“The origins of life cannot be dated as precisely, but there is evidence that bacteria-like organisms lived on Earth 3.5 billion years ago, and they may have existed even earlier”—National Academy of Science, 1999. The best estimate for the Earth’s age is about 4.54 billion years, and the first life that populated it was microorganisms less than one billion years later. To put this in perspective, the oldest homo sapiens fossil dates to approximately 300,000 years ago. This precedence of bacteria on Earth allowed them to be a source for energy and sustenance. In other words, they know the “planet” better, and they are fit to manage and utilize its resources to the maximum.

The oral cavity is a major front in the human body where the microbial challenge can be encountered, and interactions take place. Within the human microbiome, which is 10 times higher than the body cell count, oral microbiota carries enormous diversity. More than 700 species and 19,000 phylotypes have been detected in the oral cavity, with more than 500 within the subgingival biofilm. Dental caries and periodontitis are two major oral diseases referred to as oral infectious diseases. The polymicrobial nature of oral diseases has been recognized through decades of microbiological studies; however, our understanding of how these species interact and their synergy and ability to induce a dysbiosis have been poorly understood.

Some early studies revealed a distinction in the microbial profiles of healthy and diseased conditions. Cross-sectional and association studies identified some putative pathogens based on their virulency and strong association with diseased sites. The early interpretation of these findings was that the transition from a healthy to diseased/destructive condition is caused by emergence of specific pathogen/s within oral biofilm. However, current evidence suggests that this transition is due to ecological disruption of the commensal oral biofilm or dysbiosis involving polymicrobial synergy. The complexity of the oral microbiome could be summarized in the multifaceted biology of the microbial component, limitation of microbial profiling in diagnostic tools, and complex host–microbial interaction. In recent years, the development of new technology platforms and the advanced understanding of microbial pathogenicity have paved the way for more sophisticated antimicrobial and specifically antibiotic approaches. This issue aims to cover recent advances in the oral microbiome as well as virulome detection and profiling and the impact of such knowledge in therapy strategies.

Dr. Ahmed El-Awady
Guest Editor

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• oral microbiome
• oral pathobiont
• periodontitis
• biofilms
• dental caries
• next-generation sequencing
• virulome
• oral infectious disease
• antibacterial
• nanoparticles
• multidrug resistance