Mycobacterium – Gastric Lavage

Limitations

Specimens obtained for initial diagnosis after the initiation of antimicrobial therapy may produce false negative results. Even a few days of antimicrobial therapy may kill or inhibit sufficient numbers of mycobacteria so as to leave the laboratory confirmation of disease in doubt.

Storage and Transport

Label the specimen container with the patient’s full name, date of 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

Store at 2-8 ◦C if transport is delayed more than one hour. Specimens should be transferred to the lab ASAP.

Test Frequency and Turnaround Time (TAT)

Mycobacterium faeces Gastric Lavage cultures are performed daily Monday to Saturday.

Turnaround time is up to 1 day from receipt by PHO laboratory for smear results from the concentrated specimen.

Turnaround time for negative cultures is 49 days from receipt by PHO laboratory.

STAT and Critical Samples Testing

STAT testing is not available.

Contact Public Health Ontario Laboratory to request approval for URGENT testing. 

If URGENT testing is approved, mark URGENT on the outside of the package as well as on the requisition. A phone number and contact person must be provided for phoning the result.

URGENT Smears Specimens that are received in the lab by 2:00 p.m. will have a smear done and phoned the same day. Specimens that arrive after 2 p.m. will have the smear result phoned first thing the following morning.

A smear, prepared from the concentrate, is stained using the Auramine-Rhodamine (AR) fluorochrome stain and fluorescence microscopy. 

A negative AFB smear does not rule out TB, the culture may still be positive. 

Specimens are set up for culture on solid and in liquid media and incubated for up to 7 weeks.

Reporting

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

Smears of concentrated specimen showing Acid Fast Bacilli are reported to the ordering physician or health Care provider and to the Medical Officer of Health.

AFB Negative smears are reported to the ordering physician or Health Care Provider indicated on the requisition.

Mycobacteria species other than M. tuberculosis (NTM) are reported to the ordering physician only.

Specimens that are positive for Mycobacterium tuberculosis are to be reported to the Medical Officer of Health as per Health Protection and Promotion Act.