Table 2.

Classification of isolates of Tuberculosis Regional Reference Laboratory in Mashhad (n = 123) based on antibiotic susceptibility testing and distribution of gyrA and gyrB genes mutation patterns

Gene	Nucleotide change	Amino acid change	Clinical isolates (n = 111)		MDR-TB (n = 12)	Polydrug resistant (n = 0)
			Pansusceptible (n = 108)	FQ mono-resistant (n = 3)a
gyrA	C(269) → T	Ala(90) → Val	–	–	–	–
	T(271) → C	Ser (91) → Pro	–	–	–	–
	A(281) → G	Asp(94) → Gly	–	1 (new case)	2 (XDR)b	–
gyrB	–	–	–	–	–	–
Phenotypically FQ resistant, without any gyrase mutations			–	2 (1 new, 1 relapse)	1	–
All phenotypically FQ resistant			–	3	3c	–

Note: Pansusceptible: susceptible to all first-line anti-TB drugs, FQ mono resistance: being resistant only to FQ, but sensitive to all first-line TB drugs, MDR-TB: resistance to at least both isoniazid and rifampin, Polydrug resistance: resistance to more than one first-line anti-TB drug, other than both isoniazid and rifampin

^aThese three isolates were all related to Iranian patients. Two of them were new TB cases and one was a TB relapse

^bThese two MDR isolates were resistant to FQs and also they were found to be resistant against kanamycin and amikacin in another study by our colleagues on these isolates [30]. Both were TB treatment failure cases, one from Afghanistan and one from Kazakhstan

^cAll were treatment failure cases