Interactions of C. albicans with Bacterial Species on Catheter Surfaces

Indwelling catheters represent an important risk factor associated with mixed-candida-bacterial infections. Objectives: a) to evaluate, quantitatively and qualitatively, the development of dual-species biofilms (DSBs) of Candida and Pseudomonas aeruginosa or Escherichia coli on catheters and compare with their mono-species biofilm (MSB) counterpart, b) determine the effect of glucose on biofilm growth and c) assess the inhibitory effects of bacterial lipopolysaccharides (LPS) on candidal growth. Methods: Biofilm growth of the microorganisms on catheters was monitored in tryptic-soy-broth medium during varying time intervals and growth conditions using a viable cell count method and confirmed by scanning electron microscopy (SEM) and confocal scanning laser microscopy (SCLM). Results: Candida and the bacterial species demonstrated significant inter- and intra- species differences (p< 0.01) in biofilm growth on catheter coupons. Candida species biofilms also demonstrated variable ultrastructural differences on catheter coupons. DSBs with P. aeruginosa significantly suppressed (P <0.001) the biofilm of C. albicans. In contrast, C. albicans biofilm growth was not inhibited in mixed biofilms of E. coli and Candida, and a growth stimulatory effect was seen. These results were also confirmed by microscopy. In glucose supplemented medium C. albicans did not demonstrate a significant difference in MSB or DSB activity whereas P. aeruginosa and E. coli showed increased biofilm growth in both MSB and DSBs compared with controls. Further, LPS of E. coli was more effective in inhibiting C. albicans biofilm growth than P. aeruginosa, LPS. Conclusion: Various bacterial species appear to modulate catheter colonization by C. albicans.