This assay uses PCR to simultaneously detect the presence of Mycobacterium species and specifically detects M. tuberculosis. Molecular detection of mycobacteria may be useful where there is a high clinical suspicion of tuberculosis and a rapid diagnosis of tuberculosis would have a positive impact on patient management or infection control, (e.g. treatment for other diseases delayed due to the possibility of tuberculosis; confirmation of smear positive sample before contact tracing; high probability of infection with MDR-TB, etc.).
Confirmation of the presence of NTM and species identification may prevent patients being started on unnecessary treatment for tuberculosis and reduce concerns regarding infection control measures and / or contact tracing. It may also be useful for diagnosis of NTM infection in patients who have an impaired immune system and are likely to have a rapid progression of disease. Direct detection of mycobacteria in histological samples can be used to confirm a histological diagnosis but where no sample is available for mycobacterial culture.
Container / Tube
Various sample types.
Collection Conditions
Mycobacterial PCR can be carried out on a variety of samples (e.g. sputum, CSF – ideally submit 5 ml of CSF for best yield -, aspirate fluids and non-fixed biopsy specimens). Histological samples (send 10 sections 10 µm thick) can also be processed though have a lower sensitivity due of the effects of histological fixatives on DNA.
Availability
Twice weekly.
Send to
Microbiology Department, Centre for Laboratory Medicine, St James’s University Hospital, Beckett Street, ĢtvƵ, LS9 7TF.
Turnaround Time
14 days.
Additional Information
All non-histological clinical specimens should be marked “Danger of Infection”. These tests should not replace culture for mycobacteria if at all possible. Following nucleic acid extraction, all samples are examined by PCR for the presence of the 16S-rRNA gene found in mycobacteria and separately for detection of M. tuberculosis complex DNA. Where M. tuberculosis DNA is not detected, positive 16S rRNA PCR products are sequenced to obtain the species identification.
Negative PCR results do not rule out a diagnosis of mycobacterial infection, although positive results can confirm a clinical / histological diagnosis. These PCR assays are not able to differentiate between the different members of the Mycobacterium tuberculosis complex. NTMs are associated with the environment and, in some cases, may reflect contamination during collection or histological processing.
ID
3679