Detection of genotypic clarithromycin-resistant Helicobacter pylori by string tests.
OBJECTIVE
To evaluate the utility of the string test to detect genotypic clarithromycin-resistant Helicobacter pylori (H. pylori) by polymerase chain reaction (PCR)-restriction fragment length polymorphism.


METHODS
Patients undergoing endoscopic examinations were enrolled in the present study. String tests were done on the next day of endoscopy. Segments of 23S rRNA were amplified from DNA obtained from string tests. PCR-restriction fragment length polymorphism was accomplished by restriction enzymes BbsI and BsaI recognizing the mutation site A to G at 2143 or at 2142 of 23S rRNA domain V, respectively.


RESULTS
One hundred and thirty-four patients with H. pylori infection underwent string tests. To compare phenotypic resistance, 43 isolates were successfully cultured in 79 patients in whom 23S rRNA was successfully amplified. Of five patients with clarithromycin-resistant H. pylori, 23S rRNA of H. pylori isolates from four patients could be digested by BsaI. In 38 susceptible isolates, 23S rRNA of H. pylori isolates from 36 patients could not be digested by either BsaI or BbsI. The sensitivity and specificity of the string test to detect genotypic clarithromycin resistance were 66.7% and 97.3%, respectively. Positive and negative predictive values were 80% and 94.7%, respectively.


CONCLUSIONS
String test with molecular analysis is a less invasive method to detect genotypic resistance before treatment. Further large-scale investigations are necessary to confirm our results.
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Jeng-Yih
JY
Wu
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Sophie S W
SS
Wang
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Yi-Chern
YC
Lee
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Yoshio
Y
Yamaoka
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
David Y
DY
Graham
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Chang-Ming
CM
Jan
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Wen-Ming
WM
Wang
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan.
Deng-Chyang
DC
Wu
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017291:Clarithromycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004724:Endoscopy; D005838:Genotype; D016481:Helicobacter Infections / Q000188:drug therapy* / Q000235:genetics; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008828:Microbiological Techniques; D009154:Mutation; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012338:RNA, Ribosomal, 23S / Q000235:genetics
D000900:Anti-Bacterial Agents; D012338:RNA, Ribosomal, 23S; D017291:Clarithromycin
Clarithromycin resistance; Helicobacter pylori; Polymerase chain reaction-restriction fragment length polymorphism; String test