Sb. Walters et Ba. Hanna, TESTING OF SUSCEPTIBILITY OF MYCOBACTERIUM-TUBERCULOSIS TO ISONIAZID AND RIFAMPIN BY MYCOBACTERIUM GROWTH INDICATOR TUBE METHOD, Journal of clinical microbiology, 34(6), 1996, pp. 1565-1567
We tested isolates of Mycobacterium tuberculosis recovered from 117 pa
tients for their susceptibilities to isoniazid (INH) and rifampin (RIF
) by the Centers for Disease Control and Prevention's disk modificatio
n of the indirect method of proportions (MOP) test and a three-tube my
cobacteria growth indicator tube (MGIT; BBL) antimycobacterial suscept
ibility test (AST). Sixty-seven of the M. tuberculosis isolates were r
ecovered from Lowenstein-Jensen (BBL) subcultures, and 50 of the isola
tes were recovered from MGIT cultures of samples from various body sit
es. For the MGIT AST method, 0.5 mi of test organism suspension was in
oculated into an MGIT with 0.1 mu g of INH per ml, an MGIT with 1.0 mu
g of RIF per mi, and growth control MGIT. The tubes were incubated at
37 degrees C and were examined daily. The MGIT AST results were inter
preted as follows: susceptible if the tubes containing INH or RIF did
not fluoresce within 2 days of the time that the positive growth contr
ol fluoresced and resistant if the tubes containing INH or RIF did flu
oresce, within 2 days of the time that the positive growth control flu
oresced. The mean time fluorescence for the positive growth control wa
s 5.5 days. The two methods were in agreement for 114 of the 117 isola
tes from patients, while for 3 isolates there were minor discordant re
sults.