Antimicrobial susceptibility testing – Aerobic bacteria

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

Antimicrobial susceptibility testing – Aerobes

Pure viable subculture of 24 – 48 hours growth of organism on an appropriate medium (e.g. Columbia sheep blood agar) or a swab of a pure culture in Amies charcoal media for susceptibility testing2,3

N/A

Submission and Collection Notes

1

Complete all fields of the Reference Bacteriology Requisition, including:

  • Test requested
  • Date of primary specimen collection
  • Primary source of isolation (mandatory)
  • Culture information including name of isolate
  • Clinical/epidemiology
  • Contact information
2

If a swab or broth is received, the turnaround time will be delayed by at least 24 hours.

3

Primary specimens (not cultured organisms) are unacceptable and will be rejected.

Limitations

Mixed or non-viable cultures will not be tested. The submitter will be contacted by telephone. A written report will be issued to indicate that the test was not performed.

Preparation Prior to Transport

Label the specimen with the patient’s full name, date of primary specimen collection and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

Special Instructions

Complete all fields of the Reference Bacteriology Requisition. Include the patient’s full name, date of birth, Health Card Number, your lab reference number (must match the specimen label). Enter the test requested, culture information, clinical/epidemiology information, date of primary specimen collection, primary source of isolation (mandatory), physician name and address and clinical diagnosis.

Transport a fresh subculture to ensure viability on receipt. 

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Antimicrobial Susceptibility testing is performed from Monday to Saturday.

Turnaround time for test results is up to 8 days from date of receipt at the PHO laboratory.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Test Methods

Antimicrobial Susceptibility testing on a bacterial isolate is performed as per current CLSI guidelines.

Testing methods in use are:

  • Agar dilution
  • Micro-broth dilution (Sensititre)
  • MIC gradient strip

Extended Antibiotic Panel

The following extended panel of antibiotics are available on special request:

ceftazidime/avibactam, ceftolozane/tazobactam, meropenem/varbobactam, imipenem/ relebactam, and plazomicin.

Antimicrobial Susceptibility Testing of the extended panel is performed on isolates that meets any of the criteria below:

  • Carbapenemase -Producing Enterobacterales (CPE) from sterile site samples, in addition to Colistin, Tigecycline and Aztreonam
  • On special requests as follows:
    • Isolates that are multidrug resistant to first line and second line antibiotics
    • Sterile site isolates (on request)
    • Non-sterile site isolates after discussion with PHO Laboratory microbiologist

The extended panel is performed by micro-broth dilution method.

Mis à jour le 14 déc. 2022