Re-decontamination of liquid mycobacterial cultures: Additional Mycobacterium tuberculosis yield in the era of Xpert MTB/RIF Ultra in Cape Town, South Africa

A retrospective review of liquid mycobacterial cultures was performed at a laboratory in South Africa from 01 January 2018 to 31 December 2018 to assess the increased yield in detecting Mycobacterium tuberculosis complex following sample re-decontamination. Only 9 of 99 (9%) re-decontaminated samples were culture positive for M. tuberculosis complex. Xpert MTB/RIF Ultra, concurrently performed on 7 of the 9 samples, detected M. tuberculosis complex in all but 1 sample. Re-decontamination of non-sterile samples did not increase the M. tuberculosis complex yield enough to offset the financial costs and additional labour in a laboratory that utilises the Xpert MTB/RIF Ultra system as a first-line diagnostic modality.