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Objective To study the drug resistance phenotype, drug resistance gene, and virulence gene of Helicobacter pylori (Hp) in patients with failed eradication therapy, and to provide reference for remedial therapy. Methods Hp was isolated and cultured from gastric mucosa of patients with failed eradication therapy. Drug sensitivity test was used to detect the resistance of isolated strains to Metronidazole (MTZ), Clarithromycin (CLA), Levofloxacin (LEV), Amoxicillin (AMX), Tetracycline (TET), and Furazolidone (FZ). CLA and LEV resistance genes 23S rRNA, gyrA and virulence genes cagA, vacA, iceA, oipA were amplified by PCR, to further explore the relationship between drug resistance phenotype and drug resistance and virulence genes. Results In total 40 strains of Hp were isolated from 58 patients (69.0%). The resistance rates to MTZ, CLA, LEV, AMX, TET, and FZ were 100.0%, 82.5%, 72.5%, 0%, 0%, and 0%, respectively. The most common mutations of 23S rRNA and gyrA genes were T2182C (78.6%) and N87K (32.0%), respectively, and new C2165T and A2219G mutations were found in CLA resistant strains. In addition, the positive rates of virulence genes cagA, vac A si, vacA s2, vacA ml, vacA m2, tceAl, tceA2, and oipA were 97.1%, 100.0%, 0%, 42.9%, 57.1%, 62.9%, 11.4%, and 68.6%, respectively, and the difference was statistically significant. Conclusion The resistance of Hp isolates to MTZ, CLA and LEV in patients with failed eradication therapy in this area is serious, and AMX, TET and FZ are recommended for remedial therapy. The relationship between CLA resistance and C2165T and A2219G mutation and LEV resistance and vacA m2 warrants further investigation. [ABSTRACT FROM AUTHOR]

The title compound, C(10)H(7)ClN(2), contains two approximately planar mol-ecules, A and B (r.m.s. deviations = 0.039 and 0.064 Å, respectively) in the asymmetric unit. In the crystal, N-H⋯N hydrogen bonds link the mol-ecules into C(7) chains of alternating A and B mol-ecules propagating along the a-axis direction. The crystal used for the data collection was found to be a racemic twin.

In the title compound, C(11)H(10)N(2)O, the cyanide group is twisted away from the indole-ring plane [C(cy)-C(me)-C(ar)-C(ar) = 70.7 (2)°; cy = cyanide, me = methyl-ene, ar = aromatic], whereas the meth-oxy C atom is almost coplanar with the ring system [displacement = 0.014 (5) Å]. In the crystal, N-H⋯N hydrogen bonds link the mol-ecules into C(7) chains propagating in [100].

In the title compound, C(11)H(10)N(2), the carbonitrile group is twisted away from the indole plane [C(cy)-C(me)-C(ar)-C(ar) = 66.6 (2)°; cy = cyanide, me = methyl-ene and ar = aromatic]. In the crystal, N-H⋯N hydrogen bonds link the mol-ecules into C(7) chains propagating in the [001] direction.

In the crystal structure of the title compound, C(8)H(5)NO(6), both carboxyl groups are involved in inter-molecular centrosymmetric cyclic O-H⋯O hydrogen-bonding associations, which give a zigzag chain structure extending along (2[Formula: see text]1). Weak π-π stacking inter-actions are also present [minimum ring centroid separation = 3.893 (4) Å].

In the crystal structure of the title compound, C(5)H(5)NO(3), all the non-H atoms are approximately coplanar: the carb-oxy O atoms deviating by 0.013 (2) and -0.075 (2) Å from the isoxazole ring plane. In the crystal, the molecules form inversion dimers linked by pairs of O-H⋯O hydrogen bonds and the dimers stack via π-π inter-actions [centroid-centroid distance = 3.234 (2) Å].

All non-H atoms of the title compound, C(7)H(7)NO(2), are nearly coplaner, the r.m.s. deviation being 0.0087 Å. In the crystal, the partially overlapped arrangement and the face-to-face distance of 3.466 (17) Å between parallel pyridine rings of neighboring mol-ecules indicates the existence of π-π stacking. Inter-molecular O-H⋯N hydrogen bonding and weak C-H⋯O hydrogen bonding are present in the crystal structure.