A 58 year old female with past medical history significant for Type II diabetes, hypertension, hyperlipidemia, chronic diastolic heart failure, and hypothyroidism was hospitalized for following a fall and was found to have compression fractures. The hospitalization was complicated by flash pulmonary edema requiring intubation. CT chest obtained during this hospitalization demonstrated lung nodules, which were biopsied and cultured.
The bacterial and mycobacterial cultures grew gram positive bacilli which were positive on Modified Kinyoun stain. They were negative for Auramine/Rhodamine. The organism grew on several media, including 7H11, Chocolate, and Buffered Charcoal Yeast Extract (BCYE). They formed chalky, white-pink colonies. The organism was confirmed as Nocardia nova by a reference laboratory.
Image 1. Modified acid fast bacilli on Modified Kinyoun stain.
Image 2. Chalky white-pink colonies on BCYE agar.
Nocardia nova is a weakly acid fast, aerobic filamentous, beaded, gram positive bacilli with right-angled branching. It is identified by a Modified Kinyoun stain. Nocardia grows best on BCYE agar; however it also can grow within 3-5 days on blood and chocolate agar. It forms chalky white-pink colonies. Molecular testing is performed to speciate Nocardia, primarily 16S ribosomal RNA gene sequencing, as well as mass spectrometry. Most infections can be treated with sulfonamides for 6-12 months, however, the CDC recommends performing speciation and susceptibility testing on every isolate due to specific susceptibility profiles and drug resistant strains. Our patient was treated with high dose sulfamethoxazole/trimethoprim and meropenem.
Nocardia nova is commonly found in soil and is one of several pathogenic Nocardia species. Nocardia is often inhaled and presents as a chronic pulmonary infection with cough, shortness of breath, and fever. Nocardia can also cause pleural effusions, empyema, pericarditis, abscesses, or dissemination to deep organs, especially the brain. Nocardia can also be contracted though trauma, causing cutaneous diseases such as a mycetoma or cellulitis. Because of its low virulence, Nocardia generally affects immunocompromised patients, however those with preexisting pulmonary disease can also be susceptible to infection.
-Mustafa Mohammad, MD is a 3rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.
-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.