Pigs
Bacteria including Salmonella, Staphylococcus, Streptococcus, Pasteurella, Listeria, E. coli and Clostridium spp. cause disease in pigs and potentially humans. All of these bacteria form biofilms that increase resistance to mechanical and chemical cleaning of farm equipment.
Salmonella is more common in indoor-bred pigs in part due to the intensive nature of these operations. Salmonella may persist on a farm for many months or years – even when cleaning and disinfection is used between production cycles. For example, cracks in floors where dust and faecal matter persist provide biofilms safe places to develop and resist even enhanced cleaning and disinfection regimes.
The ability of Salmonella to form a biofilm varies markedly, even between closely related strains, and there is growing evidence that persistence between production cycles selects for strains with increased biofilm formation capacity.
Further reading on biofilms and pig farms
Francesca Martelli, Victor M. Andres, Rob Davies, Richard P. Smith. Observations on the introduction and dissemination of Salmonella in three previously low prevalence status pig farms in the United Kingdom, Food Microbiology, Volume 71, 2018, Pages 129-134, https://doi.org/10.1016/j.fm.2017.05.004.
Tassinari, E., Duffy, G., Bawn, M. et al. Microevolution of antimicrobial resistance and biofilm formation of Salmonella Typhimurium during persistence on pig farms. Sci Rep 9, 8832 (2019). https://doi.org/10.1038/s41598-019-45216-w
Seixas, R., Machado, J., Bernardo, F. et al. Biofilm Formation by Salmonella Enterica Serovar 1,4,[5],12:i:- Portuguese Isolates: A Phenotypic, Genotypic, and Socio-geographic Analysis. Curr Microbiol 68,670–677 (2014). https://doi.org/10.1007/s00284-014-0523-x