Typhoid toxin hijacks Wnt5a to establish host senescence and Salmonella infection

Combined In Situ Transcriptomic and Immunofluorescence to Assess the Effects on DNA Damage and Innate Immune Responses Induced by Bacterial Genotoxin in In Vivo Models

Understanding complex pathophysiological processes involves studying intercellular responses and phenotypes within the organ microenvironment, preserving the spatial tissue architecture. This chapter explores a practical and cost-effective method for combining techniques such as in situ immunostaining and transcriptomics analysis. These protocols are adaptable to various mRNA targets, antibodies, tissue types, and tissue fixation appealing to a wide scientific community. We demonstrate their application in studying the host response to infection with a Salmonella enterica strain producing a toxin that induces DNA breaks. Specifically, we assessed the: (i) innate immune response to DNA breaks; (ii) co-detection of Salmonella mRNA fljB with the DNA damage marker γH2AX; (iii) co-detection of mRNAs for the cell cycle arrest marker p16INK4A and the proinflammatory and anti-inflammatory cytokines, Il6 and Il10, respectively. Considering that DNA damage is one of the leading causes of oncogene- and stress-induced-senescence, these protocols can be suitable to assess the cytokine profile associated with cellular phenotype and types of DNA damage of senescent cells in situ.

Isolation and Characterization of a Bacteriophage with Potential for the Control of Multidrug-Resistant Salmonella Strains Encoding Virulence Factors Associated with the Promotion of Precancerous Lesions

BACKGROUND

Antimicrobial-resistant bacteria represent a serious threat to public health. Among these bacteria, Salmonella is of high priority because of its morbidity levels and its ability to induce different types of cancer.

AIM

This study aimed to identify Salmonella strains encoding genes linked to the promotion of precancerous lesions and to isolate a bacteriophage to evaluate its preclinical potential against these bacteria.

METHODOLOGY

An epidemiological approach based on wastewater analysis was employed to isolate Salmonella strains and detect genes associated with the induction of precancerous lesions. Antimicrobial susceptibility was assessed by the disk diffusion method. A bacteriophage was isolated via the double agar technique, and its morphological characteristics, stability, host range, replication dynamics, and ability to control Salmonella under different conditions were evaluated. The bacteriophage genome was sequenced and analyzed using bioinformatics tools.

RESULTS

Thirty-seven Salmonella strains were isolated, seventeen of which contained the five genes associated with precancerous lesions' induction. These strains exhibited resistance to multiple antimicrobials, including fluoroquinolones. A bacteriophage from the Autographiviridae family with lytic activity against 21 bacterial strains was isolated. This phage exhibited a 20 min replication cycle, releasing 52 ± 3 virions per infected cell. It demonstrated stability and efficacy in reducing the Salmonella concentration in simulated gastrointestinal conditions, and its genome lacked genes that represent a biosafety risk.

CONCLUSION

This bacteriophage shows promising preclinical potential as a biotherapeutic agent against Salmonella.

Mitochondrial injury induced by a Salmonella genotoxin triggers the proinflammatory senescence-associated secretory phenotype

Bacterial genotoxins damage host cells by targeting their chromosomal DNA. In the present study, we demonstrate that a genotoxin of Salmonella Typhi, typhoid toxin, triggers the senescence-associated secretory phenotype (SASP) by damaging mitochondrial DNA. The actions of typhoid toxin disrupt mitochondrial DNA integrity, leading to mitochondrial dysfunction and disturbance of redox homeostasis. Consequently, it facilitates the release of damaged mitochondrial DNA into the cytosol, activating type I interferon via the cGAS-STING pathway. We also reveal that the GCN2-mediated integrated stress response plays a role in the upregulation of inflammatory components depending on the STING signaling axis. These SASP factors can propagate the senescence effect on T cells, leading to senescence in these cells. These findings provide insights into how a bacterial genotoxin targets mitochondria to trigger a proinflammatory SASP, highlighting a potential therapeutic target for an anti-toxin intervention.