Review Question - QID 109048

This patient presents with fever, cough, and consolidation on chest radiograph, which suggests pneumonia, and the Gram stain from his bronchoalveolar lavage demonstrates a gram-positive, filamentous rod consistent with Nocardia. The treatment of choice for Nocardia is trimethoprim-sulfamethoxazole.

Nocardia can cause pneumonia, central nervous system disease, or skin lesions in immunocompromised hosts. Actinomyces most commonly causes a subacute cervicofacial infection of the cheek or jaw and very rarely causes isolated disease in the lung. For that reason, Nocardia is the most likely cause in this case, and trimethoprim-sulfamethoxazole would be the most appropriate treatment. Although not necessary for the diagnosis in this case, Nocardia can also be differentiated from Actinomyces by the fact that Nocardia is partially acid-fast.

Figure A demonstrates consolidation most prominent in the right lower lung zone on chest radiograph, which is consistent with Nocardia pneumonia. Figure B demonstrates a gram-positive, filamentous rod consistent with Nocardia.

Incorrect Answers:
Answer 1: Amphotericin may be used to treat fungal pneumonia, including that caused by Aspergillus. Although immunocompromised hosts are at increased risk of fungal pneumonia and Aspergillus branches on histology, the Gram stain in this case demonstrates gram-positive bacteria.

Answer 2: Levofloxacin is the treatment of choice for community-acquired pneumonia (CAP). This patient’s Gram stain of a gram-positive, filamentous rod rules out any of the typical bacteria that cause CAP (Streptococcus pneumoniae).

Answer 3: Pencillin is the treatment of choice for Actinomyces, which appears similarly to Nocardia on Gram stain, as they are both gram-positive filamentous rods. Actinomyces typically presents as a cervicofacial infection rather than as pneumonia.

Answer 4: Rifampin, isoniazid, pyrazinamide, and ethambutol is the treatment of choice for tuberculosis. Although tuberculosis may cause a similar syndrome of fever, night sweats, and pulmonary symptoms, the Gram stain in this case shows a gram-positive rod.

Bullet Summary:
Nocardia most commonly presents in immunocompromised patients with pulmonary, central nervous system, or cutaneous involvement that may mimic tuberculosis. The treatment of choice is trimethoprim-sulfamethoxazole.