The Value of the inhA Mutation Detection in Predicting Ethionamide Resistance Using Melting Curve Technology

Figures & data

Table 1 Demographic and Clinical Characteristics of Patients

Characteristics	Sum (n, %)	ETH-Sensitive (n,%)	ETH-Resistant (n,%)	P
Number of patients	382(100)	354(92.7)	28(7.3)
Gender(male)	253(66.2)	238(93.7)	15(53.6)	0.003
Age	44.7±19.3	45.2±19.3	38.4±19.3	0.073
No. of recurrent case	90(23.6)	74(20.9)	16(57.1)	<0.001
Place of residence
Beijing	214(56%)	209(59%)	5(17.9%)	<0.001
Other regions	168	145	23
Tuberculosis type
Pulmonary tuberculosis	341	315	26
Tubercular meningitis	1	1	0
Bone tuberculosis	40	37	2
Tuberculous empyema	1	1	0
Types of drug-resistant
MDR-TB	42	38(90.5%)	4(9.5%)
Per-XDR-TB	39	27(69.2%)	12(30.8%)
XDR-TB	16	5(31.3%)	11(68.8%)
INH-R and not MDR-TB	21	21(100%)	0
Other types	285

Abbreviations: ETH, ethionamide; INH, isoniazid.

Table 2 Frequency of Ethionamide Resistance in Low-and High-Level Isoniazid Resistant and Isoniazid Susceptible Mycobacterium tuberculosis Isolates

INH Phenotypic DST (n)	ETH Phenotypic DST	Frequency	inhA (with or without katG Mutation) (n)
High-level INH- resistant(98)	ETH-R	25	9^a
	ETH-S	73	9^b
Low-level INH -resistant(20)	ETH-R	2	2
	ETH-S	18	9^c
INH- sensitive (264)	ETH-R	1	1
	ETH-S	263	4

Notes: ^a2 of the 9 isolates with katG mutation; ^b2 of the 9 isolates with katG mutation; ^c1 of the 9 isolates with katG mutation. The ETH resistance rate was not significantly different between isolates with low- and high-level INH resistance (Χ²=2.264, P=0.132, Fisher’s exact test); The inhA mutation rate in isolates with low-level INH resistance (with or without katG mutation) was significantly higher than that in isolates with high-level INH resistance (Χ²=12.025, P<0.001, Fisher’s exact test); The single inhA mutation rate (not combined with katG mutation) was also significantly different between the two groups (Χ²=13.076, P<0.001, Fisher’s exact test).

Abbreviations: DST, drug susceptibility testing; INH, isoniazid; ETH, ethionamide; S, sensitive; R, resistant.

Figure 1 Phenotypic DST results of ETH in MTB with inhA gene mutation enrolled in this study.