DEPARTMENT OF PATHOLOGY
The Johns Hopkins Medical Institutions
 

Vol. 18, No. 15
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Monday, April 19, 1999
 

  1. Provided by Leslie Edwards Reger, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.
No information provided this week.
  1. The Johns Hopkins Hospital. Information provided by Joseph D Kronz, M.D., Department of Pathology.
Clinical Presentation: This is a 29-year-old man with recurrent thymoma status post resection in 1990, status post chemotherapy with Cytoxan, cisplatin, Adriamycin, vincristine and prednisone for six cycles in 1993 for recurrent mediastinal mass. The patient’s thymoma subsequently relapsed requiring more chemotherapy and autologous bone marrow transplantation for consolidative therapy. In 1995 he received radiotherapy to drop metastases in the left pleura with good response. An abdominal mass was noted 1-1/2 years ago and more recently a recurrent chest mass was noted on the left side. The patient had suffered from pancytopenia secondary to autoimmune disease related to the thymoma and he is also has alopecia totalis. He underwent radiotherapy to the chest 1-1/2 weeks prior to his admission. Since then the patient has had an upper respiratory symptoms which include increasing shortness of breath, severe cough with nausea and vomiting, and a fever. The patient was admitted for work-up of a presumed pneumonia. A spiral CT scan of the chest revealed a patchy infiltrate involving mainly the right upper lung, which was new. The infiltrate was compatible with a pneumonitis but may represent post-radiation changes per the radiology report. Bronchioalveolar lavage, expectorated sputum, and nasopharyngeal samples all grew Nocardia sp.
Nocardia Pneumonia

Background: The genus Nocardia contain type IV cell walls which consists of mycolic acids of 40-60 carbons in length. This is in contrast to Mycobacteria that contain much longer fatty acids in their cell walls. This difference in carbon content of the cell wall also explains why Nocardia will not stain with the traditional acid fast stain but requires a modified acid fast stain. The clinically significant Nocardia species are found in soil.

Clinical Presentation: Nocardia infections occur primarily in immunocompromised patients with underlying lung disease, such as in the current patient. Although there is a predilection for lung disease Nocardia infections can also occur in skin after traumatic abrasions. Patients with the pulmonary infections frequently present with pulmonary complaints including cough, shortness of breath and fever. Severe infections can cause cavitary lung lesions. Infections caused by Nocardia asteroides have a propensity to disseminate via the blood stream and cause brain abscesses. Dissemination carries a high mortality rate. A previous case report of disseminated Nocardia infection in a patient who received corticosteroids for malignant thymoma has been reported.

Diagnosis: Diagnosis is made by culture of the organism with the correct morphology (see figure 1) and biochemical profile. Nocardia sp. can grow on routine laboratory media (sheep blood agar) but overgrowth by other bacteria is a common problem. At Hopkins, the organism identification is diagnosis frequently confirmed using gas-liquid chromatography because the cell wall of Nocardia gives a unique pattern easily recognized by this method.

Therapy: Therapy varies with the severity of the disease and the immune status of the patient. In general trimethoprim-sulfamethoxazole is the first line of therapy in non-critically ill patients. For critically ill patients additional agents are used such as minocycline, amikacin and imipenem.

 

References:

  1. Koneman EW, Allen SD, Janda WM, Schreckenberger PC and Winn, Jr. WC (eds). Color Atlas and Textbook of Diagnostic Microbiology. p 691, 5th ed. Lippincott, New York 1997.
  2. Karakayali G, Karaarslan A, Artz F, Alli N, Tekeli A. Primary cutaneous Nocardia asteroides. Br J Dermatol 1998 Nov;139(5):919-20.
  3. Borges AA, Krasnow SH, Wadleigh RG, Cohen MH. Nocardiosis after corticosteroid therapy for malignant thymoma. Cancer 1993 Mar 1;71(5):1746-50.
  4. McClatchey KD. (ed). Clinical Laboratory Medicine. pp 1265-8. Williams and Wilkins, Baltimore 1994.
 

Figure 1: Modified acid fast stain of Nocardia asteroides. Note the
filamentous morphology with a tendency for the "filaments" to disassociate and form small cocci.

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