Evaluation of microscopic observation drug susceptibility assay for diagnosis of multidrug-resistant Tuberculosis in Viet Nam

Table 2 Discrepant DST results between MODS and LJ resolved by MAS-PCR

Isolate N0	DST-MODS		DST-LJ		MAS-PCR (mutation point)		Remarks
	RIF 1 μg/ml	INH 0.4 μg/ml	RIF 40 μg/ml	INH 0.2 μg/ml	RIF resistant mutation	INH resistant mutation
1	R	R	S	S	None	R (katG)	MDR by MODS
2	S	R	R	R	_		RIF-MODS resistant on day 20. MDR by LJ. rpoB sequencing: synonymous mutation (H445C, CAC > TGC)
3	S	S	R	S	None	None
4	S	R	R	R	R (531)		RIF-MODS resistant on day 20. MDR by LJ
5	S	R	S	S		None
6	S	R	S	S		None
7	S	R	S	S		None
8	S	R	S	S		None
9	S	S	S	R		R (katG)	INH-MODS resistant on day 30
10	S	S	S	R		None	INH-MODS resistant on day 30
11	S	S	S	R		R (katG)	INH-MODS resistant on day 40
12	S	S	S	R		R (inhA)
13	S	S	S	R		R (inhA)
14	S	S	S	R		R (inhA)
15	S	S	S	R		R (katG)
16	S	S	S	R		R (inhA)
17	S	S	S	R		R (katG)	INH-MODS resistant on day 30
18	S	S	S	R		R (inhA)
19	S	S	S	R		R (inhA)
20	S	S	S	R		None
21	S	S	S	R		R (inhA)
22	S	S	S	R		R (inhA)
23	S	S	S	R		R (katG)
24	S	S	S	R		None
25	S	S	S	R		R (katG)

rpoB Sequencing was done for one isolate which failed to amplify for MAS-PCR
25/300 isolates (8.3%) had discrepant DST results between MODS and LJ for INH or RIF. R: resistant, S: sensitive, blank (−): no PCR product, blank cells: concordance results between MODS and LJ therefore MAS-PCR was not attempted

ISSN: 1471-2334