application/pdf Text Wissenschaftlicher Artikel The zoonotic pathogen S. Infantis is of emerging importance, making detection in poultry critical. Phenotypic changes, which are significant for standardized control programs via EN/ISO 6579-1:2017, could lead to pathogens remaining undetected, increasing the risk of food-borne outbreaks. This study investigates an S. Infantis strain with both normal growth (NCP) and atypical HAS-negative colony variant (ACV) from an Austrian broiler farm. NCP and ACV underwent comprehensive analyses, including stability tests, electron microscopy, whole-genome sequencing, transcriptomics, and proteomics. Our findings demonstrate a stable atypical colony variant exhibiting acquired resistance against cefoxitin in ACV. Genomic analysis identified 9 single nucleotide polymorphisms (SNPs) and two deletions, affecting genes involved in porphyrin and sulfur metabolism. Key factors were a mutation disrupting cysG, which is essential for siroheme biosynthesis and a vital cofactor in sulfur metabolism, and a stop codon in menD (2-oxoglutarate decarboxylase), crucial for small colony variant appearance. Consequently, we hypothesize that these mutations lead to a deficiency in siroheme, as well as anaerobic sulfur respiration altogether resulting in the HAS-negative phenotype. Functional network analysis highlighted compensatory upregulation of alternative metabolic pathways, including nitrate metabolism, propanoate metabolism and mixed-acid fermentation, which may aid ACV's persistence and adaptation under anaerobic conditions. Reduced flagellin expression suggests a mechanism for immune evasion. These genetic and metabolic adaptations likely respond to environmental stressors, such as oxidative stress from disinfectants or antimicrobial pressure, leading to the emergence of the HAS-negative phenotype. Consequently, this study provides insights into the genetic and biochemical adaptations of an atypical S. Infantis variant. eng doi:10.1016/j.fm.2025.104744 © 2025 The Authors open access Comprehensive phenotyping combined with multi-omics of<i> Salmonella</i> Infantis and its H2S negative variant- Resolving adaption mechanisms to environmental changes Elsevier Food Microbiology 2025 http://creativecommons.org/licenses/by/4.0/ Victoria Drauch Nicola Palmieri Joachim Spergser Karin Hummel Marlene Brandstetter Christian Kornschober Michael Hess Enterica Serovar Typhimurium Small-Colony Variants Hydrogen-Sulfide Electron-Acceptor Ethanolamine Resistance Emergence Men Testo Articolo di rivista Text journal article https://phaidra.vetmeduni.ac.at/o:4007