Flashcards in micro: Ear infections, Felton Deck (14):
What are some of the main normal flora living in the ear?
Normal flora, about the same as the oily areas of the skin. Staphylococcus sp., mainly epidermidis, also Micrococcus, Corynebacterium, Propionibacterium.
What is swimmer's ear? What normally causes it? What are the symptoms?
Diseases of the External Ear (Otitis Externa).
Most often caused by Pseudomonas aeruginosa
symptoms: Fullness, itching, pain, hearing loss due to occlusion of lumen, blue-green serous discharge
What are predisposing factors of otitis externa?
a) Elevated environmental humidity
b) High temperature
c) Maceration of skin following prolonged exposure to moisture
d) Local trauma
e) Introduction of exogenous bacteria, especially Pseudomonas (because loves water)
What is Bullous external otitis? What generally causes it? How is this different from otitis media?
hemorrhagic bullae on osseus canal walls; rupture of bullae causes bloody discharge.
also caused by pseudomonas aeruginosa
Important to differentiate from middle ear infection. In this case there is no previous respiratory infection
What is Granular external otitis?
May develop from untreated diffuse otitis externa.
Skin of meatus is raw and coated with scanty creamy pus and granulations on osseous meatus.
--> can be secondary
What is Necrotizing external otitis (Malignant external otitis)? What generally causes it?
Necrosis with granulation tissue on floor of external auditory canal at junction of osseous and cartilaginous canals. It may spread through the clefts, expose bone and cartilage and spread into deep tissues, and even cause osteomyelitis and meningitis.
Pseudomonas aeruginosa but pts with this generally have some underlying factor, such as diabetes.
What kind of infections do gram + infections tend to cause? What are some common ones?
infections of the outer ear, similar to diseases of the skin.
Furuncle and carbuncle - Staphylococcus aureus (Acute localized otitis externa)
Abscess - usually Staphylococcus aureus
Cellulitis - Streptococcus or Staphylococcus
Erysipelas - Group A beta-hemolytic Streptococcus
Ecthyma - Group A beta-hemolytic Streptococcus with an occasional coagulase-positive Staphylococcus aureus as secondary invader.
Impetigo Contagiosum - Group A beta-hemolytic Streptococcus or coagulase-positive Staphylococcus aureus.
Infectious eczematoid dermatitis, a consequence of perforated otitis media. The discharge from the primary affected area will irritate, sensitize, or infect adjacent skin. Etiology usually Staphylococcus aureus.
What can saprophytic fungi cause? What can predispose pts to this?
Acute Otomycosis (Mycotic Otitis Externa)--> caused by apergillus niger and other fungi, such as Mucor
1. hot weather
2. use of ear drops containing antibiotics and/or steroids over a period of weeks
What are some viruses that can affect the outer ear? How do they do so?
Herpes simplex, Herpes zoster, Verrucae (warts) (Papovavirus group), Molluscum contagiosum (Poxvirus group)
they affect the skin or mucous membrane but can affect the ear as well
What are other causes of outer ear infections?
arthropod parasites and hypersensitivity reactions
What are predisposing factors to otitis media?
1. upper respiratory tract infection
2. age of the child
3. previous otitis media
5. cigarette smokingby parents
6. abnormal middle ear or eustachain tube
7. exposure to other children in day care of to a sibling with recurrent otitis media
How does the Eustachian tube of a child compare to that of an adult?
The Eustachian tube is longer in adults than in children.
The tube in adults enters the nasopharynx at an angle of up to 45 degrees from the horizontal (steep); in children it enters an an angle of around 10 degrees from the horizontal (flat)--> easier for bacteria to get in in adults
What is the key predisposing factor to otitis media?
abnormality of the Eustachian tube