Infectious Disease | Nocardiosis

0:00Hi everyone, welcome back to the Med Bullets Step 2 and 3 podcast. In today's episode, we covered the topic of necardiosis found under the infectious disease section at MedBullets.com. Let's begin with a clinical snapshot. A 40-year-old woman presents to the emergency room for fever and cough for the past few nights. Her past medical history includes systemic lupusarithematosis, for which she is currently on a long prednisone taper. On physical exam, she is in moderate distress and dyspaniac. There are bilateral crackles and bronchi on pulmonary exam. A chest radiograph demonstrates multi-focal consolidation. She has started antibiotics following a broncoelviola lavache. Let's continue with an introduction to necardiosis. Necardia is classified as an aerobic, gram-positive bacteria with branching filaments. It is weakly acid-fast and it is urease-positive and catalyse-positive.

1:01It is transmitted via inhalation or direct contact with the skin break. Conditions that are associated include pulmonary necardiosis and immunocompromised patients and cutaneous necardiosis, which can happen in immunocompetent patients. In terms of the demographics, this mainly occurs in immunocompromised patients. The pulmonary system is most common, but it may spread to the central nervous system. Risk factors include immunocompromised status, chronic steroid use, HIV infection, and trauma. In terms of the pathogenesis, nocardia can inhibit vagal lysosome fusion. Immunocompromised patients, especially those with defective, cell-mediated immunity, are at higher risk. Depending on the presentation, symptoms may include constitutional symptoms such as weight loss and night sweats. On exam, one may note a fever and impulmonary necardiosis, there may be cough, dysnia, sputum production, chest pain, and pleural effusions.

2:05In neurologic necardiosis, one may note focal neurologic defects based on the location of the abscess and patients may have an altered mental status. Incutaneous necardiosis, one may note nodular lymphangitis, which is painful lymphatonopathy with drainage, as well as cellulitis. In terms of further imaging, chest radiography is indicated for pulmonary necardiosis. Findings may include multifocal consolidation and cavitary lesions. Computed tomography of the brain is indicated if their suspected central nervous system involvement. This may include abscesses that appear as re-enhancing lesions. In terms of further studies, labs may demonstrate gram-positive staining with multi-branching beaded filamentous bacteria. Zealne Nielsen staining will demonstrate weakly acid-fast organisms, and one may also perform a culture. When making the diagnosis, remember that this is based on clinical presentation and isolation of the organism. In terms of the differential, make sure to think about actinomycesanfection, distinguishing

3:10factors include that although actinomyces is also gram-positive and form-spranching filaments, it is not acid-fast and causes oral and facial abscesses associated with dental procedures. Treatment for both organisms can be remembered with a mnemonic snap, sofa for no cardia, and actinomyces uses penicillin. Also think about tuberculosis, with distinguishing factors being that patient with no cardiosis will present with a negative PPD test. In terms of treatment, medical options include trimethoprim and sulfamethoxysol. This is indicated for all patients. Another option is carpet penems. This is indicated in patients with contraindications to TMPSMX, and lastly, complications related to no cardiosis include disseminated infection. Now that we've discussed the major points relating to no cardiosis, let's walk through a question to apply what we've learned and get a sense of how the topic might be tested. For this question, consider the following clinical scenario.

4:11A 28-year-old male presents to the emergency department with the fever and cough. He reports that two days ago, he developed a productive cough with the associated shortness of breath. He also endorses drenching sweats for the last several nights. The patient's past medical history is otherwise significant for Crohn's disease, for which he has been taking prednisone for the past several months. He reports that the symptoms of his Crohn's disease have largely remitted since being on the prednisone. He has a 10-pack your smoking history and drinks 2-3 beers a few nights per week. He is sexually active with the male partner and has a recent negative HIV test. The patient's temperature is 101.0 degrees Fahrenheit or 38.3 degrees Celsius. Blood pressure is 121 over 68. Blood pressure is 110 beats per minute and respirations are 22 breaths per minute. On physical exam, he is in moderate distress into Kipnik. He has crackles and rails throughout the right middle and lower lung zones.

5:15A chest radiograph is obtained which demonstrates a consolidation in the right lower lung zone. Gramstain of a sample obtained from a bronchial alveolar lavage demonstrates a gram-positive filamentous rod. Which of the following is the treatment of choice for this patient? In the answer choices are choice one, amphotericin, choice two, levofloxacin, choice three, penicillin, choice four, refampin, isonisid, pyrazinamide, and ethambudal, or choice five, trimethoprimsulfum ethoxazol. The best answer to this question is choice five, trimethoprimsulfum ethoxazol. This patient presents with fever, cough, and consolidation on chest radiograph, which suggests pneumonia, and the gramstain from his bronchial alveolar lavage demonstrates a gram-positive filamentous rod, consistent with nocardia.

6:15The treatment of choice for nocardia is trimethoprimsulfum ethoxazol. Acidia can cause pneumonia, central nervous system disease, or skin lesions, and immunocompromised hosts. Actinomyces most commonly causes a subacute cervical facial 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 trimethoprimsulfum ethoxazol 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. Let's also discuss why the other choices are incorrect. Choice one, amphotarousin may be used to treat fungal pneumonia, including that caused by aspergillis. Although immunocompromised hosts are at increased risk of fungal pneumonia and aspergillis branches on histology, the gramstain in this case demonstrates gram-positive bacteria.

7:15Choice two. Livofloxacin is the treatment of choice for community acquired pneumonia. This patient's gramstain of a gram-positive filamentous rod rolls out any of the typical bacteria that cause community acquired pneumonia. Choice three. Penicillin is the treatment of choice for actinomyces, which appears similarly to nocardia on gramstain, as they are both gram-positive filamentous rods. Actinomyces typically presents as a cervical facial infection rather than as pneumonia. Choice four. Refampin, isonisid, pyrazinamide, and ethymbutyl is the treatment of choice for tuberculosis. Although tuberculosis may cause a similar syndrome of fever, night sweats, and pulmonary symptoms, the gramstain in this case demonstrates a gram-positive rod. Finally, a bullet summary. Nocardia most commonly presents in immunocompromised patients with pulmonary, central nervous system, or cutaneous involvement that may mimic tuberculosis.

8:16The treatment of choice is trimetoprimsofamethoxysol. That's all for this review about nocardiosis. We hope that was helpful. This is the Med Bullets Step Two and Three Podcast, a daily audio review session for Med Bullets, the free learning and collaboration community for medical student education. As a reminder, you can follow along with these podcast episodes by reviewing the topics directly on medbullets.com. You can listen to these episodes on the Med Bullets website or phone app while reading through the topic. If the Med Bullets Podcast has been valuable to you, we'd be thrilled if you consider leaving us a five-star rating and writing us a review on Apple Podcasts. It will help us spread the word and increase our discoverability tremendously. Thanks for tuning in. We'll see you all tomorrow, right here, on the Med Bullets Step Two and Three Podcast.