Candida auris promotes Pseudomonas aeruginosa tolerance to meropenem in a mature dual-species biofilm.

Co-infections involving Pseudomonas aeruginosa and Candida auris are becoming increasingly common in hospitals and represent an emerging clinical challenge, as these pathogens can form mixed biofilms during catheter-associated infections, which complicates treatment, prolongs the disease and poses a significant threat to public health. In this study, we formed individual- and dual-species biofilms with Pseudomonas aeruginosa and Candida auris, and then treated mature biofilms with or without meropenem to determine the number of viable cells (colony-forming units). Moreover, Pseudomonas aeruginosa biofilms plus total or fractionated Candida auris supernatant were exposed to meropenem to calculate biofilm-associated viable cells. The results showed that Pseudomonas aeruginosa exhibits increased survival to meropenem in dual-species biofilms compared to individual-species biofilms. Furthermore, we demonstrated that the molecule that promotes meropenem tolerance is present in the supernatant of Candida auris biofilms with a molecular mass <10 kDa. In conclusion, Candida auris induces meropenem tolerance in Pseudomonas aeruginosa during mixed biofilms.