The Basis for Variations in the Biofilm Formation by Different Salmonella Species and Subspecies: An In Vitro and In Silico Scoping Study

This study examined whether the presence/absence of biofilm-associated genes may indicate the potential for differences in the biofilm formation among the Salmonella species/subspecies. We conducted an in vitro study on the biofilm formation by eighteen Salmonella strains of different species/subspecies. Strains belonging to subspecies enterica were generally poorer biofilm formers than strains belonging to species bongori and subspecies arizonae, diarizonae, and indica. A broader in silico study was subsequently conducted. The presence/absence of 57 biofilm-associated genes was further investigated among 323 Salmonella whole genomes of various species/subspecies. The lpfE gene was present in in 88.2% of subspecies enterica but was absent in ~90.2–100% of other subspecies. The sirA gene was present in 11.8% of subspecies enterica and 2.9% of S. diarizonae genomes while absent in other species/subspecies. The lpfe gene and sirA gene in subspecies enterica negatively correlated with environmental biofilm formation. The csrB gene was present in 71.4% of the S. arizonae and 94.3% of S. diarizonae genomes but absent in other species/subspecies. The absence of csrB in subspecies enterica positively correlated with weaker environmental biofilm formation. This may contribute to subspecies arizonae and diarizonae being better biofilm formers.