Proton motive force-dependent efflux of tetracycline in clinical isolates of Helicobacter pylori

Rapid diagnosis and precision treatment of Helicobacter pylori infection in clinical settings

Helicobacter pylori is a gram-negative bacterium that colonizes the stomach of approximately half of the worldwide population, with higher prevalence in densely populated areas like Asia, the Caribbean, Latin America, and Africa. H. pylori infections range from asymptomatic cases to potentially fatal diseases, including peptic ulcers, chronic gastritis, and stomach adenocarcinoma. The management of these conditions has become more difficult due to the rising prevalence of drug-resistant H. pylori infections, which ultimately lead to gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. In 1994, the International Agency for Research on Cancer (IARC) categorized H. pylori as a Group I carcinogen, contributing to approximately 780,000 cancer cases annually. Antibiotic resistance against drugs used to treat H. pylori infections ranges between 15% and 50% worldwide, with Asian countries having exceptionally high rates. This review systematically examines the impacts of H. pylori infection, the increasing prevalence of antibiotic resistance, and the urgent need for accurate diagnosis and precision treatment. The present status of precision treatment strategies and prospective approaches for eradicating infections caused by antibiotic-resistant H. pylori will also be evaluated.

Enhanced Efficacy of Ciprofloxacin and Tobramycin against Staphylococcus aureus When Combined with Corydalis Tuber and Berberine through Efflux Pump Inhibition

One way that bacteria develop antibiotic resistance is by reducing intracellular antibiotic concentrations through efflux pumps. Therefore, enhancing the efficacy of antibiotics using efflux pump inhibitors provides a way to overcome this type of resistance. Notably, an increasing number of pathogenic Staphylococcus aureus strains have efflux pump genes. In this study, the extract from Corydalis ternata Nakai tuber (Corydalis Tuber) at 512 mg/L was demonstrated to have an antibiotic synergistic effect with ciprofloxacin at 2 mg/L and tobramycin at 1024 mg/L against methicillin-resistant S. aureus (MRSA). Berberine, an isoquinoline alkaloid identified in Corydalis Tuber, was identified as contributing to this effect. Ethidium bromide efflux pump activity assays showed that Corydalis Tuber extract and berberine inhibited efflux, suggesting that they are efflux pump inhibitors. Molecular docking simulations suggested that berberine binds to S. aureus efflux pump proteins MepA, NorA, NorB, and SdrM. Additionally, berberine and Corydalis Tuber extract inhibit biofilm formation, which can confer antibiotic resistance. This study's findings suggest that Corydalis Tuber, a traditional herbal medicine, and berberine, a medicinal supplement, act as S. aureus efflux pump inhibitors, synergistically increasing the efficacy of ciprofloxacin and tobramycin and showing promise as a treatment for antibiotic-resistant S. aureus infections, including MRSA.

Antibiotic Resistance, Susceptibility Testing and Stewardship in Helicobacter pylori Infection

Despite the declining trend of Helicobacter pylori (H. pylori) prevalence around the globe, ongoing efforts are still needed to optimize current and future regimens in view of the increasing antibiotic resistance. The resistance of H. pylori to different antibiotics is caused by different molecular mechanisms, and advancements in sequencing technology have come a far way in broadening our understanding and in facilitating the testing of antibiotic susceptibility to H. pylori. In this literature review, we give an overview of the molecular mechanisms behind resistance, as well as discuss and compare different antibiotic susceptibility tests based on the latest research. We also discuss the principles of antibiotic stewardship and compare the performance of empirical therapies based on up-to-date resistance patterns and susceptibility-guided therapies in providing effective H. pylori treatment. Studies and clinical guidelines should ensure that the treatment being tested or recommended can reliably achieve a pre-agreed acceptable level of eradication rate and take into account the variations in antibiotic resistance across populations. Local, regional and international organizations must work together to establish routine antibiotic susceptibility surveillance programs and enforce antibiotic stewardship in the treatment of H. pylori, so that it can be managed in a sustainable and efficient manner.

Multidrug resistance in Helicobacter pylori infection

Helicobacter pylori (Hp), a well-known human pathogen, causes one of the most common chronic bacterial infections and plays an important role in the emergence of chronic progressive gastric inflammation and a variety of gastrointestinal diseases. The prevalence of Hp infection varies worldwide and is indirectly proportional to socio-economic status, especially during childhood. The response to the eradication therapy significantly depends on the antibiotic resistance specific to each geographical region; thus, currently, given the increasing prevalence of antimicrobial resistance (especially to clarithromycin, metronidazole, and levofloxacin), successful treatment for Hp eradication has become a real challenge and a critical issue. The most incriminated factors associated with multidrug resistance (MDR) in Hp proved to be the overuse or the improper use of antibiotics, poor medication adherence, and bacterial-related factors including efflux pumps, mutations, and biofilms. Up to 30% of first-line therapy fails due to poor patient compliance, high gastric acidity, or high bacteremia levels. Hence, it is of great importance to consider new eradication regimens such as vonoprazan-containing triple therapies, quintuple therapies, high-dose dual therapies, and standard triple therapies with probiotics, requiring further studies and thorough assessment. Strain susceptibility testing is also necessary for an optimal approach.

Bacterial Stress Responses as Potential Targets in Overcoming Antibiotic Resistance

Bacteria can be adapted to adverse and detrimental conditions that induce general and specific responses to DNA damage as well as acid, heat, cold, starvation, oxidative, envelope, and osmotic stresses. The stress-triggered regulatory systems are involved in bacterial survival processes, such as adaptation, physiological changes, virulence potential, and antibiotic resistance. Antibiotic susceptibility to several antibiotics is reduced due to the activation of stress responses in cellular physiology by the stimulation of resistance mechanisms, the promotion of a resistant lifestyle (biofilm or persistence), and/or the induction of resistance mutations. Hence, the activation of bacterial stress responses poses a serious threat to the efficacy and clinical success of antibiotic therapy. Bacterial stress responses can be potential targets for therapeutic alternatives to antibiotics. An understanding of the regulation of stress response in association with antibiotic resistance provides useful information for the discovery of novel antimicrobial adjuvants and the development of effective therapeutic strategies to control antibiotic resistance in bacteria. Therefore, this review discusses bacterial stress responses linked to antibiotic resistance in Gram-negative bacteria and also provides information on novel therapies targeting bacterial stress responses that have been identified as potential candidates for the effective control of Gram-negative antibiotic-resistant bacteria.

Role of the Two-Component System CiaRH in the Regulation of Efflux Pump SatAB and Its Correlation with Fluoroquinolone Susceptibility

Streptococcus suis is an important pathogen in both pigs and humans. Although the diseases associated with S. suis can typically be treated with antibiotics, such use has resulted in a sustained increase in drug resistance. Bacteria can sense and respond to antibiotics via two-component systems (TCSs). In this study, the TCS CiaRH was identified as playing an important role in the susceptibility of S. suis to fluoroquinolones (FQs). We found that a ΔciaRH mutant possessed lower susceptibility to FQs than the wild-type strain, with no observed growth defects at the tested concentrations and lower levels of intracellular drugs and dye. Proteomic data revealed that the levels of SatA and SatB expression were upregulated in the ΔciaRH mutant compared with their levels in the wild-type strain. The satA and satB genes encode a narrow-spectrum FQ efflux pump. The phenomena associated with combined ciaRH-and-satAB deletion mutations almost returned the ΔciaRH ΔsatAB mutant to the phenotype of the wild-type strain compared to the phenotype of the ΔciaRH mutant, suggesting that the resistance of the ΔciaRH strain to FQs could be attributed to satAB overexpression. Moreover, SatAB expression was regulated by CiaR (a response regulator of CiaRH) and SatR (a regulator of the MarR family). The ciaRH genes were consistently downregulated in response to antibiotic stress. The results of electrophoretic mobility shift assays (EMSAs) and affinity assays revealed that both regulator proteins directly controlled the ABC transporter proteins SatAB. Together, the results show that cascade-mediated regulation of antibiotic export by CiaRH is crucial for the ability of S. suis to adapt to conditions of antibiotic pressure. Our study may provide a new target for future antibiotic research and development. IMPORTANCE Streptococcus suis is a zoonotic pathogen with high incidence and mortality rates in both swine and humans. Following antibiotic treatment, the organism has evolved many resistance mechanisms, among which efflux pump overexpression can promote drug extrusion from the cell. This study clarified the role of CiaRH in fluoroquinolone resistance. A mutant with the ciaRH genes deleted showed decreased susceptibility to the antibiotics tested, an invariant growth rate, and reduced intracellular efflux pump substrates. This research also demonstrated that overexpression of the efflux pump SatAB was the main cause of ΔciaRH resistance. In addition, CiaR could combine with the promoter region of satAB to further directly suppress target gene transcription. Simultaneously, satAB was also directly regulated by SatR. Our findings may provide novel insights for the development of drug targets and help to exploit corresponding inhibitors to combat bacterial multidrug resistance.

Phenolic Compound Ethyl 3,4-Dihydroxybenzoate Retards Drug Efflux and Potentiates Antibiotic Activity

The World Health Organization indicated that antibiotic resistance is one of the greatest threats to health, food security, and development in the world. Drug resistance efflux pumps are essential for antibiotic resistance in bacteria. Here, we evaluated the plant phenolic compound ethyl 3,4-dihydroxybenzoate (EDHB) for its efflux pump inhibitory (EPI) activity against drug-resistant Escherichia coli. The half-maximal inhibitory concentration, modulation assays, and time-kill studies indicated that EDHB has limited antibacterial activity but can potentiate the activity of antibiotics for drug-resistant E. coli. Dye accumulation/efflux and MALDI-TOF studies showed that EDHB not only significantly increases dye accumulation and reduces dye efflux but also increases the extracellular amount of antibiotics in the drug-resistant E. coli, indicating its interference with substrate translocation via a bacterial efflux pump. Molecular docking analysis using AutoDock Vina indicated that EDHB putatively posed within the distal binding pocket of AcrB and in close interaction with the residues by H-bonds and hydrophobic contacts. Additionally, EDHB showed an elevated postantibiotic effect on drug-resistant E. coli. Our toxicity assays showed that EDHB did not change the bacterial membrane permeability and exhibited mild human cell toxicity. In summary, these findings indicate that EDHB could serve as a potential EPI for drug-resistant E. coli.

A comprehensive review on pharmacology of efflux pumps and their inhibitors in antibiotic resistance

The potential for the build-up of resistance to a particular antibiotic endangers its therapeutic application over time. In recent decades, antibiotic resistance has become one of the most severe threats to public health. It can be attributed to the relentless and unchecked use of antibiotics in healthcare sectors, cell culture, animal husbandry, and agriculture. Some classic examples of resistance mechanisms employed by bacteria include developing antibiotic degrading enzymes, modifying target sites previously targeted by antibiotics, and developing efflux mechanisms. Studies have shown that while some efflux pumps selectively extrude certain antibiotics, others extrude a structurally diverse class of antibiotics. Such extrusion of a structurally diverse class of antibiotics gives rise to multi-drug resistant (MDR) bacteria. These mechanisms are observed in gram-positive and gram-negative bacteria alike. Therefore, efflux pumps find their place in the list of high-priority targets for the treatment of antibiotic-resistance in bacteria mediated by efflux. Studies showed a significant escalation in bacteria's susceptibility to a particular antibiotic drug when tested with an efflux pump inhibitor (EPI) compared to when it was tested with the antibiotic drug alone. This review discusses the pharmacology, current status, and the future of EPIs in antibiotic resistance.

The Acid-Base Equilibrium of Pyrazinoic Acid Drives the pH Dependence of Pyrazinamide-Induced Mycobacterium tuberculosis Growth Inhibition

Pyrazinamide, a first-line antibiotic used against Mycobacterium tuberculosis, has been shown to act in a pH-dependent manner in vitro. Why pyrazinamide, an antitubercle prodrug discovered more than 65 years ago, exhibits this pH-dependent activity was unclear. Upon entering mycobacterial cells, pyrazinamide is deamidated to pyrazinoate by an enzymatic process and exists in an acid-base equilibrium with pyrazinoic acid. Thus, the effects of total pyrazinoic acid (pyrazinoic acid + pyrazinoate) on M. tuberculosis growth, pH homeostasis, and proton motive force over a range of pH values found in host tissues were investigated. Although M. tuberculosis was able to maintain pH homeostasis over an external pH range of 7.0 to 5.5, total pyrazinoic acid induced growth inhibition increased as culture medium pH was decreased from 7.3 to 6.4. Consistent with growth inhibition, total pyrazinoic acid increased both acidification of the bacterial cytoplasm and dissipation of membrane potential as the environmental pH decreased when added to the bacterial suspensions. The results suggest pyrazinoic acid is the active form of the drug, which acts as an uncoupler of proton motive force, likely a protonophore, providing a mechanistic explanation for the pH dependence of the drug activity.

Efflux pumps as interventions to control infection caused by drug-resistance bacteria

Antibiotic resistance has become a global concern for healthcare workers and physicians. Efflux pumps are one of the major mechanisms of resistance. Hence, we describe examples of natural efflux pump inhibitors used to combat antibiotic resistance.

The increasing antimicrobial resistance of Helicobacter pylori in Iran: A systematic review and meta-analysis

BACKGROUND

Antimicrobial resistance of Helicobacter pylori can result in eradication failure. Metadata on the antimicrobial resistance of H pylori in Iran could help to formulate H pylori eradication strategies in Iran.

METHODS

A systematic review was performed after searching in MEDLINE, Scopus, Embase, Web of Science, and the Cochrane Library. A meta-analysis was performed, and a comparison of the rates between children and adults; time periods (1999-2010, 2011-2016, 2017-2019); and the methods used was carried out.

RESULTS

A total of 66 studies investigating 5936 H pylori isolates were analyzed. The weighted pooled resistance (WPR) rates were as follows: clarithromycin 21% (95% CI 16-26), metronidazole 62% (95% 57-67), clarithromycin in combination with metronidazole 16% (95% CI 10-23), ciprofloxacin 24% (95% CI 15-33), levofloxacin 18% (95% CI 9-30), erythromycin 29% (95% CI 12-50), furazolidone 13% (95% CI 4-27), tetracycline 8% (95% CI 5-13), and amoxicillin 15% (95% CI 9-22). During the three time periods, there was an increased resistance to amoxicillin, clarithromycin, ciprofloxacin, furazolidone, and tetracycline (P ˂ .05). Furazolidone and a clarithromycin/metronidazole combination had the higher resistance rates in children (P ˂ .05).

CONCLUSION

An increasing rate of resistance to amoxicillin, clarithromycin, ciprofloxacin, furazolidone, and tetracycline in Iranian H pylori isolates was identified. In children, the resistance to furazolidone and a combination of clarithromycin and metronidazole is higher compared to adults. As a stable, high resistance to metronidazole was found in children and adults in all Iranian provinces, we suggest that metronidazole should not be included in the Iranian H pylori eradication scheme.

Transporters HP0939, HP0497, and HP0471 participate in intrinsic multidrug resistance and biofilm formation in Helicobacter pylori by enhancing drug efflux

BACKGROUND

The multidrug resistance of Helicobacter pylori is becoming an increasingly serious issue. It is therefore necessary to study the mechanism of multidrug resistance of H pylori. We have previously identified that the HP0939, HP0497, and HP0471 transporters affect the efflux of drugs from H pylori. As efflux pumps participate in bacterial multidrug resistance and biofilm formation, we hypothesized that these transporters could be involved in the multidrug resistance and biofilm formation of H pylori.

MATERIALS AND METHODS

We therefore constructed three knockout strains, Δhp0939, Δhp0497, and Δhp0471, and three high-expression strains, Hp0939^he , Hp0497^he , and Hp0471^he , using the wild-type (WT) 26 695 strain of H pylori as the template. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of wild strains, knockout strains, and high-expression strains to amoxicillin, metronidazole, and other antibiotics were measured. The efflux capacity of high-expression strains and wild strains was compared by Hoechst 33 342 accumulation assay.

RESULTS

Determination of the MIC and MBC of the antibiotics revealed that the knockout strains were more sensitive to antibiotics, while the high-expression strains were less sensitive to antibiotics, compared to the WT. The ability of the high-expression strains to efflux drugs was significantly higher than that of the WT. We also induced H pylori to form biofilms, and observed that the knockout strains could barely form biofilms and were more sensitive to several antibiotics, compared to the WT. The mRNA expression of hp0939, hp0497, and hp0471 in the clinically sensitive and multidrug-resistant strains was determined, and it was found that these genes were highly expressed in the multidrug-resistant strains that were isolated from the clinics.

CONCLUSIONS

In this study, we found three transporters involved in intrinsic multidrug resistance of H pylori.

Optimizing the MIC breakpoints of amoxicillin and tetracycline for antibiotic selection in the rescue therapy of H. pylori with bismuth quadruple regimen

PURPOSE

H. pylori with triple-drug resistance (TR) to clarithromycin, metronidazole, and levofloxacin limits the success of rescue therapy. We aimed to identify the optimal breakpoints of antibiotic minimal inhibitory concentration (MIC) to predict the success of rescue therapy for TR H. pylori infection.

METHODS

We consecutively enrolled 430 patients with at least one course of failed H. pylori eradications to receive an H. pylori culture for antibiotic MIC test. Seventy-three (17%) had TR H. pylori infection (MIC of clarithromycin > 0.5, levofloxacin > 1, and metronidazole > 8 mg/L, respectively). Sixty-nine cases with TR H. pylori infection received rescue therapy with either ATBP (amoxicillin, tetracycline, bismuth, and PPI) or MTBP (metronidazole, tetracycline, bismuth and PPI) for 7-14 days. Fourteen patients with positive ¹³C-urea breath test after the first rescue therapy were retreated with a crossover second rescue therapy.

RESULTS

The MTBP regimen had higher eradication success than the ATBP regimen as the first rescue therapy for TR H. pylori (intent-to-treat (ITT) analysis, 70.3 vs. 46.9%, p = 0.048; per protocol (PP) analysis, 78.8% vs. 51.7%, p = 0.025). For MTBP regimen, tetracycline MIC ≤ 0.094 mg/L (p < 0.001) with a 14-day treatment duration (p = 0.037) could predict eradication success with 100% accuracy. For the ATBP regimen, amoxicillin MIC selected as ≤ 0.032 mg/L could optimally determine eradication success (72.2 vs. 33.3%, p = 0.025).

CONCLUSION

Optimizing the MIC breakpoints of amoxicillin and tetracycline resistance better predicts the outcome of bismuth quadruple therapy. Further prospective studies using the revised MIC breakpoints to select antibiotics are warranted.

Novel Mobilizable Genomic Island GEI-D18A Mediates Conjugational Transfer of Antibiotic Resistance Genes in the Multidrug-Resistant Strain Rheinheimera sp. D18

Aquatic environments act as reservoirs of antimicrobial-resistant bacteria and antimicrobial resistance (AMR) genes, and the dissemination of antibiotic resistance from these environments is of increasing concern. In this study, a multidrug-resistant bacterial strain, identified as Rheinheimera sp. D18, was isolated from the sea water of an industrial maricultural system in the Yellow Sea, China. Whole-genome sequencing of D18 revealed the presence of a novel 25.8 kb antibiotic resistance island, designated GEI-D18A, which carries several antibiotic resistance genes (ARGs), including aadA1, aacA3, tetR, tet(B), catA, dfrA37, and three sul1 genes. Besides, integrase, transposase, resolvase, and recombinase encoding genes were also identified in GEI-D18A. The transferability of GEI-D18A was confirmed by mating experiments between Rheinheimera sp. D18 and Escherichia coli 25DN, and efflux pump inhibitor assays also suggested that tet(B) in GEI-D18A was responsible for tetracycline resistance in both D18 and the transconjugant. This study represents the first characterization of a mobilizable antibiotic resistance island in a species of Rheinheimera and provides evidence that Rheinheimera spp. could be important reservoirs and vehicles for ARGs in the Yellow Sea area.

Efflux pump inhibitors for bacterial pathogens: From bench to bedside

With the advent of antibiotics, bacterial infections were supposed to be a thing of past. However, this instead led to the selection and evolution of bacteria with mechanisms to counter the action of antibiotics. Antibiotic efflux is one of the major mechanisms, whereby bacteria pump out the antibiotics from their cellular interior to the external environment using special transporter proteins called efflux pumps. Inhibiting these pumps seems to be an attractive strategy at a time when novel antibiotic supplies are dwindling. Molecules capable of inhibiting these pumps, known as efflux pump inhibitors (EPIs), have been viewed as potential therapeutic agents that can rejuvenate the activity of antibiotics that are no longer effective against bacterial pathogens. EPIs follow some general mechanisms of efflux inhibition and are derived from various natural as well as synthetic sources. This review focuses on EPIs and identifies the challenges that have kept these futuristic therapeutics away from the commercial realm so far.

In Vitro Activity of Sertraline, an Antidepressant, Against Antibiotic-Susceptible and Antibiotic-Resistant Helicobacter pylori Strains

Antibiotic resistance of Helicobacter pylori, a spiral bacterium associated with gastric diseases, is a topic that has been intensively discussed in last decades. Recent discoveries indicate promising antimicrobial and antibiotic-potentiating properties of sertraline (SER), an antidepressant substance. The aim of the study, therefore, was to determine the antibacterial activity of SER in relation to antibiotic-sensitive and antibiotic-resistant H. pylori strains. The antimicrobial tests were performed using a diffusion-disk method, microdilution method, and time-killing assay. The interaction between SER and antibiotics (amoxicillin, clarithromycin, tetracycline, and metronidazole) was determined by using a checkerboard method. In addition, the study was expanded to include observations by light, fluorescence, and scanning electron microscopy. The growth inhibition zones were in the range of 19–37 mm for discs impregnated with 2 mg of SER. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) counted for 2–8 µg/mL and 4–8 µg/mL, respectively. The time-killing assay showed the time-dependent and concentration-dependent bactericidal activity of SER. Bacteria exposed to MBCs (but not sub-MICs and MICs ≠ MBCs) underwent morphological transformation into coccoid forms. This mechanism, however, was not protective because these cells after a 24-h incubation had a several-fold reduced green/red fluorescence ratio compared to the control. Using the checkerboard assay, a synergistic/additive interaction of SER with all four antibiotics tested was demonstrated. These results indicate that SER may be a promising anti-H. pylori compound.

Resistance mechanisms of Helicobacter pylori and its dual target precise therapy

Helicobacter pylori drug resistance presents a significant challenge to the successful eradication of this pathogen. To find strategies to improve the eradication efficacy of H. pylori, it is necessary to clarify the resistance mechanisms involved. The mechanisms of H. pylori drug resistance can be investigated from two angles: the pathogen and the host. A comprehensive understanding of the molecular mechanisms of H. pylori resistance based on both pathogen and host would aid the implementation of precise therapy, or ideally "dual target precise therapy" (bacteria and host-specific target therapy). In recent years, with increased understanding of the mechanisms of H. pylori resistance, the focus of eradication has shifted from disease-specific to patient-specific treatment. The implementation of "precision medicine" has also provided a new perspective on the treatment of infectious diseases. In this article, we systematically review current research on H. pylori drug resistance from the perspective of both the pathogen and the host. We also review therapeutic strategies targeted to pathogen and host factors that are aimed at achieving precise treatment of H. pylori.

Novel and Effective Therapeutic Regimens for Helicobacter pylori in an Era of Increasing Antibiotic Resistance

Helicobacter pylori (H. pylori) is a common gastrointestinal bacterial strain closely associated with the incidence of chronic gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue lymphoma, and gastric cancer. A current research and clinical challenge is the increased rate of antibiotic resistance in H. pylori, which has led to a decreased H. pylori eradication rate. In this article, we review recent H. pylori infection and reinfection rates and H. pylori resistance to antibiotics, and we discuss the pertinent treatments. A PubMed literature search was performed using the following keywords: Helicobacter pylori, infection, reinfection, antibiotic resistance, bismuth, proton pump inhibitors, vonoprazan, susceptibility, quintuple therapy, dual therapy, and probiotic. The prevalence of H. pylori has remained high in some areas despite the decreasing trend of H. pylori prevalence observed over time. Additionally, the H. pylori reinfection rate has varied in different countries due to socioeconomic and hygienic conditions. Helicobacter pylori monoresistance to clarithromycin, metronidazole or levofloxacin was common in most countries. However, the prevalence of amoxicillin and tetracycline resistance has remained low. Because H. pylori infection and reinfection present serious challenges and because H. pylori resistance to clarithromycin, metronidazole or levofloxacin remains high in most countries, the selection of an efficient regimen to eradicate H. pylori is critical. Currently, bismuth-containing quadruple therapies still achieve high eradication rates. Moreover, susceptibility-based therapies are alternatives because they may avoid the use of unnecessary antibiotics. Novel regimens, e.g., vonoprazan-containing triple therapies, quintuple therapies, high-dose dual therapies, and standard triple therapies with probiotics, require further studies concerning their efficiency and safety for treating H. pylori.

Primary Antibiotic Resistance of Helicobacter pylori in China

BACKGROUND AND AIMS

Antibiotic resistance is the most important factor leading to the failure of eradication regimens; thus, it is important to obtain regional antibiotic resistance information. This review focuses on the prevalence of Helicobacter pylori primary resistance to clarithromycin, metronidazole, amoxicillin, levofloxacin, tetracycline, and furazolidone in China.

METHODS

We searched the PubMed, EMBASE, the China National Knowledge Infrastructure, and Chinese Biomedical databases from the earliest date of each database to October 2016. The search terms included the following: H. pylori, antibiotic (including clarithromycin, metronidazole, amoxicillin, levofloxacin, tetracycline, and furazolidone) resistance with or without China or different regions of China. The data analysis was performed using MedCalc 15.2.2. Each article was weighted according to the number of isolated H. pylori strains. A pooled proportion analysis was performed.

RESULTS

Twenty-three studies (14 studies in English and 9 in Chinese) were included in this review. A total of 6274, 6418, 3921, 5468, 2802, and 275 H. pylori strains were included in this review to evaluate the prevalence of H. pylori primary resistance to clarithromycin, metronidazole, levofloxacin, amoxicillin, tetracycline, and furazolidone, respectively. Overall, the primary resistance rates of clarithromycin, metronidazole, levofloxacin, amoxicillin, tetracycline, and furazolidone were 28.9, 63.8, 28.0, 3.1, 3.9, and 1.7%, respectively.

CONCLUSIONS

In China, the prevalence of H. pylori primary resistance to clarithromycin, metronidazole, and levofloxacin was high and increased over time, whereas the resistance rates to amoxicillin, tetracycline, and furazolidone were low and stable over time.

Helicobacter pylori and Antibiotic Resistance, A Continuing and Intractable Problem

Helicobacter pylori, a human pathogen with a high global prevalence, is the causative pathogen for multiple gastrointestinal diseases, especially chronic gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue lymphoma, and gastric malignancies. Antibiotic therapies remain the mainstay for H. pylori eradication; however, this strategy is hampered by the emergence and spread of H. pylori antibiotic resistance. Exploring the mechanistic basis of this resistance is becoming one of the major research questions in contemporary biomedical research, as such knowledge could be exploited to devise novel rational avenues for counteracting the existing resistance and devising strategies to avoid the development of a novel anti-H. pylori medication. Encouragingly, important progress in this field has been made recently. Here, we attempt to review the current state and progress with respect to the molecular mechanism of antibiotic resistance for H. pylori. A picture is emerging in which mutations of various genes in H. pylori, resulting in decreased membrane permeability, altered oxidation-reduction potential, and a more efficient efflux pump system. The increased knowledge on these mechanisms produces hope that antibiotic resistance in H. pylori can ultimately be countered.

Association of hp1181 and hp1184 Genes With the Active Efflux Phenotype in Multidrug-Resistant Isolates of Helicobacter pylori

Background

During the last decades the rate of multidrug resistance among clinical Helicobacter pylori isolates has increased. Active pumping out of the drugs may be an important mechanism for multidrug resistance in H. pylori strains.

Objectives

The aim of this study was to evaluate the association of two H. pylori efflux-genes, hp1181 and hp1184 with the active-efflux phenotype in MDR clinical-strains of H. pylori.

Materials and Methods

Minimal inhibitory concentration (MIC) and drug accumulation for β-lactames, Tetracycline (TET), Erythromycin (ERY), Metronidazole (MTZ), Ciprofloxacin (CIP) and Ethidium Bromide (EtBr) was performed in the presence and absence of carbonyl cyanide M-Chlorophenyl Hydrazone (CCCP). Presence of hp1181 and hp1184 genes was detected by the polymerase chain reaction (PCR). RT-PCR was performed to compare expression of efflux genes by MDR strains, demonstrating active efflux with the strains without active efflux.

Results

Two- to four-fold decrease in minimum inhibitory concentration (MIC) and two-fold increase in accumulation were observed for EtBr in the presence of CCCP for 67% (8) of 12 MDR strains. With CCCP, two- to four-fold decrease in MIC and 1.4- to 1.8-fold increase in the accumulation of β-lactames, TET, CIP and MTZ were obtained for 42% (5) of the MDR strains. Six, five and three of the 12 MDR strains amplified hp1184, hp1181, and both of them, respectively. The RT-PCR product for expression of hp1181 by MDR strains was approximately 100 bp shorter than that of the 26695 susceptible standard strain.

Conclusions

Expression of the genes hp1184 and hp1181 are associated with the specific active efflux of EtBr and non-related antibiotics, respectively. For displaying these phenotypes, a post-transcriptional regulation step may be required.

Real-time PCR detection of 16S rRNA novel mutations associated with Helicobacter pylori tetracycline resistance in Iran

BACKGROUND

Tetracycline is an antibiotic widely used for the treatment of Helicobacter pylori infection, but its effectiveness is decreasing due to increasing bacterial resistance. The aim of this study was to investigate the occurrence of 16S rRNA mutations associated with resistance or reduced susceptibility to tetracycline of Helicobacter pylori by real-time PCR (RT-PCR) assays from culture.

MATERIALS AND METHODS

Tetracycline susceptibility and minimal inhibition concentration (MIC) was determined by the Epsilometer test (Etest) method. A LightCycler assay developed to detect these mutations was applied to DNA extracted from culture. The 16S rRNA of these isolates was sequenced and resistance-associated mutations were identified. From 104 isolates of H. pylori examined, 11 showed resistance to tetracycline.

RESULTS

LightCycler assay was applied to DNA extracted from 11 tetracycline-susceptible and 11 tetracycline resistance H. pylori isolates. In our study the sequencing of the H. pylori wild types in 16 s rRNA gene were AGA 926-928 with MIC (0.016 to 0.5 μg/ml), while the sequencing and MIC for resistant were GGA and AGC, (0.75 to 1.5 μg/ml), respectively. Also we found a novel mutation in 2 strains with 84° as their melting temperatures and exhibition of an A939C mutation.

CONCLUSIONS

We conclude that real-time PCR is an excellent method for determination of H. pylori tetracycline resistance related mutations that could be used directly on biopsy specimens.

Recent Insights into Antibiotic Resistance in Helicobacter pylori Eradication

Antibiotics have been useful in the treatment of H. pylori-related benign and malignant gastroduodenal diseases. However, emergence of antibiotic resistance often decreases the eradication rates of H. pylori infections. Many factors have been implicated as causes of treatment failure, but the main antibiotic resistance mechanisms described to date are due to point mutations on the bacterial chromosome, a consequence of a significantly phenotypic variation in H. pylori. The prevalence of antibiotic (e.g., clarithromycin, metronidazole, tetracycline, amoxicillin, and furazolidone) resistance varies among different countries; it appears to be partly determined by geographical factors. Since the worldwide increase in the rate of antibiotic resistance represents a problem of relevance, some studies have been performed in order to identify highly active and well-tolerated anti-H. pylori therapies including sequential, concomitant quadruple, hybrid, and quadruple therapy. These represent a promising alternatives in the effort to overcome the problem of resistance. The aim of this paper is to review the current status of antibiotic resistance in H. pylori eradication, highlighting the evolutionary processes in detail at alternative approaches to treatment in the past decade. The underlying resistance mechanisms will be also followed.

Geographic map and evolution of primary Helicobacter pylori resistance to antibacterial agents

Antibiotic resistance in Helicobacter pylori is the major cause of eradication failure. Primary H. pylori susceptibility patterns, however, are becoming less predictable. Currently, high (> or =20%) clarithromycin resistance rates have been observed in the USA and in developed countries in Europe and Asia, while the highest (> or =80%) metronidazole-resistance rates have been reported in Africa, Asia and South America. Primary quinolone-resistance rates of 10% or more have already been reported in developed countries in Europe and Asia. Primary amoxicillin resistance has been low (0 to <2%) in Europe but higher (6-59%) in Africa, Asia and South America. Similarly, tetracycline resistance has been absent or low (<5%) in most countries and higher (9-27%) in Asia and South America. The increasing clarithromycin and quinolone resistance, and multidrug resistance detected in 0 to less than 5% in Europe and more often (14.2%) in Brazil are worrying. Growing resistance often parallels national antibiotic consumption and may vary within patient groups according to the geographic region, patient's age and sex, type of disease, birthplace, other infections and other factors. The geographic map and evolution of primary H. pylori resistance are clinically important, should be considered when choosing eradication regimens, and should be monitored constantly at national and global levels in an attempt to reach the recently recommended goal of eradication of more than 95%.