 Although most cases are due to "Pseudomonas aeruginosa" infection, there are recent reports of this skin lesion in association with other microorganisms, such as "Escherichia coli", "Citrobacter freundii", "Klebsiella pneumoniae", various other "Pseudomonas" species, and "Morganella morganii".The primary skin lesion usually starts with a macule that is painless, round and erythematous.Then, it develops into a pustule, and then a bulla with central hemorrhagic focus.