Ecthyma gangrenosum is caused by

Ecthyma gangrenosum (EG) is a rare skin infection caused by Pseudomonas aeruginosa. EG is usually seen in immunocompromised and critically ill patients. Almost all EG lesions occur in patients with pseudomonas sepsis. It has rarely been repoed in the absence of sepsis or among healthy subjects. The characteristic lesions of EG are hemorrhagic vesicles and pustules that evolve into necrotic ulcers surrounded by a tender erythematous border. iadvl Textbook of dermatology page 243