Cystic fibrosis (CF) is a genetic disorder affecting the lungs and other organs, leading to the production of thick, sticky mucus. The CF lung provides a unique environment for microbial pathogens, as the impaired mucociliary clearance and dehydrated secretions allow bacteria to colonize and cause chronic infections. The most common pathogen in CF is mucoid Pseudomonas aeruginosa, which produces a polysaccharide called alginate that contributes to its virulence. This review discusses the pathogenesis of mucoid P. aeruginosa and Burkholderia cepacia in CF, highlighting the role of alginate in bacterial survival and the challenges of treating these infections. The review also addresses the host's immune response to these pathogens and the factors that contribute to their persistence in the CF lung. The study emphasizes the importance of understanding the molecular mechanisms underlying the development of mucoidy and the role of alginate in the pathogenesis of CF. The review concludes with a discussion of the implications of these findings for the treatment and management of CF.Cystic fibrosis (CF) is a genetic disorder affecting the lungs and other organs, leading to the production of thick, sticky mucus. The CF lung provides a unique environment for microbial pathogens, as the impaired mucociliary clearance and dehydrated secretions allow bacteria to colonize and cause chronic infections. The most common pathogen in CF is mucoid Pseudomonas aeruginosa, which produces a polysaccharide called alginate that contributes to its virulence. This review discusses the pathogenesis of mucoid P. aeruginosa and Burkholderia cepacia in CF, highlighting the role of alginate in bacterial survival and the challenges of treating these infections. The review also addresses the host's immune response to these pathogens and the factors that contribute to their persistence in the CF lung. The study emphasizes the importance of understanding the molecular mechanisms underlying the development of mucoidy and the role of alginate in the pathogenesis of CF. The review concludes with a discussion of the implications of these findings for the treatment and management of CF.