Ear Infections, Chronic (World of Microbiology and Immunology)
Chronic ear infection, which is also referred to as chronic otitis media, is a recurring infection of the middle ear that occurs in animals and in humans. In humans, children between a few months of age and about six years of age are the most susceptible. The infection can be caused by bacteria and, occasionally, by viruses.
The ear consists of outer, middle, and inner regions. The outer ear is the visible portion that channels sound vibrations to the middle ear. The middle ear contains three small bones that pass on the vibration to the nerve endings housed in the inner ear. The middle ear is connected to the nasal cavity and the throat by a drainage tube known as the Eustachian tube. Improper drainage from the Eustachian tubes result in a retention of fluid in the middle ear, which can become infected by bacteria.
Such infections are common in children. Each year in the United States, over 10 million children are treated for ear infections. However, ear infections tend to be infrequent and disappear as the construction of the ear changes with age. Specifically, the Eustachian tube becomes more slanted in orientation, which promotes drainage that is more efficient. However, in some children the normally short-term (or acute) middle ear infections begin to recur. For these children, many ear infections can occur in the first six or so years of life. Chronic ear infections affects about two out of every 10,000 people.
In some cases, surgical intervention is necessary to install a plastic drainage tube (a procedure called myringotomy) or to remove infected adenoids or tonsils, which can swell and block the eustachian tube. Myringotomy is one of the most common operations that are performed in the United States. As the ear matures structurally and the eustachian tube acquires the ability to drain more freely, the tube is removed.
As with other chronic bacterial infections, the symptoms associated with chronic ear infections can be less severe and uncomfortable than those of the acute form of the infection. Chronic infections may thus escape detection for long periods of time.
Usually a chronic ear infection is more inconvenient and uncomfortable than a health threat. However, in some cases, the chronic bacterial or viral ear infections can lead to complications that are much more serious. The infection can spread into the bones of the ear. Also, the increased pressure from the build-up of fluid can rupture the eardrum. Such damage can produce permanent impairment of hearing.
Another damaging aspect of chronic ear infections, which is shared with other chronic bacterial infections, is the damage to tissues that results from a prolonged immune response to the infection. The failure to clear the infection can produce a prolonged immune response. This response, particularly inflammation, can be damaging to tissue.
Treatment consists of decongestants or antihistamines to promote drainage through the Eustachian tube, and of antibiotics in the case of a bacterial infection. Even with treatment a chronic infection can take weeks or months to completely clear. Adherence to the treatment schedule is critical, especially since the symptoms of chronic ear infections can pass before the infection is fully cleared. Stopping therapy when the symptoms fade may allow the bacteria that are still surviving to become re-established as another infection. Moreover, because the bacteria were exposed to an antibacterial agent, resistance to that agent can develop, making the recurrent infection harder to eradicate.
See also Bacteria and bacterial infection