A 52-year-old male with recent bilateral lung transplantation is hospitalized with three weeks fever, cough, and dyspnea. He received his transplant five months prior due to idiopathic pulmonary fibrosis. He is adherent to immunosuppression with tacrolimus, mycophenolate, and prednisone, as well as infectious prophylaxis with valganciclovir and atovaquone. He has no known drug allergies.
Physical exam reveals a tender, ulcerating lesion of the right forehead, where the patient denies preceding trauma. Computed tomography of the chest reveals a new, cavitating right upper lobe lesion shown below.
A biopsy of the skin lesion is performed, which is positive on both gram (pictured) and FITE staining.
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CORRECT ANSWER: D) Trimethoprim-sulfamethoxazole and imipenem
Explanation
This is a case of disseminated Nocardia with cutaneous and pulmonary manifestations. Preferred empiric regimen with this severe disease includes trimethoprim-sulfamethoxazole with imipenem.
Our patient is an immunosuppressed host following lung transplantation. His prophylaxis has been with atovaquone (active against pneumocystis, but not Nocardia) increasing risk. Ulcerating skin lesions are part of a range of cutaneous manifestations of Nocardia which includes cellulitis, lymphangitis, and mycetoma. He also has a cavitating lung lesion (pulmonary Nocardia may present as single or multiple lesions, and may be lobar or interstitial).
The characteristic laboratory finding is a branching, filamentous, and sometimes beaded grampositive rod which stains positive on a modified acid-fast stain (or FITE staining)
Nocardia may be treated with trimethoprim-sulfamethoxazole for isolated disease. In cases of disseminated disease, combination therapy with the addition of imipenem or amikacin is recommended. Myast.org has a nice review on Nocardia management in transplant patients.
Source: https://pubmed.ncbi.nlm.nih.gov/30817024/
Distractor choices
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Penicillin would treat actinomyces, another filamentous gram-positive rod
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Azithromycin, rifampin, and ethambutol would treat Mycobacterium avium, an acid-fast organism.
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Vancomycin and cefepime provide broad antibacterial coverage when sepsis is suspected without identified pathogen, they would not cover nocardia.
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Moxifloxacin and clarithroymcin have activity against some isolates of nocardia but would not offer broad enough coverage to be considered as an empiric regimen
Question written by Shilpa Vasishta from Mt. Sinai, question mentor Nathan Nolan, image credit PHIL #21742
https://pubmed.ncbi.nlm.nih.gov/30817024/
https://pubmed.ncbi.nlm.nih.gov/31337957/
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