Kenya Yukawa, Sohei Harada, Kohji Komori, Brian Hayama, Daisuke Ohkushi, Koichi Takeda, Taisuke Enokida, Akira Yarimizu, Kazumi Takehana, Kageto Yamada, Michihiko Goto, Kazuhiro Tateda

Among Corynebacterium species, Corynebacterium striatum is relatively frequently involved in invasive human infections. In this study, we collected clinical information from patients diagnosed with C. striatum infection at a single cancer center and performed antimicrobial susceptibility testing and whole-genome sequencing of the causative strains. Of the 51 patients with C. striatum infections, 15 (29.4%) had postoperative intra-abdominal infections, eight (15.7%) had postoperative skin and soft tissue infections of the neck, and eight (15.7%) had osteoarticular infections. In 15 patients, C. striatum was detected concomitantly with other bacteria. The median duration of antimicrobial therapy was 25 days, with 43 patients (84.3%) showing clinical improvement by day 14. The crude mortality up to 90 days post-diagnosis was 15.7%. Vancomycin was the most commonly used definitive therapy, and 40 patients (78.4%) received multiple antimicrobial agents. Oral minocycline was often administered in patients requiring long-term treatment. Antimicrobial susceptibility testing of 53 strains, including two strains from follow-up cultures from the same patient, showed that most strains were susceptible to daptomycin and tetracyclines. However, non-susceptibility was noted in two strains (3.8%) for daptomycin and four strains (7.5%) for tetracyclines, each associated with psgA2 mutation and tet(W) carriage. Core-genome single-nucleotide polymorphism analysis of the strains and epidemiological reviews of the source patients identified three suspected clusters of nosocomial transmission involving seven patients. This study demonstrated that C. striatum can cause a range of infections in patients with underlying diseases, such as malignancy, and that nosocomial spread of this pathogen may also occur. The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, employed for bacterial species identification in this study, has enhanced the recognition of Corynebacterium striatum as an important human pathogen in clinical microbiology laboratories. Our study demonstrated that C. striatum is associated with various healthcare-associated infections, including those requiring prolonged antimicrobial therapy, and that nosocomial transmission of this pathogen can result in the development of infections. In addition, several agents other than vancomycin, such as teicoplanin, tetracyclines, and trimethoprim/sulfamethoxazole, have demonstrated favorable activities. The results of this study indicate the need for further research on the mechanisms and modes of nosocomial transmission of C. striatum, as well as the clinical efficacy of alternative agents to vancomycin, particularly those suitable for prolonged treatment, given the potential side effects associated with vancomycin use.