Co-infection with Pseudomonas aeruginosa and Mycobacterium avium complex in patients with bronchiectasis: coincidence or inevitability?

The burden of bronchiectasis is rapidly escalating worldwide, with its airway microbiome shifting from a "single-pathogen" paradigm to "multiple-pathogen coexistence." Both <i>Mycobacterium avium</i> complex and <i>Pseudomonas aeruginosa</i> infections have been demonstrated to exacerbate airway destruction, yet they are rarely examined concurrently. Emerging evidence suggests these pathogens exhibit a long-term coexistence pattern within the same patient, with one dominating when the other recedes. Furthermore, existing studies indicate that the disease burden in coinfected patients is higher than in those with either pathogen alone. However, the specific competitive and synergistic interactions between <i>M. avium</i> complex and <i>P. aeruginosa</i> in bronchiectasis patients remain poorly recognized, posing substantial therapeutic challenges. This review summarizes current understanding of the epidemiology and clinical manifestations of <i>M. avium</i> complex and <i>P. aeruginosa</i> co-infection in patients with bronchiectasis, along with potential mechanisms of microbial interaction between the two pathogens.