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 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 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 Mechanism of Metronidazole Resistance inHelicobacter pylori: Comparison of the rdxA Gene Sequences in 30 Strains

2000 ◽  
Vol 44 (8) ◽  
pp. 2207-2210 ◽  
Author(s):  
Nadia Maggi Solcà ◽  
Marco Valerio Bernasconi ◽  
Jean-Claude Piffaretti
Keyword(s):  
Phylogenetic Analysis ◽  
Helicobacter Pylori ◽  
Amino Acid ◽  
Resistant Strain ◽  
Point Mutations ◽  
Housekeeping Genes ◽  
Amino Acid Substitutions ◽  
Metronidazole Resistance ◽  
Nucleotide Mutation ◽  
Nucleotide Insertion

ABSTRACT The rdxA gene of 30 independently isolatedHelicobacter pylori strains was sequenced. A comparison of the rdxA sequences revealed a higher percentage of amino acid substitutions in the corresponding protein than in other housekeeping genes. Out of 122 point mutations, 41 were missense and 4 were nonsense. A resistant strain with a nucleotide insertion in therdxA sequence was also found. With the exception of the point mutations and the insertion generating a stop signal, no particular nucleotide mutation or amino acid substitution could be associated to metronidazole resistance. Moreover, phylogenetic analysis of the 30 nucleotide sequences did not demonstrate specific clusters associated with the resistance phenotype.

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.

The development of drug-resistant strains of Eimeria maxima in the laboratory

Parasitology ◽  
1975 ◽  
Vol 71 (1) ◽  
pp. 153-165 ◽  
Author(s):  
C. C. Norton ◽  
L. P. Joyner
Keyword(s):  
Drug Administration ◽  
Resistant Strain ◽  
Parent Strain ◽  
Drug Resistant ◽  
Development Of Resistance ◽  
Eimeria Maxima ◽  
Resistant Strains ◽  
Drug Dependent ◽  
Drug Resistant Strains

The development of strains of Eimeria maxima resistant to buquinolate, methyl benzoquate, clopidol, sulphaquinoxaline and robenidine is described. It was not possible to standardize a schedule of inoculations and drug administration, which would enable the development of resistance to the different drugs to be compared directly. Resistance developed most readily to the quinolones. One robenidine-resistant strain proved to be drug-dependent. Dinitolmide showed unusual effects upon sporogony and three attempts to develop resistance against this activity failed. Chicks previously immunized with the parent strain were completely protected against infection with the drug-resistant strains.

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.

The development of resistance to glycarbylamide and 2-chloro-4-nitrobenzamide in Eimeria tenella in chicks

Parasitology ◽  
1966 ◽  
Vol 56 (1) ◽  
pp. 25-37 ◽  
Author(s):  
S. J. Ball
Keyword(s):  
Drug Resistance ◽  
Resistant Strain ◽  
Parent Strain ◽  
Technical Assistance ◽  
Eimeria Tenella ◽  
Single Test ◽  
Normal Parent ◽  
Twofold Increase ◽  
Development Of Resistance ◽  
Resistant Strains

A twofold increase in resistance to glycarbylamide was induced in a strain of Eimeria tenella in chicks. This strain remained susceptible to amprolium, nicarbazin, nitrofurazone, zoalene, 3,5-dinitrobenzamide, 2-chloro-4-nitrobenzamide (M & B 5921) and spiramycin.At least an eightfold resistance to 2-chloro-4-nitrobenzamide (M & B 5921) was developed in another strain of E. tenella. This strain was also resistant to nitrofurazone, zoalene and 3,5-dinitrobenzamide, but not to glycarbylamide, amprolium, nicarbazin and spiramycin.A single test showed no transfer of drug-resistance when the two resistant strains were given simultaneously to the same birds.When a small number of parasites of a glycarbylamide-resistant strain of E. tenella was introduced into a larger inoculum of the normal parent strain, the resistant individuals appeared to diminish in number during passages through untreated chicks.I wish to thank Mrs B. M. Mitchell, Miss C. A. Hitchcock and Miss J. Watkins for technical assistance at various stages of the work.

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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