Also Known As: Ear infection, otitis media, inner ear infection, infected ear drum
Otitis is a general term for inflammation or infection of the ear, in both humans and other animals.
It is subdivided into the following: Inner ear infection (Otitis media) and outer ear infection (otitis externa) often referred to as swimmers ear. This aritical reffers to treatment options for inner ear infections. (Otitis Media)
When the middle ear becomes acutely infected, pressure builds up behind the eardrum (tympanic membrane), frequently causing intense pain. It may result in bullous myringitis (myring means "eardrum"), which means that the tympanic membrane is blistered and inflamed.
In severe or untreated cases, the tympanic membrane may rupture, allowing the pus in the middle ear space to drain into the ear canal. If there is enough of it, this drainage may be obvious. Even though the rupture of the tympanic membrane suggests a highly painful and traumatic process, it is almost always associated with the dramatic relief of pressure and pain. In a simple case of acute otitis media in an otherwise healthy person, the body's defenses are likely to resolve the infection and the ear drum nearly always heals.
Instead of the infection and eardrum perforation resolving, however, drainage from the middle ear can become a chronic condition. As long as there is active middle ear infection, the eardrum will not heal. The World Health Organization defines chronic suppurative otitis media (CSOM) as "a stage of ear disease in which there is chronic infection of the middle ear cleft, a non-intact tympanic membrane (i.e. perforated eardrum) and discharge (otorrhoea), for at least the preceding two weeks" (WHO 1998). (Notice WHO's use of the term serous to denote a bacterial process, whereas the same term is generally used by ear physicians in the United States to denote simple fluid collection within the middle ear behind an intact eardrum. Chronic otitis media is the term used by most ear physicians worldwide to describe a chronically infected middle ear with eardrum perforation.)
Otitis media is most commonly caused by infection with viral, bacterial, or fungal pathogens. The most common bacterial pathogen is Streptococcus pneumoniae. Others include Pseudomonas aeruginosa, nontypeable Haemophilus influenzae, and Moraxella catarrhalis. Among older adolescents and young adults, the most common cause of ear infections is Haemophilus influenzae. Viruses such as respiratory syncytial virus (RSV) and those that cause the common cold may also result in otitis media by damaging the normal defenses of the epithelial cells in the upper respiratory tract.
A major risk factor for developing otitis media is Eustachian tube dysfunction, which leads to the ineffective clearing of bacteria from the middle ear.
The bacterial infections are caused by Trimeric Autotransporter Adhesins (TAA). The UspA1 protein domain is a TAA found in the bacteria Moraxella catarrhalis which causes middle ear infections in humans. TAAs are virulence factors or in other words, an infective agent that infects the host cell by attaching to them and secreting the virulence factor by a secretion pathway.
The role of the anti-H. influenzae vaccine that children are regularly given is to prevent invasive disease such as meningitis and pneumonia. This vaccine is active only against strains of serotype b, which has been found to cause meningitis and pneumonia in children under five years, with children between 4 and 18 months the most susceptible. Isolates of serotype b rarely cause otitis media.
Susceptibility is heritable, though the specific genetic markers are still under investigation. Casselbrant et al. found in 2009 that the "best-supported linkage regions may contain susceptibility genes that influence the risk for recurrent/persistent OM. Plausible candidates in 17q12 include AP2B1, CCL5, and a cluster of other CCL genes, and in 10q22.3, SFTPA2."
Typically, acute otitis media follows a cold: after a few days of a stuffy nose, the ear becomes involved and can cause severe pain. The pain will usually settle within a day or two, but can last over a week. Sometimes the ear drum ruptures, discharging pus from the ear, but the ruptured drum will usually heal rapidly.
Pathophyisiology / progression of acute otitis media: the tissues surrounding the Eustachian tube swell due to an upper respiratory infection, allergies, or dysfunction of the tubes. The Eustachian tube remains blocked most of the time. The air present in the middle ear is slowly absorbed into the surrounding tissues. A strong negative pressure creates a vacuum in the middle ear, and eventually the vacuum reaches a point where fluid from the surrounding tissues accumulates in the middle ear. This is seen as a progression from a Type A tympanogram to a Type C to a Type B tympanogram. The fluid may become infected. It has been found that dormant bacteria behind the tympanic membrane (eardrum) multiply when the conditions are ideal, infecting the middle ear fluid.
Children younger than seven are much more prone to otitis media due to shorter Eustachian tubes, which are at a more horizontal angle than in the adult ear. They also have not developed the same resistance to viruses and bacteria as adults. Numerous studies have correlated the incidence in children with various factors such as nursing in infancy, bottle feeding when supine, parental smoking, diet, allergies, and automobile emissions; but the most obvious weakness of such studies is the inability to control the variable of exposure to viral agents during the studies. Breastfeeding for the first twelve months of life is associated with a reduction in the number, and duration of all OM infections.
Pacifier use has been associated with more frequent episodes of AOM.