Analysis of drug resistance and virulence‐factor genotype of Irish <i>Helicobacter pylori</i> strains: is there any relationship between resistance to metronidazole and <i>cagA</i> status?

Abstract

BACKGROUND: Helicobacter pylori infection is eradicated with antimicrobial agents and drug-resistant strains make successful treatment difficult. Geographical variations in virulence-factor genotype also exist. AIM: To evaluate prevalence of drug resistance and virulence-factor genotype in Irish H. pylori strains and to investigate if there is any relationship between drug resistance and genotype. METHODS: Helicobacter pylori strains isolated from 103 patients were examined. Antimicrobial susceptibilities were tested by Etest. The virulence-factor genotypes were determined using PCR. Frequencies of spontaneous metronidazole-resistance were measured in vitro. RESULTS: Metronidazole resistance was present in 37.9% of strains examined. 16.5% of strains were clarithromycin-resistant and resistance to both agents observed was found in 12.6% of strains. 68% of strains were cagA(+). The dominant vacA type was s1/m2, followed by s1/m1 and s2/m2. The metronidazole resistance rate in cagA(-) group was significantly higher than in cagA(+) (P = 0.0089). Spontaneous resistance to metronidazole in cagA(-) occurred in higher frequency when compared with cagA(+). CONCLUSIONS: cagA(+) and vacAs1/m2 type was the dominant genotype in Irish H. pylori strains. Significant rates of metronidazole resistance were observed in cagA(-) group. cagA(-) strains tend to acquire metronidazole resistance in vitro. Absence of cagA might be a risk factor in development of metronidazole resistance.