Microbiology Case Study–Pleural Thickening in Lung Transplant Patient

Case history:

A 71-year-old man with a past medical history of idiopathic pulmonary fibrosis and asbestosis status post recent single lung transplant presented with worsening dyspnea. He had a right pleural catheter since the time of his lung transplant surgery five months ago. A chest CT scan was performed and revealed a right pleural effusion with pleural thickening. A sample of the pleural fluid was sent to the microbiology laboratory with the following gram stain and colony morphology:

Gram stain showing gram positive bacilli with subtle palisading arrangements and formations that resemble Chinese letters.

Blood agar plate with gray-white, moist, smooth, non-hemolytic bacterial colonies.

Laboratory Identification:

The pleural fluid grew bacterial colonies on blood agar plates as shown above. No growth was present on MacConkey agar (selective for gram negative bacteria). The colony morphology and gram stain was suggestive of Corynebacterium species. Mass spectrometry confirmed the bacteria as Corynebacterium striatum.

Discussion:

Corynebacterium striatum are gram-positive bacilli that are normal skin and mucosal membrane flora. C. striatum is commonly regarded as a contaminant but may be an opportunistic pathogen in immunocompromised patients such as the patient presented in the above case. Transmission of C. striatum most likely occurs when the patient’s endogenous strain gains access to a normally sterile site of the body. C. striatum has also been documented to spread nosocomially in patients with severe chronic obstructive pulmonary disease. C. striatum is associated with a spectrum of diseases including infectious endocarditis, bacteremia, pneumonia, lung abscess, arthritis, chorioamnionitis and foreign medical device infections. Patients with C. striatum infections are empirically treated with vancomycin because the susceptibility to other antibiotics is variable. Additionally, removal of foreign medical device should be performed if indicated.

Jill Miller, MD is a 2nd 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.