Rapid and improved recovery rate of Mycobacterium tuberculosis in Mycobacteria Growth Indicator Tube combined with solid Löwenstein Jensen medium.

SETTING

Clinical microbiology laboratory with limited resources in a developing country.

OBJECTIVE

To determine the recovery rate of Mycobacterium tuberculosis (MTB) in Mycobacteria Growth Indicator Tube (MGIT) combined with Löwenstein Jensen (LJ) culture medium.

DESIGN

Stock cultures and reference strains of mycobacteria and clinical specimens were inoculated into MGIT and onto LJ. The combined recovery rate was determined and time to positive culture in each medium was compared.

RESULTS

All known stock and reference cultures of mycobacteria grew in both media. MGIT combined with LJ increased the recovery rate from 109 (63.4%) to 122 (70.9%) of 172 clinical specimens. Of those isolated, the yield in MGIT (99.2%) exceeded that in LJ (89.3%). The average day to detection of MTB in MGIT was earlier by 14.2 days compared to LJ (15.7 days vs. 29.9 days). For mycobacteria other than tuberculosis (MOTT), there was little difference in the recovery time, except for M. kansasii where growth in MGIT was earlier by one week and M. triviale where growth in MGIT was detected later than LJ.

CONCLUSION

MGIT is an excellent system for the rapid isolation of mycobacteria. It increases the recovery rate of MTB when combined with LJ.