Resistotype of Helicobacter pylori isolates: the impact on eradication outcome

Abstract

Antibiotic resistance is increasing worldwide, and it has been regarded as the main factor reducing the efficacy of Helicobacter pylori therapy. The aim of this study was to determine the phenotype and genotype of antibiotic-resistant strains of H. pylori in the Malaysian population and to evaluate the impact of antibiotic resistance to eradication outcome. One hundred and sixty-one H. pylori isolates were analysed in this study. Metronidazole, clarithromycin, fluoroquinolone, amoxicillin and tetracycline susceptibilities were determined by Etest. PCR followed by DNA sequencing was carried out to determine mutations. The medical records of the patients infected with resistant strains were reviewed to determine the eradication outcome. Metronidazole resistance was encountered in 36.6 % of H. pylori isolates, whereas clarithromycin and fluoroquinolone resistance was observed in 1.2 and 1.9 % of isolates, respectively. All strains tested were susceptible to amoxicillin and tetracycline. Frameshift and nonsense mutations in rdxA and frxA genes resulting in stop codons contributed to metronidazole resistance, which leads to reduced eradication efficacy. A2142G and A2143G mutations of 23S rRNA were identified as causing failure of the eradication therapy. Mutation at either codon 87 or 91 of the gyrA gene was identified in fluoroquinolone-resistant strains. However, the effect of resistance could not be assessed. This study showed that frameshift and nonsense mutations in rdxA or frxA genes and point mutations in the 23S rRNA affected the efficacy of H. pylori eradication therapy.

Validation of a High-Throughput Multiplex Genetic Detection System for Helicobacter pylori Identification, Quantification, Virulence, and Resistance Analysis

“…The severity of clinical manifestations is associated with bacterial load (Kusters et al, 2006). Meanwhile, the growing H. pylori drug resistance in Asia countries severely influences the efficacy of eradication treatment, which required drug resistance analysis before treatment (Katelaris, 2009; Cammarota et al, 2012; Alfizah et al, 2014; Smith et al, 2014). Therefore, it is important to analyze the virulence, bacterial load and resistance profiles during the identification of H. pylori .…”

Analysis of allelic variants of rdxA associated with metronidazole resistance in Helicobacter pylori: detection of common genotypes in rdxA by multiplex allele-specific polymerase chain reaction

“…A previous analysis of the rdxA and frxA nucleotide sequences of individual resistant and sensitive strains revealed a large number of point mutations (Mirzaei et al, 2014). Frameshift and nonsense mutations in rdxA and frxA genes are believed to cause Mtz resistance, affecting the efficiency of H. pylori eradication (Alfizah et al, 2014). Molecular characterization of sensitive and resistant strains has yielded information that could be useful in assessing the genotypic association with Mtz resistance, phylogenetic evolution, and epidemiological study.…”

Risk factors of rescue bismuth quadruple therapy failure for Helicobacter pylori eradication

“…However, there have been limited evidences for the relationship between resistance factors and eradication outcomes. According to our previous study, rdxA mutation is associated with eradication failure of H. pylori in 53 patients treated with sequential or quadruple therapy. Particularly, among mutation types, nonsense mutation of rdxA was associated with eradication failure.…”