David A. Scott

Marijuana, an emerging risk factor for periodontitis, contains multiple potent antibacterials, particularly the phytocannabinoids. Microbial dysbiosis is a hallmark of this destructive oral disease. We examined a panel of oral bacteria for susceptibility to the major cannabinoid, cannabidiol (CBD), portended by an initial in vivo microbiome analysis of marijuana users and non-users with periodontitis. Multiple oral bacteria were found to be sensitive to physiologically relevant CBD doses– Aggregatibacter actinomycetemcomitans , Fusobacterium nucleatum , several strains of Porphyromonas gingivalis , Streptococcus mutans , Streptococcus gordonii and Tannerella forsythia . Other oral bacteria, however, were resistant to even superphysiological CBD concentrations– Campylobacter gracilis, Corynebacterium durum, Haemophilus parainfluenzae , several oral Treponema species and Veillonella parvula . Enrichment of phytocannabinoid resistant bacterial pathobionts may help explain increased periodontitis prevalence in cannabis users who, like tobacco smokers, may have distinct therapeutic and preventive needs. To this end, a library of membrane permeabilizing peptoids ( N -substituted glycine oligomers), based on an endogenous mammalian antimicrobial peptide, cathelicidin, was screened for activity against Treponema denticola . This spirochete was sensitive to a sub-set of stable and inexpensive antimicrobial peptoids that, presumably due to peptoid-induced outer membrane instability, also rendered CBD toxic to normally resistant spirochetes. The tobacco-stable, cannabinoid-labile pathobiont, P. gingivalis , was also sensitive to specific antimicrobial peptoids. Electron micrographs clearly suggest altered ultrastructure in both CBD-treated P. gingivalis and peptoid-exposed T. denticola . In summary, cannabis use may promote specific oral bacteria while suppressing others. The associated dysbiosis may help explain marijuana-exacerbated periodontitis. While more comprehensive studies of cannabis-induced microbial fluxes are warranted, adjunctive antimicrobial agents, such as cathelicidin-mimicking peptoids, that target cannabis-promoted pathobionts may also be worth exploring for therapeutic potential.

Enrichment of the oral microorganism Filifactor alocis is strongly associated with the progression of periodontitis. However, F. alocis is part of a complex dysbiotic microbial community, and the organism’s direct pathogenic potential remains uncharacterized. Using the oral gavage model of experimental periodontitis, we revealed that F. alocis promotes alveolar bone loss, as well as significant overexpression of proinflammatory markers associated with osteoclastogenesis and inflammation in oral tissues. Interestingly, despite colonizing in low abundance, F. alocis infection promoted the perturbation of the homeostatic oral microbial community toward a dysbiotic state. Systemically, high levels of proinflammatory cytokines, chemokines, and antibody titers against F. alocis were detected in the sera of infected animals. Germ-free mice or TLR2-deficient mice did not develop alveolar bone loss when infected with F. alocis , demonstrating that the commensal microbial community and the presence of TLR2 are required for F. alocis to display its pathogenic potential. These findings identify F. alocis as an oral pathogen that can disrupt the homeostatic relationship between the host and the oral microbiome, causing inflammation and alveolar bone resorption. Our findings provide novel insights into the pathogenic potential of F. alocis in periodontitis.

Porphyromonas gingivalis is a Gram-negative, anaerobic oral pathobiont, an etiological agent of periodontitis and the most commonly studied periodontal bacterium. Multiple low passage clinical isolates were sequenced, and their genomes compared to several laboratory strains. Phylogenetic distances were mapped, a gene absence-presence matrix generated, and core (present in all genomes) and accessory (absent in one or more genomes) genes delineated. Subsequently, a second pangenome delineating the prevalence of inherently essential genes was generated. The prevalence of genes conditionally essential for surviving tobacco exposure, abscess formation and epithelial invasion was also determined, in addition to genes encoding key proteolytic enzymes containing putative signal peptides. While the absolutely essential pangenome was highly conserved, significant differences in the complete and conditionally essential pangenomes were apparent. Thus, genetic plasticity appears to lie primarily in gene sets facilitating adaptation to variant disease-related environments. Those genes that are highly pervasive in the P. gingivalis absolutely essential pangenome or are highly prevalent and essential for fitness in disease-relevant models, may represent particularly attractive therapeutic targets worthy of further investigation. As mutations in absolutely essential genes are expected to be lethal, the data provided herein should also facilitate improved planning for P. gingivalis gene mutation strategies.

The acidic byproducts of bacteria in plaque around orthodontic brackets contribute to white spot lesion (WSL) formation. Nitric oxide (NO) has antibacterial properties, hindering biofilm formation and inhibiting the growth of oral microbes. Materials that mimic NO release could prevent oral bacteria-related pathologies. This study aims to integrate S-nitroso-acetylpenicillamine (SNAP), a promising NO donor, into orthodontic elastomeric ligatures, apply an additional polymer coating, and evaluate the NO-release kinetics and antimicrobial activity against Streptococus mutans. SNAP was added to clear elastomeric chains (8 loops, 23 mm long) at three concentrations (50, 75, 100 mg/mL, and a control). Chains were then coated, via electrospinning, with additional polymer (Elastollan^®) to aid in extending the NO release. NO flux was measured daily for 30 days. Samples with 75 mg/mL SNAP + Elastollan^® were tested against S. mutans for inhibition of biofilm formation on and around the chain. SNAP was successfully integrated into ligatures at each concentration. Only the 75 mg/mL SNAP chains maintained their elasticity. After polymer coating, samples exhibited a significant burst of NO on the first day, exceeding the machine’s reading capacity, which gradually decreased over 29 days. Ligatures also inhibited S. mutans growth and biofilm formation. Future research will assess their mechanical properties and cytotoxicity. This study presents a novel strategy to address white spot lesion (WSL) formation and bacterial-related pathologies by utilizing nitric oxide-releasing materials. Manufactured chains with antimicrobial properties provide a promising solution for orthodontic challenges, showing significant potential for academic-industrial collaboration and commercial viability.

Microbial biofilms promote pathogenesis by disguising antigens, facilitating immune evasion, providing protection against antibiotics and other antimicrobials and, generally, fostering survival and persistence. Environmental fluxes are known to influence biofilm formation and composition, with recent data suggesting that tobacco and tobacco‐derived stimuli are particularly important mediators of biofilm initiation and development in vitro and determinants of polymicrobial communities in vivo. The evidence for tobacco‐augmented biofilm formation by oral bacteria, tobacco‐induced oral dysbiosis, tobacco‐resistance strategies, and bacterial physiology is summarized herein. A general overview is provided alongside specific insights gained through studies of the model and archetypal, anaerobic, Gram‐negative oral pathobiont, Porphyromonas gingivalis.

Aim: The use of cannabis, which contains multiple antimicrobials, may be a risk factor for periodontitis. We hypothesized that multiple oral spirochetes would be phytocannabinoid-resistant and that cannabidiol (CBD) would act as an environmental stressor to which Treponema denticola would respond transcriptionally, thereby providing first insights into spirochetal survival strategies.Materials and Methods: Oral spirochete growth was monitored spectrophotometrically in the presence and absence of physiologically relevant phytocannabinoid doses, the transcriptional response to phytocannabinoid exposure determined by RNAseq, specific gene activity fluxes verified using qRT-PCR and orthologues among fully sequenced oral spirochetes identified.Results: Multiple strains of oral treponemes were resistant to CBD (0.1-10 mu g/mL), while T. denticola ATCC 35405 was resistant to all phytocannabinoids tested (CBD, cannabinol [CBN], tetrahydrocannabinol [THC]). A total of 392 T. denticola ATCC 35405 genes were found to be CBD-responsive by RNAseq. A selected subset of these genes was independently verified by qRT-PCR. Genes found to be differentially activated by both methods included several involved in transcriptional regulation and toxin control. Suppressed genes included several involved in chemotaxis and proteolysis.Conclusions: Oral spirochetes, unlike some other periodontal bacteria, are resistant to physiological doses of phytocannabinoids. Investigation of CBD-induced transcriptomic changes provided insight into the resistance mechanisms of this important periodontal pathogen. These findings should be considered in the context of the reported enhanced susceptibility to periodontitis in cannabis users.

Cannabinoid receptor 2 (CB2) is of interest as a much-needed target for the treatment or prevention of several neurogenerative diseases. However, CB2 agonists, particularly phytocannabinoids, have been ascribed antimicrobial properties and are associated with the induction of microbiome compositional fluxes. When developing novel CB2 therapeutics, CB2 engagement and antimicrobial functions should both be considered. This review summarizes those cannabinoids and cannabis-informed molecules and preparations (CIMPs) that show promise as microbicidal agents, with a particular focus on the most recent developments. CIMP–microbe interactions and anti-microbial mechanisms are discussed, while the major knowledge gaps and barriers to translation are presented. Further research into CIMPs may proffer novel direct or adjunctive strategies to augment the currently available antimicrobial armory. The clinical promise of CIMPs as antimicrobials, however, remains unrealized. Nevertheless, the microbicidal effects ascribed to several CB2 receptor-agonists should be considered when designing therapeutic approaches for neurocognitive and other disorders, particularly in cases where such regimens are to be long-term. To this end, the potential development of CB2 agonists lacking antimicrobial properties is also discussed.

While definitive evidence awaits, cannabis is emerging as a likely risk factor for periodontal tissue destruction. The mechanisms that underlie potential cannabis-induced or cannabis-enhanced periodontal diseases, however, remain to be elucidated. Herein, we 1) examine insights obtained from the endocannabinoid system, 2) summarize animal models of exposure to cannabinoid receptor agonists and antagonists, 3) review the evidence suggesting that cannabis and cannabis-derived molecules exert a profound influence on components of the oral microbiome, and 4) assess studies indicating that marijuana and phytocannabinoids compromise the immune response to plaque. Furthermore, we address how knowledge of cannabinoid influences in the oral cavity may be exploited to provide potential novel periodontal therapeutics, while recognizing that such medicinal approaches may be most appropriate for nonhabitual marijuana users. The suspected increase in susceptibility to periodontitis in marijuana users is multifaceted, and it is clear that we are only beginning to understand the complex toxicological, cellular, and microbial interactions involved. With marijuana consumption increasing across all societal demographics, periodontal complications of use may represent a significant, growing oral health concern. In preparation, an enhanced research response would seem appropriate.

RagA and RagB proteins are major components of the outer membrane of the oral pathogen Porphyromonas gingivalis and, while recently suggested to represent a novel peptide uptake system, their full function is still under investigation. Herein, we (a) discuss the evidence that the rag locus contributes to P. gingivalis virulence; (b) provide insight to Rag protein potential biological function in macromolecular transport and other aspects of bacterial physiology; (c) address the host response to Rag proteins which are immunodominant and immunomodulatory; and (d) review the potential of Rag‐focused therapeutic strategies for the control of periodontal diseases.