Ear infection - Introduction, Otitis externa, Otitis media, Otitis interna

Introduction to Ear infection

The ear is divided into 3 anatomic parts:

• The external ear

• The middle ear

• The inner ear

Normal microbial flora of the ear includes- Pneumococci, Streptococcus pneumoniae, Propionibacterium acnes, Staphylococcus aureus, Enterobacteriaceae, etc. Pseudomonas aeruginosa is found on occasion.

The ear infection is known as otitis. It is classified into 3 types:

1. Otitis externa

2. Otitis media

3. Otitis interna

Otitis externa

Otitis externa is the inflammation of the pinna and external auditory canal and is more like skin infections. This condition is also called “swimmers ear” because infection usually occurs after swimming in the infected pool. Symptoms are localized and appear like skin infections and discharge may or may not be present. This ear infection might spread to cause otitis media.

Two major types of otitis externa exist:

• Acute otitis externa

• Chronic otitis externa

Acute otitis externa

• Acute otitis external may be localized or diffused

• typically caused by Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pyogenes occur in form of pustule or furuncle

• erysipelas caused by group A streptococci involve the external ear canal and soft tissue of the ear

• “Swimmer’s ear” is related to maceration (softening of tissue) of the ear from swimming or hot, humid weather

• gram-negative bacilli such as Pseudomonas aeruginosa cause severe, hemorrhagic otitis externa that are difficult to treat and are related to hot tub use.

Chronic otitis externa

• Chronic otitis external results from the irritation of drainage from the middle ear in patients with chronic, suppurative otitis media and a perforated eardrum

• causative agent Pseudomonas aeruginosa and anaerobes

• malignant otitis externa is a necrotizing infection that spreads to adjacent areas of soft tissue, cartilage, and bones

If allowed to progress, it spreads to CNS or vascular channels resulting in life-threatening conditions.

* Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis also cause otitis externa while Mycoplasma pneumoniae is rarely associated with this condition.

[Enterococcus = Streptoccus faecalis]

Otitis media

Otitis media is an ear infection of the middle ear called otitis media. It occurs most commonly in children. The causative agents include

• pneumococci (33%)

• H. influenzae (20%)

• S. pyogens [Group A streptococci] (8%)

• Moraxella catarrhalis (1-6%)

• S. aureus (1-6%)

• gram negative enteric bacilli (1-6%)

• anaerobes

• occasional pathogens => Chlamydia trachomatis, Mycoplasma pneumoniae

It is classified into 2 types

• Acute supurative otitis media

• Chronic supurative otitis media

Acute suppurative otitis media

Acute suppurative otitis media is an acute inflammation of the middle ear in which the eustachian tube and middle ear are involved. Commonly, the infection occurs secondarily to the bacterial infection in URT.

A common route of infection is through the eustachian tube which joins the ear with the throat. Common symptoms are congestion, ear pain, and disturbed sleep. Complications may arise after the infection advances to otitis interna.

Chronic suppurative otitis media

Chronic suppurative otitis media is a chronic infection of the mucous lining of the middle ear for more than 2 weeks. The mucopurulent discharge might be present in 1^st stage and might be absent in later stages.

The most common pathogen is Pseusomonas aeuroginosa, Staphylococcus aureus, Proteus spp. However other pathogens including Alloiococcus otitis might be involved and anaerobes such as Peptostreptococcus spp. may also cause infection.

Complications might be otitis media. Other complications include mastoiditis where microorganisms find their way into mastoid sinuses. It may further spread to CNS. Mastoidectomy is performed to prevent this.

Otitis interna

The ear infection of the inner ear is called Otitis interna. The inner ear is composed of a semi-circular canal filled with endolymph and perilymph. Severe symptoms include vertigo. In less severe cases nausea and dizziness are present.