Tehran University of Medical Sciences Journal of Medical Bacteriology 2251-8649 13 1 2025 02 16 50 53 Zahra Davtalab Tousi Msc of medical microbiology Kiarash Ghazvini Department of Microbiology and Virology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Neda Mohammadzadeh Msc of medical microbiology Hadi Farsiani Department of Microbiology and Virology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran 2024 11 02 2024 11 11 Background:   Cupriavidus pauculus is a gram-negative, aerobic bacillus found in environment. This microorganism can rarely cause serious infections in immunocompromised patients. Catheter-related bloodstream infection caused by Cupriavidus pauculus is a hospital acquired infection which is an infrequent state with very few cases reported in the literature. In this research, we report the first case of Cupriavidus pauculus infection in Iran. Methods:   Blood cultures were performed using the BD BACTEC (Becton, Dickinson, USA) automated haemoculture system and subsequently the gram negative bacilli with regular borders, smooth consistency and dry appearance colonies were identified as Cupriavidus pauculus by the BD Phoenix M50 Compact automated system. Results:   In this paper, we report the first case of Cupriavidus pauculus infection in Iran.  this strain was susceptible to Piperacillin-Tazobactam, Ceftazidime, Cefepime, Trimethoprim-Sulfamethoxazole, Ciprofloxacin, Levofloxacin and resistant to Cefazolin, Ampicillin and Amoxicillin-Clavulanate and is intrinsically resistant to Aminoglycosides, first generation Cephalosporins, Aminopenicillins, Ampicillin-Sulbactam, Ticarcillin and Ceftriaxone. Conclusion:   There are little evidence in the literature about infections caused by Cupriavidus pauculus. Catheter-related bloodstream infection caused by Cupriavidus pauculus is an infrequent infection in humans, but this microorganism should be considered as a potential pathogen in hospitalized immunocompromised patients which can cause serious infections in these individuals, requiring broad-spectrum antibiotic therapy. https://jmb.tums.ac.ir/index.php/jmb/article/view/545