Personalized antibiotic selection in periodontal treatment improves clinical and microbiological outputs

Introduction

Periodontitis is a biofilm-mediated disease that is usually treated by non-surgical biofilm elimination with or without antibiotics. Antibiotic treatment in periodontal patients is typically selected empirically or using qPCR or DNA hybridization methods. These approaches are directed towards establishing the levels of different periodontal pathogens in periodontal pockets to infer the antibiotic treatment. However, current methods are costly and do not consider the antibiotic susceptibility of the whole subgingival biofilm.

Methods

In the current manuscript, we have developed a method to culture subgingival samples ex vivo in a fast, label-free impedance-based system where biofilm growth is monitored in real-time under exposure to different antibiotics, producing results in 4 hours. To test its efficacy, we performed a double-blind, randomized clinical trial where patients were treated with an antibiotic either selected by the hybridization method (n=32) or by the one with the best effect in the ex vivo growth system (n=32).

Results

Antibiotic selection was different in over 80% of the cases. Clinical parameters such as periodontal pocket depth, attachment level, and bleeding upon probing improved in both groups. However, dental plaque was significantly reduced only in the group where antibiotics were selected according to the ex vivo growth. In addition, 16S rRNA sequencing showed a larger reduction in periodontal pathogens and a larger increase in health-associated bacteria in the ex vivo growth group.

Discussion

The results of clinical and microbiological parameters, together with the reduced cost and low analysis time, support the use of the impedance system for improved individualized antibiotic selection.

Real-time monitoring of biofilm growth identifies andrographolide as a potent antifungal compound eradicating Candida biofilms

Candida species cause life-threatening infections with high morbidity and mortality rates and their resistance to conventional therapy is closely linked to biofilm formation. Thus, the development of new approaches to study Candida biofilms and the identification of novel therapeutic strategies could yield improved clinical outcomes. In the current study, we have set up an impedance-based in vitro system to study Candida spp. biofilms in real-time and to evaluate their sensitivity to two conventional antifungal groups used in clinical practice - azoles and echinocandins. Both fluconazole and voriconazole were unable to inhibit biofilm formation in most strains tested, while echinocandins showed biofilm inhibitory capacity at relatively low concentrations (starting from 0.625 mg/L). However, assays performed on 24 h Candida albicans and C. glabrata biofilms revealed that micafungin and caspofungin failed to eradicate mature biofilms at all tested concentrations, evidencing that once formed, Candida spp. biofilms are extremely difficult to eliminate using currently available antifungals. We then evaluated the antifungal and anti-biofilm effect of andrographolide, a natural compound isolated from the plant Andrographis paniculata with known antibiofilm activity on Gram-positive and Gram-negative bacteria. Optical density measures, impedance evaluation, CFU counts, and electron microscopy data showed that andrographolide strongly inhibits planktonic Candida spp. growth and halts Candida spp. biofilm formation in a dose-dependent manner in all tested strains. Moreover, andrographolide was capable of eliminating mature biofilms and viable cell numbers by up to 99.9% in the C. albicans and C. glabrata strains tested, suggesting its potential as a new approach to treat multi-resistant Candida spp. biofilm-related infections.

Nitrate and a nitrate-reducing Rothia aeria strain as potential prebiotic or synbiotic treatments for periodontitis

A few studies indicate that nitrate can reduce dysbiosis from a periodontitis point of view. However, these experiments were performed on samples from healthy individuals, and it is unknown if nitrate will be effective in periodontal patients, where the presence of nitrate-reducing bacteria is clearly reduced. The aim of this study was to test the effect of nitrate and a nitrate-reducing R. aeria (Ra9) on subgingival biofilms of patients with periodontitis. For this, subgingival plaque was incubated with 5 mM nitrate for 7 h (n = 20) or 50 mM nitrate for 12 h (n = 10), achieving a ~50% of nitrate reduction in each case. Additionally, Ra9 was combined with 5 mM nitrate (n = 11), increasing the nitrate reduced and nitrite produced (both p < 0.05). The addition of nitrate to periodontitis communities decreased biofilm mass (50 mM > 5 mM, both p < 0.05). Five millimolar nitrate, 50 mM nitrate and 5 mM nitrate + Ra9 led to 3, 28 and 20 significant changes in species abundance, respectively, which were mostly decreases in periodontitis-associated species. These changes led to a respective 15%, 63% (both p < 0.05) and 6% (not significant) decrease in the dysbiosis index. Using a 10-species biofilm model, decreases in periodontitis-associated species in the presence of nitrate were confirmed by qPCR (all p < 0.05). In conclusion, nitrate metabolism can reduce dysbiosis and biofilm growth of periodontitis communities. Five millimolar nitrate (which can be found in saliva after vegetable intake) was sufficient, while increasing this concentration to 50 mM (which could be achieved by topical applications such as a periodontal gel) increased the positive effects. Ra9 increased the nitrate metabolism of periodontitis communities and should be tested in vivo.

Ficin-Cyclodextrin-Based Docking Nanoarchitectonics of Self-Propelled Nanomotors for Bacterial Biofilm Eradication

Development of bioinspired nanomotors showing effective propulsion and cargo delivery capabilities has attracted much attention in the last few years due to their potential use in biomedical applications. However, implementation of this technology in realistic settings is still a barely explored field. Herein, we report the design and application of a multifunctional gated Janus platinum-mesoporous silica nanomotor constituted of a propelling element (platinum nanodendrites) and a drug-loaded nanocontainer (mesoporous silica nanoparticle) capped with ficin enzyme modified with β-cyclodextrins (β-CD). The engineered nanomotor is designed to effectively disrupt bacterial biofilms via H₂O₂-induced self-propelled motion, ficin hydrolysis of the extracellular polymeric matrix (EPS) of the biofilm, and controlled pH-triggered cargo (vancomycin) delivery. The effective synergic antimicrobial activity of the nanomotor is demonstrated in the elimination of Staphylococcus aureus biofilms. The nanomotor achieves 82% of EPS biomass disruption and a 96% reduction in cell viability, which contrasts with a remarkably lower reduction in biofilm elimination when the components of the nanomotors are used separately at the same concentrations. Such a large reduction in biofilm biomass in S. aureus has never been achieved previously by any conventional therapy. The strategy proposed suggests that engineered nanomotors have great potential for the elimination of biofilms.

Real-time monitoring of Pseudomonas aeruginosa biofilm growth dynamics and persister cells' eradication

Biofilm formation and the appearance of persister cells with low metabolic rates are key factors affecting conventional treatment failure and antibiotic resistance. Using impedance-based measurements, crystal violet staining and traditional culture we have studied the biofilm growth dynamics of 13 Pseudomonas aeruginosa strains under the effect of seven conventional antibiotics. Real-time growth quantifications revealed that the exposure of established P. aeruginosa biofilms to certain concentrations of ciprofloxacin, ceftazidime and tobramycin induced the emergence of persister cells, that showed different morphology and pigmentation, as well increased antibiotic resistance. Whole-genome sequencing of wildtype and persister cells identified several SNPs, a genomic inversion and a genomic duplication in one of the strains. However, these mutations were not uniquely associated with persisters, suggesting that the persistent phenotype may be related to metabolic and transcriptional changes. Given that mannitol has been proposed to activate bacterial metabolism, the synergistic combination of mannitol and ciprofloxacin was evaluated on clinical 48 h P. aeruginosa biofilms. When administered at doses ≥320 mg/L, mannitol was capable of preventing persister cell formation by efficiently activating dormant bacteria and making them susceptible to the antibiotic. These results were confirmed using viable colony counting. As the tested ciprofloxacin-mannitol combination appeared to fully eradicate mature biofilms, we conclude that impedance-based biofilm diagnostics, which permits antibiotic susceptibility testing and the identification of persister cells, is of great potential for the clinical practice and could aid in establishing treatment breakpoints for emerging biofilm-related infections.

Antibiofilm activity of flavonoids on staphylococcal biofilms through targeting BAP amyloids

The opportunistic pathogen Staphylococcus aureus is responsible for causing infections related to indwelling medical devices, where this pathogen is able to attach and form biofilms. The intrinsic properties given by the self-produced extracellular biofilm matrix confer high resistance to antibiotics, triggering infections difficult to treat. Therefore, novel antibiofilm strategies targeting matrix components are urgently needed. The Biofilm Associated Protein, Bap, expressed by staphylococcal species adopts functional amyloid-like structures as scaffolds of the biofilm matrix. In this work we have focused on identifying agents targeting Bap-related amyloid-like aggregates as a strategy to combat S. aureus biofilm-related infections. We identified that the flavonoids, quercetin, myricetin and scutellarein specifically inhibited Bap-mediated biofilm formation of S. aureus and other staphylococcal species. By using in vitro aggregation assays and the cell-based methodology for generation of amyloid aggregates based on the Curli-Dependent Amyloid Generator system (C-DAG), we demonstrated that these polyphenols prevented the assembly of Bap-related amyloid-like structures. Finally, using an in vivo catheter infection model, we showed that quercetin and myricetin significantly reduced catheter colonization by S. aureus. These results support the use of polyphenols as anti-amyloids molecules that can be used to treat biofilm-related infections.