UK SMI notes – Ear Infections.

Type of specimen:

Ear swab

Middle ear fluid

Scraping of material from the ear canal (for fungal infection)

Expected organisms

Otitis Externa

Acute localised otitis externa	Staphylococcus aureus Group A Streptococcus	furuncle Erysipelas
Acute diffuse otitis externa	Pseudomonas aeruginosa S. aureus Anaerobes	Treatment – topical cleaning of debris. Antibiotics are not useful.
Chronic otitis externa	Colonisation by Enterobacteriaceae Fungi	Treatment – topical, cleaning of debris. Antibiotics are not useful.
Malignant otitis externa	P. aeruginosa.	Invasive, necrotising infection. Needs aggressive antibiotic therapy and debridement. At-risk groups are diabetic, older people, immunocompromised people.

Otitis media

Acute otitis media	Streptococcus pneumoniae, Haemophilus influenza and Moraxella catarrhalis Respiratory viruses. Less common: Staph aureus Group A Streptococcus Gram-negative organisms	co-existence of fluid in the middle ear and signs and symptoms of acute illness.
Chronic suppurative otitis media	Pseudomonads MRSA Anaerobes	Chronic, suppurative destructive infection leading to hearing loss.

Specimen processing:

• Processing is done in containment level 2, except for the process which develops infectious aerosols (use microbiological safety cabinet).
• Gram stain – if middle ear effusion is sent.
• Expected turnaround time – 16–72hr

Plates

Otitis Externa	Blood agar (pick up target organisms, pick up any pure growth) Staph/strep selective agar (may not be available in some labs, pick up Staph aureus, GAS) CLED (Enterobacteriaceae, Pseudomonads) SAB (Fungi)
Otitis media – swab	Blood agar (pick up target organisms, pick up any pure growth) Staph/strep selective agar (may not be available in some labs, pick up Staph aureus, GAS) CLED (Enterobacteriaceae, Pseudomonads) SAB (Fungi) and Neomycin fastidious anaerobe agar with metronidazole 5 µg disc (Anaerobes)
Middle ear effusion	Chocolate agar (any organism) Fastidious anaerobe agar with metronidazole 5 µg disc (anaerobes)
Note:	If chocolate agar has bacitracin, a separate blood agar should be used for M. catarrhalis and S. pneumoniae.

Up to what level identification is required?

• Fungi – genus level
• Yeast – yeast level
• Pseudomonas spp. and anaerobes – Pseudomonads and anaerobe level, respectively.
• Enterobacteriaceae – coliform
• Beta haemolytic Strep – Lancefield group level.
• Pseumococcus, Staph aureus, Neisseria, Moraxella, Haemophilus – species level

Management of otitis externa:

Localised otitis externa – 

• Analgesic, local heat (warm flannel)
• Oral antibiotic (flucloxacillin/clarithromycin 7 days) –only when spreading inflammation, systemic signs of infection, or a patient is at risk of complications.
• Drainage of pus (not required in most cases).

Acute diffuse otitis externa – 

• Cleaning the ear canal – under direct visualisation; may need ENT input, esp. if the tympanic membrane is compromised.
• Topical agents – Astringent (Aluminium acetate)/ corticosteroid/ antibiotics (neomycin, clioquinol, chloramphenicol, aminoglycoside, quinolone, polymyxin). Some antibiotics (aminoglycoside/ polymyxin) are contraindicated in the presence of a tympanic membrane perforation unless advised by a specialist (ENT).
• ENT input.
• The usual duration of treatment is 7-days
• Oral antibiotics are rarely needed (inflammation extending beyond the ear canal, Unable to use topical treatment or patient at risk of complications).
• Abstain from water sports for 7-10 days and use.

Chronic diffuse otitis externa –

• Avoiding exposure to offending agent/chemical.
• Treatment of fungal infection – Clotrimazole, clioquinol containing preparation.
• Topical steroids, topical antifungal trial in some cases

(Ref: NICE CKS, BNF)

Malignant Otitis externa –

• For Pseudomonas, antiPseudomonas antibiotic – Systemic. Ciprofloxacin +/-  an antipseudomonal beta-lactam for 6-8 weeks.
• For Aspergillus – Voriconazole/ isavuconazole/ amphotericin 8 – 12 weeks.
• Surgery – selected cases [Peled, Singh, medscape]

Acute otitis media:

• Usually, resolve in 3-7 days.
• Admission needed/considered in – children <3mo, children <6mo with fever, acute complications or severe infection (specialist/ENT opinion)
• Antibiotic- severe/systemic infection/complication, otorrhoea, children with bilateral disease, deteriorating signs and symptoms.
• Antibiotics that can be used: Preferred – Amoxicillin or macrolide. 2nd line – coamoxiclav.
• Recurrent cases may need a specialist opinion and removal of potential contributory factors – GORD, smoking etc.