Odontogenic Infections

The complexity of the oral and gingival flora has prevented the clear elucidation of specific etiologic agents in most forms of oral and dental infections. In the gingival crevice, there are approximately 1.8 X1011 anaerobes per gram (1). Because anaerobic bacteria are part of the normal oral flora and outnumber aerobic organisms by a ratio of 1:10 to 1:100 at this site, it is not surprising that they predominant in dental infections. There are at least 350 morphological and biochemically distinct bacterial groups or species that colonize the oral and dental ecologic sites (1). Most odontogenic infections result initially from the formation of dental plaque (2). Once pathogenic bacteria become established within the plaque, they can cause local and disseminated complications including bacterial endocarditis, infection of orthopedic or other prosthesis, pleuropulmonary infection, cavernous sinus infection, septicemia, maxillary sinusitis, mediastinal infection, and brain abscess (3).

The microorganisms recovered from odontogenic infections generally reflect the host's indigenous oral flora (Table 1) (4). The organisms most commonly isolated are anaerobic streptococci, Capnocytophaga, Actinobacillus, Fusobacterium, Prevotella and Porphyromonas spp. Among the potential pathogens associated with oral and dental infection, the anaerobic black-pigmented gram-negative bacilli received the most attention (5). Porphyromonas gingivalis and Prevotella intermedia appear to be the most frequently isolated from periodontal lesions. Other groups of bacteria are consistently recovered from odontogenic and orofacial infections, suggesting that many pathogens may be capable of producing clinical signs and symptoms of disease (6). Fusobacterium nucleatum has been recovered more often from patients with severe odontogenic infections (7). The difference in recovery of these organisms is influenced by age, underlying systemic disease, and local factors (8). Most pathogens are indigenous to the oral cavity but in the immunocompromised host, bacteria such as Escherichia coli and Bacteroides fragilis can also colonize and cause infection.

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