We are the SUPERORGANISMS!Part 3: The Oral Microbiome

oral microbeThe oral cavity or mouth is the major portal into the human body. The food is taken up by the mouth, masticated and mixed with saliva, making its way to the oesophagus and intestinal tract for the process called digestion. The oral cavity or the buccal cavity habours a number of bacterial species. It includes several distinct microbial habitats like teeth, gingival sulcus, tongue, cheeks, lips, hard palate, soft palate, tongue and saliva. The oral microbiome include microorganisms found within the oral cavity to the distal end of the oesophagus. But most of the studies have been obtained from within the oral cavity.

It has been estimated that around 600-700 microbial species inhabit the oral cavity. The oral microbiome majorily includes Streptococci, Neisseria, Veillonella, Actinomyces and other obligate anerobes.These species ehibit mutalistic relationship with their host, preventing other pathogens from adhering to the oral mucosa. The gingival sulcus has the highest concentration of the anerobic species, mainly Spirochaete, Vibrio and S. melaninogenicus. 

Both Gram-negative and Gram-positive bacteria colonise the buccal cavity. Some the common species found are briefed below:

Gram-positive Bacteria

  1. ActinomycesThese are facultative anaerobes that normally inhabit the mouth. They are found in the gum region. In oral cavity they are opportunistic pathogens. Their number increases in gingivitis and are found to be associated with root caries. A. israelli , an opportunistic pathogen, causes Actinomycosis which is marked by the oral abscess and leads to a condition commonly referred to as ‘lumpy jaw’. The infection can also end up in locked jaw, where mouth does not open normally. Antibiotics like  Penicillin, Tetracyclins, Erythromycins are supplemented to curb the infectious state. The best precaution to be taken is a proper oral care and practise good oral hygiene.
  2. Lactobacillus: Lactobacilli species are found in the oral cavity in the early years of a child’s life. In adults they are found in the root caries. They are highly concentrated in the saliva, on the dorsum of the tongue, in the mucuous membrane, in dental plaque and in lesser number on the tooth surface. In general, they are known to have symbiotic relationship with their host and help in preventing the adherence of other pathogenic strains in the buccal cavity. But some strains like L.acidophillus and L.paracasei are known to possess carcinogenic properties.
  3. Streptococci: These are facultative anaerobes that are the majoroty colonizers of the oral cavity. About 25 species have been known to inhabit the mouth. In general they share a commensal relationship with their host but under special circumstances they become pathogenic.  S. mutans and S. sanguinis colonise the dental surface and gingivia. Other species include S.salivarius, S. mitis, S.angiosus.  The species are associated with dental plaques and toothe decay owning to their ability to form biofilms.

Gram-Negative Bacteria

  1. Porphyromonas: P. gingivilis is an anaerobic oral microbe. It is periodontopathic pathogen that is responsible for the inflammatory response and a condition called periodontitis. It is accumulated in and around gingival crevice.The bacterium along with Trepanoma denticola and Tenerella forsythia forms the so called “red complex” , which is strongly associated periodontal destruction. Another species P.endodontalis , anaerobe , also causes peridontitis, endodontic infections , gingivitis and tooth pulp necrosis. It colonises majorly in gingival epithelial cells.
  2. Veillonella: V.parvula  is a strict anaerobe that is normally found in buccal cavity. In general, it is non-pathogenic but have been associated to cause periodontitis.Together with S.mutans it forms biofilms that are known to cause dental plaques. It is susceptible to the antibiotic penicillin.
  3. Actinobacillus actinomycetemcomitans: It is facultative anaerobe and are found in periodontal pocket of the oral cavity. It is most completely studied periodontal bacteria. It is the major cause of periodontitis, bacterial infection of the teeth that ultimately results in tooth loss. It is associates with other oral bacteria to form biofilms.
  4. Trepenoma denticola: It is a motile anaerobic bacteria found in oral cavity, concentrated in subgingival dental plaque. It is associated periodontal disease and gum inflammation. It also interacts with other oral microflora to form biofilms.

These are some of the studied bacterial populatioin found in the oral cavity and the diseases associated with them. The most given advice by the dentists to keep away the pathogenic strains is to maintain a good and healthy oral hygiene and avoiding high sugar content food supplements.


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