Exploring Metal Ions as Potential Antimicrobial Agents to Combat Future Drug Resistance in Mycoplasma bovis.

Abstract

The rise in antimicrobial resistance (AMR) in Mycoplasma bovis underscores the urgent need for alternative treatments. This study evaluated the minimal inhibitory concentrations (MICs) of four metal ions (cobalt, copper, silver, and zinc) and colloidal silver against 15 clinical M. bovis isolates, alongside conventional antimicrobials (florfenicol, tetracycline, tulathromycin, and tylosin). Colloidal silver demonstrated the most effective antimicrobial activity, inhibiting 81.25% of isolates at 1.5 mg/L, while silver inhibited 93.7% of isolates at concentrations above 1.5 mg/L. Copper exhibited notable efficacy, inhibiting 37.5% of isolates at 1.5 mg/L, with a small proportion responding at 0.1 mg/L. Cobalt and zinc displayed variable activity, with MIC values ranging from 0.7 to 12.5 mg/L. In contrast, conventional antimicrobials showed limited effectiveness: tetracycline inhibited 31.25% of isolates at ≥16 mg/L, tylosin inhibited 25% at 16 mg/L, and tulathromycin MICs ranged from 0.5 to 8 mg/L. Time-kill assays revealed a reduction in M. bovis viability after eight hours of exposure to silver and colloidal silver, though higher concentrations (4×-8× MIC) were required for complete eradication. These findings highlight the significant potential of colloidal silver and copper as alternatives for treating M. bovis infections and combating AMR. Further research is essential to explore their standalone and synergistic applications for therapeutic use.