Resilient Communities: The Role of Biofilms in Salmonella enterica Ecology, Persistence and Pathogenesis

Salmonella enterica is a major global foodborne pathogen whose success across environmental, agricultural and host-associated niches is closely linked to its ability to form biofilms. Importantly, biofilm formation capacity varies substantially among S. enterica serovars, with broad-host-range serovars such as Salmonella typhimurium and Salmonella enteritidis typically exhibiting robust curli- and cellulose-based biofilms, while host-restricted serovars and recently evolved invasive lineages may display reduced or altered biofilm phenotypes. In this review, we synthesise current knowledge on the molecular regulation, ecological significance and public health impact of biofilm formation in S. enterica, with particular emphasis on conserved CsgD-mediated regulatory pathways characterised in strong biofilm-forming serovars. We describe how biofilm development is controlled by interconnected networks involving CsgD, cyclic-di-GMP signalling and environmental sensing systems. Biofilm growth enhances tolerance to environmental stress, disinfectants, antimicrobials and host immune defenses, facilitating long-term persistence on food-processing surfaces, in agricultural environments and within host niches such as the gallbladder. We further discuss emerging antibiofilm strategies, including matrix-degrading enzymes, quorum-sensing inhibitors, bacteriophages and nanotechnology-based approaches. By integrating molecular mechanisms with ecological and serovar-specific perspectives, this review highlights biofilms as a central adaptive strategy of S. enterica and a critical challenge for food safety and public health.