Infections and Management
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MICROBIOLOGY OF INFECTION
Aerobic bacteria account for 25% of the oral microbiome, anaerobic 75%. Bacteria can be further categorized as gram positive or negative. Recall gram positive bacteria are “positive” to the gram stain test appearing purple in color (absorb crystal violet staining). They have a thick peptidoglycan outer cell wall surrounding a single small periplasmic space and interior plasma membrane. Some have a polysaccharide capsule, and some are flagellates. The S-layer is attached to the peptidoglycan layer. Flagella have two supporting basal body rings.
Gram-negative bacteria do not absorb the violet stain, taking up the counterstain (safranin or fuchsine) appearing pink/red. Instead of a peptidoglycan outer cell wall they have an outer membrane consisting of polysaccharides and proteins which the S-layer is attached to. This lipopolysaccharide layer (LPS) contains lipid A which can cause toxic reactions when released (endotoxin). They have two periplasmic spaces with a relatively thin peptidoglycan layer (cell wall) in between them, and an inner plasma membrane. The outer membrane can provide protection against antibiotics like penicillin, detergents, lysozyme and antimicrobial enzymes. If flagellated, flagella have four supporting rings instead of two.
Typical examples of bacterial cell shape include:
- coccus (circle or spherical)
- bacillus (rod-like)
- coccobacillus (combination of sphere and rod)
- spiral (corkscrew shape)
- filamentous (elongated)
Aerobic bacteria:
- Gram-positive cocci: Streptococcus spp. (mostly α-hemolytic) and Staphylococcus spp.
- Gram-positive rods (Corynebacterium spp.)
- Gram-negative cocci (Neisseria spp.)
- Gram-negative rods (Haemophilus, Eikenella, and Enterobacteriaceae spp.)
Anaerobic bacteria:
- Gram-positive cocci: Streptococcus spp and Peptostreptococcus spp.
- Gram-positive rods: Eubacterium spp., Lactobacillus spp., Actinomyces spp., Clostridia spp.
- Gram-negative cocci (Veillonella spp.)
- Gram-negative rods: Bacteroides spp., Fusobacterium spp.
ODONTOGENIC INFECTIONS
Recall, from the OPERATIVE DENTISTRY module, the pellicle layer is initially seeded with (primarily) aerobic gram-positive species, and transitions towards gram-negative anaerobic as the plaque matures. Subgingival plaque also favors anaerobic bacteria. The end result of untreated caries is pulpal infection and subsequent polymicrobial periapical infection. Streptococcus viridans was the most frequently isolated bacteria among the aerobes, whereas Bacteroides, Fusobacterium, and Prevotella were the most common bacterial species among anaerobes. As an infected area matures (abscess formation) it too pushes towards favoring anaerobic bacteria.
The spread of infection depends on many factors including the virulence of the organism(s), the patient’s immune defense, and the anatomical features adjacent to the infection (bone density, neighboring roots, muscle and ligament/tendon attachment). Infection travels along the path of least resistance. Fascial spaces/tissue spaces are potential areas bounded by anatomical structures (mainly fascia). They are not true spaces, only created by a pathological process. Infection in any of the fascial spaces should be treated as serious.
MAXILLARY FASCIAL SPACES
Maxillary fascial spaces:
- Buccal – bounded anteriorly by the corner of the mouth (modiolus), posteriorly by the angle of the mandible, superiorly by the zygomatic arch, inferiorly by the border of the mandible, laterally by skin and adipose tissue, medially by the buccinator muscle. The bony landmarks of the zygomatic arch and mandible should be palpable in buccal space infection. If not palpable, this could indicate spread past the space boundaries.
- Canine – bounded anteriorly by the orbicularis oris muscle, posteriorly by the buccal space, superiorly by the quadratus labi superioris, inferiorly by the caninus muscle, laterally by the zygomaticus major muscle, medially by the levator labi superioris alaque nasi. An infection in the canine space most likely came from the maxillary canine or first premolar. Infections can spread to and from the buccal space.
- Infratemporal – bounded anteriorly by the the infra-temporal surface of the maxilla, posteriorly by the condyle and the lateral pterygoid muscle, superiorly by the greater wing of the sphenoid bone, inferiorly by the lateral pterygoid muscle, laterally by the temporalis muscle and coronoid process, medially by the lateral pterygoid plate. Infections here result in severe trismus, and can spread to the pterygoid plexus of veins and to the cavernous sinus leading to cavernous sinus thrombosis. The most likely causative tooth is the upper third molar.
MANDIBULAR FASCIAL SPACES
Mandibular fascial spaces:
- Buccal – bounded anteriorly by the corner of the mouth (modiolus), posteriorly by the angle of the mandible, superiorly by the zygomatic arch, inferiorly by the border of the mandible, laterally by skin and adipose tissue, medially by the buccinator muscle. The bony landmarks of the zygomatic arch and mandible should be palpable in buccal space infection. If not palpable, this could indicate spread past the space boundaries.
- Submental – bounded anteriorly by the inferior border of the mandible, posteriorly by the hyoid bone, superiorly by the mylohyoid muscle, inferiorly by the platysma, superficial fascia and skin, laterally by the anterior bellies of the digastric muscles. The submental space communicates with the submandibular space posteriorly. An erosion through the mylohyoid muscle would see it connect to the sublingual space. Infections from mandibular anterior teeth can spread through the cortical bone on the lingual surface on the mandible.
- Sublingual – bounded anteriorly by the mandible, posteriorly by the muscles of the base of the tongue, superiorly by the thin mucosa of the floor of the mouth, inferiorly by the mylohyoid muscle, laterally by the mandible, medially the tongue separates the two sides. Infection can spread posteriorly past the free border of the mylohyoid muscle into the submandibular space, or erode through the mylohyoid muscle into the submental space. An infected tooth with its apex above the mylohyoid attachment can seed a sublingual space infection.
- Submandibular – bounded anteriorly by the mandible, posteriorly by the hyoid bone, superiorly by the mylohyoid muscle, inferiorly platysma, superficial fascia and skin, laterally by the mandible, medially by the anterior belly of the digastric muscle. Medially and anteriorly the submandibular space connects with the submental space, posteriorly it connects with sublingual space along the free border of the mylohyoid bone. Infection can spread inferiorly to the lateral pharyngeal space.
SECONDARY FASCIAL SPACES
Secondary fascial spaces:
- Retropharyngeal
- Pterygomandibular
- Prevertebral
- Superficial and deep temporal
- Masseteric/masticator
- Lateral pharyngeal
The masticator space consists of the pterygomandibular, masseteric, superficial temporal and deep temporal spaces. It is bounded by the buccal space, parotid space, and parapharyngeal space. The masticator space contains the muscles of mastication, ramus and body of the mandible, the trigeminal nerve (CN V), inferior alveolar artery and vein, and pterygoid venous plexus. Masticator space infections are almost always caused by a dental infection, presenting with trismus, pain and swelling.
Ludwig’s angina refers to cellulitis involving the submandibular, sublingual and submental spaces bilaterally. Swallowing can be difficult and the airway can become compromised. Without surgical intervention it can be life threatening. Canine space infections and deep temporal space infections cause cavernous sinus thrombosis (through the ophthalmic vein). Lateral pharyngeal infections can spread to retro pharyngeal and prevertebral spaces which can spread to the mediastinum.
The pterygopalatine fossa is a small space behind and below the orbital cavity lying between the pterygoid plates of the sphenoid bone and the palatine bone. The maxillary branch of the trigeminal nerve and trigeminal artery pass through the pterygopalatine fossa. The pterygopalatine ganglion lies in the pterygopalatine fossa. It communicates:
- Laterally with the infratemporal fossa through the pterygomaxillary fissure.
- Medially with the nasal cavity through the sphenopalatine foramen.
- Posteriorly with the foramen lacerum through the pterygoid canal.
- Anteriorly with the orbit through the inferior orbital fissure.
- Superiorly with middle cranial fossa through foramen rotundum.
MANAGEMENT
The management of odontogenic infections depends on the severity, location, rate of progression, and airway status (severe trismus, dysphagia, dyspnea, dysphonia), signs of systemic infection (fever, malaise, chills, paresthesia etc.) and the quality of the patient’s immune response.
Surgical drainage of an abscess is recommended. This can be accomplished through endodontic treatment or extraction (most commonly) or incision and drainage. The contents of the infection may be cultured to establish which organisms are present and tailor the antibiotic prescription accordingly. This isn’t done routinely but useful when dealing with chronic infections or in patients with compromised immune systems.
Empiric antimicrobial therapy is more commonly followed: selecting the antibiotic most likely to be effective against the anticipated/likely cause of infectious disease.
Antibiotics are commonly used in dental practice, as an addition to appropriate treatment to help the patient’s immune system clear infection. It is not recommended to be used as a primary treatment option. Antibiotics are indicated in dental practice for treating immunocompromised patients (uncontrolled diabetes, cancer, HIV, alcoholic etc.), where there is evidence of systemic infection, and rapid progression of infection.
Penicillin is the drug of choice for treating odontogenic infections since both aerobic and anaerobic organisms are susceptible. A narrow spectrum specific to the offending bacteria is (generally) preferred over a broad spectrum antibiotic to reduce the altering of normal flora and the development of resistant bacteria. Bactericidal antibiotics are preferred to bacteriostatic antibiotics. Empiric antimicrobial therapy for odontogenic infections:
- Penicillin (drug of choice) – Amoxicillin, Augmentin (amoxicillin-clavulanate).
- Clindamycin (drug of choice if allergic to penicillin).
- Azithromycin.
- Clarithromycin.
- Metronidazole (Flagyl).
The cavernous sinus in one of the dural venous sinuses of the head. The internal carotid artery and cranial nerves III, IV, V1, V2, and VI all pass through the blood filled cavernous sinus. Immediately above the carotid sinus lies the optic tract and optic chiasma. A blood clot in this area is called a Cavernous sinus thrombosis and can be a serious medical emergency. The cause is usually infection spreading to this area from the nose, sinuses, ears or teeth (~10%), usually Staphylococcus aureus and Streptococci. Recall the head and neck is drained by valveless veins, allowing for retrograde movement within the vasculature.
There is an anterior route via the angular and inferior ophthalmic veins and a posterior route via the transverse facial vein and the pterygoid plexus of veins. Signs and symptoms include loss of vision, chemosis (swelling/edema of the conjunctiva), exophthalmos, headaches, fever, and disruption of the cranial nerves. Treatment includes broad spectrum intravenous antibiotics and occasional surgical drainage via the sphenoid sinus (sphenoidotomy), followed by a prolonged course (3-4 weeks) of antibiotics.
Sinusitis refers to inflammation in the paranasal sinuses, most commonly the maxillary sinus, and can be triggered by an allergic response or infection. 90% of infection cases are caused by viruses, and generally only palliative treatment is recommended. An acute (less than one month in duration) bacterial infection is often linked with Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Chronic sinusitis lasts for 3 months or more and is seen in cases with obstructed sinus drainage.
Signs and symptoms of maxillary sinusitis include facial pain and pressure (discomfort when tilting head position), blocked nose, nasal discharge, and reduced sense of smell. A fever, halitosis, or toothache can also be seen. Treatment is usually Amoxicillin or Augmentin (in case of bacterial infection), nasal decongestant, antihistamines, and analgesia. Surgery may be required to improve drainage. Maxillary sinusitis can commonly be confused with odontogenic pain due to the innervation of CN V2 and close proximity to teeth. Multiple maxillary molars tender to percussion suggests maxillary sinusitis.
Antibiotic-associated colitis is inflammation of the large intestine caused by an infection, seen when there is a disruption in the normal bacteria after taking antibiotics (amoxicillin, clindamycin), allowing Clostridium difficile to grow. Colitis can lead to diarrhea and abdominal cramping. Treatment: metronidazole or vancomycin.
Osteomyelitis means inflammation of the cancellous/medullary bone. Infection, ischemia and inflammation can all lead to osteomyelitis, which will eventually erode through the cortical bone and spread into surrounding soft tissue. Trauma is the most likely cause of infection, but osteomyelitis is relatively rare (unless immunocompromised), and less likely in the maxilla compared to the mandible. The microbiological profile of osteomyelitis is similar to odontogenic infections. Treatment involves surgical debridement and antibiotics.
ANTIBIOTIC PROPHYLAXIS
Antibiotics can also be used for the prevention of infectious endocarditis. Patients with a prosthetic heart valve, rheumatic heart disease or congenital heart malformation may require antibiotic prophylaxis. Devices that do not involve the endocardium (pacemaker, healed stent etc) do not require antibiotic prophylaxis.
The following guidelines are from the American Dental Association as recommended by the American Hearth Association’s Prevention of Viridans Group Streptococcal Infective Endocarditis paper. These recommendations may change, so keep an eye on any alterations.
Not many patients need antibiotic prophylaxis before dental treatment.
- VGS IE is more likely caused by transient bacteremia from daily activities (e.g., toothbrushing) than from dental procedures.
- Only a very small number of VGS IE cases could potentially be prevented by AP, even if it were 100% effective.
The risk of an adverse reaction to the antibiotics needs to be weighed against the risk of possible infection after the procedure. Drug resistance is also an important issue. Prosthetic joints no longer routinely require a pre-surgical antibiotic regime. Prophylaxis is not suggested for routine dental activities like radiographs, orthodontic adjustments, or shedding of primary teeth.
When indicated, prophylaxis is recommended for any patient who receives dental treatment that involves the manipulation of gingival tissue or the periapical region of the teeth, or perforation of the oral mucosa. The current infective endocarditis/valvular heart disease guidelines state that use of preventive antibiotics before certain dental procedures is reasonable for patients with:
- prosthetic cardiac valves, including transcatheter-implanted prostheses and homografts.
- prosthetic material used for cardiac valve repair, such as annuloplasty rings and chords.
- a history of infective endocarditis.
- a cardiac transplant with valve regurgitation due to a structurally abnormal valve.
- the following congenital (present from birth) heart disease.
- unrepaired cyanotic congenital heart disease, including palliative shunts and conduits.
- any repaired congenital heart defect with residual shunts or valvular regurgitation at the site of or adjacent to the site of a prosthetic patch or a prosthetic device.
- Pulmonary artery valve or conduit placement (e.g., Melody valve).
Important Notes:
- Clindamycin may no longer be recommended for AP due to risks of adverse reactions, including Clostridioides difficile infection.
- Cephalosporins should not be used in individuals with a history of anaphylaxis, angioedema, or urticaria with penicillin or ampicillin.
- IM indicates intramuscular; and IV, intravenous.
