Ear infection

Resident Microbial Flora of Ear

i. Acute localized disease:

ii. Acute diffuse otitis externa (swimmer’s ear):

It is related to softening of tissue(maceration) of the ear.
It results from swimming or hot, humid weather.
Pseudomonas aeruginosa, play an important role.
aeruginosa also causes external otitis which can be severe and hemorrhagic.
Occasionally it is found to be related to hot tub use which is also difficult to treat.

In the patients with chronic, suppurative otitis and the persons having perforated eardrums, the irritation of drainage from the middle ear results in chronic otitis externa.
Malignant otitis externa is a necrotizing infection.
It spreads to adjacent areas of soft tissue, cartilage, and bone.
It may result in a life-threatening condition when the infection spreads to the central nervous system or vascular channel.
It is caused by P. aeruginosa and anaerobes.
In the diabetic patient having blood vessel disease, Malignant otitis media is seen.
Occasionally, external otitis can spread to the cartilage of the ear.

Different parts of the ears like an external auditory canal, the soft tissue of the ear, or the tympanic membrane may be infected with the virus.

Though it’s not established suspicion is made to the influenza A virus.
Within the soft tissue of the ear and the ear canal. VZV causes painful vesicles.
Viral agents such as influenza are the bacterial agents typically associated with acute otitis media:
- pneumonia
- influenza
- catarrhalis
Mycoplasma pneumoniae is rarely associated with this condition.

It is the most common infection in children.
Causative agents are:
- Pneumococci
- Haemophilus influenza
- Group A streptococci (Streptococcus pyogenes)
- Moraxella catarrhalis
- Staphylococcus aureus,
- gram-negative enteric bacilli
- anaerobes
- Respiratory syncytial virus (RSV)
- Influenza virus
Otitis media with effusion (fluid) is considered a chronic sequela of acute otitis media.
From the patients with otitis media with effusion, Alloiococcus otitis has been isolated.
Pathogens of Chronic otitis media:
- Peptostreptococcus
- Bacteroides fragilis group,
- Prevotella melaninogenica
- Porphyromonas
- Prevotella
- Fusobacterium nucleatum a less
The complication of chronic otitis media is mastoiditis.

External ear infection (otitis media) can be caused due to many reasons such as:
- Local trauma
- the presence of foreign bodies
- excessive moisture can lead to otitis externa
Infection can progress up to the external ear by the purulent drainage from the middle ear.
Otitis media also can be developed by anatomic or physiologic abnormalities.
Infection may occur when the fluid develops in the middle ear.
The auditory tube plays a major role in the protection of the middle ear:
- protects from the nasopharyngeal secretion.
- drains the secretions which are produced in the middle ear into the nasopharynx
- Ventilates the middle ear
- Maintains the air pressure in the equilibrium state with the external ear canal
When there occurs any malfunctioning of these conditions, the infection may occur.
Example: There is inflammation and swelling of the auditory canal when there is a viral upper respiratory infection. It hampers the ventilating function in the middle ear. These alternations in the pressure allow the potentially pathogenic bacteria present in the nasopharynx to get the entrance into the middle ear.

Specimen Collection and Transport

Generally, culture is not done for the diagnosis of middle ear infection or otitis media.
Diagnosis of external otitis is done by culture.
Using mild germicide such as 1:1000 aqueous solution of benzalkonium chloride, the external ear should be cleansed.
It helps to reduce the number of contaminating skin flora.
Materials are obtained by spontaneous perforation of the eardrum or by the needle aspiration of the middle ear fluid (tympanocentesis) using sterile equipment.
Specimens from the mastoid are generally taken on swabs during surgery, although actual bone is preferred.
Specimens should be transported anaerobically.

Direct Visual Examination:

Aspiration is done from the middle ear or mastoid, the direct examination is done for bacteria and fungi.
Fungal elements can be revealed from the calcofluor white or PAS stains.
Bacterial, fungal, and several parasitic species can be stained efficiently by the use of Methenamine silver stains.

Culture and Nonculture Methods:

Inoculation of the ear specimens should be done in blood agar, MacConkey agar, and Chocolate agar.
On the specimens obtained by tympanocentesis or those obtained from patients with chronic otitis media or mastoiditis, anaerobic culture also should be done.
To detect the common middle ear pathogens, conventional and real-time PCR can be done because, in only 20% to 30% of patients, cultures are positive.