Pseudomonas aeruginosa initially invades the subcutaneous vessels and moves superficially to involve the dermal veins. There is greater involvement of the dermal veins than the dermal arteries. The base of EG reveals a necrotizing vasculitis with minimal neutrophilic infiltration. Gram-negative rods infiltrate the perivascular area, adventitia and media of blood vessels. The intima is usually spared.
Ulcers form as a result of the perivascular and vascular necrosis.
Ecthyma gangrenosum requires prompt diagnosis and treatment with antipseudomonal antibiotics. Further adjustment of antibiotics may be required after sensitivity results are known. Antibiotics - Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting. Antibiotic selection should be guided by blood culture sensitivity whenever feasible. Used in combination with both an agent against gram-positive organisms and one that covers anaerobes.