Virulence and pathogenicity of Candida albicans is enhanced in biofilms containing oral bacteria

Abstract

This study examined the influence of bacteria on the virulence and pathogenicity of candidal biofilms. Mature biofilms (Candida albicans-only, bacteria-only, C. albicans with bacteria) were generated on acrylic and either analysed directly, or used to infect a reconstituted human oral epithelium (RHOE). Analyses included Candida hyphae enumeration and assessment of Candida virulence gene expression. Lactate dehydrogenase (LDH) activity and Candida tissue invasion following biofilm infection of the RHOE were also measured. Candida hyphae were more prevalent (p < 0.05) in acrylic biofilms also containing bacteria, with genes encoding secreted aspartyl-proteinases (SAP4/SAP6) and hyphal-wall protein (HWP1) up-regulated (p < 0.05). Candida adhesin genes (ALS3/EPA1), SAP6 and HWP1 were up-regulated in mixed-species biofilm infections of RHOE. Multi-species infections exhibited higher hyphal proportions (p < 0.05), up-regulation of IL-18, higher LDH activity and tissue invasion. As the presence of bacteria in acrylic biofilms promoted Candida virulence, consideration should be given to the bacterial component when managing denture biofilm associated candidoses.

Keywords:

• biofilm
• Candida albicans
• candidosis
• co-infection
• RHOE
• virulence

Acknowledgements

The input of Mrs Kath Allsopp for processing and sectioning tissue samples is gratefully acknowledged.

Conflict of interest disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the following research funding agencies: CAPES (Brazil) under research grant [grant number 007355/2013-00]; FAPESP (Brazil) under research grant [grant number 2012/07436-6]; and GlaxoSmithKline under EPSRC-CASE award.