Association Between the Phenotype and Genotype of Isoniazid Resistance Among Mycobacterium tuberculosis Isolates in Thailand

Figures & data

Figure 1 Genotypic drug resistance and level of resistance to isoniazid.

Figure 2 Isoniazid MIC distribution and gene mutations of Mycobacterium tuberculosis.

Table 1 Performance Characteristics of the Isoniazid Gene Mutation and the Levels of Isoniazid Resistance in Clinical Isolates (N = 69)^a

Gene Mutation	Detection Level of Resistance	Sensitivity, % (95% CI)	Specificity, % (95% CI)	Positive Likelihood Ratio	Negative Likelihood Ratio	PPV, % (95% CI)	NPV % (95% CI)
katG	High level	98.2 (90.1–100)	100 (78.2–100)	–	0.02 (0–0.1)	100	93.8 (68.3–99.1)
	Low level	0 (0–21.8)	1.9 (0.1–9.9)	0	54 (7.8–376.4)	0	6.3 (1–31.7)
inhA	High level	1.9 (0.1–9.9)	0 (0–21.8)	0.02 (0–0.1)	–	6.3 (1–31.7)	0
	Low level	100 (78.2–100)	98.2 (90.1–100)	54 (7.8–376.4)	0	93.8 (68.3–99.1)	100

Notes: ^aAll isolates with katG mutation had high-level resistance (51 isolates had katG S315T mutation and 2 had katG deletion mutation). Fifteen isolates with InhA mutation had low level of resistance and 1 had high level of resistance.

Abbreviations: PPV, positive predictive value; NPV, negative predictive value.

Table 2 Gene Mutation Profiles of MTB Isolates (N = 74)

Gene Mutation Profiles	No. of Isolates (%)
Monoresistant TB
Isoniazid	57 (77.0)
katG S315T   inhA c-15T	43 (75.4) 14 (24.6)
Poly-resistant-TB^a
Fluoroquinolones	1 (1.4)
gyrA D94G	1 (100.0)
MDR-TB
Isoniazid + rifampicin	11 (14.9)
katG S315T + rpoB S531L	4 (36.4)
katG S315T + rpoB D516V	1 (9.1)
katG S315T + rpoB deletion	3 (27.3)
katG deletion + rpoB S531L	1 (9.1)
katG deletion + rpoB deletion	1 (9.1)
inhA C-15T + rpoB S531L	1 (9.1)
Pre-XDR-TB
Isoniazid + rifampicin + aminoglycosides	1 (1.4)
inhA C-15T + rpoB H526Y + rrs A1401G	1 (100)
Without mutation^a	4 (5.4)

Note: ^aPhenotype was isoniazid-resistant without an isoniazid gene mutation.

Abbreviations: MDR-TB, multidrug-resistant Mycobacterium tuberculosis; Pre-XDR-TB, pre-extensively drug-resistant Mycobacterium tuberculosis.