The flora of the nose consists of prominent corynebacterial, staphylococci (S. epidermidis, S. aureus), and streptococci.

In direct contrast to the highly differentiated communities of their mothers, neonates harbored bacterial communities that were undifferentiated across multiple body habitats, regardless of delivery mode. Thus, at its earliest stage of community development (<5 minutes postdelivery), the human microbiota is homogeneously distributed across the body. Vaginally delivered infants harbor bacterial communities (in all body habitats) that are most similar in composition to the vaginal communities of the mothers; C-section babies lack bacteria from the vaginal community (eg, Lactobacillus, Prevotella, Atopobium, and Sneathia spp.). Infants delivered via C-section harbor bacterial communities (across all body habitats) that are most similar to the skin communities of the mothers (eg, Staphylococcus, Corynebacterium, or Propionibacterium spp.).

Within 4–12 hours after birth, viridans streptococci become established as the most prominent members of the resident flora and remain so for life. These organisms probably originate in the respiratory tracts of the mother and attendants. Early in life, aerobic and anaerobic staphylococci, Gram-negative diplococci (neisseriae, Moraxella catarrhalis), diphtheroids, and occasional lactobacilli are added. When teeth begin to erupt, the anaerobic spirochetes, Prevotella species (especially Prevotella melaninogenica), Fusobacterium species, Rothia species, and Capnocytophaga species (see below) establish themselves along with some anaerobic vibrios and lactobacilli. Actinomyces species are normally present in tonsillar tissue and on the gingivae in adults, and various protozoa may also be present. Yeasts (Candida species) occur in the mouth.

In the pharynx and trachea, a similar flora establishes itself, but few bacteria are found in normal bronchi. Small bronchi and alveoli are normally sterile. The predominant organisms in the upper respiratory tract, particularly the pharynx, are nonhemolytic and α-hemolytic streptococci and neisseriae. Staphylococci, diphtheroids, haemophili, pneumo cocci, mycoplasmas, and prevotellae are also encountered.

More than 600 different microbial species have been described from the human oral cavity, but only limited information is available on the normal microbiota of healthy individuals. The human oral microbiome, as represented by the human salivary microbiome, was characterized in samples obtained from 120 healthy individuals from 12 worldwide locations by 16S rRNA sequencing. There is considerable diversity in the saliva microbiome, both within and among individuals; however, it does not vary substantially around the world. The 16S rRNA sequences could be assigned to 101 known bacterial genera, of which 39 were not previously reported from the human oral cavity; phylogenetic analysis suggests that an additional 64 unknown genera are also present.

Infections of the mouth and respiratory tract are usually caused by mixed oronasal flora, including anaerobes. Periodontal infections, perioral abscesses, sinusitis, and mastoiditis may involve predominantly P. melaninogenica, Fusobacterium spp., and Peptostreptococcus spp. Aspiration of saliva (containing up to 102 of these organisms and aerobes) may result in necrotizing pneumonia, lung abscess, and empyema.

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مواضيع ذات صلة

Rickettsia

The Role of the Normal Mouth Microbiota in Dental Plaque and Caries

Normal Microbiota of the Skin

Role of the Resident Microbiota

Actinomyces israelii

Mycobacterium leprae

Mycobacterium tuberculosis

Bacterial Virulence Factors : Toxins

Laboratory Diagnosis of Vibrio, Aeromonas, Chromobacterium, and Related Organisms

Pathogenesis and Spectrum of Disease of Vibrio, Aeromonas, Chromobacterium, and Related Organisms

Laboratory Diagnosis of Alcaligenes, Bordetella (Non-pertussis), Comamonas, and Similar Organisms

Antimicrobial Susceptibility Testing and Therapy of Rhizobium, Ochrobactrum, and Similar Organisms