Corynebacterium Species Rarely Cause Orthopedic Infections.

Corynebacterium spp. are rarely considered pathogens, but data on Corynebacterium spp. as a cause of orthopedic infections are sparse. Therefore, we asked how often Corynebacterium spp. caused an infection in a defined cohort of orthopedic patients with a positive culture. In addition, we aimed to determine the species variety and the susceptibility of isolated strains to define potential treatment strategies. We retrospectively assessed all bone and joint samples that were collected between 2006 and 2015 from an orthopedic ward and that were positive for Corynebacterium spp. by culture. The isolates were considered relevant to an infection if the same Corynebacterium sp. was present in at least two samples. We found 97 orthopedic cases with isolation of Corynebacterium spp. (128 positive samples). These were mainly Corynebacterium tuberculostearicum (n = 26), Corynebacterium amycolatum (n = 17), Corynebacterium striatum (n = 13), and Corynebacterium afermentans (n = 11). Compared to the species found in a cohort of patients with positive blood cultures hospitalized in nonorthopedic wards, we found significantly more C. striatum- and C. tuberculostearicum-positive cases but no C. jeikeium-positive cases in our orthopedic cohort. Only 16 out of 66 cases (24.2%) with an available diagnostic set of at least two samples had an infection. Antibiotic susceptibility testing (AST) showed various susceptibility results for all antibiotics except vancomycin and linezolid, to which 100% of the isolates were susceptible. The rates of susceptibility of corynebacteria isolated from orthopedic samples and of isolates from blood cultures were comparable. In conclusion, our study results confirmed that a Corynebacterium sp. is most often isolated as a contaminant in a cohort of orthopedic patients. AST is necessary to define the optimal treatment in orthopedic infections.