1. Introduction
Antimicrobial resistance (AMR) has, over the past few decades, shifted from being a largely clinical concern to a profound global health challenge that increasingly threatens the foundations of modern medicine. Antibiotics once transformed the management of infectious diseases, turning previously fatal conditions into treatable ailments. Yet the growing prevalence of multidrug-resistant (MDR) pathogens now casts uncertainty over that legacy. The pace at which bacteria evolve resistance mechanisms—through mutation, horizontal gene transfer, and ecological selection—has, in many respects, outstripped the development of new antimicrobial agents. As a result, clinicians and researchers alike are confronting a difficult reality: the therapeutic strategies that once defined infectious disease management may no longer be sufficient for the microbial landscapes of the twenty-first century (Shim, 2023).
Part of the difficulty arises from the long-standing reliance on broad-spectrum antibiotics. These drugs, while lifesaving in acute clinical contexts, exert powerful selective pressures across microbial communities. Rather than targeting specific pathogens alone, they frequently disrupt entire microbial ecosystems, inadvertently accelerating resistance evolution and altering host–microbe interactions. Narrow-spectrum agents have therefore been proposed as a more targeted alternative, capable of limiting collateral ecological damage while maintaining therapeutic efficacy (Melander et al., 2018). Still, the transition toward precision antimicrobial strategies has been uneven, and many healthcare systems continue to depend on empiric antibiotic therapy—often initiated before the causative pathogen is definitively identified.
Diagnostic limitations have historically reinforced this practice. Conventional culture-based pathogen identification can take several days, a delay that frequently compels clinicians to prescribe broad-spectrum antibiotics while awaiting laboratory confirmation. Advances in rapid diagnostic technologies, however, are beginning to reshape this paradigm. Methods such as nucleic acid amplification tests and matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry enable faster and more accurate pathogen detection, thereby supporting targeted antimicrobial therapy and improved stewardship (Caliendo et al., 2013; Maurer et al., 2017). Although these innovations have not entirely eliminated empiric prescribing, they represent an important step toward aligning clinical decision-making with microbiological precision.
At the same time, a deeper appreciation of the human microbiome has fundamentally altered how scientists conceptualize infection and immunity. The trillions of microorganisms inhabiting the human body—particularly those within the gastrointestinal tract—are now understood to function as an integral component of host physiology. Disruptions to this microbial community, commonly referred to as dysbiosis, can influence susceptibility to infection, inflammatory disease, and metabolic disorders. Indeed, mounting evidence suggests that the microbiome functions not merely as a passive bystander but as an active participant in immune regulation and pathogen defense (Mindt & DiGiandomenico, 2022).
The concept of the gut–lung axis illustrates this interplay particularly well. Microbial communities residing in the intestine communicate with distant organs through metabolic and immunological signaling pathways, shaping host responses to respiratory pathogens. Alterations in gut microbiota composition have been associated with increased susceptibility to pulmonary infections, including tuberculosis and viral respiratory illnesses (Comberiati et al., 2021). More recently, dysbiosis has also been implicated in the pathogenesis and severity of COVID-19, reinforcing the idea that microbial ecology and systemic immunity are closely intertwined (Martin Giménez et al., 2023).
Central to this interaction are microbiome-derived metabolites such as short-chain fatty acids (SCFAs). Produced through the fermentation of dietary fibers by commensal bacteria, SCFAs—including acetate, propionate, and butyrate—exert profound immunomodulatory effects. These molecules regulate immune cell differentiation and maintain regulatory T-cell homeostasis, thereby helping to preserve mucosal immune balance (Smith et al., 2013). In addition to their immunological roles, SCFAs can directly influence bacterial virulence and antimicrobial susceptibility, suggesting that metabolic interactions within the microbiome may also shape pathogen behavior (Kadry et al., 2023). Dietary fiber–derived metabolites have even been shown to enhance antiviral immunity by modulating immune cell metabolism and hematopoiesis, highlighting the systemic consequences of microbiome-host interactions (Trompette et al., 2018).
These discoveries have prompted growing interest in microbiome-centered therapeutic strategies. Probiotics, prebiotics, and postbiotics are increasingly investigated as tools for restoring microbial balance and strengthening host defenses. Probiotic organisms may act as immune modulators and antiviral adjuvants, potentially contributing to improved outcomes in respiratory infections and viral diseases (Tomkinson et al., 2023). Meanwhile, postbiotics—defined as non-viable microbial products or metabolites that confer health benefits—offer a standardized and potentially safer alternative to live microbial therapies (Salminen et al., 2021). Other microbiome-derived factors, including antimicrobial peptides, also demonstrate promising antibacterial activity, suggesting that microbial ecosystems themselves may represent an untapped reservoir of therapeutic molecules (Mulkern et al., 2022).
More direct microbiome interventions are also being explored. Fecal microbiota transplantation (FMT), for example, has emerged as an effective treatment for recurrent infections caused by Clostridioides difficile. Beyond this specific indication, FMT is increasingly considered a potential strategy for controlling antimicrobial resistance by restoring microbial diversity and reducing reservoirs of resistance genes within the gut ecosystem (Shawcross et al., 2023). Experimental studies further indicate that targeted modulation of intestinal microbiota—through compounds such as sulfated oligosaccharides—may alleviate inflammatory disorders while reshaping microbial composition (Xiao et al., 2022).
Alongside microbiome modulation, a new generation of targeted antimicrobial approaches is beginning to take shape. Next-generation antibiotics emphasize specificity, evolvability, and minimal immunogenicity, reflecting an effort to design therapies that are both effective and ecologically considerate (Shim, 2023). Bacteriophage therapy exemplifies this strategy. Phages—viruses that selectively infect bacteria—can eliminate specific pathogens without broadly disrupting commensal microbial communities. Recent clinical reports describing the use of phages against Pseudomonas aeruginosa infections suggest that such therapies may offer viable alternatives for treating MDR pathogens in complex clinical settings (Elfadadny et al., 2025).
Monoclonal antibody therapies represent another promising frontier. Unlike conventional antibiotics, these biologics neutralize pathogen virulence factors rather than directly killing bacteria, thereby reducing selective pressure for resistance. Bispecific antibodies targeting Pseudomonas aeruginosa have demonstrated protective effects in experimental models and early clinical investigations (DiGiandomenico et al., 2014). Similarly, antibody-based therapies targeting Staphylococcus aureus toxins have shown potential in preventing ventilator-associated pneumonia among high-risk patients (François et al., 2021). Importantly, such therapies appear capable of preserving intestinal microbial communities, suggesting that targeted immunological interventions may minimize the ecological disruptions associated with traditional antimicrobials (Jones Nelson et al., 2020).
Parallel efforts are underway to address the inflammatory consequences of severe infections. Excessive cytokine production—often referred to as a cytokine storm—can exacerbate tissue damage and worsen clinical outcomes. Small-molecule inhibitors targeting Toll-like receptor signaling pathways are therefore being investigated as potential modulators of pathological inflammation (Zheng et al., 2023). Agents such as enpatoran, a TLR7/8 inhibitor currently under pharmacological evaluation, exemplify this strategy of controlling immune dysregulation while allowing pathogen-directed therapies to act more effectively (Klopp-Schulze et al., 2022). Nutraceutical compounds like resveratrol may also contribute to this therapeutic landscape by modulating both inflammatory signaling pathways and gut microbiota composition (Prakash et al., 2024). In addition, host-derived molecules such as lactoferrin have been proposed as natural protective barriers capable of limiting mucosal infection and inflammation in respiratory and intestinal tissues (Campione et al., 2020).
Taken together, these developments suggest that combating MDR pathogens will likely require a shift away from antibiotic-centric thinking toward a more integrated, ecosystem-based framework. Future antimicrobial strategies may depend not only on directly targeting pathogens but also on preserving microbiome integrity, modulating immune responses, and leveraging microbial ecology as a therapeutic resource. Rapid diagnostics, microbiome restoration, targeted biologics, and next-generation antimicrobials each represent pieces of a broader solution.
The present review therefore examines emerging approaches that integrate microbiome modulation with next-generation antimicrobial therapeutics. By considering both pathogen-specific interventions and host-centered strategies, it seeks to outline a more comprehensive framework for addressing the complex challenge of multidrug-resistant infections. In doing so, it highlights an evolving perspective within infectious disease research—one that recognizes the microbiome not merely as collateral damage in antimicrobial therapy, but as a critical ally in the ongoing effort to control resistant pathogens.
