The emergence and global dissemination of multidrug-resistant bacterial pathogens at the interface between wildlife, domestic animals, and humans represents one of the most critical challenges to contemporary One Health systems. Among these pathogens, Pseudomonas aeruginosa and Klebsiella pneumoniae have attracted increasing attention due to their intrinsic virulence, remarkable ecological adaptability, and escalating antimicrobial resistance profiles. While these organisms have traditionally been studied in clinical and hospital environments, a growing body of evidence indicates that wild and captive birds serve as important reservoirs, amplifiers, and dissemination vectors of both pathogens, often in co-infection contexts that exacerbate disease severity and transmission potential. The present article synthesizes and critically analyzes the available scientific evidence on P. aeruginosa and K. pneumoniae in avian hosts, drawing exclusively on the provided reference corpus.

This integrative review explores the ecological niches of both bacteria in avian populations, the pathological manifestations of mono- and co-infections, and the molecular and phenotypic mechanisms that underpin their persistence, virulence, and resistance. Empirical findings from outbreaks in ostriches, kori bustards, flamingos, goldfinches, and diverse wild and captive bird species demonstrate that these bacteria are not merely opportunistic contaminants but active drivers of disease, mortality, and population-level impacts in birds (Momotani et al., 1995; Bailey et al., 2000; Kock and Kock, 1995; Abbate et al., 2025). The review further integrates recent advances in diagnostic and molecular epidemiology, including species-specific PCR targets, multilocus sequence typing, and gene-based identification approaches, which have enabled more precise tracking of avian and environmental strains and their relationship to human and veterinary lineages (Lavenir et al., 2007; Diancourt et al., 2005; He et al., 2016).

A central focus of this work is the One Health dimension of avian-associated P. aeruginosa and K. pneumoniae. Wild birds, companion birds, and farmed avian species occupy ecological and social positions that bridge natural ecosystems, agricultural systems, and human settlements, making them powerful sentinels and vectors for antimicrobial-resistant bacteria (Abd El-Ghany, 2021; Khan et al., 2025; Abdullahi et al., 2025). By integrating data on prevalence, resistance profiles, environmental contamination, and zoonotic potential, this article demonstrates that avian-borne strains of these bacteria represent not only a veterinary problem but also a significant public health and environmental threat.

Through extensive theoretical elaboration and critical synthesis, this article provides a comprehensive, publication-ready account of how P. aeruginosa and K. pneumoniae circulate within and beyond avian populations. It identifies key knowledge gaps, methodological limitations, and research priorities, while also highlighting the urgent need for integrated surveillance, biosecurity, and antimicrobial stewardship strategies that include wildlife and companion birds as essential components of the One Health framework.