Oral diseases (e.g., dental caries, periodontitis) are developed when the healthy oral microbiome is imbalanced allowing the increase of pathobiont strains. Common practice to prevent or treat such diseases is the use of antiseptics, like chlorhexidine. However, the impact of these antiseptics on the composition and metabolic activity of the oral microbiome is poorly addressed. Using two types of oral biofilms—a 14-species community (more controllable) and human tongue microbiota (more representative)—the impact of short-term chlorhexidine exposure was explored in-depth. In both models, oral biofilms treated with chlorhexidine exhibited a pattern of inactivation (>3 log units) and fast regrowth to the initial bacterial concentrations. Moreover, the chlorhexidine treatment induced profound shifts in microbiota composition and metabolic activity. In some cases, disease associated traits were increased (such as higher abundance of pathobiont strains or shift in high lactate production). Our results highlight the need for alternative treatments that selectively target the disease-associated bacteria in the biofilm without targeting the commensal microorganisms.
A key step toward energy-positive sewage treatment is the development of mainstream partial nitritation/anammox, a nitrogen removal technology where aerobic ammonium-oxidizing bacteria (AerAOB) are desired, while nitrite-oxidizing bacteria (NOB) are not. To suppress NOB, a novel return-sludge treatment was investigated. Single and combined effects of sulfide (0-600 mg S L), anaerobic starvation (0-8 days), and a free ammonia (FA) shock (30 mg FA-N L for 1 h) were tested for immediate effects and long-term recovery. AerAOB and NOB were inhibited immediately and proportionally by sulfide, with AerAOB better coping with the inhibition, while the short FA shock and anaerobic starvation had minor effects. Combinatory effects inhibited AerAOB and NOB more strongly. A combined treatment of sulfide (150 mg S L), 2 days of anaerobic starvation, and FA shock (30 mg FA-N L) inhibited AerAOB 14% more strongly compared to sulfide addition alone, while the AerAOB/NOB activity ratio remained constant. Despite no positive change being observed in the immediate-stress response, AerAOB recovered much faster than NOB, with a nitrite accumulation ratio (effluent nitrite on nitrite + nitrate) peak of 50% after 12 days. Studying long-term recovery is therefore crucial for design of an optimal NOB-suppression treatment, while applying combined stressors regularly may lead toward practical implementation.
The development of viability qPCR (v-qPCR) has allowed for a more accurate assessment of the viability of a microbial sample by limiting the amplification of DNA from dead cells. Although valuable, v-qPCR is not infallible. One of the most limiting factors for accurate live/dead distinction is the length of the qPCR amplicon used. However, no consensus or guidelines exist for selecting and designing amplicon lengths for optimal results. In this study, a wide range of incrementally increasing amplicon lengths (68-906 bp) was used on live and killed cells of nine bacterial species treated with viability dye (PMA). Increasing amplicon lengths up to approximately 200 bp resulted in increasing quantification cycle (Cq) differences between live and killed cells, while maintaining a good qPCR efficiency. Longer amplicon lengths, up to approximately 400 bp, further increased Cq difference, but at the cost of qPCR efficiency. Above 400 bp, no valuable increase in Cq differences was observed. Importance Viability qPCR (v-qPCR) has evolved to a valuable, mainstream technique for determining the number of viable micro-organisms in samples by qPCR. Amplicon length is known to be positively correlated with the ability to distinguish between live and dead bacteria but is negatively correlated with qPCR efficiency. This trade-off is often not taken into account and might have an impact on the accuracy of v-qPCR data. Currently there is no consensus on the optimal amplicon length. This paper provides methods to determine the optimal amplicon length and suggests an amplicon length range for optimal v-qPCR, taking into consideration the trade-off between qPCR efficiency and live-dead distinction.
Physicochemical water disinfection methods result in the reduction of bacterial concentrations by orders of magnitude, but not in the total elimination of the bacterial community. As such, the dead bacterial biomass may act as a carbon and nutrient source for the survivor populations. The ability of bacterial strains to grow on dead bacterial cells has been described before as necrotrophy. We investigated the impact of killed bacterial biomass of two different bacterial strains on the growth potential of natural drinking water microbial communities. Many indigenous bacterial taxa could grow on dead biomass, with the total bacterial concentration increasing from 10 4 to 10 8 cells/ml. Necrotrophic growth was specific (43 enriched taxa) and selective (i.e. enriched taxa were dependent on the type of dead biomass). The potential of natural water communities to grow necrotrophically has remained underexplored. Nevertheless the phenomenon can have a big impact in water quality and deserves more attention.
Objective Chlorhexidine mouthrinses are marketed in different formulations. This study aimed at investigating qualitative and quantitative changes in in‐vitro multispecies oral biofilms, induced by different chlorhexidine‐containing mouthrinses. Background data Earlier studies comparing chlorhexidine mouthrinses are either clinical studies or in‐vitro studies assessing the antimicrobial efficacy of the mouthrinses. However, no clear investigations are available regarding ecological impact of different chlorhexidine formulations on in‐vitro multispecies oral biofilms after rinsing with different chlorhexidine formulations. Methods Nine commercially available chlorhexidine mouthrinses were selected. Multispecies oral communities (14 species) were grown for 48 h in a Biostat‐B Twin bioreactor. After that, they were used to develop biofilms on the surface of hydroxyapatite disks in 24‐well pates for 48 h. Biofilms were then rinsed once or multiple times with the corresponding mouthrinse. Biofilms were collected before starting the rinsing experiment and every 24 h for 3 days and vitality quantitative PCR was performed. The experiment was repeated 3 independent times on 3 different days and the results were analyzed using a linear mixed model. Results The mouthrinses provoked different effects in terms of change in total viable bacterial load (VBL), ecology, and community structure of the multispecies biofilms. There was no relation between chlorhexidine concentrations, presence, or absence of cetylpyridinium chloride and/or alcohol, and the observed effects. Some tested chlorhexidine mouthrinses (MC, HG, HH, and HI) strongly lowered the total VBL (≈1007 Geq/ml), but disrupted biofilm symbiosis (≥40% of the biofilms communities are pathobionts). On the other hand, other tested chlorhexidine mouthrinses (MD, ME, and HF) had limited impact on total VBL (≥1010 Geq/ml), but improved the biofilm ecology and community structure (≤10% of the biofilms communities are pathobionts). Conclusion Not all chlorhexidine mouthrinses have the same effect on oral biofilms. Their effect seems to be strongly product dependent and vary according to their compositions and formulations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.