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Abstract Background Listeriosis is a severe foodborne infection caused by Listeria monocytogenes, an important foodborne pathogen of animals and humans. Listeriosis is a rare disease in cats. Objective To describe the clinical, diagnostic imaging, histological, and microbiological features of L. monocytogenes‐associated mesenteric lymphadenitis in a cat. Animals Listeria monocytogenes‐associated mesenteric lymphadenitis was confirmed in a cat by histology and microbiology. Results Two distinct isolates of L. monocytogenes were cultured from the affected mesenteric lymph node and whole genome sequencing was performed. Conclusion and Clinical Importance This report should alert veterinary clinicians and microbiologists to the syndrome, which may have implications for health and food safety in animals and humans.

Summary: Here, we present a protocol for microinjection of bacteria into mouse small intestinal organoids that recapitulates the natural route of infection of intestinal epithelial cells from the intestinal lumen. We describe steps for visualizing bacteria-cell interactions by live imaging of infected organoids using light sheet microscopy. We then detail procedures for generating doxycycline-inducible expression of mutant proteins in organoids to study essential gene functions. The different techniques described in this protocol can be used independently as required.For complete details on the use and execution of this protocol, please refer to Kim et al. (2021).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Summary: Background: Large-scale studies are needed to clarify antimicrobial resistance in the foodborne pathogen Listeria monocytogenes (Lm) and the effectiveness of listeriosis treatment options. Here we examined the antimicrobial resistance patterns in Lm over time and assessed genotype-phenotype concordances. Methods: We analyzed 5339 Lm isolates (2908 clinical and 2431 food isolates) collected in France and overseas territories, between 2012 and 2019. Whole genome sequencing was performed for all isolates and antimicrobial resistance profiles inferred from draft assemblies. Antimicrobial susceptibility towards 22 antimicrobials was determined for all clinical isolates, and in food isolates with acquired resistance genes. Findings: All tested isolates were resistant to at least 3 different classes of antimicrobials, consistent with Lm intrinsic traits. Acquired antimicrobial resistance in Lm was rare (2.23% isolates) and more prevalent in food (mainly lineage II) compared to clinical isolates (mainly lineage I) (3.74% vs 0.98%, p 99%), except for ciprofloxacin. Acquired antimicrobial phenotypes were towards tetracyclines (mostly due to tetM), trimethoprim (dfrD), lincosamides (lnuG), macrolides (ermB, mphB) and phenicols (fexA). Interpretation: The reference treatment for listeriosis (aminopenicillins/aminoglycosides) remains effective, with no acquired resistance observed. Continuous surveillance of antimicrobial resistance in clinical and food isolates is crucial to detect the emergence of novel resistance. Funding: Institut Pasteur, INSERM, Santé Publique France, Investissement d’Avenir program Laboratoire d’Excellence ‘Integrative Biology of Emerging Infectious Diseases’ (ANR-10-LABX-62-IBEID).