Assessing the Strength and Interaction of Streptococcus mutans and Candida albicans in Mixed Oral Biofilm

Oral gingivitis with mixed biofilms, specifically in immune-debilitated patients, is of great medical concern. The ability of the yeast Candida albicans to produce strong mixed biofilms with the oral bacterium Streptococcus mutans complicates the medical treatment and immunological response in those patients. To investigate how specific oral Streptococcus species influence Candida albicans biofilm formation, hyphal transformation, and biofilm stability in dual-species biofilms. A total of 100 samples (50 cancer patients and 50 non-cancer patients) suffering from oral gingivitis. Cancer patients were collected from different grades in Nanakali Hospital in Erbil, and non-cancer patients from Khanzad and Rzgary attended dentists’ clinics in the teaching hospital in Erbil, during the period of April 2024 to October 2024. Only 21 clinical isolates of Streptococcus spp. and 24 of Candida albicans. The identification of the fungal and bacterial isolates was conducted using morphological analysis, selective media for both microorganisms, and molecular identification via Multiplex Nested Polymerase Chain Reaction. The experimental and laboratory work was performed in the microbiology laboratories in the Research Center of Salahaddin University-Erbil. The results elucidated that these microorganisms, when occurring together, have a great potential to form biofilms both in vitro and in vivo. This exposes a medical challenge in the treatment of such infections, as biofilm eradication and removal require extensive efforts. The study also emphasizes new records of three species of Streptococcal bacterium (Streptococcus parauberis, Streptococcus thermophilus, and Streptococcus sobrinus), which, to our knowledge, is the first time for these strains to be isolated in the Erbil, Iraq.