Otitis externa due to pseudomonas aeruginosa: causes, symptoms, diagnosis, and treatment

The external auditory canal is one of the parasitic parts of pseudomonas aeruginosa, and pseudomonas aeruginosa can be cultured in up to 70% of patients with otitis externa. Otitis externa is more common in swimmers and can occur after ear surgery.


Causes

Pseudomonas aeruginosa is an aerobic Gram-negative bacillus, is widely present in moist natural environments, mainly in the soil, water, and intestines of few persons, and can also temporarily parasitize the anus, genitals, armpits, and external auditory canal. Under normal circumstances, its growth is inhibited by Gram-positive cocci, generally nonpathogenic. However, the bacterium can quickly reproduce in the burns, ulcers, and moist skin, causing skin infections. Systemic infections usually occur in persons with low immunity, such as patients whose normal microflora being inhibited by antibiotics or glucocorticoids, tumor patients, patients with granulocytopenia caused by various causes, patients with immunodeficiency caused by chronic wasting diseases, frail old adults, and malnourished infants. If a healthy person is immersed in water for a long time, the infection of the bacteria can also occur. The bacteria can also cause nosocomial infections by contamination of hospital bedpans and sheets, and has become one of the main pathogens of nosocomial infections in recent years.

Studies have shown that the pathogenicity of the bacteria is mainly caused by the secreted exotoxin, and the collagenase, elastase, and phospholipase secreted by the bacteria are involved in the disease. A typical strain produces two pigments of blueish green pyocyanin and yellowish green pyoverdin.

Systemic pseudomonas aeruginosa infection can cause sepsis, and patients present with fever, jaundice, splenomegaly, pneumonia, urinary tract infection, and meningitis. Cutaneous pseudomonas aeruginosa infection often occurs in the persistently moist lesion sites, especially on the periumbilical and burned surfaces of infants, as well as in macerated toes, external auditory canal, and auricle.


Signs and Symptoms

The clinical manifestations are swelling, impregnation, and pain in the external auditory canal. In old patients with diabetes or granulocytopenia, more serious local redness and swelling and significant pain are present, and pus and malodor may be present. In severe cases, facial nerve palsy and chondronecrosis may occur, which is called malignant otitis externa.


Diagnosis

On the basis of clinical presentations and results of bacterial culture, diagnosis is not difficult.


Treatment

Wet compress with acetic acid for 1 - 2 days before ear surgery can help prevent this complication. Neomycin and polymyxin B sulfates and hydrocortisone otic suspension help to eliminate local infections, and topical neomycin-containing glucocorticosteroid ointment can be used. Systemic antibiotics should be administered in patients with malignant otitis externa or severe inflammatory symptoms.