Antimicrobial Treatment Options in the Management of Odontogenic Infections

Antimicrobial Treatment Options In the Management Of Odontogenic Infections G.K.B. Sandor, DDS, MD, FRCD(C), FRCS(C), FACS D.E. Low, MD, FRCP(C) P.L. Judd, B.Sc., DDS, M.Sc., Dip. Pedo. R.J. Davidson, PhD Most acute orofacial infections are of odontogenic origin. In normal hosts, however, they usually do not occur without some type of predisposing condition. Early recognition and management of acute orofacial infections is critical, because rapid systemic involvement can occur, especially in children. Antimicrobial therapy has an essential role in the management of these infections. If it is initiated before surgery, it can shorten the period of infection and minimize associated risks. The etiology of odontogenic infections is usually attributed to the endogenous flora of the mouth, and not to the introduction of non-resident bacteria. Odontogenic infections are typically polymicrobial; however, anaerobes generally outnumber aerobes by at least four fold. The penicillins have historically been used as the first-line therapy in these cases, but increasing rates of resistance have lowered their usefulness. Bacterial resistance to this class of agents is predominately achieved through the production of ß-lactamases. Clindamycin, because of its broad spectrum of activity and resistance to ß-lactamase degradation, is an attractive first-line therapy in the treatment of odontogenic infections. Introduction | Methods | Odontogenic Infections | Microbiology | Antimicrobial Therapy |Summary | Acknowledgments | References ] Introduction Most acute orofacial infections are of odontogenic origin. 1 The majority of odontogenic infections are self limiting, and may drain spontaneously. However, these infections may drain into the anatomical spaces adjacent to the oral cavity and spread along the contiguous fascial planes, leading to more severe infection.1 Due to the proximity of the central nervous system and critical respiratory passages, timely efforts are required to establish a patent airway, mechanical debridement and drainage, and appropriate antimicrobial therapy.2 This article will focus on the etiology of odontogenic infections, and the antimicrobial therapy used to treat them. [ Top ] Methods

The content of this review was discussed during a meeting of specialists in pediatric dentistry, oral and maxillofacial surgery, infectious diseases, and microbiology (Toronto, 1997). Current information concerning the etiology, antimicrobial treatment, and antimicrobial resistance of odontogenic infections from 1990 to the present was obtained using a MEDLINE search. Key search phrases included odontogenic and infection, etiology, treatment, antibiotics, and resistance. Expert opinion and observations concerning the changing behavior of odontogenic infections were included where published data was lacking. [ Top ] Odontogenic Infections Odontogenic infections are among the most common infections of the oral cavity. They can be caused by dental caries, deep restorations that approximate the pulp chamber, pulpitis, periapical abscess, periodontitis, periodontal abscess, and pericoronitis. Odontogenic infections may develop into osteoperiostitis of the jaw, osteomyelitis, and deep fascial space infections. In normal hosts, acute odontogenic infections usually do not occur without some type of predisposing condition, such as periodontal accumulations, necrotic pulp tissue, or tissue damage associated with trauma or surgery. The increasing rates of antimicrobial resistance are well recognized and described in the literature. However, there is some evidence to suggest that virulence has also changed in some bacteria.3 The epidemic of Brazilian purpuric fever in 1990, which was associated with a new clonal variation of Haemophilus influenzae, and the more recent devastating invasive infections caused by group A Streptococcus provide convincing evidence of this.3 There has also been a notable change in the behavior of odontogenic infections at our institutions. The inappropriate and increased use of resin restorations in the pediatric population has caused severe odontogenic infections to become an apparent and growing problem in this group.4Furthermore, the severity of these infections in the adult population is far greater than in the past, with a more rapid and dramatic spread through the fascial planes surrounding the airways. This change has necessitated the use of CT scans to diagnose and determine the extent of severe odontogenic infections, as well as the more frequent use of a lifesaving surgical airway such as a tracheotomy, and broader incision and drainage techniques. The length of hospitalization for patients with these infections has also increased. Late referral makes the treatment of such patients more precarious. Dentists must therefore be prepared to refer their patients in a timely and appropriate manner. It is important for the dentist to develop an algorithm, or organized approach, when dealing with odontogenic infections (Fig. 1).

Click to see the larger image Fig 1: Algorithm for selecting antimicrobial therapy and referal to specialist. This approach should include the use of appropriate first-line antimicrobial therapy, and timely referral to a specialist if the results of such therapy are less than ideal. This will minimize potentially catastrophic and lethal complications such as airway obstruction and/or mediastinitis. Although severe odontogenic infections are surprisingly common in the young child, there is a paucity of papers on the management of this patient group. 4 Early management of these infections is essential because of the rapid systemic involvement that can occur, especially in children. Consequently, all infections should be treated as emergent or at least urgent. [ Top ] Microbiology The microbial flora of the oral cavity contains a complex population of microorganisms. In fact, the oral cavity is unique in that it cannot be regarded as a single uni-form environment, and resident microorganisms can be cultured from most areas of the mouth. However, certain sites such as the tongue, tooth surfaces, and gingival crevice tend to favor colonization by specific microorganisms. Odontogenic infections are usually attributed to the endogenous flora of the mouth, and not to the introduction of non-resident bacteria. An important feature of suppurative odontogenic infections is that they are typically polymicrobial in nature, with mixed aerobic and anaerobic bacteria present. 7-9 However, the anaerobes generally outnumber the aerobic bacteria by a factor of three to four fold.2,5,6 The mixed aerobic-anaerobic composition of the bacteria involved in suppurative odontogenic infections is thought to be important in the pathogenesis of infection. Barclay reported that if bacteria involved in mixed odontogenic infections are isolated in pure culture and transferred to healthy animals, they are often incapable of producing disease.10 Thus, a synergistic interdependence be-tween aerobic and anaerobic bacteria is thought to be necessary for the development of infection. Essentially, the respiration of aerobic bacteria depletes the local environment of oxygen, creating an oxygen-poor, nutrient-rich habitat suitable for anaerobic growth. Once anaerobiosis is achieved, anaerobes proliferate, secreting toxins and enzymes that result in tissue destruction and abscess formation.

The predominant bacterial species isolated from odontogenic infections are listed in Table I. Streptococcus (anaerobic), Peptostreptococcus, Veillonella, Lactobacillus, and Actinomyces account for approximately 80 per cent of the total cultivable microflora in the healthy oral cavity.11,12 Streptococcus spp account for approximately 95 per cent of the aerobic and facultative organisms colonizing the oral cavity. Aerobic gram negative bacilli are uncommon in healthy adults, but occur more frequently in hospitalized patients and the elderly.12 The microflora's bacterial composition is slightly different in patients with healthy tissue and patients with dental caries, gingivitis, and periodontitis. Streptococcus mutans' role in dental caries has been well established. 13,14 With gingivitis and periodontitis, the predominant subgingival flora shifts to a greater proportion of anaerobic gram negative bacilli.15 In patients with pericoronitis, the predominant species recovered are Peptostreptococci, Fusobacterium, and Bacteroides, while Prevotella intermedia, Fusobacterium, and Capnocytophaga are frequently recovered from periodontal abscesses.9,16,17 Heimdahl et al examined orofacial infections and correlated their clinical appearance with the observed microbial etiology.17 Anaerobic gram negative rods (Bacteroides, Prevotella, Fusobacterium) were more frequently isolated from patients with severe infections than from those deemed to have mild infections (p