Filling the Void: An Optimized Polymicrobial Interkingdom Biofilm Model for Assessing Novel Antimicrobial Agents in Endodontic Infection

Abstract

There is a growing realization that endodontic infections are often polymicrobial, and may contain Candida spp. Despite this understanding, the development of new endodontic irrigants and models of pathogenesis remains limited to mono-species biofilm models and is bacterially focused. The purpose of this study was to develop and optimize an interkingdom biofilm model of endodontic infection and use this to test suitable anti-biofilm actives. Biofilms containing Streptococcus gordonii, Fusobacterium nucleatum, Porphyromonas gingivalis, and Candida albicans were established from ontological analysis. Biofilms were optimized in different media and atmospheric conditions, prior to quantification and imaging, and subsequently treated with chlorhexidine, EDTA, and chitosan. These studies demonstrated that either media supplemented with serum were equally optimal for biofilm growth, which were dominated by S. gordonii, followed by C. albicans. Assessment of antimicrobial activity showed significant effectiveness of each antimicrobial, irrespective of serum. Chitosan was most effective (3 log reduction), and preferentially targeted C. albicans in both biofilm treatment and inhibition models. Chitosan was similarly effective at preventing biofilm growth on a dentine substrate. This study has shown that a reproducible and robust complex interkingdom model, which when tested with the antifungal chitosan, supports the notion of C. albicans as a key structural component.

Recent Advances and Opportunities in the Study of Candida albicans Polymicrobial Biofilms

“…It was found that although there were differences in biofilm formation on the various parts of the tooth, generally the PMBs grew better in the microaerophilic atmosphere. Similarly, when the influence of different atmospheric condition (aerobic, 5% CO 2 , and anaerobic -85% N 2 , 10% CO 2 , 5% H 2 ) was evaluated on PMBs consisting of C. albicans-S. gordonii-Fusobacterium nucleatum-Porphyromonas gingivalis (Abusrewil et al, 2020), it was found that the greats biofilm formation occurred under 5% CO 2 conditions. This may be due to the ability of both S. gordonii and C. albicans to grow well under this condition.…”

“…One of the host niches that is almost synonymous with biofilms is the oral cavity and several models for PMB formation have recently been developed to more closely approximate the conditions in the host. These models include models that better mimic the availability of nutrients (Montelongo-Jauregui et al, 2016), the oxygen levels present in root canals (Toral et al, 2017;Abusrewil et al, 2020) as well as the various bacteria associated with either caries or soft tissue infection in vitro (Abusrewil et al, 2020;Young et al, 2021). In addition, commercially available organotypic oral mucosal models have been used to study the interaction between C. albicans and bacteria (Krishnamoorthy et al, 2020).…”

Irrigation in Endodontics: Polyhexanide Is a Promising Antibacterial Polymer in Root Canal Treatment

“…It must remain active in the presence of pus, blood, and other biological fluids. It should be noted that, in addition to the optimal antimicrobial spectrum of action, the ‘ideal irrigant’ should act on the organic components of the biofilms and the inorganic components of the lubricated layer for better disinfection and penetration of siler into dentine tubules [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”

Chitosan Enhances the Anti-Biofilm Activity of Biodentine against an Interkingdom Biofilm Model

“…An established interkingdom endodontic biofilm model, previously described by our group, was used throughout this study [ 36 ]. Briefly, biofilms containing Candida albicans SC5314 (ATCC MYA-2876), Streptococcus gordonii (ATCC 35105), Porphyromonas gingivalis (ATCC 33277) and Fusobacterium nucleatum (ATCC 10953) were constructed.…”

“…Other studies have shown that the antimicrobial effect of calcium-silicate-based sealers was enhanced by the incorporation of chitosan nanoparticles (CNps) in root canal sealers [ 29 , 34 ]. We and others have also shown the antimicrobial effectiveness of chitosan when used as a root canal irrigant [ 30 , 35 , 36 ]. Therefore, in the current study, we aimed to assess the anti-biofilm effects against complex polymicrobial biofilms of chitosan when incorporated into endodontic calcium silicate cements.…”