Mig-14 may contribute to Salmonella enterica serovar Typhi resistance to polymyxin B by decreasing the permeability of the outer-membrane and promoting the formation of biofilm

Mig-14 is essential for Salmonella enterica serovar Typhimurium (S. Typhimurium) resistance to antimicrobial peptides, including polymyxin B (PB). However, the molecular mechanism is as yet unknown. In this study, we demonstrated that mig-14 also played a crucial role in Salmonella enterica serovar Typhi (S. Typhi) resistance to PB. A series of genes associated with drug-resistance controlled by Mig-14 were identified in the presence of PB. Among which, ompF and ompC were up-regulated 8 and 6 folds in mig-14 mutant (Delta mig-14) strains, respectively. Further, the deletion of ompF or/and ompC in Delta mig-14 strains decreased their sensitivity to PB. Besides, the biofilm formation ability was reduced in Delta mig-14 strains. Our results indicate that Mig-14 may contribute to PB resistance in S. Typhi by decreasing the permeability of the outer membrane and promoting biofilm formation.