Background: Â As a normal flora in the upper respiratory tract, Corynebacterium (C.) pseudodiptheriticum is not often considered as the causative bacterium for community-acquired pneumonia.

Findings: In this case report, a patient with bronchiectasis was initially suspected as being infected with Mycobacterium avium. When antibiotic treatment was not successful, bronchial alveolar lavage was obtained for microbiological culturing. Once C. pseudodiptheriticum was recovered from this less-frequently requested respiratory sample, its antibiotic susceptibility profile was obtained to allow appropriate antimicrobial intervention to arrest the infection. The patient experienced full recovery.

Conclusion: This report shows the importance of considering non-routine, sometimes invasive clinical specimens to make a diagnosis. Furthermore, commensal microbes should not be dismissed as possible etiological agents in pulmonary infections.