Otitis Media and Otitis Externa
Laura L. Bio
Infections of the ear are a common problem in children due to anatomical predisposition, but they can also affect adults. Acute otitis media (AOM), otitis media with effusion (OME), and otitis externa (OE; also known as swimmer’s ear) are the most common infection or inflammatory conditions of the ear. Although antibiotics and vaccination programs have decreased the frequency of infections, identification, diagnosis, and management of these infections are essential to prevent permanent hearing loss, chronic or recurrent ear infections, mastoiditis, meningitis, and speech or language delay.
OTITIS MEDIA AND OTITIS EXTERNA
Otitis media (OM) may manifest as AOM or chronic OME (Lieberthal et al., 2013). OM has historically posed a major social and economic burden, occurring at an alarming rate of 19 million cases per year. It continues to impact antibiotic expenditures because it is the most common infection for which antibiotics are prescribed for children. In spite of the strict 2004 American Academy of Pediatrics (AAP) AOM guideline, the rate of antibiotic prescribing for OM has remained constant. The recent 2013 AAP AOM guideline and clinical reports emphasize the need for judicious antibiotic prescribing for upper respiratory infections (URIs) to reduce the risk of antibiotic resistance and adverse effects (Hersh et al., 2013).
AOM is defined as an acute onset of signs and symptoms of a middle ear infection and inflammation, such as middle ear effusion and erythema, respectively (Table 18.1). AOM is the most common bacterial respiratory tract infection in children and predominantly effects infants and children age 6 months to 2 years. During the year 2006, 11.8% of all children under age 18 years were diagnosed with OM (8.8 million cases) (Soni, 2006). Meanwhile, OME is inflammation of the middle ear with fluid collection behind the TM, but signs and symptoms of an acute infection are absent (Pelton, 2012). OME typically precedes or follows AOM (Pichichero, 2013).
Otitis externa (OE) may present in acute and chronic forms. OE is defined as an inflammation of the outer ear and ear canal. Acute OE roughly affects 1 in 123 persons in the United States based on the 2.4 million visits to ambulatory care centers and emergency departments in 2007 (CDC, 2011). Children 5 to 14 years of age account for approximately half of all visits. OE is most often associated with swimming, local trauma, use of hearing aids, and high, humid temperatures (Table 18.1). Unlike AOM, in which the mainstay of treatment is systemic antibiotics, topical antibiotic therapy is usually adequate for the treatment of OE. Oral antibiotics may be recommended for patients with acute OE infections extending outside the ear canal or certain host factors such as diabetes, immune deficiency, or inability to effectively deliver topic therapy. Systemic antibiotics should also be considered for patients with recurrent episodes of OE or clinical signs of necrotizing (i.e., malignant) OE, which is a serious and potentially life-threatening complication of the infection extending to the mastoid or temporal bone. Immunocompromised patients, including the elderly with diabetes and human immunodeficiency virus, are at the highest risk of necrotizing OE. Chronic OE is a single episode lasting longer than 3 months or four or more episodes in 1 year and often the result of allergies, chronic dermatologic conditions, or inadequately treated acute OE (Rosenfeld et al., 2004; Schaefer & Baugh, 2012).
TABLE 18.1 Comparing Types of Otitis | ||||||||||||||||||||
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CAUSES
Acute Otitis Media and Otitis Media with Effusion
The most frequently isolated bacteria from middle ear fluid are Streptococcus pneumoniae, nontypable Haemophilus influenzae, and Moraxella catarrhalis, followed by the less common group A Streptococcus and Staphylococcus aureus. The precise frequency for each AOM pathogen has changed over time due to changes in vaccination coverage. Historically, S. pneumoniae dominated AOM etiology, but after implementation of the 13-serotype conjugate vaccine, beta-lactamase producing H. influenzae and M. catarrhalis has emerged as more common (Pichichero, 2013).
Although many cases are caused by bacterial pathogens, viruses play a significant role in the pathogenesis and course of treatment. Viral pathogens, such as respiratory syncytial virus, influenza A and B, parainfluenza, enterovirus, and rhinovirus, have all been isolated in nasopharyngeal secretion of children with URI (Pichichero, 2013). Most cases of AOM follow viral URI since it facilitates bacterial AOM by enhancing the bacteria’s ability to ascend the nasopharynx and infect the middle ear (Pelton, 2012). Single virus isolates are recovered from 2% to 20% of AOM tympanocenteses.
Otitis Externa
Ninety-eight percent of OE cases in the United States are caused by bacteria, most commonly Pseudomonas aeruginosa and S. aureus (Schaefer & Baugh, 2012). The etiology of OE is different than that of OM because the flora of the external auditory canal is similar to that of the skin including Staphylococcus epidermidis, S. aureus, Corynebacteria species, and Propionibacterium acnes. Fungi, predominantly Aspergillus and Candida species, cause less than 5% of OE in the United States but may be more common in subtropical or tropical climates (Boyce, 2012). Fungal OE, otomycosis, may also occur in cases in which prolonged antibiotic courses are given for bacterial OE, causing an alteration in ear canal skin flora. Chronic OE may be noninfectious but caused by inflammatory skin disorders and allergic reactions (Schaefer & Baugh, 2012). Necrotizing (malignant) OE is caused by P. aeruginosa.
PATHOPHYSIOLOGY
Otitis Media
AOM frequently follows a URI (usually of viral etiology) in which the eustachian tube closes secondary to inflamed mucous membranes (Lieberthal et al., 2013). The pathophysiology of AOM is multifactorial but is mainly the result of eustachian tube dysfunction. The eustachian tube protects the middle ear from nasopharyngeal secretions, provides drainage of secretions produced in the middle ear into the nasopharynx, and permits equilibration of air pressure to atmospheric pressure in the middle ear. The structure of a child’s eustachian tube differs from that of an adult’s. The adult eustachian tube lies at 45 degrees to the horizontal plane and allows for secretions to drain from the middle ear to the nasopharynx. The child’s eustachian tube, however, is short and horizontal. When a child develops mild inflammation or edema of the eustachian tube, the ear has difficulty clearing secretions due to the almost
horizontal placement of the eustachian tube. Persistent secretions, incomplete drainage, and the absence of aeration breed an environment for bacterial growth within the middle ear, resulting in AOM (Pelton, 2012). The incidence of AOM is highest during winter months, which coincide with the seasonal peak of URIs. Risk factors for AOM include congenital defects such as cleft palate and Down syndrome, young age (highest incidence in children below age 2), family history, and children who attend day care or are relatives of children in day care. The following risk factors have also been associated, however inconsistently, with an increased risk of AOM: male sex, exposure to secondhand smoke, allergies, and lack of exclusive breast-feeding for the first 6 months of life (Hoberman et al., 2002).
horizontal placement of the eustachian tube. Persistent secretions, incomplete drainage, and the absence of aeration breed an environment for bacterial growth within the middle ear, resulting in AOM (Pelton, 2012). The incidence of AOM is highest during winter months, which coincide with the seasonal peak of URIs. Risk factors for AOM include congenital defects such as cleft palate and Down syndrome, young age (highest incidence in children below age 2), family history, and children who attend day care or are relatives of children in day care. The following risk factors have also been associated, however inconsistently, with an increased risk of AOM: male sex, exposure to secondhand smoke, allergies, and lack of exclusive breast-feeding for the first 6 months of life (Hoberman et al., 2002).
OME is thought to result from prolonged blockage of the eustachian tube, which in turn causes negative pressure within the middle ear that allows fluid to accumulate and persist, and may result in conductive hearing loss (Pelton, 2012). The presence of effusion does not always correlate to the presence of an infection. In fact, bacterial pathogens are reported in only 20% to 30% of middle ear effusions (Pelton, 2012).
Otitis Externa
OE is a cellulitis of the ear canal skin and subdermis with or without infection (Rosenfeld et al., 2013). Children, adolescents, and adults are all at risk for developing this infection. This condition may occur as a result of many different factors. The most common predisposing factor is swimming, especially in freshwater. Additional OE risk factors include eczema or seborrhea resulting in excessive itching, trauma from cerumen removal, use of hearing aids, chronic otorrhea, and immunocompromised states such as diabetes (Schaefer & Baugh, 2012). Disruption of the ear canal homeostasis from prolonged periods of water exposure (head immersion), loss of protective cerumen barrier, and disruption of the epithelium all result in varied pH and compromised local immune defenses, which allows bacteria and other pathogens to harbor infection.
Resistance
The increasing rates of antimicrobial resistance are a major cause and concern for treatment failure of AOM. The increasing incidence warrants the judicious use of antibiotics. Mechanisms of resistance include alteration of drug binding sites and the production of antibiotic inactivating enzymes, for example, beta-lactamases. Organisms such as H. influenzae and M. catarrhalis can produce these enzymes, which essentially render many beta-lactam antibiotics useless. It is for this reason that antibiotics that remain stable in the presence of beta-lactamase-producing enzymes must be chosen to ensure treatment success. A detailed discussion of treatment options is discussed in the management section of this chapter.
Drug-resistant S. pneumoniae (DRSP) remains a threat in the treatment of AOM. Penicillin, historically, has been the mainstay of treatment against S. pneumoniae. However, the increasing prevalence of penicillin-intermediate and penicillin-resistant strains has discouraged the use of penicillin and its derivatives. Furthermore, penicillin-resistant strains may also confer resistance to other antibiotics such as macrolides, trimethoprim-sulfamethoxazole, and clindamycin. The mechanism of penicillin-resistant S. pneumoniae is the alteration of the penicillin-binding site resulting in elevated minimum inhibitory concentration (MIC). This may be overcome by administering high-dose amoxicillin if deemed intermediate susceptibility based on the MIC. It should be noted that infections caused by penicillin-resistant S. pneumoniae have mostly been reported in children younger than age 2.
Beta-lactamase production is the mechanism by which organisms such as H. influenzae and M. catarrhalis develop resistance. Beta-lactamase inhibitors in combination with beta-lactam therapy, such as amoxicillin-clavulanic acid or beta-lactamase stable cephalosporins (i.e., cefixime, cefpodoxime), can overcome this mechanism of resistance. Therefore, these agents should be recommended for treatment if these organisms are suspected, specifically in the setting of treatment failure or recurrent infection.
DIAGNOSTIC CRITERIA AND CLINICAL PRESENTATION
Acute Otitis Media
The presentation of AOM includes abrupt onset of symptoms such as fever, otalgia, irritability, and tugging on the affected ear; the tympanic membrane (TM) appears bulging, erythematous, and immobile to pneumatic otoscopy upon inspection indicating middle ear effusion. The averbal infant may express otalgia by tugging, rubbing, or holding the affected ear, excessive crying, fever, or changes in sleep or behavior pattern. The diagnosis of AOM requires abrupt onset of symptoms (less than 48 hours), presence of middle ear effusion, and signs or symptoms of middle ear inflammation, including erythema of the TM, hearing loss, and otalgia (Lieberthal et al., 2013). Otorrhea may also be present and will affect management (Table 18.2).
TABLE 18.2 Diagnostic Criteria for Acute Otitis Media | |
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The absence of acute inflammatory signs and symptoms presumes a diagnosis of OME. Patients with OME are usually asymptomatic but may complain of a full sensation in the ear and hearing loss. Upon examination, the TM may not appear bulging, but air-fluid levels may be apparent. AOM and OME require differentiation since OME should not be treated with antibiotics due to probable viral etiology or result of AOM resolution.
Tympanocentesis, the process by which fluid is drained from the middle ear, is recommended for recurrent treatment failure to ensure proper diagnosis of the causative organism and determine the presence of bacterial resistance. This process relieves pressure in the middle ear cavity and promotes drainage, but it is reserved for treatment failures due to the potential risk of permanent hearing loss and facial paralysis.
INITIATING DRUG THERAPY
Goals of Drug Therapy
The goals of therapy for AOM include symptomatic pain relief, appropriate use of antibiotics to prevent complications, and judicious use of antibiotics to prevent future antimicrobial resistance. Symptomatic pain relief can be achieved with the use of acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen. Antibiotics are utilized to eradicate the infecting organism and prevent complications such as mastoiditis and hearing impairment. Antibiotic use is not without concerns, such as resistance and adverse effects. For these reasons, clinicians should avoid unnecessary use of antibiotics.
Over-the-Counter Therapy
Acetaminophen and NSAIDs should be offered early to relieve pain regardless of antibiotic use, unless hypersensitivity exists. Local topical anesthetics containing benzocaine or procaine may provide brief additional pain relief for children over 5 years of age.
Observational Therapy
The decision to manage AOM with antibiotics is based on patient-specific characteristics such as age, bilateral involvement, presence of otorrhea, and severity of illness (Lieberthal et al., 2013). All patients with suspected AOM who are younger than age 6 months should receive antibiotics. For patients with nonsevere, unilateral AOM without otorrhea who are older than age 6 months, the role of antibiotics is unclear, and the decision to provide symptomatic relief with close observation can be made. The decision to observe and withhold antibiotics is based on the high rate of spontaneous resolution (approximately 80%) and overlap of nonspecific AOM symptoms with viral URIs (Hersh et al., 2013). In addition, judicious antibiotic prescribing reduces the risk of resistance and reduces common adverse effects associated with antibiotic therapy.
Patients with otorrhea or severe symptoms (i.e., toxic-appearing child, persistent otalgia more than 48 hours, temperature ≥102.2°F in the past 48 hours, or uncertain access to follow-up after visit) require antibiotic therapy regardless of age. Bilateral AOM requires antibiotic therapy only if the patient is less than 2 years of age. Patients 2 years old or greater with bilateral AOM without otorrhea or severe symptoms may initially be managed with observation therapy after a discussion with the child’s family to understand the decision. Observation therapy requires implementation of follow-up within 48 to 72 hours to ensure antibiotics can be initiated if the child’s condition worsens or fails to improve. The technique for observational therapy is controversial: observe with or without a prescription with instructions to fill after 2 to 3 days if symptoms persist (Chao et al., 2008). This decision should be based on the prescriber’s discussion with the caregiver and assessment of likelihood to adhere to the plan.
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