Biology subjects

Titecat, M.

Publications and source records attributed to Titecat, M..

3 recordsLinked to original sources

bioRxiv2024

Cell wall arabinogalactan is responsible for Fungitell(R) cross reactivity in nocardiosis

Nocardiosis is a serious infection in immunosuppressed patients, especially transplant recipients. The slow-growing phenotype of the bacterium and the variety of symptoms complicate diagnosis and delay antimicrobial therapy, which results in high mortality rates despite effective treatments. Incidentally, some nocardiosis patients test positive in fungal diagnostics that detect (1,3) {beta}-D-glucan (the Fungitell(R) assay), but the basis for this cross-reactivity remains unknown. We demonstrate that nocardial cell wall arabinogalactan is a cryptic antigen responsible for cross reactivity in the Fungitell(R) assay and that this antigen is revealed in vivo following bacterial cell lysis. We further show that the reactivity results from {beta}-glucose substitution of the galactan domain, a modification specific to Nocardia, and identify the optimal antigen as a tetramer of the trisaccharide repeating unit. By providing structural evidence for Fungitell(R) cross-reactivity during nocardiosis, this work paves the way for developing specific diagnostic tools that are presently lacking.

microbiology↗

bioRxiv2024

Macrophage-induced reduction of bacteriophage density limits the efficacy of in vivo pulmonary phage therapy

The rise of antimicrobial resistance has led to renewed interest in evaluating phage therapy. In murine models highly effective treatment of acute pneumonia caused by Pseudomonas aeruginosa relies on the synergistic antibacterial activity of bacteriophages with neutrophils. Here, we show that depletion of alveolar macrophages (AM) shortens the survival of mice without boosting the P. aeruginosa load in the lungs. Unexpectedly, upon bacteriophage treatment, pulmonary levels of P. aeruginosa were significantly lower in AM-depleted than in immunocompetent mice. To explore potential mechanisms underlying the benefit of AM-depletion in treated mice, we developed a mathematical model of phage, bacteria, and innate immune system dynamics. Simulations from the model fitted to data suggest that AM reduce bacteriophage density in the lungs. We experimentally confirmed that the in vivo decay of bacteriophage is faster in immunocompetent compared to AM-depleted animals and that AM phagocytize therapeutic bacteriophage. These findings demonstrate the involvement of feedback between bacteriophage, bacteria, and the immune system in shaping the outcomes of phage therapy in clinical settings.

microbiology↗

bioRxiv2022

Chromosome folding and prophage activation reveal gut-specific genome dynamics of bacteria in the OMM12 consortium

Bacteria and their viruses, bacteriophages, are the most abundant entities of the gut microbiota, a complex community of microorganisms associated with human health and disease. In this ecosystem the interactions between these two key components are still largely unknown. In particular, the impact of the gut environment on bacteria and their associated prophages is yet to be deciphered. To gain insight into the activity of lysogenic phages within the context of their host genomes, we performed Hi-C on the 12 strains of the OMM12 synthetic bacterial community stably associated within mice gut (gnotobiotic mouse line OMM12) in both in vitro and in vivo conditions. High-resolution contact maps of the chromosome 3D organization of the bacterial genomes revealed a wide diversity of architectures, differences between environments and an overall stability over time in the gut of mice. The DNA contacts also pointed at 3D signatures of prophages leading to predict 16 of them as functional. We identified circularization signals and observed different 3D patterns depending on the condition. Concurrent virome analysis showed that 11 of these prophages produced viral particles in vivo and/or in vitro, and that OMM12 mice do not carry other intestinal viruses. By predicting functional prophages, the Hi-C approach unlocks the study of phage-bacteria interaction dynamics.

microbiology↗