Corynebacterium pseudodiphtheriticum: a respiratory tract pathogen in adults.

Corynebacterium pseudodiphtheriticum has been reported to be an uncommon respiratory pathogen. We describe the clinical and microbiologic features of 17 patients from whose sputum C. pseudodiphtheriticum was isolated. Patients were identified through a review of the reports from the clinical microbiology laboratory at York Hospital, a community teaching hospital, from October 1990 through April 1993; 17 patients with respiratory infection caused by C. pseudodiphthriticum were identified. There were 12 cases of bronchitis and five of pneumonia. An underlying systemic condition, particularly congestive heart failure, chronic obstructive pulmonary disease, diabetes mellitus, or malignancy, was common. Onset of symptomatology was acute for most patients, but fever was noticeably absent in almost two-thirds of the cases. Isolates were uniformly susceptible to the beta-lactam antibiotics, vancomycin, and trimethoprim-sulfamethoxazole, but resistance to clindamycin and erythromycin was common. The isolation of diphtheroids from a properly obtained sputum sample from a patient with respiratory tract infection should not always be dismissed as due to contamination. The isolation, identification, and susceptibility testing of C. pseudodiphtheriticum from respiratory tract specimens may provide information useful for treatment of patients.