Using Reduced Inoculum Densities of Mycobacterium tuberculosis in MGIT Pyrazinamide Susceptibility Testing to Prevent False-Resistant Results and Improve Accuracy: A Multicenter Evaluation

Table 1

Characteristics of 20 M. tuberculosis strains used in the multicenter evaluation.

Isolate number (duplicate)	Susceptibility to PZA (100 µg/ml)			pncA mutation		Other; drug resistance
	(multiple tests)		PZA MIC	Nucleotide	Amino
	Consistently	Predominately	(ug/ml)	number	acid
1	Susceptible	—	≤25	C 195 T	Ser65Ser	CIP
4	Resistant	—	>800	A(-11) G	NA	RIF, CIP
7	Susceptible	—	50	None	NA	None
8	Susceptible	—	≤25	None	NA	None
11 (23)	Susceptible	—	≤25	None	NA	None
12 (24)	—	Susceptible	75	None	NA	None
13 (25)	—	Susceptible	75	None	NA	None
14	Resistant	—	>100	T 37 C	Phe13Leu	INH
16 (26)	—	Susceptible	75	None	NA	FQ
17	—	Resistant	200	A 139 G	Thr47Ala	INH, RIF, AMK, EMB
18	Susceptible	—	75	C 509 T	Ala170Val	None
19	Inconclusive	Inconclusive	100	C 244 T	His82Tyr	None
20	Susceptible	—	75	G 538 A	Val180Ile	None
21 (27)	Inconclusive	Inconclusive	100	G 82 A	Ala28Thr	INH, RIF, EMB
22	Susceptible	—	50	A 110 T	Glu37Val	None

Number of tests varied by isolate. When multiple tests were performed, the value is the approximate median. CIP: ciprofloxacin; RMP: rifampin; INH: isoniazid; AMK: amikacin; EMB: ethambutol. Regulatory mutation.