Detection of Antibiotic Resistance by Phenotypic and Genotypic Methods in Helicobacter Pylori and its Association with Genotypes

Objectives: This study aimed to determine the prevalence of Helicobacter pylori infection in patients with dyspeptic symp-toms, to evaluate antibiotic resistance rates using both phenotypic and genotypic methods, and to investigate the association between resistance and the presence of cagA and vacA virulence genotypes.
Methods: A total of 103 consecutive patients (64 female, 39 male; mean age 47.7 +/- 15.9 years) who underwent upper gastrointestinal endoscopy for dyspepsia were included in this cross-sectional study. Biopsy samples were obtai-ned from both the antrum and corpus of each patient. H. pylori culture was performed on selective media under microaerophilic conditions. Antibiotic susceptibility testing for amoxicillin, clarithromycin, tetracycline, and le-vofloxacin was conducted using the E-test method. DNA extracted from biopsy samples was amplified by polymerase chain reaction (PCR) using specific primers targeting the glmM, cagA, and vacA genes. Clarith-romycin resistance was confirmed by PCR-restriction fragment length polymorphism (PCR-RFLP) targeting the 23S rRNA gene. Levofloxacin resistance was confirmed by DNA sequence analysis of the gyrA gene. Histopat-hological examination was performed using Giemsa staining.
Results: H. pylori positivity was detected in 76 of 103 patients (73.8%) by glmM PCR, whereas culture positivity was ob-served in only 58 patients (56.3%), indicating significantly higher sensitivity of PCR (p < 0.001). Among the 58 culture-positive isolates, E-test resistance rates were as follows: amoxicillin 1.7% (1/58), clarithromycin 10.3% (6/58), tetracycline 0% (0/58), and levofloxacin 6.9% (4/58). No statistically significant association was found between antibiotic resistance and patient gender or endoscopic findings (p > 0.05). Among the 76 PCR-positive samples, the cagA gene was positive in 46 (60.5%) and the vacA gene was positive in 73 (96.0%). The ca-gA+/vacA+ (Type I) genotype was present in 46 pa-tients (60.5%). No significant association was detected between antibiotic resistance and the presence of cagA or vacA genotypes (p > 0.05). Molecular analysis revea-led that among clarithromycin-resistant isolates, the A2143G mutation was present in 71.4% (5/7) and the A2142G mutation in 28.6% (2/7). All four levofloxacin-resistant isolates harbored gyrA point mutations: Asp-91 in three isolates (75%) and Asn-87 in one isolate (25%).
Conclusion: The clarithromycin resistance rate (10.3%) in the Kahramanmaraş region remains within the range reported in European countries and below the 15% threshold. However, levofloxacin resistance (6.9%) is emerging and requires careful monitoring. Amoxicillin and tetracycline resistance remain low. No association was found between cagA or vacA genotypes and antibiotic resistance. PCR-based methods demonstrated superior sensiti-vity compared to culture for H. pylori detection. Periodic regional surveillance of antibiotic resistance patterns is essential to guide appropriate empiric treatment and preserve the efficacy of H. pylori eradication regimens.

Keywords: Helicobacter pylori, antibiotic resistance, clarithromycin, levofloxacin, cagA, vacA