Clinical relevance of Corynebacterium pseudodiphtheriticum in lower respiratory tract specimens

Corynebacterium pseudodiphtheriticum may be present as commensal flora of the respiratory tract and therefore it may be difficult to assess clinical relevance when it is cultured from lower respiratory tract specimens. Our objective was to determine the clinical relevance of C. pseudodiphtheriticum as a lower respiratory tract pathogen and to define patients at risk of developing lower respiratory tract infections caused by C. pseudodiphtheriticum.

We retrospectively identified all lower respiratory tract cultures positive for C. pseudodiphtheriticum over a 10-year period and assessed clinical relevance by predefined criteria.

Clinical relevance was likely or possible in 86% of patients. Pre-existent comorbidity was present in 86% of patients, mostly underlying cardiac or pulmonary disease. All isolates were susceptible to amoxicillin.

C. pseudodiphtheriticum should be considered a clinically relevant pathogen when cultured from the lower respiratory tract in symptomatic patients.