Brief Article
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World J Gastroenterol. Mar 28, 2014; 20(12): 3343-3349
Published online Mar 28, 2014. doi: 10.3748/wjg.v20.i12.3343
Detection of genotypic clarithromycin-resistant Helicobacter pylori by string tests
Jeng-Yih Wu, Sophie S W Wang, Yi-Chern Lee, Yoshio Yamaoka, David Y Graham, Chang-Ming Jan, Wen-Ming Wang, Deng-Chyang Wu
Jeng-Yih Wu, Wen-Ming Wang, Department of Internal Medicine, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung 807, Taiwan
Sophie S W Wang, Yi-Chern Lee, Chang-Ming Jan, Wen-Ming Wang, Deng-Chyang Wu, Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan
Jeng-Yih Wu, Wen-Ming Wang, Deng-Chyang Wu, Department of Medicine, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
Yoshio Yamaoka, David Y Graham, Department of Medicine, Veterans Affairs Medical Center and Baylor College of Medicine, Houston, TX 77030, United States
Deng-Chyang Wu, Division of Internal Medicine, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan
Author contributions: Wu JY designed the study and wrote the manuscript; Wu DC designed and supervised the study and directed its implementation; Wu JY, Jan CM, Wang SSW, Wang WM and Wu DC helped to conduct the literature review, obtain informed consent and perform personal data collection; Lee YC conducted the experiments; Yamaoka Y and Graham DY offered the idea of this study; all authors have approved the final draft submitted.
Supported by Grants from National Science Council of Republic of China, No. NSC96-3111-P-042A-004-Y and No. NSC97-2314-B-037-047-MY3; and from Kaohsiung Medical University Hospital, No. KMUH97-7R32 and No. KMUH97-7G49
Correspondence to: Deng-Chyang Wu, MD, PhD, Division of Internal Medicine, Kaohsiung Municipal Hsiao-Kang Hospital, 482 Shanming Rd, Hsiaogang Dist, Kaohsiung 807, Taiwan. dechwu@yahoo.com
Telephone: +886-7-3121101 Fax: +886-7-3135612
Received: August 23, 2013
Revised: September 17, 2013
Accepted: October 19, 2013
Published online: March 28, 2014
Abstract

AIM: 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.

CONCLUSION: 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.

Keywords: Helicobacter pylori, String test, Clarithromycin resistance, Polymerase chain reaction-restriction fragment length polymorphism

Core tip: According to region, antibiotic resistance is mostly detected by culture of endoscopic biopsy. The study aimed to detect genotypic clarithromycin resistance by string tests. Amplified 23S rRNA from strings was digested by restriction enzymes to discriminate A2142G or A2143G mutations conferring clarithromycin resistance. Culture was also done to compare genotypic and phenotypic resistance. Sensitivity and specificity of the method were 66.7% and 97.3%, respectively. Positive and negative predictive values were 80% and 94.7%, respectively. Our study demonstrates that the string test, rather than endoscopic biopsy culture, could provide an option for molecular analysis in future.