Bs. Reisner et al., EVALUATION OF MYCOBACTERIA GROWTH INDICATOR TUBES FOR SUSCEPTIBILITY TESTING OF MYCOBACTERIUM-TUBERCULOSIS TO ISONIAZID AND RIFAMPIN, Diagnostic microbiology and infectious disease, 22(4), 1995, pp. 325-329
The reliability of mycobacteria growth indicator tubes (MGIT) for dete
rmining the susceptibility of Mycobacterium tuberculosis to isoniazid
(0.1 mu g/ml) and rifampin (2.0 mu g/ml) was evaluated by comparing MG
IT results to those obtained by the radiametric BACTEC TB method. We t
ested 29 isolates, many selected for resistance. The turnaround times
were 3-8 days (median 6) for MGIT and 4-10 days (median 6) for BACTEC.
Isoniazid results by both methods agreed for all isolates tested: 20
resistant and nine susceptible. Rifampin results agreed for 28 isolate
s: 10 resistant and 18 susceptible. One isolate yielded discrepant res
ults: resistant to rifampin by BACTEC, bur susceptible by Men. This is
olate was also rifampin-resistant by the traditional Method of Proport
ion and when tested by the MGIT method using 1.0 mu g/ml of rifampin.
The MGIT system is a nonradiometric alternative to the BACTEC for rapi
d susceptibility testing of M. tuberculosis to isoniazid and rifampin;
however, additional testing is needed to determine the optimal concen
tration of rifampin.