Chlorhexidine digluconate mouthwash alters the oral microbial composition and affects the prevalence of antimicrobial resistance genes.

Introduction: Chlorhexidine (CHX) is a commonly used antiseptic in situations of limited oral hygiene ability such as after periodontal surgery. However, CHX is also considered as a possible factor in the emergence of cross-resistance to antibiotics. The aim of this study was to analyze the changes in the oral microbiota and the prevalence of antimicrobial resistance genes (ARGs) due to CHX treatment. Materials and methods: We analyzed the oral metagenome of 20 patients who applied a 0.2% CHX mouthwash twice daily for 4 weeks following periodontal surgical procedures. Saliva and supragingival plaque samples were examined before, directly after 4 weeks, and another 4 weeks after discontinuing the CHX treatment. Results: Alpha-diversity decreased significantly with CHX use. The Bray-Curtis dissimilarity increased in both sample sites and mainly streptococci showed a higher relative abundance after CHX treatment. Although no significant changes of ARGs could be detected, an increase in prevalence was found for genes that encode for tetracycline efflux pumps. Conclusion: CHX treatment appears to promote a caries-associated bacterial community and the emergence of tetracycline resistance genes. Future research should focus on CHX-related changes in the microbial community and whether the discovered tetracycline resistance genes promote resistance to CHX.

Antimicrobial therapy using VIS plus water-filtered infrared-A as an alternative method to treat oral diseases.

Oral biofilm is the main cause of pathologies affecting the hard and soft oral tissues around teeth. Its main components are the periodontal pathogens and other bacteria of the supragingival and subgingival biofilm. Different alternative strategies that could be adjuvants to the usual periodontal treatments used to eliminate biofilms are available. One of these methods is antimicrobial photodynamic therapy using VIS and water-filtered infrared-A combined with a photosensitizer. In this review, different recent studies were collected to evaluate the antimicrobial effects of antimicrobial photodynamic therapy and the effectiveness of different types of photosensitizers.

This review summarizes different types of photodynamic therapy, a type of treatment that uses light to kill cells, which can be used to decontaminate the mouth and teeth. There are many bacteria in our mouths and on the surface of our teeth that can cause infections, such as dental caries, periodontitis and peri-implantitis. This review also looks at how effective these treatments are and suggests the use of clinical trials to confirm our findings.

Metallibacterium scheffleri: genomic data reveal a versatile metabolism.

This study describes the physiological properties of the widespread and recently described acid-tolerant microorganism Metallibacterium scheffleri DKE6. Despite that casitone was reported to be the only growth substrate of the organism, using a combination of proteomic, genomic and transcriptomic approaches as well as microbiological assays, we could identify a rather versatile metabolism. The detected casein hydrolysis was corroborated by the detection of proteases in the supernatant of the organism as well as in transcriptome studies. Genomic analysis identified amino acid auxotrophies, which were revealed as the reason for the observed growth deficiency with other substrates in the absence of casein. It was verified that glucose could serve as a growth substrate in the presence of amino acids as building blocks, a finding that was supported by the detection of three glycolytic pathways. Additionally, genes for sulfur and hydrogen oxidation were found, and sulfate formation could be shown during growth with tetrathionate. Metallibacterium scheffleri is able to raise the pH in acidic environments via ammonium production. Overall, the distribution of related Metallibacterium species demonstrates an adaption of this genus to diverse environments with varying pH values. Growth in biofilms or sediments also seems to be a common trait. We hypothesize that this biofilm growth supports the ability of Metallibacterium species to adapt to different pH values via formation of pH microniches.