Aim of the test Isolate and identify aerobic

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, Mac. Conkey 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.