Alimentary tract
Primary and secondary antibiotic resistance of Helicobacter pylori strains isolated in central Italy during the years 1998–2002

https://doi.org/10.1016/S1590-8658(03)00265-2Get rights and content

Abstract

Background. Antibiotic resistance of Helicobacter pylori is the most common reason for failure in its eradication.

Aim. To determine the incidence of primary and secondary resistance to tinidazole, clarithromycin and amoxycillin in Helicobacter pylori isolates from dyspeptic patients in central Italy and to evaluate the modifications of resistance over the period from 1998 to 2002.

Methods. H. pylori strains were isolated from antral biopsies taken during upper endoscopy in 406 dyspeptic patients with no previous therapy against H. pylori, and in 96 patients who had already undergone one or more triple therapies. Antibiotic susceptibility test was performed using the screening agar method and agar dilution method.

Results. Overall primary resistance to tinidazole, clarithromycin and amoxycillin was 36.7, 23.4 and 0.2%, respectively. Secondary resistance rates were: tinidazole 69.8%, clarithromycin 82.3% and amoxycillin 1%. Resistance to clarithromycin was often associated with tinidazole resistance and was significantly higher in female patients (p<0.05). Primary and secondary antibiotic resistance did not change during the 4 years of observation.

Conclusions. The dyspeptic population with H. pylori infection in central Italy shows high levels of antibiotic resistance. Primary resistance to clarithromycin is most frequent in female patients. In patients with secondary resistance, dual resistance to clarithromycin and tinidazole is found in the majority of cases.

Introduction

As more than 50% of the world’s population is supposedly infected by Helicobacter pylori, this may therefore be considered the most common chronic bacterial infection in humans [1]. Eradication treatment usually consists of a proton pump inhibitor (PPI) together with two of the following antibiotics: clarithromycin, a nitroimidazole derivative (metronidazole or tinidazole) and amoxycillin [2]. Resistance of H. pylori to some of the antibiotics included in the therapeutic regimens has been reported as a major reason for treatment failure [3], [4], [5]. It has been shown that, in Europe, antimicrobial primary resistance has been increasing in recent years, ranging from 10 to 50% for metronidazole and from 0 to 15% for clarithromycin, with wide variability from region to region [6], [7]. Amoxycillin-resistant human isolates of H. pylori are quite rare and have recently been identified in Italy, the USA and Canada [8], [9]. Resistance to metronidazole and/or clarithromycin after treatment failure (secondary resistance) is still much higher: 40–70% for metronidazole, 50–70% for clarithromycin, 30–90% for both metronidazole and clarithromycin [10], [11], [12], [13]. In Italy, the information on general H. pylori resistance is rather scarce, with few studies published in the scientific literature on this topic [11], [14], [15], [16].

Therefore, the aim of this study has been to determine the frequency of primary and secondary resistance to tinidazole, clarithromycin and amoxycillin in H. pylori isolates from an urban population of dyspeptic patients in central Italy and to evaluate the modification of antibiotic resistance over four consecutive 12-month periods from March 1998 to June 2002.

Section snippets

Patients

From March 1998 to June 2002, 502 H. pylori-positive patients with dyspeptic symptoms undergoing endoscopy in our Unit in Pescara, a city in central Italy, were included. Four hundred and six patients (206 females, range 18–87 years, mean age 52.5 years; 200 males, range 22–86 years, mean age 54 years) had not received previous H. pylori treatment; and 96 patients (59 females, range 28–86 years, mean age 57 years; 37 males, range 34–81 years, mean age 57.5 years) had been treated previously for

Results

A total of 502 patients who satisfied the inclusion and exclusion criteria were included in the present study. Endoscopic evaluation of the patients revealed 391 subjects with gastritis, 48 with duodenal ulcer, five with gastric ulcer, two with gastric and duodenal ulcers and 56 with no gastric alteration.

Table 1 shows the prevalence of primary resistance of 406 H. pylori strains to clarithromycin, tinidazole and amoxycillin according to the period of isolation. Overall antibiotic resistance

Discussion

This is the first large study investigating the incidence of H. pylori antibiotic resistance in dyspeptic patients in central Italy. The study shows that: (a) in our geographic area there is high prevalence of H. pylori primary resistance to tinidazole, clarithromycin and both antibiotics; (b) primary resistance to clarithromycin and both clarithromycin and tinidazole is more frequent in females but is not linked to age; (c) secondary resistance is characterized by high incidence of resistance

Conflict of interest statement

None declared.

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