Artemisinins inhibit oral candidiasis caused by Candida albicans through the repression on its hyphal development

Candida albicans is the most abundant fungal species in oral cavity. As a smart opportunistic pathogen, it increases the virulence byswitching its forms from yeasts to hyphae and becomes the major pathogenic agent for oral candidiasis. However, the overuse ofcurrent clinical antifungals and lack of new types of drugs highlight the challenges in the antifungal treatments because of the drugresistance and side effects. Anti-virulence strategy is proved as a practical way to develop new types of anti-infective drugs. Here,seven artemisinins, including artemisinin, dihydroartemisinin, artemisinic acid, dihydroartemisinic acid, artesunate, artemether andarteether, were employed to target at the hyphal development, the most important virulence factor of C. albicans. Artemisininsfailed to affect the growth, but significantly inhibited the hyphal development of C. albicans, including the clinical azole resistantisolates, and reduced their damage to oral epithelial cells, while arteether showed the strongest activities. The transcriptomesuggested that arteether could affect the energy metabolism of C. albicans. Seven artemisinins were then proved to significantlyinhibit the productions of ATP and cAMP, while reduced the hyphal inhibition on RAS1 overexpression strain indicating thatartemisinins regulated the Ras1-cAMP-Efg1 pathway to inhibit the hyphal development. Importantly, arteether significantlyinhibited the fungal burden and infections with no systemic toxicity in the murine oropharyngeal candidiasis models in vivo causedby both fluconazole sensitive and resistant strains. Our results for the first time indicated that artemisinins can be potentialantifungal compounds against C. albicans infections by targeting at its hyphal development.

Transmission routes of 2019-nCoV and controlsin dental practice

A novel β-coronavirus(2019-nCoV) caused severe and even fatal pneumonia explored in a seafood market of Wuhan city, Hubei province, China, and rapidly spread to other provinces of China and other countries. The 2019-nCoV was different from SARS-Co V,but shared the same host receptor the human angiotensin-converting enzyme 2(ACE2). The natural host of 2019-nCoV may be the bat Rhinolophus affinis as 2019-nCoV showed 96.2% of whole-genome identity to Bat Co V Ra TG13. The person-to-person transmission routes of 2019-nCoV included direct transmission, such as cough, sneeze, droplet inhalation transmission, and contact transmission, such as the contact with oral, nasal, and eye mucous membranes. 2019-nCoV can also be transmitted through the saliva, and the fecal–oral routes may also be a potential person-to-person transmission route. The participants in dental practice expose to tremendous risk of 2019-nCoV infection due to the face-to-face communication and the exposure to saliva, blood, and other body fluids, and the handling of sharp instruments. Dental professionals play great roles in preventing the transmission of2019-nCoV. Here we recommend the infection control measures during dental practice to block the person-to-person transmission routes in dental clinics and hospitals.

Salivary mycobiome dysbiosis and its potential impact on bacteriome shifts and host immunity in oral lichen planus

The biodiversity of the mycobiome,an important component of the oral microbial community,and the roles of fungal–bacterial and fungal–immune system interactions in the pathogenesis of oral lichen planus (OLP) remain largely uncharacterized.In this study,we sequenced the salivary mycobiome and bacteriome associated with OLP.First,we described the dysbiosis of the microbiome in OLP patients,which exhibits lower levels of fungi and higher levels of bacteria.Significantly higher abundances of the fungi Candida and Aspergillus in patients with reticular OLP and of Alternaria and Sclerotiniaceae_unidentified in patients with erosive OLP were observed compared to the healthy controls.Aspergillus was identified as an “OLP-associated” fungus because of its detection at a higher frequency than in the healthy controls.Second,the co-occurrence patterns of the salivary mycobiome–bacteriome demonstrated negative associations between specific fungal and bacterial taxa identified in the healthy controls,which diminished in the reticular OLP group and even became positive in the erosive OLP group.Moreover,the oral cavities of OLP patients were colonized by dysbiotic oral flora with lower ecological network complexity and decreased fungal–Firmicutes and increased fungal–Bacteroidetes sub-networks.Third,several keystone fungal genera (Bovista,Erysiphe,Psathyrella,etc.) demonstrated significant correlations with clinical scores and IL-17 levels.Thus,we established that fungal dysbiosis is associated with the aggravation of OLP.Fungal dysbiosis could alter the salivary bacteriome or may reflect a direct effect of host immunity,which participates in OLP pathogenesis.

Oral microbiota in human systematic diseases

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment.The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling,hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases,and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.

Oral bacteria colonize and compete with gut microbiota in gnotobiotic mice

The oral microbiota is associated with oral diseases and digestive systemic diseases.Nevertheless,the causal relationship between them has not been completely elucidated,and colonisation of the gut by oral bacteria is not clear due to the limitations of existing research models.The aim of this study was to develop a human oral microbiota-associated (HOMA) mouse model and to investigate the ecological invasion into the gut.By transplanting human saliva into germ-free (GF) mice,a HOMA mouse model was first constructed.16S rRNA gene sequencing was used to reveal the biogeography of oral bacteria along the cephalocaudal axis of the digestive tract.In the HOMA mice,84.78% of the detected genus-level taxa were specific to the donor.Principal component analysis (PCA) revealed that the donor oral microbiota clustered with those of the HOMA mice and were distinct from those of specific pathogen-free (SPF) mice.In HOMA mice,OTU counts decreased from the stomach and small intestine to the distal gut.The distal gut was dominated by Streptococcus,Veillonella,Haemophilus,Fusobacterium,Trichococcus and Actinomyces.HOMA mice and human microbiota-associated (HMA) mice along with the GF mice were then cohoused.Microbial communities of cohoused mice clustered together and were significantly separated from those of HOMA mice and HMA mice.The Source Tracker analysis and network analysis revealed more significant ecological invasion from oral bacteria in the small intestines,compared to the distal gut,of cohoused mice.In conclusion,a HOMA mouse model was successfully established.By overcoming the physical and microbial barrier,oral bacteria colonised the gut and profiled the gut microbiota,especially in the small intestine.

Quaternary ammonium-induced multidrug tolerant Streptococcus mutans persisters elevate cariogenic virulence in vitro

Dental caries are the most prevalent chronic infections in the oral cavity, and Streptococcus mutans acts as the main cariogenic bacterial species. Antibacterial quaternary ammonium compounds （QAs） have been developed to preveFnt or treat dental caries. However, there is no report on the tolerance of S. mutans to QAs. In this study, we investigated the development of S. mutans persistence induced by a novel dental caries defensive agent, dimethylaminododecyl methacrylate （DMADDM）, for the first time. Typical biphasic killing kinetics for persisters were observed in both S. mutans planktonic and biofilm cultures challenged by DMADDM at concentrations of 20 and 200 pg.mL- z respectively. The persisters tolerated six other antibiotics with different antibacterial mechanisms, while only daptomycin and vancomycin could slightly reduce the persister numbers in planktonic cultures. The distribution of persisters in DMADDM-treated biofilms was similar to that in the untreated control, except that the total biomass and biofilm height were significantly reduced. A higher exopolysaccharides （EPS）：bacteria ratio was observed in DMADDM-treated biofilms. Persisters in biofilms significantly upregulated gtf gene expression, indicating an increase in the bacteria＇s ability to produce EPS and an elevated capability of cariogenic virulence. Carbon source metabolism was significantly reduced, as related metabolic genes were all downregulated in persisters. Concentrations of 0.1 mM, 1 mM and 10 mM of extra glucose significantly reduced the number of persisters both in planktonic and biofilm conditions. The formation of non- inheritable and multidrug tolerant persisters induced by DMADDM suggested that drug tolerance and new persistent eradication strategies should be considered for oral antibacterial agents.

Research Progress on Toxicity of Natural Compounds

There are many active substances in natural resources.After years of research,researchers at home and abroad have extracted active compounds and proved that these compounds have low toxicity and high efficiency,but the toxicity of these compounds cannot be ignored.In this paper,the research progress on the toxicity of compounds isolated from various natural substances is reviewed,which provides a reference for the further development and rational utilization of natural compounds.

小檗碱通过挟持药物外排泵Mdr1p逆转白色念珠菌的多药耐药

药物外排泵的过量表达是病原微生物产生多药耐药(MDR)的重要原因之一.逆转药物外排泵的功能有望对抗多药耐药问题.在能危及人类生命的真菌病原菌白色念珠菌中,主要易化子超家族(MFS)类型转运蛋白Mdr1p能非特异性地向细胞外转运很多结构上不相关的抗真菌化合物,从而导致了白色念珠菌的多药耐药.本研究报道了一个有悖过往认知的案例:一个天然产物小檗碱不仅不会被白色念珠菌Mdr1p外排,而且还能特异性地挟持过表达的Mdr1p把自己运输进细胞.进一步研究发现,进入白色念珠菌细胞后的小檗碱能够在线粒体中积累,通过破坏线粒体膜电势和线粒体复合物I引起线粒体功能紊乱,从而杀死Mdr1p过表达的多药耐药白色念珠菌.在用Mdr1p过表达的白色念珠菌小鼠感染模型中,小檗碱治疗组小鼠的平均存活时间(MST)得到了显著延长.本研究提示找寻药物外排泵的逆转剂可能为如何克服多药耐药问题提供了一个新的思路.

Novel dental implant modifications with two-staged double benefits for preventing infection and promoting osseointegration in vivo and in vitro

Peri-implantitis are a major problem causing implant failure these days.Accordingly,anti-infection during the early stage and subsequent promotion of osseointegration are two main key factors to solve this issue.Micro-arc oxidation(MAO)treatment is a way to form an oxidation film on the surface of metallic materials.The method shows good osteogenic properties but weak antibacterial effect.Therefore,we developed combined strategies to combat severe peri-implantitis,which included the use of a novel compound,PD,comprising dendrimers poly(amidoamine)(PAMAM)loading dimethylaminododecyl methacrylate(DMADDM)as well as MAO treatment.Here,we explored the chemical properties of the novel compound PD,and proved that this compound was successfully synthesized,with the loading efficiency and encapsulation efficiency of 23.91%and 31.42%,respectively.We further report the two-stage double benefits capability of PD+MAO:(1)in the first stage,PD+MAO could decrease the adherence and development of biofilms by releasing DMADDM in the highly infected first stage after implant surgery both in vitro and in vivo;(2)in the second stage,PD+MAO indicated mighty anti-infection and osteoconductive characteristics in a rat model of peri-implantitis in vivo.This study first reports the two-staged,double benefits of PD+MAO,and demonstrates its potential in clinical applications for inhibiting peri-implantitis,especially in patients with severe infection risk.

Beauvericin counteracted multi-drug resistant Candida albicans by blocking ABC transporters

Multi-drug resistance of pathogenic microorganisms is becoming a serious threat,particularly to immunocompromised populations.The high mortality of systematic fungal infections necessitates novel antifungal drugs and therapies.Unfortunately,with traditional drug discovery approaches,only echinocandins was approved by FDA as a new class of antifungals in the past two decades.Drug efflux is one of the major contributors to multi-drug resistance,the modulator of drug efflux pumps is considered as one of the keys to conquer multi-drug resistance.In this study,we combined structure-based virtual screening and whole-cell based mechanism study,identified a natural product,beauvericin(BEA)as a drug efflux pump modulator,which can reverse the multi-drug resistant phenotype of Candida albicans by specifically blocking the ATP-binding cassette(ABC)transporters;meantime,BEA alone has fungicidal activity in vitro by elevating intracellular calcium and reactive oxygen species(ROS).It was further demonstrated by histopathological study that BEA synergizes with a sub-therapeutic dose of ketoconazole(KTC)and could cure the murine model of disseminated candidiasis.Toxicity evaluation of BEA,including acute toxicity test,Ames test,and hERG(human ether-a-go-go-related gene)test promised that BEA can be harnessed for treatment of candidiasis,especially the candidiasis caused by ABC overexpressed multi-drug resistant C.albicans.