Application of quantitative second-line drug susceptibility testing at a multidrug-resistant tuberculosis hospital in Tanzania

Table 3 Molecular targets of resistance distributed by Bactec MGIT result or category of minimum inhibitory concentration (MIC) (N = 13 isolates)

Drug; gene	MGIT	MGIT	MIC	MIC	MIC
	Susceptible	Resistant	Susceptible	Borderline	Resistant
	Susceptible	Resistant	Susceptible	susceptible	Resistant
Rifampin; rpoB
wildtype	5	0	4	N/A	1
mutation	0	8	0	N/A	8
Isoniazid; inhA or katG
wildtype	4	0	2	N/A	1
mutation	0	9	0	N/A	10
Ethambutol; embB
wildtype	6	1	2	4	1
mutation	6	0	1	3	2
Ofloxacin; gyrA
wildtype/silent mutation	N/A	N/A	6	7	N/A
mutation	N/A	N/A	0	0	N/A
Amikacin; rrs or eis
wildtype	N/A	N/A	8	4	1
mutation	N/A	N/A	0	0	0
Ethionamide; inhA
wildtype	N/A	N/A	5	7	1
mutation	N/A	N/A	0	0	0

embB mutation included: Glu378Ala in 2 isolates; Met306Val, Met306Ile, Gly406Asp, Gly406Cys, Tyr319Cys in single isolates. Pyrazinamide susceptibility was not performed but pncA mutations included: Val128Gly in 2 isolates; Glu111stop, Asp49Gly, Ser179Ile, and Val169Ala in single isolates. Val128Gly and Val169Ala have not previously been reported. Five isolates (63%) resistant to both isoniazid and rifampin had pncA mutation.

ISSN: 1471-2334