Introduction

Antibiotic resistance in Helicobacter pylori (H. pylori) poses an increasing challenge for infection management. Genotypic antibiotic susceptibility testing (GAST) is proposed as cost-effective approach for successful treatment.

Aims & Methods

Aim of our study was to evaluate GAST for detecting clarithromycin and levofloxacin resistance in gastric aspirates from H. pylori-positive patients compared to conventional phenotypic AST (PAST).
Patients undergoing upper GI endoscopy (UGE) between February 2022 and April 2023 were prospectively recruited. Real-time diagnosis of H. pylori was pursued during UGE through gastric juice analysis by Endofaster¹. In case of intraprocedural H. pylori detection, two types of gastric aspirates were collected: a) undiluted gastric juice (GJ) and b) water rinse aspirate (WR). The WR was obtained after complete removal of the GJ and instillation of 30 mL sterile saline solution against the wall of the stomach corpus. Furthermore, gastric biopsies were collected for histology and culture-based PAST by E-test. Sanger sequencing of the 23S rRNA and gyrA genes from H. pylori was performed using gastric aspirates to detect polymorphisms associated with resistance to macrolides and fluoroquinolones, respectively. The test accuracy of GJ-GAST and WR-GAST was determined using PAST as the gold standard. The McNemar test was used to compare sensitivities and specificities between GJ- and WR-GAST. The level of agreement among different AST was assessed by Cohen’s κ-value.

Results

Seventy-two consecutive patients (29/43 male/female; mean age, 47.0 ± 13.5 years) tested H. pylori-positive during the UGE were included in the study. According to PAST the resistance rates were 15.3% (11/72) for clarithromycin and 18.1% (13/72) for levofloxacin. The diagnostic measures of GJ-GAST and WR-GAST for resistance detection, as well as their agreement with PAST are shown in Table 1. Overall, GAST and PAST results showed substantial agreement (κ-value ranging from 0.67 to 0.77) and a very high level of concordance (>93%) for detecting clarithromycin and levofloxacin resistance using both GJ and WR.
There were no significant differences in diagnostic performances between GJ- and WR-GAST (p > 0.05), as confirmed by an almost perfect agreement with a κ-value of 0.93 for both clarithromycin and levofloxacin. Additionally, molecular analysis, involving the inspection of Sanger chromatograms, enabled an increase in the detection of heteroresistance cases by 33% for clarithromycin and up to 50% for levofloxacin, compared to PAST.

Conclusion

Genotypic AST from gastric aspirates, following intraprocedural diagnosis of H. pylori, provides highly accurate results for detecting clarithromycin and levofloxacin resistances, comparable to conventional phenotypic AST. This novel method of GAST, performed using water rinse aspirates collected during UGE, is a valid and practical tool for tailoring eradication regimens.

References

1. Vasapolli R, Ailloud F, Suerbaum S, et al. Intraprocedural gastric juice analysis as compared to rapid urease test for real-time detection of Helicobacter pylori. World J Gastroenterol 2023;29:1638-1647.