Infections Related to the Upper and Middle Airways

Etiologic Agents

Cultures of aspirates from peritonsillar abscesses often yield polymicrobial growth of aerobic and anaerobic bacteria. Streptococcus pyogenes is the most commonly isolated aerobic bacterium. ^, Further aerobic organisms that have been isolated are other β-hemolytic streptococci such as group B, C, G and F streptococci, α-hemolytic (viridans) streptococci, Staphylococcus aureus , Haemophilus influenzae and parainfluenzae , and less frequently, Arcanobacterium haemolyticum, S. pneumoniae, Moraxella catarrhalis, as well as Neisseria and Enterococcus species. ^, Anaerobic bacteria, including Fusobacterium , Prevotella , Bacteroides , Peptostreptococcus , Porphyromonas , and Veillonella species, are further frequent isolates. ^, Gram negative rods have been found in rare cases. ^{, ,}

Synergy between bacteria likely plays a role in the formation of peritonsillar abscesses; for example, aerobic bacteria such S. pyogenes can lower the redox potential, thus creating an anaerobic environment for the growth of Fusobacterium necrophorum and other anaerobic bacteria. Conversely, F. necrophorum can produce growth factors and leukotoxins which help other bacteria to grow and protect them from phagocytosis.

Tonsils are heavily and diversely colonized, making the distinction between a true pathogen and a colonizing organism difficult. Contamination of the aspirate can occur as the needle passes through the mucosal surface and peritonsillar tissue. Many bacteria that are isolated from peritonsillar abscesses are also isolated in cultures from tonsils removed for hypertrophy. A study comparing culture results from patients with peritonsillar abscess with those from patients undergoing elective tonsillectomy found that only S. pyogenes, S. aureus, and Fusobacterium species were isolated more frequently from tonsils and pus in patients with peritonsillar abscess. However, peritonsillar abscess starts with surface ulceration of the tonsils and lymphatic transit of bacteria towards the capsule, so it is not surprising that bacteria from the oral flora are isolated commonly.

More than half of all patients with peritonsillar abscess receive antibiotics before aspiration/drainage; ^{, , ,} Depending on the antibiotic agent, this can lower the detection rate of S. pyogenes and increase recovery rates of anaerobes, for example F. necrophorum , which should be taken into account when interpreting culture results . ^{, ,}

Viral tonsillitis, which can be caused by Epstein-Barr virus (EBV) or adenovirus, predisposes a patient to bacterial superinfections. For EBV infection, an association with the development of peritonsillar abscess has been described. In vitro studies have shown that EBV decreases bacterial coating with lactoferrin, lysozyme, and immunoglobulin A. ^,

Epidemiology and Pathogenesis

The peak incidence of peritonsillar abscess is during adolescence and early adult life. ^{, , , , , , ,} However, although uncommon, peritonsillar abscess can occur in very young children, including infants. An apparent increase in the incidence has been reported recently. ^, Males are more commonly affected, except in the age group of 0–9 years. ^, F. necrophorum is isolated more commonly in patients aged 15–24 years, while S. pyogenes is found at similar rates throughout all age groups. No seasonal pattern in the incidence of peritonsillar abscesses has been observed. ^{, ,} Smoking is a risk factor for the development of peritonsillar abscess.

Peritonsillar abscess traditionally has been regarded invariably to be the result of extension of acute exudative pharyngotonsillitis. However, some evidence suggests this condition can also result from abscess formation within Weber glands, which are small salivary glands located in the supratonsillar fossa. Tissue scarring or blockage of the ducts of Weber glands likely increase the risk of abscess formation. Furthermore, it has also been proposed that dental infections might play a role in the etiology of peritonsillar infections. ^, An association between periodontal disease and the development of peritonsillar abscess has also been described. ^{, ,}

Clinical Manifestations and Diagnosis

The patient almost invariably comes to medical attention with severe sore throat and odynophagia, ^{, ,} which can lead to decreased oral intake and dehydration. The patient may also be unable to swallow saliva, which results in drooling. Fever is reported in the majority of cases, but is not universal. Common clinical signs include trismus, tonsillar exudate, peritonsillar swelling, uvula edema and deviation towards the contralateral tonsil, muffling of the voice (“hot potato voice”), and cervical lymphadenopathy. ^{, , ,} Uvular deviation and trismus can help to distinguish peritonsillar abscess from pharyngotonsillitis, as these findings are not usually present in the latter. ^{, ,} Bilateral disease is rare but can be more difficult to diagnose as the typical asymmetry is absent. ^{, ,} When drooling is present, epiglottitis needs to be considered in the differential diagnosis, and examination of the oral cavity should be performed in a setting that allows emergency intubation.

Inflammatory markers, including white blood cell (WBC) count, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR), are usually elevated. ^{, ,} Imaging is not generally necessary to make the diagnosis. However, in cases where there is doubt, transcutaneous or intraoral ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) with contrast can be useful for confirmation. ^{, ,} Although MRI is more sensitive for soft tissue and vascular changes, it takes longer and requires sedation in young children, which is problematic in children with potential airway compromise. CT is often preferred; a peritonsillar abscess appears as a hypodense mass with ring enhancement. An important differential diagnosis of peritonsillar abscess is acute peritonsillitis, where the infection has spread from the tonsils to the peritonsillar tissue without abscess formation.

Management

There is an increasing trend towards non-surgical management of peritonsillar abscesses; ^, two large studies report over 20,000 children and adults who were successfully treated with antibiotics alone. ^, A further, smaller study showed no difference in treatment success or complication rates between patients who were managed with antibiotics alone compared with drainage. The non-surgical group had lower use of analgesia and fewer days with pain. In another study which investigated recurrence rates, recurrence was less common in patients treated with antibiotics alone compared with those managed with incision and drainage.

A trial of antibiotic treatment can be considered in children without signs of respiratory compromise, severe trismus, sepsis, or other complications. If there is no improvement after 24–48 hours of treatment or the course worsens, surgery should be performed. ^, Surgical options for management of peritonsillar abscess are needle aspiration, incision and drainage, and tonsillectomy. ^, Pus obtained during the procedure should be sent for Gram stain as well as aerobic and anaerobic culture. The choice of the intervention partly depends on the size and location of the abscess (e.g., difficulty of aspiration of the lower tonsillar pole), patient cooperation, and the locally available expertise. There are currently no convincing data to suggest that one approach is superior to another. ^, Incision and drainage has a slightly higher initial success rate compared with needle aspiration, which sometimes requires multiple attempts for adequate abscess decompression. ^{, ,} However, incision and drainage is considered to be more painful. Tonsillectomy is regarded as the most definitive treatment and is potentially associated with lower recurrence rates in children who suffer from recurrent tonsillitis. However, tonsillectomy is associated with increased length of hospital stay, increased cost, and increased risk of postoperative hemorrhage and is therefore not performed routinely. ^, There is no difference in outcome between patients who are managed with tonsillectomy during acute infection (“quinsy tonsillectomy”) or after convalescence (“interval tonsillectomy”), although the latter has the disadvantage of requiring a second hospitalization. Data from a retrospective nationwide study of >20,000 children with peritonsillar abscess admitted to US hospitals show that one-half were managed conservatively, while incision and drainage was performed in approximately one-third of cases; fewer than 20% underwent tonsillectomy.

There is no consensus regarding the optimal choice for empiric antibiotic treatment for peritonsillar abscess, but sufficient coverage should be provided for anaerobic and β-lactamase-producing bacteria. Regimens that are recommended include penicillin plus metronidazole, a second- or third-generation cephalosporins plus clindamycin or metronidazole, amoxicillin-clavulanate with or without metronidazole, ampicillin-sulbactam, ticarcillin-clavulanate, or clindamycin. ^{, , , , ,} In patients with moderate to severe disease who do not respond to initial treatment, addition of vancomycin or linezolid should be considered to cover resistant gram-positive bacteria. However, since the differentiation between pathogens and colonizers is difficult, it is uncertain whether such broad cover is truly needed. In uncomplicated cases, the usual treatment duration is 7–10 days. Some data suggest postoperative antibiotic treatment is not necessary for uncomplicated cases after tonsillectomy.

The role of adjuvant corticosteroid treatment remains controversial. ^{, , , ,} Data from two randomized controlled trials (RCTs) in adults suggest that corticosteroids may expedite symptomatic improvement and decrease length of hospitalization. ^, However, it is not standard therapy for children.

The choice whether to manage a patient with peritonsillar abscess as an outpatient or inpatient has to be made on an individual basis, taking into account the patient’s age, co-existing morbidities, and the need for intravenous hydration, antibiotics, pain control, and airway monitoring. ^, The recurrence rates in patients managed in the outpatient setting is similar to those managed as inpatients.

Complications and Prognosis

Complications of appropriately managed peritonsillar abscess are relatively rare. The course of the illness can be complicated by extension of the infection to the retropharyngeal or parapharyngeal space. ^{, ,} Other potential complications include aspiration pneumonia, mediastinitis, necrotizing fasciitis, erosion of the carotid artery or development of carotid artery pseudoaneurysm, thrombosis or thrombophlebitis of the jugular vein, brain abscess, sepsis, and toxic shock syndrome. Only a relatively small proportion of patients with peritonsillar abscess require intensive care support, usually for management of airway compromise. Fatal outcome is rare. Relapse or recurrence occur in 2%–25% of cases and is more common in patients with previous recurrent tonsillitis. ^{, , , , , , , ,} Non-suppurative sequelae of S. pyogenes , such as acute rheumatic fever, poststreptococcal reactive arthritis, and acute glomerulonephritis are also possible.

Etiologic Agents

Polymicrobial infection is common, and mixed aerobic and anaerobic infection occurs frequently. Commonly isolated aerobic bacteria include S. pyogenes , viridans streptococci, S. aureus, Haemophilus , and Neisseria species . ^{, , , , ,} Although less common, cases due to methicillin-resistant S. aureus (MRSA) can occur. ^{, , ,} A report of children with retropharyngeal abscess caused by S. aureus from Texas highlighted that in their series, MRSA was more frequently implicated than is methicillin-susceptible S. aureus (MSSA). Common anaerobic isolates include Peptostreptococcus , Prevotella , Bacteroides , Fusobacterium , and Veillonella species. Retropharyngeal abscess due to Mycobacterium tuberculosis is rare and is usually associated with osteomyelitis of the spine (Pott’s disease).

Epidemiology and Pathogenesis

Retropharyngeal abscess can occur at any age, but most commonly affects children <5 years of age. ^{, , , , , , , ,} Age propensity is likely due to prominent retropharyngeal lymphatic tissue and the higher frequency of respiratory tract infections in this age group. In most reports there is some male predominance. ^{, , , , , , ,} In the US and Europe the reported peak incidence is during the winter and spring months, ^{, , ,} and some data suggest that the incidence of retropharyngeal abscess has increased in the US over the last decade. ^{, , , , ,} Similar observations have been reported from the UK; the incidence is currently estimated to be 2–4 per 100,000 children per year. ^,

Retropharyngeal abscess in children predominately results from infection and suppuration of the retropharyngeal chains of lymph nodes, which drain the nasopharynx, the paranasal sinuses, and the adenoids. ^{, ,} Common primary infectious foci include pharyngitis, tonsillitis, adenitis, and less frequently, sinusitis, otitis media, mastoiditis, and dental infections. Unlike in adults, local trauma and foreign body ingestion play a relatively minor role. ^{, , , , , , ,}

Clinical Manifestations and Differential Diagnosis

Common manifestations include fever, sore throat, dysphagia, odynophagia, neck pain, neck swelling, limited neck extension, and torticollis; ^{, , , , , , ,} trismus and drooling are less common. The majority of patients have evidence of pharyngitis or tonsillitis and cervical lymphadenitis on examination. ^, Symptoms can be more subtle, especially in infants, who may have only fever, irritability (especially when moving the head), and decreased oral intake. In most reports, the proportion of cases with symptoms indicative of airway obstruction (such as difficulty in breathing and stridor) is relatively small and predominately affects infants and young children. ^{, , , ,} These children often appear anxious and project a posture with a forward-leaning head (“sniffing position”).

WBC count, CRP, and ESR are commonly elevated. ^{, , , , , ,} In most cases, enlargement of the retropharyngeal space/prevertebral tissue can be seen on plain lateral neck radiograph ( Fig. 28.1 ). ^{, , ,} If the radiograph is taken in a true lateral position and during inspiration with the neck in normal extension, a prevertebral tissue space of >7 mm at the level of the second cervical vertebra, or >22 mm at the sixth cervical vertebra, is considered abnormal. However, this method has a high false-positive rate due to variations in positioning, swallowing, respiration, and crying. Furthermore, it is difficult to differentiate a phlegmon from an abscess. MRI is the most sensitive imaging technique. ^, However, CT generally is more readily available and easier to do and is therefore often preferred. Both methods are useful in differentiating between retropharyngeal abscess and cellulitis/phlegmon, but their specificity is limited (45–82%). ^{, , , , ,} Forced supine position with either modality presents concern for airway obstruction and therefore requires close monitoring.

Management

There is not consensus regarding the optimal empiric antibiotic treatment. Penicillin or ampicillin alone provide insufficient coverage, as S. aureus , β-lactamase-producing organisms, and anaerobic bacteria are isolated in a significant proportion of cases. Suggested empiric antibiotic regimens include a second- or third-generation cephalosporin plus clindamycin or metronidazole, amoxicillin-clavulanate, or ampicillin-sulbactam. ^{, , , ,} Some authors suggest that clindamycin alone may be sufficient. ^, However, clindamycin may not be active against some S. pyogenes and S. aureus (MSSA and MRSA) strains. Therefore, in areas where MRSA is prevalent and in patients who do not respond to initial treatment, addition of vancomycin or linezolid should be considered. The usual duration of treatment in uncomplicated cases is 3–5 days of intravenous treatment, followed by oral antibiotics to complete a total course of 10–14 days.

The role of surgical drainage remains controversial. ^{, , , , , ,} Patients with significant respiratory distress require urgent airway management and surgical drainage, which is usually performed via the transoral approach, and less commonly via the transcervical route.. ^{, , , , , ,} However, conservative management with intravenous antibiotics for a 24- to 48-hour period in conjunction with close monitoring might be appropriate for patients who are stable and have no respiratory distress, with surgery if there is no improvement. ^{, , , ,} A decrease in operative interventions for retropharyngeal abscesses in children in the US has been reported. The reported success rates with conservative management alone vary considerably between different studies, and there are no data from RCTsfn13. ^{, , , , ,} Non-surgical management is not recommended if the abscess has a diameter of >2.5 cm, or if imaging shows complete rim enhancement and scalloping consistent with a mature abscess. ^{, ,}

Complications and Prognosis

Potential complications, although rare, include internal jugular vein thrombosis or thrombophlebitis, mycotic aneurysm of the carotid artery, Grisel syndrome (atlantoaxial subluxation), aspiration pneumonia, mediastinitis, sepsis, and toxic shock syndrome. ^{, , , , , , ,} Only a small proportion of patients require repeated surgical intervention. ^{, ,} Children below the age of 2 years have higher rates of complications. ^, The vast majority of patients have an uncomplicated course and can be discharged with oral antibiotics within a few days. ^, Non-suppurative post-streptococcal complications are possible. Fatal outcomes have been rare in recent studies.

Etiologic Agents, Epidemiology, and Pathogenesis

The spectrum and frequency of causative organisms are similar to those of retropharyngeal abscess. ^{, ,} Studies on deep neck space infections in children suggest that parapharyngeal abscesses are less common than retropharyngeal abscesses. ^{, , ,} The incidence is estimated to be 1 per 100,000 children per year. In contrast to retropharyngeal abscess, parapharyngeal abscess occurs in all age groups without predilection for younger children. ^, As reported for peritonsillar and retropharyngeal abscesses, there is slight male predominance, ^{, , ,} and peaks have been reported in winter and spring.

Parapharyngeal abscess is thought to result primarily from infection and subsequent suppuration of lymph nodes in the lateral pharyngeal space, which are part of the lymphatic drainage of the nasopharynx and the middle ear. ^, In most cases there is a history of preceding pharyngitis or tonsillitis. Pharyngeal space infection can also arise from contiguous spread from a peritonsillar or retropharyngeal abscess. Direct spread from dental infections is a rare cause of parapharyngeal abscess.

Clinical Manifestations and Differential Diagnosis

Clinical features closely resemble those associated with retropharyngeal abscess. Fever, sore throat, and neck swelling are common features, while dysphagia, odynophagia, torticollis, trismus, and cervical lymphadenopathy can be present. ^{, , , , , ,} A key distinguishing feature from retropharyngeal abscess is the frequent finding of deviation of the lateral wall of the oropharynx to the midline in parapharyngeal abscess. ^,

WBC count, CRP and ESR elevations are common. ^{, ,} Contrast-enhanced CT or MRI are the imaging modality of choice in suspected cases. ^{, , , , , , , , ,} Unlike in retropharyngeal abscess, plain lateral neck radiographs are not useful, and ultrasound does not provide adequate delineation of deep tissues.