Peritoneal infection due to Ochrobactrum anthropi producing a novel OCH beta-lactamase variant in a patient on peritoneal dialysis: case report and genomic analysis

ABSTRACT Background Peritoneal dialysis (PD)-associated peritonitis is a major cause of hospitalization, catheter loss, and technique failure. Ochrobactrum anthropi is an environmental, low-virulence, non-fermenting gram-negative bacillus that may cause device-associated infections and exhibits intrinsic beta-lactam resistance mediated by the chromosomal beta-lactamase bla OCH . Case Summary A young adult with Bardet-Biedl syndrome receiving long-term PD presented with cloudy effluent, marked peritoneal leukocytosis, and minimal systemic symptoms. Empirical intraperitoneal cefazolin plus ceftazidime was initiated. Repeated peritoneal-fluid cultures yielded O. anthropi , whereas peripheral blood cultures remained negative. Susceptibility testing showed high MICs for beta-lactam/beta-lactamase inhibitor combinations and preserved carbapenem activity. Intravenous meropenem produced partial clinical improvement; however, fever and cloudy effluent recurred after treatment, requiring catheter removal. A new catheter was inserted 1 month later without recurrence.Whole-genome sequencing (WGS) was performed on the O. anthropi isolate recovered on day 11, the second culture-positive peritoneal-fluid sample, generating a 5.31-Mb draft genome used to confirm species assignment and identify resistance genes. The isolate carried a chromosomal ampR-ampC module encoding a novel OCH beta-lactamase variant, designated OCH-17. Conclusion This case highlights O. anthropi as a device-associated PD pathogen and illustrates the importance of source control when infection persists despite targeted antimicrobial therapy. WGS supported species identification and characterized a novel chromosomal OCH variant.