scholarly journals Mutations of the Helicobacter pyloriGenes rdxA and pbp1 Cause Resistance against Metronidazole and Amoxicillin

2001 ◽  
Vol 45 (3) ◽  
pp. 962-965 ◽  
Author(s):  
Ralf Paul ◽  
Stefan Postius ◽  
Klaus Melchers ◽  
Klaus P. Schäfer
Keyword(s):  
Helicobacter Pylori ◽  
Resistance Genes ◽  
Resistant Strain ◽  
Parent Strain ◽  
Metronidazole Resistance ◽  
Pcr Products ◽  
Resistant Strains ◽  
H Pylori

ABSTRACT To investigate amoxicillin and metronidazole resistance ofHelicobacter pylori, we compared putative resistance genes between resistant strains obtained in vitro and their sensitive parent strain. All metronidazole-resistant strains hadrdxA mutations, and an amoxicillin-resistant strain hadpbp1 and pbp2 mutations. By transforming PCR products of these mutated genes into antibiotic-sensitive strains, we showed that rdxA null mutations were sufficient for metronidazole resistance, while pbp1mutations contributed to amoxicillin resistance of H. pylori.

scholarly journals Analysis of rdxA and Involvement of Additional Genes Encoding NAD(P)H Flavin Oxidoreductase (FrxA) and Ferredoxin-Like Protein (FdxB) in Metronidazole Resistance of Helicobacter pylori

2000 ◽  
Vol 44 (8) ◽  
pp. 2133-2142 ◽  
Author(s):  
Dong-Hyeon Kwon ◽  
Fouad A. K. El-Zaatari ◽  
Mototsugu Kato ◽  
Michael S. Osato ◽  
Rita Reddy ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Resistant Strain ◽  
Resistance Mechanisms ◽  
Sensitive Strain ◽  
Metronidazole Resistance ◽  
Genes Encoding ◽  
Resistant Strains ◽  
Flavin Oxidoreductase ◽  
H Pylori

ABSTRACT Metronidazole (Mtz) is a critical ingredient of modern multidrug therapies for Helicobacter pylori infection. Mtz resistance reduces the effectiveness of these combinations. Although null mutations in a rdxA gene that encodes oxygen-insensitive NAD(P)H nitroreductase was reported in Mtz-resistant H. pylori, an intact rdxA gene has also been reported in Mtz-resistant H. pylori, suggesting that additional Mtz resistance mechanisms exist in H. pylori. We explored the nature of Mtz resistance among 544 clinical H. pyloriisolates to clarify the role of rdxA inactivation in Mtz resistance and to identify another gene(s) responsible for Mtz resistance in H. pylori. Mtz resistance was present in 33% (181 of 544) of the clinical isolates. There was marked heterogeneity of resistance, with Mtz MICs ranging from 8 to ≥256 μg/ml.rdxA inactivation resulted in Mtz MICs of up to 32 μg/ml for 6 Mtz-sensitive H. pylori strains and 128 μg/ml for one Mtz-sensitive strain. Single or dual (with rdxA) inactivation of genes that encode ferredoxin-like protein (designatedfdxB) and NAD(P)H flavin oxidoreductase (frxA) also increased the MICs of Mtz for sensitive and resistant strains with low to moderate levels of Mtz resistance. fdxB inactivation resulted in a lower level of resistance than that from rdxAinactivation, whereas frxA inactivation resulted in MICs similar to those seen with rdxA inactivation. Further evidence for involvement of the frxA gene in Mtz resistance included the finding of a naturally inactivated frxA but an intact rdxA in an Mtz-resistant strain, complementation of Mtz sensitivity from an Mtz-sensitive strain to an Mtz-resistant strain or vice versa by use of naturally inactivated or functionalfrxA genes, respectively, and transformation of an Mtz-resistant Escherichia coli strain to an Mtz sensitive strain by a naturally functional frxA gene but not an inactivated frxA gene. These results are consistent with the hypothesis that null mutations in fdxB,frxA, or rdxA may be involved in Mtz resistance.

scholarly journals A Redox Basis for Metronidazole Resistance in Helicobacter pylori

2009 ◽  
Vol 53 (5) ◽  
pp. 1884-1891 ◽  
Author(s):  
N. O. Kaakoush ◽  
C. Asencio ◽  
F. Mégraud ◽  
G. L. Mendz
Keyword(s):  
Helicobacter Pylori ◽  
Resistant Strain ◽  
Gene Mutations ◽  
Thioredoxin Reductase ◽  
Matched Pair ◽  
Specific Gene ◽  
Two Dimensional Gel Electrophoresis ◽  
Development Of Resistance ◽  
Metronidazole Resistance ◽  
Resistant Strains

ABSTRACT Metronidazole resistance in Helicobacter pylori has been attributed to mutations in rdxA or frxA. Insufficient data correlating RdxA and/or FrxA with the resistant phenotype, and the emergence of resistant strains with no mutations in either rdxA or frxA, indicated that the molecular basis of H. pylori resistance to metronidazole required further characterization. The rdxA and frxA genes of four matched pairs of metronidazole-susceptible and -resistant strains were sequenced. The resistant strains had mutations in either rdxA, frxA, neither gene, or both genes. The reduction rates of five substrates suggested that metabolic differences between susceptible and resistant strains cannot be explained only by mutations in rdxA and/or frxA. A more global approach to understanding the resistance phenotype was taken by employing two-dimensional gel electrophoresis combined with tandem mass spectrometry analyses to identify proteins differentially expressed by the matched pair of strains with no mutations in rdxA or frxA. Proteins involved in the oxireduction of ferredoxin were downregulated in the resistant strain. Other redox enzymes, such as thioredoxin reductase, alkyl hydroperoxide reductase, and superoxide dismutase, showed a pI change in the resistant strain. The data suggested that metronidazole resistance involved more complex metabolic changes than specific gene mutations, and they provided evidence of a role for the intracellular redox potential in the development of resistance.

scholarly journals In Vitro Activity of a Novel Antimicrobial Agent, TG44, for Treatment of Helicobacter pylori Infection

2006 ◽  
Vol 50 (9) ◽  
pp. 3062-3069 ◽  
Author(s):  
Osamu Kamoda ◽  
Kinsei Anzai ◽  
Jun-ichi Mizoguchi ◽  
Masatoshi Shiojiri ◽  
Toshiharu Yanagi ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Antibacterial Activity ◽  
Bactericidal Activity ◽  
Structural Formula ◽  
Therapeutic Modalities ◽  
Resistant Strains ◽  
H Pylori ◽  
Ph Range ◽  
Drug Resistant Strains

ABSTRACT Due to concerns about the current therapeutic modalities for Helicobacter pylori infection, e.g., the increased emergence of drug-resistant strains and the adverse reactions of drugs currently administered, there is a need to develop an anti-H. pylori agent with higher efficacy and less toxicity. The antibacterial activity of TG44, an anti-H. pylori agent with a novel structural formula, against 54 clinical isolates of H. pylori was examined and compared with those of amoxicillin (AMX), clarithromycin (CLR), and metronidazole (MNZ). Consequently, TG44 inhibited the growth of H. pylori in an MIC range of 0.0625 to 1 μg/ml. The MIC ranges of AMX, CLR, and MNZ were 0.0078 to 8 μg/ml, 0.0156 to 64 μg/ml, and 2 to 128 μg/ml, respectively. The antibacterial activity of TG44 against AMX-, CLR-, and MNZ-resistant strains was nearly comparable to that against drug-susceptible ones. In a pH range of 3 to 7, TG44 at 3.13 to 12.5 μg/ml exhibited potent bactericidal activity against H. pylori in the stationary phase of growth as early as 1 h after treatment began, in contrast to AMX, which showed no bactericidal activity at concentrations of up to 50 μg/ml at the same time point of treatment. TG44 at 25 μg/ml exhibited no antibacterial activity against 13 strains of aerobic bacteria, suggesting that its antibacterial activity against H. pylori is potent and highly specific. The present study indicated that TG44 possesses antibacterial activity which manifests quickly and is potentially useful for eradicating not only the antibiotic-susceptible but also the antibiotic-resistant strains of H. pylori by monotherapy.

scholarly journals Role of the rdxA and frxA genes in oxygen-dependent metronidazole resistance of Helicobacter pylori

2004 ◽  
Vol 53 (11) ◽  
pp. 1123-1128 ◽  
Author(s):  
Monique M Gerrits ◽  
Egbert-Jan van der Wouden ◽  
Dorine A Bax ◽  
Anton A van Zwet ◽  
Arnoud HM van Vliet ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Cell Viability ◽  
Protein Synthesis Inhibitor ◽  
Low Oxygen ◽  
Anaerobic Conditions ◽  
Metronidazole Resistance ◽  
Oxygen Conditions ◽  
H Pylori

Almost 50 % of all Helicobacter pylori isolates are resistant to metronidazole, which reduces the efficacy of metronidazole-containing regimens, but does not make them completely ineffective. This discrepancy between in vitro metronidazole resistance and treatment outcome may partially be explained by changes in oxygen pressure in the gastric environment, as metronidazole-resistant (MtzR) H. pylori isolates become metronidazole-susceptible (MtzS) under low oxygen conditions in vitro. In H. pylori the rdxA and frxA genes encode reductases which are required for the activation of metronidazole, and inactivation of these genes results in metronidazole resistance. Here the role of inactivating mutations in these genes on the reversibility of metronidazole resistance under low oxygen conditions is established. Clinical H. pylori isolates containing mutations resulting in a truncated RdxA and/or FrxA protein were selected and incubated under anaerobic conditions, and the effect of these conditions on the MICs of metronidazole, amoxycillin, clarithromycin and tetracycline, and cell viability were determined. While anaerobiosis had no effect on amoxycillin, clarithromycin and tetracycline resistance, all isolates lost their metronidazole resistance when cultured under anaerobic conditions. This loss of metronidazole resistance also occurred in the presence of the protein synthesis inhibitor chloramphenicol. Thus, factor(s) that activate metronidazole under low oxygen tension are not specifically induced by low oxygen conditions, but are already present under microaerophilic conditions. As there were no significant differences in cell viability between the clinical isolates, it is likely that neither the rdxA nor the frxA gene participates in the reversibility of metronidazole resistance.

scholarly journals Effect of mupirocin in Helicobacter pylori in vitro

2021 ◽  
Vol 8 (1) ◽  
pp. 160-165
Author(s):  
Masaaki Minami ◽  
Takafumi Ando ◽  
Hidemi Goto ◽  
Michio Ohta
Keyword(s):  
Helicobacter Pylori ◽  
Bactericidal Effect ◽  
Dependent Manner ◽  
Antibiotic Effect ◽  
Resistant Strains ◽  
Kill Curve ◽  
H Pylori ◽  
Time Kill ◽  
Post Antibiotic Effect

Mupirocin (MUP) is an effective antibiotic against MRSA. Its bactericidal effect is stable under acid condition. By validating its antibacterial effect of Helicobacter pylori, we try to clarify MUP effect on H. pylori. The present study was conducted to investigate the effect of MUP on clarithromycin (CLR) / metronidazole (MNZ) -resistant and -susceptible strains of H. pylori, the time-kill effect of MUP, and the post antibiotic effect (PAE). We investigated the minimal inhibitory concentration (MIC) and the minimal bactericidal effect (MBC) of MUP against 140 H. pylori, which include clinical strains, ATCC43504, 26695 and J99. Ten of them were CLR -resistant strains and 3 were MNZ-resistant strains. The MIC90 and MBC of MUP on all 140 strains is 0.064 μg / ml, and 0.1 μg / ml, respectively. There were no differences of MUP effect between susceptible and resistant strains either for CLR or MNZ. Time-kill curve test and PAE test of MUP on ATCC43504 were performed. By adding MUP, time-kill curve showed that bacterial quantities decreased in dose and time-dependent manner. No viable colony was found after 12-hour culture with 0.1 μg / ml MUP. The value of PAE is 12. MUP is a potential effective antibiotic for H. pylori even those for CLR / MNZ -resistant strains.

scholarly journals Antibiotic Susceptibilities ofHelicobacter pyloriStrains Isolated in the Province of Alberta

1998 ◽  
Vol 12 (4) ◽  
pp. 295-298 ◽  
Author(s):  
Diane E Taylor ◽  
Qin Jiang ◽  
Richard N Fedorak
Keyword(s):  
Helicobacter Pylori ◽  
Antibiotic Resistance ◽  
Gastric Biopsy ◽  
Minimal Inhibitory Concentrations ◽  
Antibiotic Susceptibilities ◽  
Biopsy Specimens ◽  
Metronidazole Resistance ◽  
Agar Dilution ◽  
Resistant Strains ◽  
H Pylori

The incidence of antibiotic resistance to amoxicillin, clarithromycin, erythromycin, metronidazole and tetracycline inHelicobacter pyloristrains isolated from gastric biopsy specimens obtained in Alberta was investigated. Results for all antibiotics were obtained using agar dilution, and in addition to metronidazole, the E test was used. Resistance to amoxicillin and tetracycline was not detected. Metronidazole resistance determined using agar dilution was approximately 12% (95% CI 4% to 26%) when minimal inhibitory concentrations (MICs) were at least 8 µg/mL, but fell to 2% (95% CI 0.1% to 13%) when MICs were set at 32 µg/mL or greater. The E test for metronidazole resistance (MIC 8 µg/mL or greater) yielded a slightly higher percentage of resistant strains compared with agar dilution tests (14%, 95% CI 5% to 29%). One of the 31 strains was resistant to clarithromycin (MIC 8 µg/mL) and erythromycin (MIC 16 µg/mL). Thus, the incidence of resistance to clarithromycin, part of the currently used triple therapy for eradication ofH pylori, was 3% (95% CI 0.1% to 17%).

Metronidazole uptake in Helicobacter pylori

1995 ◽  
Vol 41 (8) ◽  
pp. 746-749 ◽  
Author(s):  
Richard A. Moore ◽  
Brenda Beckthold ◽  
L. E. Bryan
Keyword(s):  
Helicobacter Pylori ◽  
Resistant Strain ◽  
Sodium Arsenate ◽  
Thin Layer Chromatography Analysis ◽  
Chromatography Analysis ◽  
Metronidazole Resistance ◽  
Carbonyl Cyanide ◽  
H Pylori ◽  
Layer Chromatography ◽  
Imidazole Compounds

Currently, the mechanism of metronidazole resistance is not understood in Helicobacter pylori. We have looked at uptake of metronidazole into a sensitive and a resistant strain of H. pylori. Both strains displayed rapid uptake of [14C]metronidazole, although the resistant strain accumulated the drug at a slower rate and to a lesser amount than the sensitive strain. Uptake was inhibited by KCN and carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) but not by sodium arsenate. Thin-layer chromatography analysis of lysed cell supernatants showed that metronidazole was metabolized in both strains. A variety of related imidazole compounds inhibited metronidazole uptake, consistent with a common transport system for this group of antibiotics. Our data do not support an absence of uptake or metabolism as a cause of resistance in the strain examined.Key words: metronidazole, uptake, Helicobacter.

scholarly journals Resistotype of Helicobacter pylori isolates: the impact on eradication outcome

2014 ◽  
Vol 63 (5) ◽  
pp. 703-709 ◽  
Author(s):  
Hanafiah Alfizah ◽  
Ahmad Norazah ◽  
Razlan Hamizah ◽  
Mohamed Ramelah
Keyword(s):  
Helicobacter Pylori ◽  
Antibiotic Resistance ◽  
Eradication Therapy ◽  
Fluoroquinolone Resistance ◽  
23S Rrna ◽  
Nonsense Mutations ◽  
Metronidazole Resistance ◽  
Resistant Strains ◽  
H Pylori ◽  
The Impact

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.

scholarly journals Mutations of Helicobacter pylori RdxA are mainly related to the phylogenetic origin of the strain and not to metronidazole resistance

2020 ◽  
Vol 75 (11) ◽  
pp. 3152-3155
Author(s):  
Shuzhen Zhang ◽  
Xiangyu Wang ◽  
Michael J Wise ◽  
Yongsheng He ◽  
Haiting Chen ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Helicobacter Pylori ◽  
Phylogenetic Analyses ◽  
Clinical Problem ◽  
23S Rrna ◽  
Rrna Gene ◽  
Metronidazole Resistance ◽  
Resistant Strains ◽  
H Pylori ◽  
Technology Mutation

Abstract Objectives Drug resistance of Helicobacter pylori is a major clinical problem worldwide. The objective of the present study was to investigate the prevalence of antibiotic-resistant H. pylori in the city of Shenzhen in China, as well as to identify the genetic mutations specifically associated with drug resistance rather than unrelated phylogenetic signals. Methods Antibiotic susceptibility testing was performed on 238 clinical strains successfully isolated from H. pylori-positive dyspeptic patients who underwent gastroscopy at the Department of Gastroenterology in Shenzhen People’s Second Hospital. Following WGS of all strains using Illumina technology, mutation and phylogenetic analyses were performed. Results The resistance rates were 84.9%, 35.3%, 25.2% and 2.1% for metronidazole, clarithromycin, ciprofloxacin and rifampicin, respectively. An A2143G conversion in the 23S rRNA gene was the primary mutation observed in clarithromycin-resistant strains, whilst N87K/I and D91G/N/Y in GyrA were detected in ciprofloxacin-resistant strains. In RdxA, our results demonstrated that only R16H/C and M21A are significant contributors to metronidazole resistance; there were 15 other sites, but these are phylogenetically related and thus unrelated to metronidazole resistance. Conclusions There is a high prevalence of metronidazole, clarithromycin and ciprofloxacin resistance and a low prevalence of rifampicin resistance in H. pylori from Shenzhen, China. Omission of phylogenetically related sites will help to improve identification of sites genuinely related to antibiotic resistance in H. pylori and, we believe, other species.

scholarly journals Appearance of a metronidazole-resistant Helicobacter pylori strain in an infected-ICR-mouse model and difference in eradication of metronidazole-resistant and -sensitive strains.

1997 ◽  
Vol 41 (12) ◽  
pp. 2602-2605 ◽  
Author(s):  
S Matsumoto ◽  
Y Washizuka ◽  
Y Matsumoto ◽  
S Tawara ◽  
F Ikeda ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Mouse Model ◽  
Resistant Strain ◽  
Sensitive Strain ◽  
Original Strain ◽  
Antibiotic Resistant ◽  
Icr Mouse ◽  
Resistant Strains ◽  
H Pylori

We tested whether antibiotic-resistant strains appeared in vivo after the failure of treatment using the Helicobacter pylori-infected euthymic mouse model. The numbers of colonies isolated from 56 ICR mice 2 weeks after 4 days of treatment with metronidazole (3.2, 10, or 32 mg/kg of body weight) or amoxicillin (1, 3.2 or 10 mg/kg), with treatment started 4 days after H. pylori CPY2052 inoculation, were counted, and the isolated strains were tested for their sensitivities to two antibiotics to rule out the presence of antibiotic-resistant strains. One metronidazole-resistant strain was detected in a mouse treated with 10 mg of metronidazole per kg, and the MIC of metronidazole for this strain was 25 microg/ml, compared to a MIC of 1.56 microg/ml for the original strain. However, no resistant strain was detected in the amoxicillin treatment group. After the examination described above, mice challenged with a metronidazole-resistant or -sensitive strain isolated from the stomach of a mouse were treated with metronidazole or amoxicillin. The metronidazole-resistant strain was more difficult to eradicate in vivo than the sensitive strain after treatment with metronidazole but not after treatment with amoxicillin. Thus, a metronidazole-resistant H. pylori strain was selected by insufficient treatment, but no resistant strain was selected with amoxicillin. Eradication of a metronidazole-resistant H. pylori strain in vivo required a higher dosage than eradication of a metronidazole-sensitive H. pylori strain. These results may explain one of the reasons for H. pylori treatment failure.

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