Evaluation of a biofilm formation by Desulfovibrio fairfieldensis on titanium implants

Microbial corrosion of metallic biomaterials in the oral environment

A wide variety of microorganisms have been closely linked to metal corrosion in the form of adherent surface biofilms. Biofilms allow the development and maintenance of locally corrosive environments and/or permit direct corrosion including pitting corrosion. The presence of numerous genetically distinct microorganisms in the oral environment poses a threat to the integrity and durability of the surface of metallic prostheses and implants used in routine dentistry. However, the association between oral microorganisms and specific corrosion mechanisms is not clear. It is of practical importance to understand how microbial corrosion occurs and the associated risks to metallic materials in the oral environment. This knowledge is also important for researchers and clinicians who are increasingly concerned about the biological activity of the released corrosion products. Accordingly, the main goal was to comprehensively review the current literature regarding oral microbiologically influenced corrosion (MIC) including characteristics of biofilms and of the oral environment, MIC mechanisms, corrosion behavior in the presence of oral microorganisms and potentially mitigating technologies. Findings included that oral MIC has been ascribed mostly to aggressive metabolites secreted during microbial metabolism (metabolite-mediated MIC). However, from a thermodynamic point of view, extracellular electron transfer mechanisms (EET-MIC) through pili or electron transfer compounds cannot be ruled out. Various MIC mitigating methods have been demonstrated to be effective in short term, but long term evaluations are necessary before clinical applications can be considered. Currently most in-vitro studies fail to simulate the complexity of intraoral physiological conditions which may either reduce or exacerbate corrosion risk, which must be addressed in future studies. STATEMENT OF SIGNIFICANCE: A thorough analysis on literature regarding oral MIC (microbiologically influenced corrosion) of biomedical metallic materials has been carried out, including characteristics of oral environment, MIC mechanisms, corrosion behaviors in the presence of typical oral microorganisms and potential mitigating methods (materials design and surface design). There is currently a lack of mechanistic understanding of oral MIC which is very important not only to corrosion researchers but also to dentists and clinicians. This paper discusses the significance of biofilms from a biocorrosion perspective and summarizes several aspects of MIC mechanisms which could be caused by oral microorganisms. Oral MIC has been closely associated with not only the materials research but also the dental/clinical research fields in this work.

Phytogenic supplement containing menthol, carvacrol and carvone ameliorates gut microbiota and production performance of commercial layers

Consumer push towards open and free-range production systems makes biosecurity on farms challenging, leading to increased disease and animal welfare issues. Phytogenic products are increasingly becoming a viable alternative for the use of antibiotics in livestock production. Here we present a study of the effects of commercial phytogenic supplement containing menthol, carvacrol and carvone on intestinal microbiota of layer hens, microbial functional capacity, and intestinal morphology. A total of 40,000 pullets were randomly assigned to two sides of the experimental shed. Growth performance, mortality, egg production and egg quality parameters were recorded throughout the trial period (18–30 weeks of age). Microbial community was investigated using 16S amplicon sequencing and functional difference using metagenomic sequencing. Phytogen supplemented birds had lower mortality and number of dirty eggs, and their microbial communities showed reduced richness. Although phytogen showed the ability to control the range of poultry pathogens, its action was not restricted to pathogenic taxa, and it involved functional remodelling the intestinal community towards increased cofactor production, heterolactic fermentation and salvage and recycling of metabolites. The phytogen did not alter the antimicrobial resistance profile or the number of antibiotic resistance genes. The study indicates that phytogenic supplementation can mimic the action of antibiotics in altering the gut microbiota and be used as their alternative in industry-scale layer production.

In Vitro Bactericidal Efficacy of Nanostructured Ti6Al4V Surfaces is Bacterial Load Dependent

The demand for medical implants globally has increased significantly due to an aging population amongst other reasons. Despite the overall increase in the survivorship of Ti6Al4V implants, implant infection rates are increasing due to factors such as diabetes, obesity, and bacterial resistance to antibiotics. Two commonly found bacteria implicated in implant infections are Staphylococcus aureus and Pseudomonas aeruginosa. Based on prior work that showed nanostructured surfaces might have potential in passively killing these bacterial species, we developed a hierarchical, hydrothermally etched, nanostructured titanium surface. To evaluate the antibacterial efficacy of this surface, etched and as-received surfaces were inoculated with S. aureus or P. aeruginosa at concentrations ranging from 10² to 10⁹ colony-forming units per disc. Live/dead staining revealed there was a 60% decrease in viability for S. aureus and greater than a 98% decrease for P. aeruginosa on etched surfaces at the lowest inoculum of 10² CFU/disc, when compared to the control surface. Bactericidal efficiency decreased with increasing bacterial concentrations in a stepwise manner, with decreases in bacterial viability noted for S. aureus above 10⁵ CFU/disc and above 10⁶ CFU/disc for P. aeruginosa. Surprisingly, biofilm depth analysis revealed a decrease in bacterial viability in the 2 μm layer furthest from the nanostructured surface. The nanostructured Ti6Al4V surface developed here holds the potential to reduce the rate of implant infections.

Assessing the Potential Association Between Microbes and Corrosion of Intra-Oral Metallic Alloy-Based Dental Appliances Through a Systematic Review of the Literature

Objective: Systematic review assessing the association between oral microorganisms and corrosion of intra-oral metallic alloy-based dental appliances. Design: PubMed, Scopus, and Web of Science were searched using keyword combinations such as microbes and oral and corrosion; microbes and dental and corrosion; microorganisms and oral and corrosion; microorganisms and dental and corrosion. Results: Out of 141 articles, only 25 satisfied the selection criteria. Lactobacillus reuteri, Streptococcus mutans, Streptococcus sanguis, Streptococcus mitis, Streptococcus sobrinus, Streptococcus salivarius, sulfate-reducing bacteria, sulfate oxidizing bacteria, Veilonella, Actinomyces, Candida albicans were found to have a potential association with corrosion of intraoral metallic alloys such as stainless steel, titanium, nickel, cobalt-chromium, neodymium-iron-boron magnets, zirconia, amalgam, copper aluminum, and precious metal alloys. Conclusion: The included studies inferred an association between oral microorganisms and intra-oral metallic alloys-based dental appliances, although, it is vital to acknowledge that most studies in the review employed an in-vitro simulation of the intra-oral condition.

Biocorrosive behavior of sulphate-reducing bacteria in kerr endodontic files: Determination of the corrosion

Aims:

This study determined the corrosion rate by mass loss caused by oral strains of sulphate-reducing bacteria (SRB) in Kerr endodontic files (KF), aiming the development of a biopharmaceutical that facilitates the removal of endodontic limb fragments from root canals.

Materials and Methods:

Nine new KF were analyzed after immersion in the modified Postgate E culture medium inoculated with Desulfovibrio desulfuricans oral (84 days), Desulfovibrio fairfieldensis in the consortium (84 days) and environmental D. desulfuricans (119 days).

Results:

Optical microscopy revealed corrosion suggestive areas in all files submitted to immersion in SRB cultures, presenting a statistical difference (P < 0.05) between the samples environmental D. desulfuricans and KF control and between oral D. desulfuricans and KF control. Epifluorescence microscopy revealed an active SRB biofilm over the entire metal surface of the KF, as evidenced by the SYTO^® 9 fluorophore.

Conclusion:

SRB were capable of promoting biocorrosion in Kerr type endodontic files, but with low rate.

Initial stage of the biofilm formation on the NiTi and Ti6Al4V surface by the sulphur-oxidizing bacteria and sulphate-reducing bacteria

The susceptibility to the fouling of the NiTi and Ti6Al4V alloys due to the adhesion of microorganisms and the biofilm formation is very significant, especially in the context of an inflammatory state induced by implants contaminated by bacteria, and the implants corrosion stimulated by bacteria. The aim of this work was to examine the differences between the sulphur-oxidizing bacteria (SOB) and sulphate-reducing bacteria (SRB) strains in their affinity for NiTi and Ti6Al4V alloys. The biofilms formed on alloy surfaces by the cells of five bacterial strains (aerobic SOB Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans, and anaerobic SRB Desulfovibrio desulfuricans-3 strains) were studied using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The protein concentrations in liquid media have also been analyzed. The results indicate that both alloys tested may be colonized by SOB and SRB strains. In the initial stage of the biofilm formation, the higher affinity of SRB to both the alloys has been documented. However, the SOB strains have indicated the higher (although differentiated) adaptability to changing environment as compared with SRB. Stimulation of the SRB growth on the alloys surface was observed during incubation in the liquid culture media supplemented with artificial saliva, especially of lower pH (imitated conditions under the inflammatory state, for example in the periodontitis course). The results point to the possible threat to the human health resulting from the contamination of the titanium implant alloys surface by the SOB (A. thiooxidans and A. ferrooxidans) and SRB (D. desulfuricans).