BACKGROUND:In 2022, the World Health Organization (WHO) adapted its pediatric tuberculosis disease (TBD) treatment guidelines, recommending a shortened 4-month treatment regimen for nonsevere TB, based on a single study in high TB prevalence, low-resource settings. This study investigated to what extent the recommendations apply to a high-resource setting. METHODS:Retrospective cohort study of patients with TBD <16 years of age treated at the Austrian Reference Centre for Paediatric TB from 2010 to 2023. RESULTS:One hundred fifty-nine patients were included in the final analysis. Based on the WHO guidelines, 104 (65.4%) met the criteria for nonsevere TBD. Compared with children with severe TBD (n = 55; 34.6%), children with nonsevere TBD were significantly more commonly asymptomatic (26.0% vs. 83.6%; P ≤ 0.0001), more commonly detected by TB screening (14.6% vs. 74.0%; P ≤ 0.0001) and less commonly microbiologically-confirmed (36.5% vs. 85.5%; P ≤ 0.0001). Eight children categorized as nonsevere had evidence of severe disease on chest computed tomography; 9 had evidence of severe disease on bronchoscopy. Nineteen children in the nonsevere group had positive polymerase chain reaction results for Mycobacterium tuberculosis complex. Taking computed tomography, bronchoscopy and polymerase chain reaction results into account, 28 (26.9%) of the 104 cases initially classified as nonsevere would have to be reclassified as severe (equating to a 50.9% increase in the severe group). Consequently, only 76 (47.8%) patients would ultimately qualify as nonsevere TBD, while 83 (52.2%) had severe TBD. CONCLUSIONS:Our results suggest there is a substantial risk of underestimating disease severity when using the WHO criteria in isolation. Incorrect classification of disease severity may result in insufficient treatment and potentially treatment failure.

Knowledge about the epidemiology of Lyme borreliosis in Austria remains limited. We conducted a nationwide cross-sectional study among blood donors from all Austrian provinces to assess the exposure to Borrelia burgorferi sensu lato. A total of 1841 serum samples from blood donors aged between 18 and 69 years were tested for Borrelia-specific IgG and IgM. Associations with age, sex, province and the residential altitude were assessed for both the one-tier and two-tier methods. IgG seroprevalence was 14% for one-tier and 7% for the two-tier. A consistent increase in age was observed for both approaches. Using the 20-29-year age group as reference, the strongest association was observed in individuals aged 60-69 years. The IgG positivity was higher among males than females for both the one-tier and two-tier tests. Regional analysis revealed substantial variation in IgG seroprevalence, with the lowest prevalence recorded in Tyrol and the highest in Carinthia. These differences were not attributable to age distribution. An additional analysis revealed a correlation between the seroprevalence and the altitude of residence. IgM seroprevalence did not differ significantly between the one-tier and two-tier approaches (7% and 6%), and no age-, sex-, or region-related trends were identified. Our findings demonstrate demographic and regional differences in exposure to Borrelia burgdorferi. Higher altitude of residence is associated with reduced exposure to the spirochetes. The findings emphasize the importance of Lyme borreliosis surveillance and help identify the groups and areas most likely to profit from targeted prevention.

Mosquitoes serve as competent vectors of various pathogens. Vector-pathogen interactions, as well as ecology and spatiotemporal distributions, are often species-specific, highlighting the need to monitor the presence and abundance of different mosquito species. While morphological examination for species identification remains widely used in monitoring programs, molecular methods, such as DNA barcoding, offer a greater taxonomic resolution. Accurate species assignment however, depends on updated and reliable reference databases. Therefore, the aim of this study was to establish a curated collection of DNA barcodes of Austrian mosquitoes, including the Anopheles maculipennis complex. In total, 304 cytochrome c oxidase subunit I (mtCOI) gene barcodes were obtained from 40 different Austrian mosquito species and subspecies across seven genera. Moreover, three An. maculipennis species complex members (An. daciae, An. maculipennis s.s., An. messeae) were detected in Austria. All sequences were uploaded to NCBI GenBank and BOLD Systems to contribute to stable and correct public databases. While these results help improve the identification and differentiation of mosquito species, this curated database can also serve as the basis for establishing future applications, such as NGS-based DNA barcoding.

Periodontal disease is one of the most prevalent chronic infections worldwide. Associations with systemic conditions, including endocarditis, type 2 diabetes mellitus, cardiovascular disease, and tumor progression, have been extensively investigated in recent studies. Furthermore, it involves pathogens that are often anaerobic, biofilm-associated, and difficult to treat owing to inherent resistance mechanisms and the protective nature of biofilms. As dentists prescribe a substantial proportion of antibiotics and antibiotic resistance is increasing globally, innovative diagnostic methods are urgently needed to ensure effective and sustainable antibiotic stewardship. In this study, anaerobic stock isolates from 30 to 35 frozen samples per genera or species were subjected to minimum inhibitory concentration testing. A multipoint inoculator was used to seed agar plates containing serial antibiotic dilutions, allowing assessment of five commonly used antibiotics: amoxicillin, amoxicillin/clavulanic acid, imipenem, clarithromycin, and levofloxacin. This enabled simultaneous testing of multiple strains under strictly anaerobic conditions, reducing the handling time and material consumption. Among the tested oral pathogens, high resistance levels were observed for clarithromycin. Amoxicillin (±clavulanic acid) remains the most reliable first-line option, whereas levofloxacin may serve as an alternative for certain gram negative anaerobes, when standard treatment protocols are unsuccessful. Mixed-inoculum experiments further showed altered antibiotic responses under biofilm-like conditions. The multipoint inoculator enables reliable testing of oxygen-sensitive anaerobes, including mixed biofilms.Clinical relevanceThe presented method enables dental practitioners and laboratories to obtain resistance data from subgingival pathogens, especially in low- and middle-income countries or remote regions where access to centralized microbiology laboratories is limited. This benefits the wider healthcare system by supporting sustainable antibiotic stewardship through reliable, cost-effective resistance testing and the patients by facilitating the selection of an effective targeted agent, particularly in complex cases where multiple empirical antibiotic therapies have failed.

BackgroundListeria (L.) monocytogenes is primarily transmitted via contaminated food and can cause listeriosis, an infection often associated with sepsis and meningitis in at-risk individuals. Accurate outbreak detection relies on whole genome sequencing (WGS) and core genome multilocus sequence typing (cgMLST), which use allele thresholds to identify related strains.MethodsThis study investigated mutation rates in L. monocytogenes, focusing on isolates with DNA repair deficiencies. Serial subcultivations were performed, comparing a repair-deficient isolate with a wild-type control. Genetic variability was assessed using WGS and cgMLST.ResultsMutation rates were significantly higher in repair-deficient isolates, exceeding typical cgMLST thresholds currently used in Listeria outbreak investigations, leading to a misclassification of related isolates as unrelated. An additional analysis of the Austrian Listeria database revealed that such deficiencies are rare among isolates.ConclusionsThe standard 7-allele cgMLST threshold effectively identifies related strains in most cases, but may require adjustments for hypermutator strains. Incorporating DNA repair data could improve the accuracy of outbreak investigations, ensuring reliable public health responses.

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.).

Hyalomma marginatum is an invasive tick species capable of transmitting pathogens that cause severe diseases such as Crimean-Congo hemorrhagic fever. In Austria, H. marginatum occurs sporadically, and migratory birds are believed to bring H. marginatum from distant regions. We report several incidents of H. marginatum imported by travelers in private cars from Croatia to Austria. One tick was positive for Rickettsia aeschlimannii. Tourist traffic may play a significant role in the northward expansion of this tick species aside from introduction by birds.

BackgroundThe COVID-19 pandemic was largely driven by genetic mutations of SARS-CoV-2, leading in some instances to enhanced infectiousness of the virus or its capacity to evade the host immune system. To closely monitor SARS-CoV-2 evolution and resulting variants at genomic-level, an innovative pipeline termed SARSeq was developed in Austria.AimWe discuss technical aspects of the SARSeq pipeline, describe its performance and present noteworthy results it enabled during the pandemic in Austria.MethodsThe SARSeq pipeline was set up as a collaboration between private and public clinical diagnostic laboratories, a public health agency, and an academic institution. Representative SARS-CoV-2 positive specimens from each of the nine Austrian provinces were obtained from SARS-CoV-2 testing laboratories and processed centrally in an academic setting for S-gene sequencing and analysis.ResultsSARS-CoV-2 sequences from up to 2,880 cases weekly resulted in 222,784 characterised case samples in January 2021-March 2023. Consequently, Austria delivered the fourth densest genomic surveillance worldwide in a very resource-efficient manner. While most SARS-CoV-2 variants during the study showed comparable kinetic behaviour in all of Austria, some, like Beta, had a more focused spread. This highlighted multifaceted aspects of local population-level acquired immunity. The nationwide surveillance system enabled reliable nowcasting. Measured early growth kinetics of variants were predictive of later incidence peaks.ConclusionWith low automation, labour, and cost requirements, SARSeq is adaptable to monitor other pathogens and advantageous even for resource-limited countries. This multiplexed genomic surveillance system has potential as a rapid response tool for future emerging threats.

Abstract Successful treatment of patients with recurring listeria episodes due to colonized foreign material is often challenging, typically requiring a combination of antimicrobial treatment and surgical removal. Here, we present a particularly challenging case of chronic invasive listeriosis with a total of six relapses, confirmed through molecular typing.

Background The number of cholera cases reported to the World Health Organization (WHO) in 2022 was more than double that of 2021. Nine countries of the WHO European Region reported 51 cases of cholera in 2022 vs five reported cases in 2021. Aim We aimed to confirm that the Vibrio cholerae O1 isolates reported by WHO European Region countries in 2022 belonged to the seventh pandemic El Tor lineage (7PET). We also studied their virulence, antimicrobial resistance (AMR) determinants and phylogenetic relationships. Methods We used microbial genomics to study the 49 V. cholerae O1 isolates recovered from the 51 European cases. We also used > 1,450 publicly available 7PET genomes to provide a global phylogenetic context for these 49 isolates. Results All 46 good-quality genomes obtained belonged to the 7PET lineage. All but two isolates belonged to genomic Wave 3 and were grouped within three sub-lineages, one of which, Pre-AFR15, predominated (34/44). This sub-lineage, corresponding to isolates from several countries in Southern Asia, the Middle East and Eastern or Southern Africa, was probably a major contributor to the global upsurge of cholera cases in 2022. No unusual AMR profiles were inferred from analysis of the AMR gene content of the 46 genomes. Conclusion Reference laboratories in high-income countries should use whole genome sequencing to assign V. cholerae O1 isolates formally to the 7PET or non-epidemic lineages. Periodic collaborative genomic studies based on isolates from travellers can provide useful information on the circulating strains and their evolution, particularly as concerns AMR.

Background Identification of mosquitoes greatly relies on morphological specification. Since some species cannot be distinguished reliably by morphological methods, it is important to incorporate molecular techniques into the diagnostic pipeline. DNA barcoding using Sanger sequencing is currently widely used for identification of mosquito species. However, this method does not allow detection of multiple species in one sample, which would be important when analysing mosquito eggs. Detection of container breeding Aedes is typically performed by collecting eggs using ovitraps. These traps consist of a black container filled with water and a wooden spatula inserted for oviposition support. Aedes mosquitoes of different species might lay single or multiple eggs on the spatula. In contrast to Sanger sequencing of specific polymerase chain reaction (PCR) products, multiplex PCR protocols targeting specific species of interest can be of advantage for detection of multiple species in the same sample.Methods For this purpose, we adapted a previously published PCR protocol for simultaneous detection of four different Aedes species that are relevant for Austrian monitoring programmes, as they can be found in ovitraps: Aedes albopictus, Aedes japonicus, Aedes koreicus, and Aedes geniculatus. For evaluation of the multiplex PCR protocol, we analysed 2271 ovitrap mosquito samples from the years 2021 and 2022, which were collected within the scope of an Austrian nationwide monitoring programme. We compared the results of the multiplex PCR to the results of DNA barcoding.Results Of 2271 samples, the multiplex PCR could identify 1990 samples, while species determination using DNA barcoding of the mitochondrial cytochrome c oxidase subunit I gene was possible in 1722 samples. The multiplex PCR showed a mixture of different species in 47 samples, which could not be detected with DNA barcoding.Conclusions In conclusion, identification of Aedes species in ovitrap samples was more successful when using the multiplex PCR protocol as opposed to the DNA barcoding protocol. Additionally, the multiplex PCR allowed us to detect multiple species in the same sample, while those species might have been missed when using DNA barcoding with Sanger sequencing alone. Therefore, we propose that the multiplex PCR protocol is highly suitable and of great advantage when analysing mosquito eggs from ovitraps.

The World Health Organization (WHO) recommendation to adopt BPaL(M) for the standard-of-care treatment of multidrug-resistant tuberculosis[ 1 World Health Organization. WHO consolidated guidelines on tuberculosis. Module 4: treatment - drug-resistant tuberculosis treatment, 2022 update. 2023. Google Scholar ] (MDR-TB, resistance to at least isoniazid and rifampicin) has sparked hope for patients who would otherwise undergo a complex and long therapy, often associated with severe and long-lasting side effects [ 2 Nyang'wa B.-T. Berry C. Kazounis E. Motta I. Parpieva N. Tigay Z. et al. A 24-Week, All-Oral Regimen for Rifampin-Resistant Tuberculosis. New England Journal of Medicine. 2022; 387: 2331-2343https://doi.org/10.1056/NEJMOA2117166/SUPPL_FILE/NEJMOA2117166_DATA-SHARING.PDF Crossref PubMed Scopus (0) Google Scholar ]. The BPaL(M) regimen includes bedaquiline in association with pretomanid, a nitroimidazole compound, and two drugs belonging to the WHO group A compounds, linezolid, and moxifloxacin. Availability of drugs and resistance testing for bedaquiline, pretomanid, linezolid, and moxifloxacin (BPaL(M)) regimen for rifampicin-resistant tuberculosis in EuropeClinical Microbiology and InfectionPreviewMultidrug-resistant/rifampicin-resistant tuberculosis is a major obstacle to successful tuberculosis control. The recommendation by the WHO to use bedaquiline, pretomanid, linezolid, and moxifloxacin (BPaL(M)) for 6 months, based on results of two trials with high efficacy and low toxicity, has revolutionized treatment options. Full-Text PDF

BACKGROUND:Men who have sex with men (MSM) are more vulnerable to acquiring sexually transmitted infections (STIs). In 2019, for instance, 74% of European Neisseria gonorrhoeae (Ng) cases among males affected MSM. A recent report by the World Health Organization showed that most of the 2020' interim targets to end STIs by 2030 had not been met. A broadened understanding of STI transmission networks could guide future elimination strategies and reduce the STI burden. Therefore, we used whole-genome sequencing (WGS) to determine Ng-clusters and assess sexual mixing. METHODS:WGS was performed on Ng-isolates collected at the Medical University of Vienna, Austria and was used for core genome multi-locus sequencing typing cluster analysis. Epidemiologic and infection-specific details were extracted from medical records. RESULTS:Genomic analysis and demographic data were available for 415 isolates, and 43.9% (182/415) were allocated to 31 Ng-clusters. Nine clusters comprised samples from heterosexual individuals only (women N = 4, human immunodeficiency virus (HIV)-negative men N = 49, HIV-positive man N = 1), nine clusters included MSM only (HIV-negative N = 22, HIV-positive N = 13) and 13 clusters included both heterosexuals and MSM (HIV-negative N = 75, HIV-positive N = 18). Current use of HIV pre-exposure prophylaxis (PrEP) was reported by 22.8% of MSM. In multivariate analysis, only 'MSM' predicted clustering with isolates from HIV-positive individuals (adjusted odds ratio 10.24 (95% CI 5.02-20.90)). CONCLUSIONS:Sexual mixing of HIV-positive, HIV-negative MSM and non-MSM was frequently observed. Furthermore, HIV-serodiscordant clustering highlights the importance of PrEP rollout to avert HIV transmission. Our findings can inform future STI prevention strategies and continuous surveillance efforts are required to keep up with transmission dynamics.

Aedes albopictus , the Asian tiger mosquito, is an invasive species not native to Europe. Due to its ability to transmit pathogens, such as dengue, chikungunya and Zika viruses, Ae. albopictus is considered a major health threat. In Austria, it was first reported in 2012 in the Western province of Tyrol and was documented in the metropolitan area of Vienna in 2020, demonstrating its ability to colonize urban areas. In July 2021, a garden owner from Graz, Styria, Austria, contacted experts because of the possible presence of tiger mosquitoes in an allotment garden complex. Accordingly, citizen scientists collected adult mosquitoes and set up ovitraps. Adults and eggs were sent to the laboratory for morphological examination and molecular DNA barcoding within the mitochondrial cytochrome c oxidase subunit I gene. In total, 217 eggs of Ae. albopictus were found at the allotment garden as well as at a second location in the city of Graz. In addition, 14 adult Ae. albopictus specimens, of which 7 were molecularly identified as an identical haplotype, were collected at the allotment garden. With its mild climate and numerous parks and gardens, Graz provides the perfect environment for reproduction of tropical/subtropical alien Aedes mosquitoes. The presence of eggs and adult specimens in the current study period indicates that Ae. albopictus is already breeding in Graz. However, monitoring efforts need to be continued to determine whether stable populations of Ae. albopictus can survive there.

Whole genome sequencing (WGS) has become the new technological standard in public health surveillance and disease control systems worldwide. WGS allows the most accurate identification and detailed characterization of microorganisms and is a significant improvement in outbreak investigation, source identification, tracking and surveillance, infection prevention and control in public health microbiology. This allows assurance and risk assessment of food microorganisms and microbial risk management. The high data quality, the reproducibility, stability and accuracy of WGS technology has been demonstrated. WGS passed its acid test with flying colors during the COVID-19 pandemic where the technology was successfully used for early detection of new virus variants improving risk assessment and public health measurements. With the ongoing development of the entire WGS system i.e. technology, metadata, new bioinformatics and machine learning algorithms, we can expect a paradigm shift from classical/ molecular microbiology towards precision microbiology.

BACKGROUND:Listeria monocytogenes is a bacterial pathogen known for causing listeriosis, a foodborne illness with a wide spectrum of clinical presentations ranging from mild gastroenteritis to severe invasive disease, particularly affecting immunocompromised individuals, pregnant women, newborns, and the elderly. Successful treatment of patients with recurring listeria episodes due to colonised foreign material is often challenging, typically requiring a combination of antimicrobial treatment and surgical removal. CASE PRESENTATION:Here, we present a particularly complex case of chronic invasive listeriosis with a total of six relapses. After extensive investigations, the patient's ICD device was identified as the focus of infection. CONCLUSION:The confirmation of relapses through cgMLST analysis highlights the persistence of Listeria monocytogenes and the potential for recurrence even after apparent resolution of symptoms in patients with foreign material. It emphasises the necessity for a comprehensive assessment to identify and mitigate the risk of relapses, thereby ensuring optimal management and outcomes.

INTRODUCTION:Recent reports implicated heater-cooler units (HCUs), which are used for warming infusions, blood or in extracorporeal membrane oxygenation devices, as a possible origin of healthcare-associated infections (HAIs) with potentially pathogenic bacteria, such as non-tuberculous mycobacteria [1]. This represents a source of contamination in a usually sterile setting. AIM:To analyse water from infusion heating devices (IHDs) for bacterial contamination, and to determine if IHDs are a potential source in the transmission of HAIs. METHODS:Thermal transfer fluid (TTF; 300-500 mL) was collected from the reservoirs of 22 independent IHDs and processed on different selective and non-selective media for colony count and identification of bacteria. Strains of Mycobacterium spp. were analysed by whole-genome sequencing. RESULTS:Bacterial growth was observed in all 22 TTF samples after cultivation at 22 °C and 36 °C. Pseudomonas aeruginosa was the most frequent pathogen identified, present in 13.64% (3/22) of samples at >100 colony-forming units/100 mL. Colonization with Mycobacterium chimaera, Ralstonia pickettii and Ralstonia mannitolilytica was detectable in 9.09% (2/22) of samples. Primary sequencing of the detected M. chimaera suggests a close relationship with a M. chimaera strain detected in an outbreak in Switzerland which led to the death of two patients. DISCUSSION:Contamination of TTF represents a germ reservoir in a sensitive setting. Handling errors of IHDs may lead to the distribution of opportunistic or facultative bacterial pathogens, increasing the risk of transmission of nosocomial infections.

It is not well established to what extent previous immunizations offer protection against infections with the SARS-CoV-2 Omicron variant in dialysis patients. We aimed to define the relevant humoral response in dialysis patients using a SARS-CoV-2 IgG chemiluminescence microparticle immunoassay (CMIA) compared to the activity of neutralizing antibodies assessed by a virus neutralization test. Next, we aimed to determine differences in humoral and cellular response levels over time among patients infected or not infected by the Omicron variant of SARS-CoV-2. Immunological parameters of cellular and humoral response to SARS-CoV-2 were analyzed at baseline and after 3 (T3), 6 (T6) and 14 months (T14). In this monocentric cohort study, we followed 110 dialysis patients (mean age 68.4 ± 13.7 years, 60.9% male) for a median of 545 days. We determined an anti-SARS-CoV-2 IgG level of 56.7 BAU/mL as an ideal cut-off value with a J-index of 90.7. Patients infected during the Omicron era had significantly lower (p < 0.001) mean antibody levels at T0 (3.5 vs. 111.2 BAU/mL), T3 (269.8 vs. 699.8 BAU/mL) and T6 (260.2 vs. 513.9 BAU/mL) than patients without Omicron infection. Patients who developed higher antibody levels at the time of the basic immunizations were less likely to become infected with SARS-CoV-2 during the Omicron era. There is a need to adjust the cut-off values for anti-SARS-CoV-2 IgG levels in dialysis patients.

Toxin-producing cyanobacteria pose significant threats to human and animal health if exposed during recreational activities in bathing waters. To better safeguard public health and reduce health risks during the bathing season, an effective monitoring and management strategy is required. Molecular tools used to monitor toxigenic cyanobacteria have been evaluated on the basis of the efficiency and applicability of the method used to (i) establish an early-warning monitoring strategy for EU bathing water sites using both targeted quantitative polymerase chain reaction (qPCR) and non-targeted high-throughput sequencing (HTS) genotype analysis and (ii) to compare the toxigenic potential of cyanobacteria with actual microcystin (MC) occurrence and concentrations. For this purpose, 16 bathing water sites were monitored according to the bathing water directive (BWD) of theEuropean Union (EU) during the bathing season of the summer of 2020 in eastern Austria. The cyanobacterial community composition was analyzed through HTS and qPCR by targeting the microcystin synthetase B gene (mcyB), which indicates MC synthesis within the genera Microcystis and Planktothrix. Within the genus Microcystis, which was identified as the primary MC producer, the mcyB genotypes formed stable subpopulations that increased linearly in correlation with the total Microcystis population. Notably, the HTS cell equivalents assigned to Microcystis and Planktothrix correlated with the corresponding qPCR estimates of genotype abundance, which serves as a confirmation of the suitability of (semi)-quantitative sequencing through HTS. In addition to the elevated trophic state, reduced transparency, increasing water temperatures, as well as cyanobacterial HTS read numbers and Microcystis cell number equivalents per mL estimated through qPCR, were associated with positive MC samples. Therefore, in combination with the monitoring of standard environmental parameters, the use of HTS and qPCR techniques is considered highly useful to ensure the timely identification of health risks to recreational users, as mandated by the BWD.