Table 1. Mechanisms of antibiotic resistance in H. pylori .

Antibiotics	Antibiotic resistance mechanism	Associated gene or sequence
Amoxicillin	Mutational change of penicillin-binding protein	pbp1A, pbp2, pbp3, pbp4
	Production of beta-lactamase
	Outer membrane protein mutations causing decreased membrane permeability	hefC, hopC, hofH
Clarithromycin	Point mutations in 23S rRNA	23S rRNA
	Increased antibiotic efflux mediated by efflux pump systems	rpl22, infB
Levofloxacin	Point mutations in quinolone resistance determination region of DNA gyrase gene	gyrA, gyrB
Metronidazole	Mutations causing reduced or abolished nitroreductase activity	rdxA, frxA
Tetracycline	Mutations in 16S rRNA	16S rRNA
Rifabutin	Point mutations in rifampicin-resistance determining region of RNA polymerase gene	rpoB