Case 2

The most common causes of otitis media are 

• Streptococcus pneumoniae (40 %)
• Hemophilus influenzae (30%)
• Moraxella catarrhalis (15%)

Rare causes

• Group A streptococcus 
• Staphylococcus aureus 

Since Hemophilus influenzae causing middle ear disease is nontypable, the vaccine for Hemophilus influenzae type b now routinely given to children has had no impact upon the prevalence of otitis media.

2. How are these organisms acquired by the host?

• These organisms colonize the upper respiratory tract, and are drawn into the normally sterile middle ear when conditions of negative pressure (see Pathogenesis below) develop in the middle ear.
  
  

3. What is known about the pathogenesis of the infection? Which structure is most important for normal drainage of the middle.ear?

• The eustachian tube is the structure which plays a major role in the development of acute otitis media. 
• The eustachian tube vents the middle ear to the nasopharynx. 
• It performs three functions: ventilation, protection, and clearance via mucociliary transport. 
• Viral upper respiratory infection or allergy causes inflammation and edema in the eustachian tube, impairing its normal functions. 
• When ventilation of the middle ear is lost, oxygen is absorbed from the air in the middle ear and negative pressure results. 
• This negative pressure draws bacteria into the middle ear. Other factors which result in Eustachian tube dysfunction include anatomic abnormalities which may be particularly common in children with facial abnormalities (Down's syndrome, cleft palate, etc). 
• The eustachian tube wall lacks stiffness in infants and young children. 
• Otitis media is most common in these younger age groups. Older individuals have eustachian tubes with stiffer walls which are less likely to collapse.
•  In addition, as the eustachian tube grows with an individual, a small amount of swelling due to an upper respiratory infection is less likely to occlude the tube or cause significant tube dysfunction.
  
  

4. How could the physician determine which bacterial agent is present in the middle ear?

• The only way to determine the specific pathogen in the middle ear is to perform a myringotomy (lancing the ear drum) or tympanocentesis (aspirating infected material from behind the drum with a needle). 
• These procedures are not commonly performed, so antibiotic therapy is generally used which will cover the most likely pathogens.
• Tympanocentesis should be considered for patients who fail to respond to therapy, for neonates in whom the bacteria causing, otitis media may be different (group B streptococcus and gram-negatives), and for immunocompromised patients.
• Myringotomy offers quick pain relief when a patient is in severe pain from otitis media. 
• Neither of these procedures is associated with any long-term complications.
  
  

5. Is prevention possible?

•  Recurrences may be prevented in patients with recurrent otitis media by either placement of tympanostomy tubes (which provide continuous ventilation of the middle ear by means of a plastic ventilation tube which has one end in the middle ear and the other end in the external ear canal) or prophylactic antibiotic therapy.
• Both pneumococcal vaccine and influenza vaccine have been shown to be effective in reducing the number of episodes of otitis media in otitis-prone patients. 
• Unfortunately, currently available pneumococcal vaccine is not effective in children less than 2 years of age, the group at greatest risk of developing recurrent otitis media. 
• Conjugate pneumococcal vacclnes analogous to the Hemophilus influenzae type b conjugate vaccines are in development and will likely be much more immunogenic in young infants and children.
  
  

6. What antimicrobial agents are effective for the treatment of acute otitis media? Is there a drug of choice?

• Amoxicillin remains the drug of choice for the treatment of acute otitis media. It will cover non-penicillin resistant Streptococcus pneumoniae, and beta-lactamase negative strains of Hemophilus influenzae and Moraxella catarrhalis.
• If a patient fails to respond, he may require treatment with a second-line agent for presumed beta-lactamase positive organisms.
• There is increasing concern regarding the rising prevalence of infections due to penicillin resistant Streptococcus pneumoniae. 
• Failure of a patient to respond to a second-line agent may suggest such an infection. In these patients, tympanocentesis to establish a bacteriologic diagnosis is helpful.
•  Optimal treatment of penicillin-resistant S. pneumoniae otitis media is currently unclear, but may include drugs such as IM ceftriaxone or oral clindamycin.
  
  

7. What are the complications and long-term consequences of the infection?

•  Mastoiditis was a very common infection in the pre-antibiotic era, and results from spread of infection from the middle ear to the mastoid air cells of the temporal bone. 
• A bulging tympanic membrane will occasionally spontaneously perforate, with purulent discharge seen from the ear canal. These perforations spontaneously heal and cause no long-term damage.
•  Persistent middle ear effusion may follow an acute otitis media, and result in hearing loss and language delay in young children. 
• Intracranial infections such as meningitis can occasionally occur.
•  Chronic otitis media may result in formation of a cholesteatoma, an overgrowth of squamous epithelium in the middle ear which must be removed by resection to restore proper hearing.