Citrobacter koseri as an emerging pathogen in orthopedic infections

Citrobacter koseri , typically linked to neonatal meningitis, is an emerging cause of serious orthopedic and surgical site infections, especially in elderly or immunocompromised patients with prolonged hospital stays. However, published data remain sparse and largely limited to isolated case reports. This case series adds new clinical evidence by documenting four postoperative orthopedic wound infections caused by C. Koseri , highlighting the organism’s emerging relevance and the need for greater diagnostic and therapeutic vigilance. This was a retrospective, single-center case series where medical records, operative notes and microbiology laboratory data were reviewed. All isolates demonstrated extensive β-lactam resistance, including universal resistance to third-generation cephalosporins and cefoxitin. Aztreonam resistance was seen in three cases, and three isolates showed phenotypic meropenem resistance, suggestive of extended-spectrum beta-lactamase, AmpC, or emerging carbapenem resistance. The patients received targeted antimicrobial therapy along with appropriate surgical wound management. Clinical improvement and wound healing were observed without major complications.