability of DAT in many countries. The European Centre for Disease Prevention and Control and World Health Organization have called for European Union-wide solutions to this DAT-shortage. In order to illustrate the importance of these efforts and underline the need for continued diphtheria surveillance, we present data on all registered cases of toxigenic and non-toxigenic C. diphtheriae, C. ulcerans and C. pseudotuberculosis in Belgium during the past decade, up to and including 2017.