Diagnosis And Treatment The Infectious Etiologies

Acute Bacterial Otitis Externa. Both the external ear and the middle ear are susceptible to infection and both can present with otorrhea. External-ear infections (acute otitis externa) are most often caused by irritation to the ear, either from manipulation (fingers, Q-tips, etc.) or from environmental factors (water, debris, etc.). External-ear infections will present with ear pain and drainage. In bacterial otitis externa, the discharge is typically purulent. The main pathogens are Pseudomonas and Staphylococcal species, with a variable amount of anaerobes, as well (3). Typically, the ear will appear red and inflamed and be extremely sensitive to touch. In some cases, the ear can swell to the point where the tympanic membrane cannot be seen through the ear canal. Less commonly, the ear will demonstrate vesicles and pustules. Generally, this appearance is driven by pathology, since the vesicular lesions that tend to drain a clear, watery fluid, are usually viral in origin. In most cases, acute otitis externa can be controlled, but if the disease is allowed to progress, complications, including a true canal stenosis, can occur (4).

In the treatment of the draining ear, the first priority is to diagnose the cause and location of the drainage. Often, this is impossible to accomplish without the use of a microscope and a set of equipment (suction, cerumen loops, etc.) capable of cleaning debris out of the ear. When the disorder is recognized as an acute otitis externa, antimicrobial ear drops should be utilized. The best eardrop is controversial. Clearly, if an eardrum perforation is seen or a tube is in place, a nonototoxic medicine should be utilized. In fact, even when the eardrum is intact, there is mounting evidence that both non-antibiotic-containing and aminoglycoside-containing eardrops are becoming less effective over time (5,6). We utilize a quinolone antibiotic drop containing steroids. This gives increased effectiveness and is safe if the eardrum becomes ruptured or opened during the disease process (6). Our standard regimen is four to five drops b.i.d., pumped in by depressing the tragus (7). If the ear canal is narrow, we will place a wick and saturate it with antibiotics twice a day. We are careful to change the wick every two to three days. Finally, if there is no response or a severe infection, systemic antibiotics may be necessary.

Noninvasive Fungal Otitis Externa. Fungal otitis externa most often presents with a clear or white discharge and may be apparent by the presence of fungal elements in the external canal. Usually, the ear has minimal pain but significant itching. In rare cases, noninvasive fungal infections can also present with granulation tissue and pain (8). Fungal otitis externa can present primarily but often is a secondary complication due to the elimination of the normal aural flora when eardrops are used for otorrhea. Although noninvasive fungal infection is usually limited to the external ear canal, a recent study discovered fungal DNA in the middle ear of individuals with otorrhea (9). The significance of this finding has not yet been fully defined.

Fungal drainage can be a difficult condition to treat. Again, good aural care is crucial in treating these infections. With a mild fungal infection, acidification of the ear canal with an acid-based eardrop can be effective, but the drop can cause pain in the patient. Filling the ear canal with an antifungal cream, such as clotrimizole, often can be effective. Due to the need to completely fill the canal with the cream, reapplication should be done in the clinic, and patients often will require several applications over a two-week period to gain control over the fungal infection.

Infectious Otitis Media. Otorrhea can also present with otitis media. Several patterns of middle-ear pathology can produce drainage. Middle-ear fluid in acute otitis media can spontaneously rupture the eardrum and spill into the external auditory canal, or a middle ear with cholesteatoma can drain. Additionally, fluid can drain from the middle ear through tympanostomy tubes that were placed to ventilate the middle ear.

Tympanostomy tube drainage is not uncommon, and typically occurs in two patterns. It has been estimated that 10% of all tubes drain during the first week after surgery. The fact that antibiotic eardrops and nonantibiotic eardrops are equally effective at controlling this drainage suggests that most of this early drainage is sterile fluid or treated acute otitis media fluid that has been sterilized (10). As for latter drainage, that fluid has been cultured and the most common pathogens found have been Streptococcus pneumonia and Haemophilus influenza (11). Antibiotic-containing eardrops approved for middle-ear use are the most effective treatment option for this drainage. In cases that are refractory to antibiotic eardrops, we add oral antibiotics and, if these fail, we consider changing the tubes. As new vaccination patterns emerge, the predominant microorganisms found in middle-ear secretions may change over time. Finally, in chronic otitis media with cholesteatoma, the middle ear is, by definition, infected and will drain into the external ear.

Infections in Immunocompromised Individuals. A special type of external otitis is termed malignant otitis externa. This is a bacterial otitis externa present in diabetic or immunocompromised patients in whom there is osteomyelitis of the skull base. The disorder is caused by Pseudomonas aeruginosa infection and may be recognized by granulation tissue in the external ear. The ear also may present with significant inflammation and erythema (12). A culture of the ear positive for Pseudomonas does not make the diagnosis, since Pseudomonas is part of the flora of a normal ear and can also be positive in simple otitis externa. The best diagnostic test is a bone scan looking for evidence of the osteomyelitis. It is important for clinicians to keep a high index of suspicion for this disorder, since, if not treated appropriately, the disorder can progress to lateral sinus thrombosis, involvement of the temporal mandibular joint (TMJ), multiple cranial nerve involvement, and meningitis (13,14).

Treatment of malignant otitis externa can be complex. Antibiotic therapy is the mainstay of treatment and must continue until there are clear signs of resolution of the osteomyelitis. The fluoroquinolone class of antibiotics represents a convenient oral group of medicines that could achieve adequate tissue levels to treat malignant otitis externa; however, resistance is possible. We recommend consultation with an infectious disease specialist in some cases. There has been significant debate over the years as to the role of debridement of granulation tissue. Some argue for limited and relatively gentle cleaning of the external ear, whereas others argue for aggressive debridement, to include an operative procedure. Perhaps the most rational approach is early debridement concomitant with appropriate antibiotic therapy, allowing the disease progression to guide treatment.

Malignant otitis externa is not the only disorder unique to immunocompromised patients such as those infected with HIV or those receiving chemotherapy. These individuals are especially likely to manifest aural discharge from a host of common and noncommon infectious agents. In this group of individuals, the practitioner must be especially vigilant to discover the pathologic agent, as well as to rule out the possibility of a malignant otitis externa. In HIV patients in particular, Pneumocystis carinii-infected aural polyps can occur and drain in the external canal (15). Fungal disease can be particularly aggressive in this group of patients. Invasive fungal disorders, while much more common in the sinuses, can also affect the ear and mastoid (16). Aggressive surgical treatment combined with systemic antifungal therapy is necessary in this group of individuals.

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