Antagonistic effect of Pseudomonas aeruginosa on Candida auris

Ana Beatriz Macedo¹Daniele de Figuerêdo Silva¹Anthony Gabriel de Medeiros¹Gustavo José Freitas²Murilo Moreira dos Santos³Kelly Ishida³Nalu Teixeira De Aguiar Peres^2,4Daniel Assis Santos^2,4Luana Rossato⁵Gustavo Henrique Goldman^4,6Rafael Wesley Bastos^1,4*

• ¹Departamento de Microbiologia e Parasitologia, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil
• ²Department of Microbiology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
• ³Departamento de Microbiologia, Universidade de São Paulo,, São Paulo, Rio Grande do Sul, Brazil
• ⁴Instituto Nacional de Ciência e Tecnologia, Ribeirão Preto, São Paulo, Brazil
• ⁵Laboratório de Pesquisa em Ciências da Saúde, Universidade Federal da Grande Dourados, Dourados, Brazil
• ⁶Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil

Candida (Candidozyma) auris and Pseudomonas aeruginosa are commonly found in hospital environments and medical equipment. Both microorganisms frequently colonize and infect hospitalized patients, causing healthcare-associated infections (HAIs). Despite sharing the same ecological niches and potentially interacting, the mechanisms underlying their interspecies communication remain largely unknown. Therefore, this study aimed to investigate the in vitro interaction between planktonic cells of C. auris and P. aeruginosa. Our findings revealed that P. aeruginosa significantly inhibited C. auris growth, regardless of yeast and bacterial concentrations. This inhibition started after 8 hours of co-culture and persisted for up to 72 hours-the longest period tested. Fluorescence microscopy suggested that the antagonistic effect of P. aeruginosa is likely fungistatic, as most yeast cells remained viable in the presence of the bacterium. Furthermore, P. aeruginosa consistently inhibited C. auris growth in different culture media. Iron supplementation was capable of partially restoring the yeast growth capacity in co-culture. Interestingly, the concentrated (lyophilized) cell-free P. aeruginosa extract also inhibited C. auris, indicating that secreted molecules are responsible for this effect. In this case, iron addition also reversed the antagonistic effect. In conclusion, P. aeruginosa appears to produce and secrete molecules with fungistatic activity against C. auris, and this effect is partially modulated by iron availability. This discovery lays the foundation for future research into the composition and mechanisms of action of these substances, as well as the broader implications of microbial interactions, which could significantly impact host outcomes during co-colonization or infection.