Upper respiratory tract flora. Normal oral flora contains the microorganisms usually present in the saliva and on the surfaces of oral tissues in healthy, immune competent individuals who have not been exposed to agents that alter the composition of oral organisms. A
complete description of this flora can be found in Chapter 15. In brief, normal oral flora consists of aerobic, gram-positive cocci (primarily streptococci), actinomysetes, anaerobic bacteria, and candidal species (Table 5-1). The total number of oral organisms is held in check
by the following four main processes: (1) rapid epithelial turnover with desquamation; (2) host immunologic factors, such as salivary IgA; (3) dilution by salivary flow and (4) competition between oral organisms for. available nutrients. and attachment sites. Any agent-physical, biologic,
or chemical-that alters any of the forces that keep oral microbes under control will permit potentially pathologic organisms to overgrow and set the stage for a wound infection.
The flora of the nose and paranasal si-nuses consists primarily of gram-positive aerobic streptococci and anaerobes. In addition, many children harbor Haeino-
Normal MicroBiologic Flora
phiiu: inttuenzuv bacteria in these areas. and many adults have Smpnylococcus aurcus as a part of their transient or resident nasal and paranasal sinus flora. The normal flora in this region of the body is limited by the presence of ciliated respiratory epithelium, secretory Imrnunoglobultns. and epithelial desquamation. The epithelial cilia mow
‘organisms trapped in blankets of mucus into the alimentary tract. •
MaxillolciaL skill flora, The skin of the maxillofacial region has surprtstngly few resident organisms in its normal flora. The bacteria Staphylococcus epidermicis and Corynebacterium dipttttierlac are the predominant species present. Propionibacterium awes is found in pores and hair
follicles, and many individuals carry S. aurcus, spread from thefr nose, on their facial skin (see Table 5-1).
The skin has several means of preventing surface organisms from entering. The most superficial layer of skin is comprised of keratinized epithelial cells able to resist mild trauma. In addition, epithelial cells are [oined
by tight bonds that resist bacterial entrance. Processes such. as the application of occlusive dressings (which prevent skin desiccation and desquamation), as well as dirt or dried blood (which provide increased nutrients for organisms) and antimicrobial agents (which disturbs the
balance between various organisms) alter skin flora.
Noninaxillofacial flora. The flora below the region of the clavicles comprises a gradually increasing number of aerobic gram-negative and anaerobic enteric organisms, especially moving toward the pelvic region and unwashed fingertips. General knowledge of these bacteria
is important for dental surgeons when preparing themselves for surgery-and when treating patients requiring venipuncture or other procedures away from the orofacial region.