Ontogenesis of Normal Oral Microflora

Bacterial entry to newborn’s oral cavity occurs initially at the time of delivery. Primary oral microflora is composed of lactobacilli, enterococci, micrococci, staphylococci and some others. In first weeks these casual microorganisms will be displaced by certain bacterial species inhabiting maternal oral cavity. Likewise, medical personnel of obstetrics care settings becomes the next source of microbial contamination. Aerobic and facultatively anaerobic microflora dominates in newborn’s oral cavity. Among them are streptococci, lactobacilli, neisseriae and candida fungi. Their total count rises up to 4th month of life; then it gradually declines. Initial amount of anaerobic bacteria is very low (veillonellas, fusobacteria, and some others). Usually they stay within the folds of oral mucous membranes.

Dentition creates new opportunities for anaerobic bacteria propagation. Anaerobes begin to spread throughout the all compartments of oral cavity. At puberty the number of anaerobic bacteria arises; bacteroids, prevotellas and spirochetes become typical this time.

In elderly people with multiple comorbidity and lowered immunity the composition of normal oral microflora is profoundly altered. The number of staphylococci as well as candida fungi elevates substantially; E. coli and enterococci can be found. The presence of removable dental prosthetic devices facilitates the shift in microbial composition resulting in emergence of prosthetic stomatitis. The plaques made of settled microorganisms and organic matrix under partial dentures accumulate acidic substances that favor candidal propagation. Oral candidiasis in patients with dental prostheses can occur in more than 70% of cases. In these situations candidae may spread from initial colonization site towards any oral compartment. In fact, they cause angular stomatitis when located in angulus oris.

Similarly, the bacteria colonizing oral cavity, can afflict airways and gastrointestinal tract.