P4HB and Burkholderia Infections: The possibility that a host protein catalyzing the formation and breakage of disulfide bonds mediates Burkholderia infection has been initially evaluated in experiments involving the broad spectrum PDI inhibitor bacitracin, which directly interacts with cysteines in the substrate-binding domain of PDI by forming a disulphide bond with an open thiol form of the bacitracin thiazoline ring39.