Antimicrobial susceptibility testing – Aerobic bacteria
Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.
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
Submission and Collection Notes
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
- Contact information
If a swab or broth is received, the turnaround time will be delayed by at least 24 hours.
Primary specimens (not cultured organisms) are unacceptable and will be rejected.
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.
Storage and 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.
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.
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.
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
Results are reported to the ordering physician or health care provider as indicated on the requisition.
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.