The Therapeutic Potential of Phages in Multi-Drug Resistance Infections and Future Directions

Phage therapy has been revisited as a biologically based strategy to tackle the escalating global crisis of multidrug-resistant (MDR) bacterial infections. Distinct from conventional antibiotics, bacteriophages target specific bacterial strains precisely, replicate locally at infection sites, penetrate bacterial biofilms, and exert synergistic effects with multiple antimicrobial agents. These inherent mechanistic advantages minimize collateral damage to the host's commensal microbiota. However, existing regulatory frameworks-originally established for chemically synthesized, mass-produced drugs-fail to accommodate personalized, living biological phage products, leading to uncertain approval pathways and inconsistent manufacturing supervision. Clinical experience of phage therapy is predominantly derived from compassionate-use cases via multiple administration routes, including intravenous, inhaled, and topical delivery. This review systematically analyzes major challenges restricting clinical application, such as standardized production, quality control, pharmacokinetic characterization, rapid pathogen identification, and regulatory adaptation, as well as the limited performance of fixed phage cocktails against genetically heterogeneous bacterial populations. Current clinical practice demonstrates that phage therapy exhibits acceptable safety profiles across intravenous, inhaled, and topical administration routes, with promising therapeutic outcomes in otherwise untreatable MDR infections. Nevertheless, stable and reproducible clinical outcomes are hindered by multiple scientific and operational obstacles: the absence of unified standards for phage production and quality control, insufficient understanding of route-dependent pharmacokinetics, the imperative demand for rapid pathogen identification to enable precise phage matching, and the limited efficacy of fixed-cocktail regimens against genetically diverse clinical isolates. The successful integration of phage therapy into routine clinical practice relies on coordinated progress in diagnostic infrastructure construction, GMP-compliant phage repository establishment, international regulatory harmonization, and high-quality evidence generation through well-designed clinical trials. Rather than serving as a universal substitute for antibiotics, phage therapy is best implemented as a precision complementary component within comprehensive antimicrobial stewardship strategies.