Evaluation of Antibiotic Resistance of <i>Helicobacter pylori</i> Strains Isolated in Bari, Southern Italy, in 2017–2018 by Phenotypic and Genotyping Methods

Abstract

<b><i>Objective</i></b><i>: Helicobacter pylori</i> antibiotic resistance is a constantly evolving process and local surveillance is warranted to guide clinicians in the choice of therapy. <b><i>Materials and Methods:</i></b> Antibiotic susceptibility testing was performed by E-test on 92 <i>H. pylori</i> strains, and resistance to clarithromycin and levofloxacin was also evaluated using a commercially available genotyping method. <b><i>Results:</i></b> In naïve patients the resistance to clarithromycin, levofloxacin, and metronidazole was 37.7%, 26.2%, and 16.4%, respectively, significantly lower than the percentage found in treated patients. Concomitant resistance to ≥2 antibiotics was also observed in naïve patients. The A2143G mutation of the 23S-rRNA gene was the most frequently detected, also in naïve patients. The highest minimum inhibitory concentration (MIC)₅₀ value (256 mg/L) was associated with A2142 mutations in all the patients carrying them. For levofloxacin resistance a mutation in codon 87 was detected in 63.9% and in codon 91 in 36.1% of the <i>H. pylori</i> strains, without significant differences in the patients groups. A mutation in codon 87 was associated with the highest MIC₅₀ value (32 mg/L). <b><i>Conclusions:</i></b> In our area, a high prevalence of <i>H. pylori</i> primary resistance was detected; these rates were higher in patients who had experienced failure of several courses of therapy. A better knowledge of the local epidemiology of resistance, and the genotypes responsible, will improve the <i>H. pylori</i> eradication rates.