Polymicrobial biofilms: biological insights and emerging directions in drug discovery

Polymicrobial infections, involving the simultaneous presence of two or more microbial species at a single infection site, are an emerging clinical challenge with increasing incidence across a wide range of healthcare settings. These infections often result in more severe disease outcomes compared to monomicrobial infections due to complex interspecies interactions that enhance microbial survival, virulence, and resistance. One of the most concerning aspects of polymicrobial infections is their strong association with multidrug resistance (MDR). The Synergistic interactions among microbial species enhance biofilm formation, impede immune clearance, and reduce antimicrobial penetration and efficacy, contributing to therapeutic failure and chronic infection. The management of polymicrobial infections is further complicated by diagnostic limitations, as standard culture-based techniques often fail to capture the full microbial diversity present at infection sites. Despite their clinical relevance, drug discovery efforts still rely largely on mono-species biofilm models that overlook the interactions, metabolic cooperation, and resilience of polymicrobial systems. This review outlines advances in polymicrobial biofilm research including improved models, high-throughput screening, and omics insights while emphasizing remaining gaps in spatial organization and host - pathogen dynamics. Addressing these gaps and adopting polymicrobial perspectives will be essential for identifying new therapeutic targets and improving outcomes in biofilm-associated infections.