Andreas Solberg Sagen

• Sagen, Andreas Solberg; Shawrob, Kazi Shefaul Mulk; Salvadori, Gabriela & Junges, Roger (2026). Genetic and functional characterization of the natural transformation system in Streptococcus constellatus. Microbiology (Reading). ISSN 1350-0872. 172(6). doi: 10.1099/mic.0.001726. Full text in Research Archive Show summary

  Streptococcus constellatus is an opportunistic pathogen frequently associated with abscess formation in various body sites. While the species has been shown to acquire exogenous DNA through natural transformation, functional analyses of its underlying mechanisms and optimized genetic editing protocols remain limited. Thus, our aim was to characterize the natural transformation system in S. constellatus and investigate environmental factors coordinating its activation. In addition, we sought to develop an optimized protocol for genome editing. Genomic analysis revealed that 73% of analyzed strains possess orthologs for essential competence regulon genes, with 58% harboring both a complete ComCDE-based operon and the putative transformation machinery required for natural competence. While all complete genomes harbored three copies of the master regulator sigX , the accessory regulator comW was seemingly absent. Lacking the peptide exporter comAB , we demonstrated that S. constellatus utilizes the bacteriocin transporter silED for competence-stimulating peptide export. Gene expression assays indicated system activation at peptide concentrations as low as 4 nM, with peak sigX expression obtained over 60 nM. With the goal of optimizing gene editing strategies, we developed a protocol utilizing rich media supplemented with BSA and calcium chloride, significantly increasing transformation frequencies. Furthermore, we observed that environmental stressors can upregulate the system, including hydrogen peroxide and subinhibitory concentrations of the antibiotics erythromycin, chloramphenicol and ampicillin. Given the increasing clinical relevance of the anginosus group, elucidating horizontal gene transfer mechanisms can provide critical insights into the evolutionary process and pathogenic potential of these species.

• Shawrob, K.S.M.; Sagen, A.S.; Lunde, Tracy Munthali; Sribasgaran, Biramitha; Ghafoor, Saba & Al-Haroni, M. [Show all 9 contributors for this article] (2026). Mapping Antibiotic Resistance Determinants in Oral Streptococci. Journal of Dental Research. ISSN 0022-0345. doi: 10.1177/00220345261462871. Full text in Research Archive Show summary

  Antibiotic resistance is a global priority in health care. Leveraging thousands of whole-genome sequences, here we reveal the core resistance determinants of oral streptococci, focusing on assessing pattern variability and gene exchange across commensals and pathogens. Genomic information was obtained from the National Center for Biotechnology Information. Determinants of antibiotic resistance were identified using AMRFinderPlus and the Comprehensive Antibiotic Resistance Database. ICEscreen was employed for calling of integrative and conjugative elements. Variability and recombination in penicillin-binding protein sequences were assessed with MMseqs2 and fastGEAR. A total of 2,087 genomes from 15 species were included, representing the mitis, mutans, anginosus, salivarius, and bovis groups. We observed 3,576 hits from 55 unique resistance genes conferring resistance to 11 antibiotic classes. The species with the most resistance determinants per genome against unique antibiotic classes were Streptococcus mitis (2.7), Streptococcus oralis (2.5), Streptococcus parasanguinis (1.9), Streptococcus gallolyticus (1.3), and Streptococcus anginosus (1.2). The 2 latter species also presented the most diverse composition of determinants. Over 1,800 integrative and conjugative elements were predicted across all genomes, with nearly 17% carrying at least 1 antibiotic resistance gene. Penicillin-binding protein variation analyses showed a high diversity in the mitis group. Even though S. mitis and S. oralis composed less than 4% of the genomes included in the analyses, they were recognized as sources of DNA for over a third of recombination events in pbp1a and nearly half for both pbp2b and pbp2x in β-lactam-resistant isolates of Streptococcus pneumoniae . In summary, we show that tetracycline and macrolide resistance were highly abundant and tightly connected to integrative and conjugative elements. Further, recent recombination data in pbp loci show frequent genetic exchange from oral streptococci to β-lactam-resistant S. pneumoniae . Fundamentally, assessing triggers and the dynamics of genetic exchange across species is central to the development of strategies aiming to mitigate the impact of antibiotic resistance.

• Haugen, Øyvind Pernell; Sagen, Andreas Solberg; Barbero, Francesco; Alcolea-Rodriguez, Victor; Portela, Raquel & Fenoglio, Ivana [Show all 10 contributors for this article] (2026). Distinct pro-inflammatory responses to pristine and microbially contaminated PET nanoplastics in a human alveolar cell co-culture. Frontiers in Toxicology. 8. doi: 10.3389/ftox.2026.1836922. Full text in Research Archive Show summary

  Background: The small size of nanoplastics (NPs; <1 µm in diameter) facilitates airborne transport, inhalation, and deposition in the lungs, raising significant concerns about potential effects on human health. In occupational settings, such as waste management and recycling facilities, exposure to NPs carrying microbial contaminants may pose an additional health risk to workers. In the present study, we investigated pulmonary cytotoxicity and pro-inflammatory responses after exposure to polyethylene terephthalate nanoplastics (PET-NPs) with or without microbial contaminants. Methods: PET-NPs were synthesized from a post-consumer juice bottle (PET b001) and commodity PET pellets (PET c000). The presence of microbial contaminants was assessed via receptor activation in HEK293 Toll-like receptor (TLR) reporter cells expressing TLR2 or TLR4. Co-cultures of human alveolar epithelial cells (A549) and monocyte-derived macrophages (dTHP-1) were exposed to PET-NPs (0, 10 or 100 μg/mL) that tested either negative or positive for TLR2 and TLR4 activation. After 24 h, cell viability was measured, and cytokine responses were quantified at both mRNA and protein levels. Results: PET b001 activated TLR2 and TLR4, indicating the presence of biologically active microbial components, whereas PET c000 showed no activation. In A549/dTHP-1 co-cultures, PET b001 (10 and 100 μg/mL) significantly increased IL-1B, IL-6, IL-8, and TNF mRNA levels and IL-6 and IL-8 protein secretion. In comparison, PET c000 selectively increased IL-8 mRNA levels and protein secretion, and only at the highest tested concentration (100 μg/mL). No changes in cell viability were observed for either particle type. Conclusion: We found that the pro-inflammatory responses to PET-NPs are largely mediated by associated microbial components rather than the polymer itself, highlighting the importance of accounting for environmental context when evaluating their health risks. No evidence of cytotoxicity was observed, as cell viability remained unchanged. Our results further emphasize the need to assess microbial contamination prior to toxicity testing and point to potential occupational health risks in plastic waste and recycling environments.

• Afanou, Anani Komlavi; Sagen, Andreas Solberg; Barbero, Francesco; Zanoni, Ilaria; Costa, Anna & Haugen, Øyvind Pernell [Show all 7 contributors for this article] (2026). Microplastics amplify the pro-inflammatory response to fungal mycelial fragments and spores in neutrophil-like cells. Frontiers in Toxicology. 8. doi: 10.3389/ftox.2026.1718466. Full text in Research Archive Show summary

  Microplastic pollution has emerged as a global environmental crisis with potential adverse consequences on human health. Mixtures of microplastics with fungal particles including mycelial fragments or spores are highly probable exposure scenarios occurring in various occupational settings or in moldy built indoor environments. However, immunotoxic outcomes associated with such exposure remain poorly characterized. Most studies have focused on single‐exposure components. Here, we investigated, for the first time, the immunotoxic effects of microplastics mixed with spores or mycelial fragments from Aspergillus fumigatus on human neutrophil-like cells. Differentiated HL60 neutrophil-like cells were exposed to 0–100 μg/mL HDPE microplastics mixed with 10 6 heat-inactivated mycelial fragments or spores for 24 h. HDPE combined with fungal fragments induced significant release of IL‐6 and IL‐8 while the mixtures with fungal spores induced only IL‐6 release from the neutrophil-like cells. Most importantly, we observed a trend of decreasing IL‐6 levels with increasing doses of HDPE microplastics in mixture with fungal particles, indicating possible dysregulation of the pro-inflammatory response. The tested doses of HDPE microplastics in mixture with fungal particles showed no significant acute effects on the cell viability. Using HEK293‐TLR reporter cells, we found no significant activation of TLR2 and TLR4 by HDPE microplastics, fungal particles, or their combination, suggesting that the release of IL‐6 and IL‐8 is induced through other innate immune-signaling pathways. Taken together, fungal particles as microbial contaminants, seem to be the main drivers of the immune responses triggered by exposure to mixed HDPE microplastics and fungal particles. Among these, fungal mycelial fragments appear to be the most potent compared to fungal spores that are typically monitored for risk assessments.

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• Sagen, Andreas Solberg; Shawrob, Kazi Shefaul Mulk; Lunde, Tracy Munthali; Sribasgaran, Biramitha; Ghafoor, Saba & Al-Haroni, Mohammed [Show all 9 contributors for this article] (2026). Mobile Genetic Elements Drive Antibiotic Resistance in Oral Streptococci. Full text in Research Archive
• Afanou, Anani Komlavi; Sagen, Andreas Solberg; Haugen, Øyvind Pernell & Zienolddiny-Narui, Shan (2026). HDPE microplastics and fungal particle mixtures: pro-inflammatory responses in neutrophil-like cells. Full text in Research Archive Show summary

  Objective: Microplastic pollution represents a growing environmental and public health concern, yet the immunotoxic effects of microplastics in combination with microbial contaminants remain largely unexplored. In occupational settings and moldy indoor environments, co-exposure to microplastics and fungal particles represents a plausible scenario. Methods: This study investigated the pro-inflammatory effects of high-density polyethylene (HDPE) microplastics mixed with heat-inactivated spores or mycelial fragments from Aspergillus fumigatus using differentiated HL60 neutrophil-like cells. Cells were exposed to HDPE microplastics (0–100 μg/mL) in combination with 10⁶ fungal particles for 24 hours, and cytokine release, cell viability, and Toll-like receptor (TLR) activation were assessed. Results: HDPE microplastics combined with mycelial fragments induced significant release of both IL-6 and IL-8, whereas mixtures with fungal spores induced only IL-6 release. Notably, IL-6 levels decreased with increasing HDPE concentrations in fungal particle mixtures, suggesting potential dysregulation of pro-inflammatory responses. No significant acute cytotoxicity was observed at the tested concentrations. Using HEK293 TLR reporter cells, neither HDPE microplastics, fungal particles, nor their combinations significantly activated TLR2 or TLR4, indicating involvement of alternative innate immune signaling pathways. These findings demonstrate that fungal particles, particularly mycelial fragments, are the primary drivers of pro-inflammatory responses in microplastic-fungal particle mixtures. Conclusion: Our results suggest that mycelial fragments may pose greater immunotoxic risks than spores, which are typically the focus of current risk assessments, and highlight the need for further investigation of realistic co-exposure scenarios in environmental health research.

• Sagen, Andreas Solberg (2025). Environmental triggers of competence in Streptococcus constellatus. Full text in Research Archive
• Sagen, Andreas Solberg; Junges, Roger & Shawrob, Kazi Shefaul Mulk (2025). External stimuli modulating the development of competence in Streptococcus constellatus. Full text in Research Archive
• Sagen, Andreas Solberg; Shawrob, Kazi Shefaul Mulk & Junges, Roger (2025). Subinhibitory Concentrations of Antibiotics Promotes Natural Transformation in Streptococcus constellatus. Full text in Research Archive
• Sagen, Andreas Solberg; Shawrob, Kazi Shefaul Mulk; Petersen, Fernanda Cristina & Junges, Roger (2024). Horizontal gene transfer and antibiotic resistance: activation of the competence system for DNA uptake in Streptococcus constellatus. Full text in Research Archive
• Sagen, Andreas Solberg (2024). Genetic exchange by natural transformation in Streptococcus constellatus. Full text in Research Archive
• Sagen, Andreas Solberg & Junges, Roger (2024). The natural transformation system of Streptococcus constellatus. Full text in Research Archive Show summary

  Streptococcus constellatus is a member of the anginosus group of streptococci (SAG) and it colonizes most notably the oral cavity and the gastrointestinal tract, being frequently involved in infections forming abscesses. S. constellatus has been shown to be able to acquire and incorporate foreign exogenous DNA through natural transformation; however, no functional analyses nor comprehensive assessment of the system have yet been performed. Thus, our aim was to characterize the natural transformation system and its downstream effects in S. constellatus and investigate environmental factors coordinating its natural transformation system.

• Sagen, Andreas Solberg; Shawrob, Kazi Shefaul Mulk; Petersen, Fernanda Cristina & Junges, Roger (2024). Incorporating antibiotic resistance through natural transformation in Streptococcus constellatus. Full text in Research Archive
• Wolf, Susann; Sagen, Andreas Solberg; Bing, Helene L.; Zienolddiny-Narui, Shan & Samulin-Erdem, Johanna Maria (2024). In vitro alveolar model for assessment of genotoxicity and inflammatory potential of nickel nanoparticles. Full text in Research Archive
• Sagen, Andreas Solberg & Junges, Roger (2024). Characterization of the Natural Transformation System in Streptococcus constellatus. Full text in Research Archive
• Haugen, Øyvind Pernell; Sagen, Andreas Solberg; Ervik, Torunn Kringlen; Graff, Pål; Brinchmann, Bendik Christian & Alcolea-Rodriguez, Victor [Show all 11 contributors for this article] (2024). Immune Effects of Pristine and Microbially Contaminated PET Nanoplastics. Full text in Research Archive
• Alsaedi, Sarah; Sagen, Andreas Solberg; Haugen, Øyvind Pernell & Afanou, Komlavi Anani (2023). Hazard effects associated with microplastics mixed with Pseudomonas Lurida in human lung alveolar A549 cells. Full text in Research Archive
• Sagen, Andreas Solberg; Alsaedi, Sarah; Haugen, Øyvind Pernell & Afanou, Komlavi Anani (2023). Hazards associated with microplastics mixed with Candida albicans in granulocyte-like cells HL-60. Full text in Research Archive
• Sagen, Andreas Solberg (2023). Cytotoxic and inflammatory effects of HDPE microplastics and fungal particle mixtures. Universitetet i Oslo. Full text in Research Archive Show summary

  Micro- and nanoplastics (MNPs) have been highlighted as a cause of concern to the environment and to human health. Humans are exposed to particles of MNPs through ingestion, inhalation, and dermal adsorption, potentially causing harm or health complications. Additives and contaminants add complexity to this problem, as these compounds have an effect of their own. Aging and exposure to the environment allow the particles to adsorb or absorb contaminants. Additionally, microbes have been shown to preferentially colonize the hydrophobic surface of MNPs. The combinatorial effects of contaminants or microbes and MNPs are still not fully understood in the context of human health. The aim of this study was to explore the effects of MNPs together with microbes on inflammation in cell models relevant to the human airway. The results from this study suggest that HDPE can modulate the cellular effects observed with microbial exposure, specifically oxidative burst and inflammatory cytokine secretion. Further research into the questions addressed is required to uncover if MNPs, and especially in combination with microbial contaminants, pose a risk to human health.

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