<i>Burkholderia cenocepacia</i> and <i>Pseudomonas aeruginosa</i> in dual-species models: Insights into population distribution, antibiotic susceptibility, and virulence

Multispecies biofilms are communities composed of different microorganisms embedded in an auto-synthesized polymeric matrix. <i>Pseudomonas aeruginosa</i> and <i>Burkholderia cenocepacia</i> are two multidrug-resistant and biofilm-forming opportunistic pathogens often found in the lungs of people living with cystic fibrosis. In this context, planktonic, static, and dynamic biofilms and <i>in vivo</i> models of both species were optimized in this work to understand their population dynamics, disposition, virulence, and antibiotic susceptibility. From the coculture models optimized in this work, we determined that <i>B. cenocepacia</i> grows in a clustered, aggregative manner at the bottom layers of biofilms, in close contact with <i>P. aeruginosa</i>, that tends to occupy the top layers. Their coexistence increases virulence-related gene expression in both species at early stages of coinfection and in <i>in vivo</i> models, while there was a general downregulation of virulence-related genes after longer coexistence periods as they eventually reach a non-competitive stage during chronic infections. When evaluating antimicrobial susceptibility, a decrease of antimicrobial tolerance was observed in both species when co-cultured. These findings shed light on the differential behavior of <i>P. aeruginosa</i> and <i>B. cenocepacia</i> in dual-species systems, stressing the relevance of multispecies studies in the clinical context.