‫بسم هللا الرحمن الرحيم‬
L/O/G/O
Diagnostic Medical Microbiology-Laboratory Manual
Ear Culture
Aim of the test
Etiological diagnosis of otitis externa or otitis media by aerobic and
anaerobic culture with identification and susceptibility test of the
isolated organism(s).
Types of specimen
Two swabs from the external or aspiration from middle ear(s).
Criteria of specimen rejection
Inappropriate specimen transport device; mislabeled specimen;
unlabeled specimen; specimen received after prolonged delay (usually
more than two hour); specimen received in expired transport media.
Common Pathogens
Commensals flora
are present in the external ear canal
Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus pyogenes
Lactobacillus spp.
Pseudomonas aeruginosa
Propionibacterium spp.
Other Gram negative bacilli
Staphylococcus aureus
Streptococcus pneumoniae
Various Enterobacteriaceae
Haemophilus influenzae
Various streptococcus spp
Anaerobic bacteria
Candida spp. other than albicans
Proteus spp.
Occasion Pseudomonas aeruginosa
Pre specimen processing
Who will collect the specimen
 Medical technologist, Microbiologist for swab from external ear.
 Otolaryngologist for aspiration from middle ear.
Who is authorized to order the test
 Physician.
Time relapse before processing the sample
 Not more than 2 hours.
Storage
 Maintain specimen swab at room temperature.
Pre specimen processing
External Ear Specimen collection
1. Collect a specimen of the discharge on a thin, sterile cotton
wool or Dacron swab.
2. Place the swab in a container with the transport medium,
breaking off the swab stick to allow the stopper to be
replaced tightly.
3. Label the specimen and send it to the laboratory.
External Ear Specimen collection
Specimen processing for Otitis externa
Specimen processing for Otitis media
Specimen processing
 Ear specimen submitted for culture should be inoculated to blood
agar, MacConkey, and chocolate agar plates, anaerobic culture also
should be setup on those specimens obtained by tympanocenthesis
or those obtained from patients with chronic otitis media, or
mastoiditis.
 Direct visual examination for material aspirated from the middle ear
or mastoid is also examined directly for bacteria or fungi.
Cultures from mastoid are generally
taken on swabs during surgery and
should be transported anaerobically.
Additional information
 For external ear infections only Staphylococcus aureus,
Streptococcus pyogenes, Pseudomonas aeruginosa, Vibrio spp. and
Aspergillus will be looked for and reported.
 For middle ear infections only pneumococcus, Streptococcus
pyogenes, Haemophilus influenzae and Staphylococcus aureus will
be reported with a susceptibility test.
 For the chronic discharging ear, Bacteroides species and fungi will
also be reported in addition to the organisms reported for middle
ear infections.
Post specimen processing
Interfering factors:
 Patient on antibiotic therapy.
 Improper sample collection.
Result reporting:
 Report Gram stain finding as an initial report.
 Report the isolated pathogen and its sensitivity pattern as a final report.
Turn around time:
 Gram stain result should be available half hour after specimen receipt.
 Isolation of a possible pathogen can be expected after 2-4 days.
 Negative culture will be reported out 1-2 days after the receipt of the
specimen.
End of Lecture