Aim of the test

• Isolate and identify aerobic and anaerobic pathogenic organisms in pus specimen.

• Types of specimen: • Swabs from the infected area or aspiration

from deep wounds. Swabs in anaerobic transport media for the isolation of anaerobes.

Criteria of specimen rejection

• Inappropriate specimen transport device; mislabeled specimen; unlabelled specimen.

• Dried samples and specimen received after prolonged delay (usually more than 72 hours).

• Specimen received in expired transport media

Pathogen and commensals

Specimen collection • Pus from abscess is best collected at the time the

abscess is incised and drained.• Using sterile technique, aspirate or collect from

drainage tube up to 5 ml of pus, transfer to sterile container.

• If pus is not being discharged use sterile cotton wool swab to sample from the infected site.

• Extend the swab deeply into the depth of the lesion.

• Immerse the swab in container of transport medium

• Label it and send to the laboratory as soon as possible.

• Quantity of specimen: sufficient amount on swab, or aspiration in transport media or syring

• Time relapse before processing the sample: 30 min.

• Storage: Maintain specimen swab at room temperature. Do not refrigerate.

Culturing procedure• Streak one blood agar plates, one chocolate,

MacConkey and inoculate thioglycollate broth tube.

• Gram stain to check the presence or absence and if present the type or types and the predominant organisms.

• Turn around time: • Gram stain results should be available 1 hour

after specimen receipt. • Isolation of a possible pathogen can be expected

after 2-3 days. • Negative culture will be reported out 1-2 days

after the receipt of the specimen

Specimen processing

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/s and its

sensitivity pattern as a final report.

Additional information

• Contamination of the specimen with normal miceobiota is one of the major obstacles in obtaining good results.

• Care should be taken to avoid contaminating the specimen with normal commensals.

• This could e accomplished by swabbing superficial infected wounds with 70% alcohol.