Annual Conference 2025 of the Association for General and Applied Microbiology - Jahrestagung 2025 der Vereinigung für Allgemeine und Angewandte Mikrobiologie

Prof.

Chair

Unravelling E. coli pathogenesis in the human gut by employing advanced intestinal cell and tissue-based model systems

FG Microbial pathogenicity

Pathogenic E. coli are a major cause of intestinal disease worldwide including acute and chronic diarrhoea, inflammatory bowel disease and colorectal cancer. Research has shown that bacterial pathogenesis is governed by environmental cues which tightly regulate virulence gene expression. In the gut, these signals comprise oxygen levels, fluid shear, pH, digestive enzymes and metabolites produced by the intestinal epithelium and resident microbiota. In addition, pathogens are highly adapted to their host and use specific binding receptors and nutrient resources to establish their niche. Therefore, it is important to take these factors into account when investigating how pathogenic bacteria cause disease. In this talk, I will give an overview of human in vitro and ex vivo intestinal model systems applied in our lab to better understand E. coli pathogenesis and contribute to the development of targeted treatment strategies.

Invited lecture

Insights from a novel commensal 3D melanoma skin model: Advanced tumorigenesis due to bacterial colonization

The skin microbiome, which comprises bacteria, fungi, mites, and viruses, has been demonstrated to play a critical role in skin homeostasis and disorders. The contribution of the skin microbiome to various skin cancer types, including melanoma, gained increasing attention, as current studies revealed an altered composition of bacterial communities at melanoma sites compared to healthy skin. However, the underlying mechanisms of the complex interplay between the skin microbiome and melanoma progression remain elusive.We established a co-culture system capable to study host microbiome interactions during melanoma progression in situ. The system is based on the commercially available Melanoma model from MatTek colonized with skin bacteria obtained from skin swabs from a healthy volunteer.The melanoma models showed a stable co-colonization over the cultivation period of 12 days, with no transcriptional activation of bacterial defense pathways. 16S rRNA gene amplicon sequencing indicated reduced bacterial diversity with Streptococcus being the most abundant genera on the last day of cultivation. Pathways related to melanoma progression, such as RAF/MAP and PI3K kinase, were induced in the transcriptome of colonized models. Those findings correlate with the increased release of cytokines GM-CSF, VEGF, and PIGF, which promote angiogenesis, and melanoma markers MIA and S100B. Additionally, epithelial-mesenchymal transition was active in colonized skin models.As a proof of concept, the results indicate a clear impact of microbial skin colonization on melanoma tumorigenesis, thereby providing an elegant method to elucidate the microbiome"s impact on cancer development. As a first approach, we colonized 3D melanoma models with a defined bacterial community that included both typical commensal bacteria and pathogens such as Staphylococcus aureus and Corynebacterium striatum, which were found to be abundant on melanoma sites. The initial results indicated more stable models regarding bacterial cell count in the presence of the bacterial mixture containing the pathogens compared to the mixture without, which might affect the progression of melanoma.

Short lecture

Prof. Dr.

Establishment of a 3D lung infection models to study A. fumigatus infection

Aspergillus fumigatus is an opportunistic fungal pathogen and one of the most common causes of invasive pulmonary aspergillosis in solid-organ transplant (SOT) and allogenic hematopoietic stem cell (HSC) recipients as well as leukemia patients. The prognosis is poor with mortality rates of 40-50 %. While neutrophils have been identified as the most important effector cell, the role of the epithelium in A. fumigatus infection is poorly understood. The reason for this is the use of 2D cell culture approaches, which do not recapitulate several important characteristics of the lung, like cell-to-cell interactions, the heterogeneity of cell types or proximal to distal patterning. On the other hand, the translation of animal models to humans is often affected by species-specific differences between mice and men and the use of laboratory animals raises ethical concerns. To address these limitations and reduce the number of used laboratory animals, in accordance with the 3R principles (refine, reduce, replace), we sought to establish the use of murine precision-cut lung slices (PCLS) and a human epithelial lung organoid model to investigate the interaction of A. fumigatus with the epithelium. PCLS were viable for up to seven days and retained the complex 3D architecture of the lung, irrespective of the experimental treatment. Furthermore, PCLS were immunocompetent and showed a strong cytokine production upon treatment with different TLR agonists and viable A. fumigatus conidia. The immune response to A. fumigatus was dependent on fungal burden and was abrogated by voriconazole treatment, highlighting their potential as a tool for the screening of antifungal compounds. In summary, murine PCLS represent a scalable tool that retain the complex 3D architecture cellular heterogeneity of the lung. This makes them suitable to analyze the spatial interaction of pathogens and host cells in a near-native environment.

3D tissue models for Neisseria gonorrhoeae infection research

Neisseria gonorrhoeae is an obligate human pathogen and a causative agent of a sexually transmitted disease gonorrhea. Apart from the infections of the urogenital tract, gonococci cause eye infection in newborns, who get infected during delivery. Newborn conjunctivitis or ophthalmia neonatorum was one of the most common causes of blindness until the introduction of routine prophylaxis. Urogenital infections are treatable with antibiotics but are becoming a growing health concern due to the increase in the antimicrobial resistance among N. gonorrhoeae strains.Our work focuses on development and testing of 3D tissue models that can be applied in the research of N. gonorrhoeae infections. In one approach, we developed tissue models using cell lines that were based on a small intestinal submucosa (SIS) scaffold derived from pigs. These models initially contained fibroblast and epithelial cells and were later refined by the addition of an endothelial cell layer, as well as neutrophils. Further on, we established a procedure to retrieve primary endometrial cells and are currently testing them for the 3D model generation. In a second approach, we used already established cornea models (collaboration with the group of Christian Lotz, Fraunhofer TLC-RT) to study the role of pilus in the eye infection with N. gonorrhoeae. Both approaches demonstrate the advantages of 3D-tissue models over 2D culture and open new possibilities for the application of such models in infection research.

FG Microbial pathogenicity
Pathogens and 3D cell models

Termin

Chair

Programm

FG Microbial pathogenicityPathogens and 3D cell models

Termin

Chair

Programm

FG Microbial pathogenicity
Pathogens and 3D cell models