Evaluation of the ability of C. albicans to form biofilm in the presence of phage-resistant phenotypes of P. aeruginosa.

Pseudomonas aeruginosa and Candida albicans are disparate microbial species, but both are known to be opportunistic pathogens frequently associated with nosocomial infections. The aim of this study was to provide a better understanding of the interactions between these microorganisms in dual-species biofilms. Several bacteriophage-resistant P. aeruginosa phenotypes have been isolated and were used in dual-species mixed-biofilm studies. Twenty-four and 48 h mixed-biofilms were formed using the isolated phenotypes of phage-resistant P. aeruginosa and these were compared with similar experiments using other P. aeruginosa strains with a defined lipopolysaccharide (LPS) deficiency based on chromosomal knockout of specific LPS biosynthetic genes. Overall, the results showed that the variants of phage-resistant P. aeruginosa and LPS mutants were both less effective in inhibiting the growth of C. albicans in mixed-biofilms compared to the wild-type strains of P. aeruginosa. Conversely, the proliferation of P. aeruginosa was not influenced by the presence of C. albicans. In conclusion, the ability of strains of P. aeruginosa to inhibit the formation of a biofilm of C. albicans appears to be correlated with the LPS chain lengths of phenotypes of P. aeruginosa, suggesting that LPS has a suppressive effect on the growth of C. albicans.