Dermatologic Clue to Bacterial Organism

Ecthyma gangrenosum. It is a characteristic skin lesion associated with Pseudomonas aeruginosa bacteremia. The organism invades tunica media and adventitia of the cutaneous blood vessels causing secondary ischemic necrosis.¹ The cutaneous lesions rapidly progress from erythematous macule to areas of induration that eventually develop a central necrotic pustule or bulla. These are commonly seen in axillary and anogenital region, but may occur at any anatomic region.² Skin lesion resembling ecthyma gangrenosum may be seen in septicemia due to various organism like Aeromonas hydrophila, Klebsiella pneumonia, Serratia marcescens, Xanthomonas maltophilia, disseminated nontuberculous mycobacteria and Fusarium solani.³ Although not pathognomonic, ecthyma gangrenosum provides a clue to pseudomonas aeruginosa as the causative organism especially in immunocompromised patients where blood culture may not always be conclusive.⁴ Early identification of these lesions may aid in deciding appropriate antibiotic regimen with antipseudomonal activity. Cefepime or piperacillin-tazobactam are recommended as first-line agents for critically ill oncology patients.⁵ Multidrug resistance is defined as non-susceptibility to at least one antibiotic in at least three classes for which P. aeruginosa susceptibility is generally expected: penicillins, cephalosporins, fluoroquinolones, aminoglycosides, and carbapenems.⁶ “Difficult-to-treat” resistance (DTR) is defined as P. aeruginosa exhibiting non-susceptibility to all of the following: piperacillin-tazobactam, ceftazidime, cefepime, Aztreonam, meropenem, imipenem-cilastin, ciprofloxacin, and levofloxacin.⁷ The preferred options for the treatment of DTR-P. aeruginosa are ceftolozane-tazobactam, ceftazidime-avibactam, and imipenem-cilastatin-relebactam.⁶ Colistin or polymyxin B can be considered in combination with the ß-lactam-ß-lactamase inhibitor as a last option if no preferred agent demonstrates activity against DTR-P. aeruginosa.⁸ The usual duration of antibiotic therapy is 10 to 14 days.⁹ Surgical debridement may be necessary for ecthyma gangrenosum with extensive skin necrosis, especially those involving peri-anal region.¹⁰

References :

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