A Single Base Change in the Promoter Resulted in Enhanced Biofilm in Swine-Derived Typhimurium.

Pathogenic strains causing gastroenteritis typically can colonize and proliferate in the intestines of multiple host species. They retain the ability to form red dry and rough () biofilms, as seen in serovar Typhimurium. Conversely, serovar like Typhi, which can cause systemic infections and exhibit host restriction, are -negative. In this study, duck-derived strains and swine-derived strains of . Typhimurium locate on independent phylogenetic clades and display relative genomic specificity. The duck isolates appear more closely related to human blood isolates and invasive non-typhoidal (iNTS), whereas the swine isolates were more distinct. Phenotypically, compared to duck isolates, swine isolates exhibited enhanced biofilm formation that was unaffected by the temperature. The transcriptomic analysis revealed the upregulation of transcription as the direct cause. This upregulation may be mainly attributed to the enhanced promoter activity caused by the G-to-T substitution at position -44 of the promoter. Swine isolates have created biofilm polymorphisms by altering a conserved base present in Typhi, iNTS, and most Typhimurium (such as duck isolates). This provides a genomic characteristics perspective for understanding transmission cycles and evolution.