Resistance pattern of Mycobacterium tuberculosis to first-line antituberculosis drugs

In this report we analyzed the resistance patterns of M. tuberculosis isolated in our laboratory from 1996 to 1998 and compared them with published data of the year 1995 from our laboratory. In our laboratory, 2360, 2468 and 1849 specimens were examined in 1996, 1997 and 1998, respectively. From these specimens, using Löwenstein-Jensen media, 164 (6.9%), 181 (7.3%) and 214 (11.6%) were found positive for M. tuberculosis in 1996, 1997, 1998 respectively. Compared with the earlier published reports from our laboratory, we found a fluctuation of the resistance rate to one or more first line antituberculosis drugs (streptomycin, INH, ethambutol, and rifampicin) from 15.9% in 1995,¹ 7.9% in 1996, 12.7% in 1997 and 8.4% in 1998. We also found different patterns of resistance in the last 4 years. During 1995 to 1997 the highest rate of resistance was to rifampicin, i.e. 14.0%, 7.9%, and 9.4% in 1995, 1996 and in 1997 respectively; while in 1998 the resistance to INH was the highest (4.7%). Resistance to ethambutol was not found in 1996 and 1997, but it was found in 2 isolates in 1998. Resistance to three or more drugs was not found in 1996 and 1997. Resistance to streptomycin, ethambutol and INH was found in one isolate in 1998. Resistance to four antituberculosis drugs was not found in 1996 to 1998.