Detection of genotypic clarithromycin-resistant Helicobacter pylori by string tests

Table 1 Polymerase chain reaction primers and sequences used in this study

Primer name	Sequence	Annealing temperature	Size (bp)
cagA	5'-GAT AAC AGG CAA GCT TTTGAC G-3'	50  °C	349
cagR	5'-CTG CAA AAG ATT GTT TGG CAG A-3'
HP-K1	5'-CCA CAG CGA TGT GGT CTC AG-3'	54  °C	425
HP-K2	5'-CTC CAT AAG AGC CAA AGC CC-3'

The annealing temperature and the size of amplicons are also listed. The reaction conditions are detailed in Materials and Methods.

Table 2 Result of polymerase chain reaction-restriction fragment length polymorphism from the string test

		String PCR-RFLP
		Sensitive	Resistant
E-test	Sensitive	36	2
	Resistant	1	4

Five were resistant to clarithromycin as confirmed by E-tests in 43 Helicobacter pylori isolates. Among these 43 patients undergoing the string test, four 23S rDNA amplicons from strings were digested by BsaI, indicating a mutation site A to G at 2142 of 23S rRNA. PCR-RFLP: Polymerase chain reaction-restriction fragment length polymorphism.