Peptidylarginine Deiminase Inhibitor Treatment is Associated with Increased Phage Susceptibility in Erwinia amylovora

Understanding the phage resistance mechanisms in Erwinia amylovora is crucial for improving phage therapy applications targeting this plant pathogen, which is responsible for fire blight disease in apple and pear orchards. This study investigated E. amylovora phage resistance in the presence of peptidylarginine deiminase (PAD) inhibitors, which have been found in other studies to prevent the conversion of arginine to citrulline as a post-translational modification that may initiate outer membrane vesicle (OMV) formation. Infection of the E. amylovora Ea6-4 strain by ΦEa21-4 phages, in the presence of either GSK199 or Cl-Amidine, demonstrated higher infection efficacy and larger phage lysis areas compared to the control infections without PAD inhibitors. Our data suggests that E. amylovora could conceivably employ OMVs as a possible passive phage resistance mechanism in addition to the previously identified regulator of capsule synthesis, the two-component Rcs-based phage resistance system.