Pus | Abscesses, Burns and sinuses | culture and sensitivity

Isolate and identify aerobic and anaerobic pathogenic organisms’ pus specimen.


Aim of the test
Isolate and identify aerobic and anaerobic pathogenic organisms’ 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; unlabeled specimen; dried samples and specimen received after prolonged delay (usually more than 72 hours); specimen received in expired transport media

Commensals bacteria




  • Alpha haemolytic streptococci
  • Corynebacterium spp.
  • Coagulase negative Staph.
  • Propionobacterium spp.
  • Bacillus spp.

Pathogenic bacteria

  • Pseudomonas aeruginosa
  • Proteus spp
  • E. coli
  • Klebsiella spp
  • Morganella
  • Providencia
  • Streptococcus pyogenes
  • Staphylococcus aureus
  • Enterococcus spp.
  • Clostridium perfringens
  • Fusobactrium spp
  • Peptostreptococcus spp
  • Mycobacterium tuberculosis
  • Nocardia spp.
  • Actinomyces israelii

Specimen collection

Pus from abscess is best to 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 syringe.
Time relapse before processing the sample: 30 min.
Storage: Maintain specimen swab at room temperature. Do not refrigerate.

Media

  • Blood Agar,
  • Chocolate Agar,
  • MacConkey Agar
  • Thioglycollate broth

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.

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.
Turnaround 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.

Additional information

Contamination of the specimen with normal flora is one of the major obstacles in obtaining good results. Care should be taken to avoid contaminating the specimen with normal flora. This could be accomplished by swabbing superficial infected wounds with 70% alcohol.



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