Contributed by Joey Oakley, MD and William Pasculle, ScD
The patient is a 76 year old gentleman with recent (~6 mos prior to admission) left lung transplantation, with a non-cytomegalovirus (CMV)- matched organ, for idiopathic pulmonary fibrosis. Following transplantation he was maintained on prednisone, pantoprazole, valganciclovir, voriconazole (for pulmonary "colonization" with Aspergillus), tacrolimus, metoprolol, and dapsone. The patient presented to the emergency room on the advice of his pulmonologist after calling the latter with complaints of nausea with a few bouts of "biliary" emesis and fevers to 100-101 degrees Farenheit over the previous week. In the emergency room, that patient denied cough, shortness of breath, and tobacco use, and confessed to an increased gag reflex thought to be secondary to medications he was taking with reduced oral intake. He has lost about 15 pounds over the past several weeks. The patient's respiratory rate was 17 breaths per minute and his oxygen saturation was 95% on room air. A computed tomography scan of the chest was significant for focal left lower lobe pneumonia with reactive mediastinal lymph nodes. Because of the patient's difficulties in swallowing from gag reflex abnormality, he was started on broad spectrum antibiotic coverage reflecting his known allergies to trimethoprim/sulfamethoxazole and penicillins. Multiple blood cultures and quantitative PCR for CMV were negative over the next 10 days. On day 10 of treatment, the patient had a repeat computed tomography scan of the chest that showed a mild to moderate left pleural effusion and left basilar consolidation, with persistent reactive mediastinal lymph nodes. The patient at this point was deemed stable enough for bronchoscopy with biopsy, to rule out possible acute cellular rejection and try to find a cause for fever. The biopsy was significant for marked necrotizing granulomas in the left lung, with Grocott silver staining showing thin, filamentous, non-septate organisms with acute angle branching and no yeast forms among the granulomas (Figure 1). These organisms were weakly Gram positive in a beaded pattern.
Culture of the organism revealed rare dry, adherent white colonies in three days of growth on chocolate agar with a smell of freshly overturned earth. The organism was weakly Gram positive in a beaded fashion, and was filamentous, non-septate, with acute angle branching The organism grew equally well at 37 degrees Celsius, 42 degrees Celsius and 45 degrees Celsius on chocolate agar. Biochemically, the organism degraded urea, grew in the presence of lysozyme, was negative for arylsulfatase activity at 14 days and acetamide hydrolysis at 3 days, and grew in the presence of, but did not hydrolyze citrate as its sole carbon source. The organism was resistant to gentamicin and tobramycin, while demonstrating susceptibility to amikacin and erythromycin using routine cutoffs for the Nocardia genus.
Sequencing of an approximately 574 bp segment of a hypervariable region of the 16S rRNA gene was performed in the 5' and 3' direction using primers obtained via the MD Anderson Cancer Center and the results compared to the reported sequences in the GenBank database (National Center for Biotechnology Information). The obtained sequence was 99% identical to numerous accessions labelled as representing Nocardia veterana 16S rRNA genes.
What is the identification of this organism?