Unusual case of Myroides odoratimimus infection in a cancer patient: addressing its antimicrobial resistance mechanisms and review of the literature

Introduction Myroides odoratimimus is a Gram-negative opportunistic pathogen primarily affecting immunocompromised individuals. However, its resistance characteristics and therapeutic response in cancer patients remain poorly defined. This study investigated the antimicrobial resistance profile of a urinary M. odoratimimus isolate from a gastric cancer patient and evaluated the influence of environmental pH on antibiotic efficacy. Methods The isolate was identified using the VITEK 2-Compact system, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 16S ribosomal ribonucleic acid (16S rRNA) sequencing. Antimicrobial susceptibility testing against 24 antibiotics was performed using the VITEK 2 system according to Clinical and Laboratory Standards Institute (CLSI) M100 (Ed33) guidelines. Resistance genes were detected by polymerase chain reaction (PCR) and sequencing. The impact of pH (5.5–8.5) on antibiotic activity was assessed using disk diffusion. In vivo efficacy of minocycline was evaluated in a murine urinary tract infection model with controlled urine pH modulation. Results The isolate showed 100% sequence identity with M. odoratimimus PR63069 and exhibited multidrug resistance, remaining susceptible only to minocycline. Molecular analysis confirmed the presence of the β-lactamase gene (blaMUS-1). Tigecycline and minocycline demonstrated optimal activity under neutral conditions (pH 7.3), whereas piperacillin–tazobactam showed relatively improved activity at alkaline pH. In vivo , urinary alkalization (pH 8.5) significantly enhanced the antibacterial efficacy of minocycline. Conclusion M. odoratimimus isolated from a gastric cancer patient demonstrated multidrug resistance mediated by blaMUS-1. Antibiotic activity varied with pH, and urine alkalinization improved minocycline efficacy, suggesting potential strategies for clinical management of Myroides infections.