Antibacterial Activity of Heteropolytungstates Against Proteus mirabilis

The emergence of multidrug-resistant Proteus mirabilis (P. mirabilis) in urinary tract infections necessitates new antimicrobial strategies. Here, we investigated the in vitro antibacterial activity of several tungstophosphates, the monovacant Keggin ion [PW₁₁O₃₉]⁷⁻ (PW₁₁), the monovacant Wells–Dawson ion [P₂W₁₇O₆₁]¹⁰⁻ (P₂W₁₇), the complete Wells–Dawson ion [P₂W₁₈O₆₂]⁶⁻ (P₂W₁₈), and the Preyssler–Pope–Jeannin ion [NaP₅W₃₀O₁₁₀]¹⁴⁻ (P₅W₃₀), at physiological pH against P. mirabilis. Antibacterial efficacy was evaluated using agar well-diffusion and broth microdilution assays. A structure–activity relationship was observed, with potency increasing in the order PW₁₁ < P₂W₁₇ < P₂W₁₈ < P₅W₃₀. The P₅W₃₀ exhibited the highest inhibitory activity with the lowest minimum inhibitory concentration (MIC) of 0.78 mg/mL, corresponding to a POM concentration of 0.095 mM, whereas P₂W₁₈ reached bactericidal levels with a minimum bactericidal concentration (MBC) of 12.5 mg/mL (2.57 mM).