The phosphoethanolamine transferase PetL of Pasteurella multocida is associated with colistin resistance

The rapid emergence and spread of colistin-resistant gram-negative bacteria has raised worldwide public health concerns, and phosphoethanolamine (PEtn) transferase modification-mediated colistin resistance has been widely documented in multiple gram-negative bacterial species. However, whether such a mechanism exists in the zoonotic pathogen Pasteurella multocida is still unknown. Recently, a novel PEtn transferase, PetL, was identified in P. multocida, but whether it is associated with colistin resistance remains to be elucidated. In this study, we found that PetL in P. multocida (PetLPM) exhibited structural characteristics similar to those of the mobile-colistin-resistant (MCR) protein and the PEtn transferase characterized in Neisseria meningitidis. The transformation of petLPM into E. coli or K. pneumoniae changed the phenotype of several tested strains from colistin sensitive to colistin resistant. Deletion of this gene decreased the colistin minimum inhibitory concentration (MIC) of P. multocida by 64-fold. Our extensive analysis by MALDI-TOF–MS demonstrated that PetLPM participated in the modification of bacterial lipopolysaccharide (LPS)-lipid A. Deletion of petLPM led to an increase in membrane charge but a decrease in cell-surface hydrophobicity and cell permeability in P. multocida. The present study is the first to report the presence of PEtn transferase-mediated colistin resistance in the zoonotic pathogen P. multocida.