Design, Synthesis, and Efficacy Testing of Nitroethylene- and 7-Nitrobenzoxadiazol-Based Flavodoxin Inhibitors against Helicobacter pylori Drug-Resistant Clinical Strains and in Helicobacter pylori-Infected Mice

Opportunities for Helicobacter pylori Eradication beyond Conventional Antibiotics

Helicobacter pylori (H. pylori) is a bacterium known to be associated with a significant risk of gastric cancer in addition to chronic gastritis, peptic ulcer, and MALT lymphoma. Although only a small percentage of patients infected with H. pylori develop gastric cancer, Gastric cancer causes more than 750,000 deaths worldwide, with 90% of cases being caused by H. pylori. The eradication of this bacterium rests on multiple drug regimens as guided by various consensus. However, the efficacy of empirical therapy is decreasing due to antimicrobial resistance. In addition, biofilm formation complicates eradication. As the search for new antibiotics lags behind the bacterium's ability to mutate, studies have been directed toward finding new anti-H. pylori agents while also optimizing current drug functions. Targeting biofilm, repurposing outer membrane vesicles that were initially a virulence factor of the bacteria, phage therapy, probiotics, and the construction of nanoparticles might be able to complement or even be alternatives for H. pylori treatment. This review aims to present reports on various compounds, either new or combined with current antibiotics, and their pathways to counteract H. pylori resistance.

Merging multi-omics with proteome integral solubility alteration unveils antibiotic mode of action

Antimicrobial resistance is responsible for an alarming number of deaths, estimated at 5 million per year. To combat priority pathogens, like Helicobacter pylori, the development of novel therapies is of utmost importance. Understanding the molecular alterations induced by medications is critical for the design of multi-targeting treatments capable of eradicating the infection and mitigating its pathogenicity. However, the application of bulk omics approaches for unraveling drug molecular mechanisms of action is limited by their inability to discriminate between target-specific modifications and off-target effects. This study introduces a multi-omics method to overcome the existing limitation. For the first time, the Proteome Integral Solubility Alteration (PISA) assay is utilized in bacteria in the PISA-Express format to link proteome solubility with different and potentially immediate responses to drug treatment, enabling us the resolution to understand target-specific modifications and off-target effects. This study introduces a comprehensive method for understanding drug mechanisms and optimizing the development of multi-targeting antimicrobial therapies.

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.

L-Thyroxine and L-thyroxine-based antimicrobials against Streptococcus pneumoniae and other Gram-positive bacteria

Objectives

The rise of antibiotic-resistant Streptococcus pneumoniae (Sp) poses a significant global health threat, urging the quest for novel antimicrobial solutions. We have discovered that the human hormone l-thyroxine has antibacterial properties. In order to explore its drugability we perform here the characterization of a series of l-thyroxine analogues and describe the structural determinants influencing their antibacterial efficacy.

Method

We performed a high-throughput screening of a library of compounds approved for use in humans, complemented with ITC assays on purified Sp-flavodoxin, to pinpoint molecules binding to this protein. Antimicrobial in vitro susceptibility assays of the hit compound (l-thyroxine) as well as of 13 l-thyroxine analogues were done against a panel of Gram-positive and Gram-negative bacteria. Toxicity of compounds on HepG2 cells was also assessed. A combined structure-activity and computational docking analysis was carried out to uncover functional groups crucial for the antimicrobial potency of these compounds.

Results

Human l-thyroxine binds to Sp-flavodoxin, forming a 1:1 complex of low micromolar Kd. While l-thyroxine specifically inhibited Sp growth, some derivatives displayed activity against other Gram-positive bacteria like Staphylococcus aureus and Enterococcus faecalis, while remaining inactive against Gram-negative pathogens. Neither l-thyroxine nor some selected derivatives exhibited toxicity to HepG2 cells.

Conclusions

l-thyroxine derivatives targeting bacterial flavodoxins represent a new and promising class of antimicrobials.

Antimicrobial combinations against Helicobacter pylori including benzoxadiazol-based flavodoxin inhibitors: in vitro characterization

IMPORTANCE

The antimicrobial resistance of Helicobacter pylori (Hp) currently poses a threat to available treatment regimens. Developing antimicrobial drugs targeting new bacterial targets is crucial, and one such class of drugs includes Hp-flavodoxin (Hp-fld) inhibitors that target an essential metabolic pathway in Hp. Our study demonstrated that combining these new drugs with conventional antibiotics used for Hp infection treatment prevented the regrowth observed with drugs used alone. Hp-fld inhibitors show promise as new drugs to be incorporated into the treatment of Hp infection, potentially reducing the development of resistance and shortening the treatment duration.

Design, Synthesis, and Biological Investigations of Novel Carbamoylguanidinyl Nitrobenzoxadiazoles against Chitinolytic Enzymes

Chitinase has been identified as an important target for insecticides. In this study, a series of novel chitinase inhibitors was designed and synthesized with nitrobenzoxadiazoles. Compound 8d, which contains the N-methylcarbamoylguanidinyl, exhibited high enzyme inhibitory activity and achieved nanomolar inhibition against OfChtI (IC50 = 12.3 nM). Delightfully, it was also found to possess significant inhibitory activity against OfHex1 (IC50 = 1.76 μM). The computational simulation results indicated that compound 8d interacted with OfChtI and OfHex1 in similar modes through hydrogen bonds and hydrophobic and π-π interactions. Insecticidal activity studies revealed that compound 8d showed high mortality against the Lepidoptera Plutella xylostella (mortality rate = 81%) at 200 mg/L. Toxicity studies indicated that compound 8d exhibited negligible toxicity to the natural enemy Trichogramma ostriniae. These results indicate that compound 8d may be a promising candidate for the development of environmentally friendly chitinase inhibitors. Moreover, this study provides a new angle for the design of innovative inhibitors of chitinolytic enzymes.

Modified quantum mechanical approach for the estimation of single-electron reduction potential of nitroaromatic compounds in aqueous medium

The midpoint single-electron reduction potential of nitroaromatic compounds in aqueous medium at pH 7.0 (potential of ArNO₂/ArNO₂·^- couple, E_m7) frequently determines their therapeutic and/or toxic properties. However, its estimation remains a complex problem. We propose a modified method of E_m7 estimation by quantum mechanical calculations, based on the use of the dielectric continuum model together with a certain number of H₂O molecules at the vicinity of nitro group. The optimal number of H₂O molecules corresponds to a minimal difference between the experimentally determined and calculated values of E_m7, and/or the most negative value of calculated E_m7. This enabled us to calculate the E_m7 values for a number of ArNO₂ (n = 19) with the average deviation of 0.027 V from the experimentally determined ones. Apart from nitrobenzene derivatives, the application of this approach for the representatives of nitropyridines, nitrofurans, nitrothiophenes, and nitrothiazoles was demonstrated. In this case, nitroimidazole derivatives are an exception, evidently due to a strong proton accepting properties of N3 atom of their free radicals.

Molecular Mechanisms of Antibiotic Resistance and Novel Treatment Strategies for Helicobacter pylori Infections

Helicobacter pylori infects approximately 50% of the world's population and is considered the major etiological agent of severe gastric diseases, such as peptic ulcers and gastric carcinoma. Increasing resistance to standard antibiotics has now led to an ever-decreasing efficacy of eradication therapies and the development of novel and improved regimens for treatment is urgently required. Substantial progress has been made over the past few years in the identification of molecular mechanisms which are conducive to resistant phenotypes as well as for efficient strategies to counteract strain resistance and to avoid the use of ineffective antibiotics. These involve molecular testing methods, improved salvage therapies, and the discovery of novel and potent antimicrobial compounds. High rates of prevalence and gastric cancer are currently observed in Asian countries, including Japan, China, Korea, and Taiwan, where concomitantly intensive research efforts were initiated to explore advanced eradication regimens aimed at reducing the risk of gastric cancer. In this review, we present an overview of the known molecular mechanisms of antibiotic resistance and discuss recent intervention strategies for H. pylori diseases, with a view of the research progress in Asian countries.

Targeting Helicobacter pylori for antibacterial drug discovery with novel therapeutics

Helicobacter pylori is an important human pathogen with increasing antimicrobial resistance to standard-of-care antibiotics. Treatment generally includes a combination of classical broad-spectrum antibiotics and a proton-pump inhibitor, which often leads to perturbation of the gut microbiome and the potential for the development of antibiotic resistance. In this review, we examine reports, primarily from the past decade, on the discovery of new anti-H. pylori therapeutics, including approaches to develop narrow-spectrum and mechanistically unique antibiotics to treat these infections in their gastric niche. Compound series that target urease, respiratory complex I, and menaquinone biosynthesis are discussed in this context, along with bivalent antibiotic approaches that suppress resistance development. With increases in the understanding of the unique physiology of H. pylori and technological advances in the field of antibacterial drug discovery, there is a clear promise that novel therapeutics can be developed to effectively treat H. pylori infections.

1,4-Dihydropyridine as a Promising Scaffold for Novel Antimicrobials Against Helicobacter pylori

The increasing occurrence of multidrug-resistant strains of the gastric carcinogenic bacterium Helicobacter pylori threatens the efficacy of current eradication therapies. In a previous work, we found that several 1,4-dihydropyridine (DHP)-based antihypertensive drugs exhibited strong bactericidal activities against H. pylori by targeting the essential response regulator HsrA. To further evaluate the potential of 1,4-DHP as a scaffold for novel antimicrobials against H. pylori, we determined the antibacterial effects of 12 novel DHP derivatives that have previously failed to effectively block L- and T-type calcium channels. Six of these molecules exhibited potent antimicrobial activities (MIC ≤ 8 mg/L) against three different antibiotic-resistant strains of H. pylori, while at least one compound resulted as effective as metronidazole. Such antimicrobial actions appeared to be specific against Epsilonproteobacteria, since no deleterious effects were appreciated on Escherichia coli and Staphylococcus epidermidis. The new bactericidal DHP derivatives targeted the H. pylori regulator HsrA and inhibited its DNA binding activity according to both in vitro and in vivo analyses. Molecular docking predicted a potential druggable binding pocket in HsrA, which could open the door to structure-based design of novel anti-H. pylori drugs.

Quinone Derivatives as Promising Anti-Helicobacter pylori Agents from Aerial Parts of Mitracarpus hirtus

Seven new naphthoquinone diglycosides (1-7), three new anthraquinones (8-10), and eight known analogues were obtained from the aerial parts of Mitracarpus hirtus collected from West Africa in a bioassay-guided phytochemical investigation. All isolated compounds were elucidated by comparison with the literature and interpretation of spectroscopic data, and the absolute configurations of the new naphthoquinone diglycosides (1-10) were confirmed by chemical methods and ECD calculations. Notably, compound 1 was found to be the first naphthoquinone diglycoside containing carboxylic acid and isopentenyl side chains isolated from a species in the genus Mitracarpus. Compounds 6-18 showed antibacterial activity against multiple Helicobacter pylori strains with MIC values ranging from 0.0625 to 64 μg/mL. Particularly, 1-hydroxybenzoisochromanquinone (17) and benzo[g]isoquinoline-5,10-dione (18), with MIC values of 0.0625 and 0.125 μg/mL, displayed 32-512-fold higher potencies than a positive control, metronidazole. Compound 18 also demonstrated high antibiofilm activity and killed biofilm-encased Helicobacter pylori cells more effectively than metronidazole.

Selective Targeting of Human and Animal Pathogens of the Helicobacter Genus by Flavodoxin Inhibitors: Efficacy, Synergy, Resistance and Mechanistic Studies

Antimicrobial resistant (AMR) bacteria constitute a global health concern. Helicobacter pylori is a Gram-negative bacterium that infects about half of the human population and is a major cause of peptic ulcer disease and gastric cancer. Increasing resistance to triple and quadruple H. pylori eradication therapies poses great challenges and urges the development of novel, ideally narrow spectrum, antimicrobials targeting H. pylori. Here, we describe the antimicrobial spectrum of a family of nitrobenzoxadiazol-based antimicrobials initially discovered as inhibitors of flavodoxin: an essential H. pylori protein. Two groups of inhibitors are described. One group is formed by narrow-spectrum compounds, highly specific for H. pylori, but ineffective against enterohepatic Helicobacter species and other Gram-negative or Gram-positive bacteria. The second group includes extended-spectrum antimicrobials additionally targeting Gram-positive bacteria, the Gram-negative Campylobacter jejuni, and most Helicobacter species, but not affecting other Gram-negative pathogens. To identify the binding site of the inhibitors in the flavodoxin structure, several H. pylori-flavodoxin variants have been engineered and tested using isothermal titration calorimetry. An initial study of the inhibitors capacity to generate resistances and of their synergism with antimicrobials commonly used in H. pylori eradication therapies is described. The narrow-spectrum inhibitors, which are expected to affect the microbiota less dramatically than current antimicrobial drugs, offer an opportunity to develop new and specific H. pylori eradication combinations to deal with AMR in H. pylori. On the other hand, the extended-spectrum inhibitors constitute a new family of promising antimicrobials, with a potential use against AMR Gram-positive bacterial pathogens.

Single- and Two-Electron Reduction of Nitroaromatic Compounds by Flavoenzymes: Mechanisms and Implications for Cytotoxicity

Nitroaromatic compounds (ArNO₂) maintain their importance in relation to industrial processes, environmental pollution, and pharmaceutical application. The manifestation of toxicity/therapeutic action of nitroaromatics may involve their single- or two-electron reduction performed by various flavoenzymes and/or their physiological redox partners, metalloproteins. The pivotal and still incompletely resolved questions in this area are the identification and characterization of the specific enzymes that are involved in the bioreduction of ArNO₂ and the establishment of their contribution to cytotoxic/therapeutic action of nitroaromatics. This review addresses the following topics: (i) the intrinsic redox properties of ArNO₂, in particular, the energetics of their single- and two-electron reduction in aqueous medium; (ii) the mechanisms and structure-activity relationships of reduction in ArNO₂ by flavoenzymes of different groups, dehydrogenases-electrontransferases (NADPH:cytochrome P-450 reductase, ferredoxin:NADP(H) oxidoreductase and their analogs), mammalian NAD(P)H:quinone oxidoreductase, bacterial nitroreductases, and disulfide reductases of different origin (glutathione, trypanothione, and thioredoxin reductases, lipoamide dehydrogenase), and (iii) the relationships between the enzymatic reactivity of compounds and their activity in mammalian cells, bacteria, and parasites.

A review on the structures and biological activities of anti-Helicobacter pylori agents

Helicobacter pylori is one of the main causal risk factor in the generation of chronic gastritis, gastroduodenal ulcers and gastric carcinoma. Thus, the eradication of H. pylori infection is an important way for preventing and managing the gastric diseases. Multiple-therapy with several antibacterial agents is used for the eradication of H. pylori infections; however the increase of resistance to H. pylori strains has resulted in unsatisfactory eradication and unsuccessful treatment. Furthermore, the combination therapy with high dosing leads to the disruption of intestinal microbial flora and undesired side effects. Therefore, the search for new therapeutic agents with high selectivity against H. pylori is a field of current interest. In recent years, diverse compounds originating from natural sources or synthetic drug design programs were evaluated and tried to optimize for applying against H. pylori. In this review, we have described various classes of anti-H. pylori compounds, their structure-activity relationship studies, and mechanism of actions, which could be useful for the development of new drugs for the treatment of H. pylori infections.

Furazans in Medicinal Chemistry

Incorporation of heterocycles into drug molecules can enhance physical properties and biological activity. A variety of heterocyclic groups is available to medicinal chemists, many of which have been reviewed in detail elsewhere. Oxadiazoles are a class of heterocycle containing one oxygen and two nitrogen atoms, available in three isomeric forms. While the 1,2,4- and 1,3,4-oxadiazoles have seen widespread application in medicinal chemistry, 1,2,5-oxadiazoles (furazans) are less common. This Review provides a summary of the application of furazan-containing molecules in medicinal chemistry and drug development programs from analysis of both patent and academic literature. Emphasis is placed on programs that reached clinical or preclinical stages of development. The examples provided herein describe the pharmacology and biological activity of furazan derivatives with comparative data provided where possible for other heterocyclic groups and pharmacophores commonly used in medicinal chemistry.

Pimarane-derived diterpenoids with anti-Helicobacter pylori activity from the tuber of Icacina trichantha

Two novel diterpenoids and ten known analogs were obtained from the tuber of Icacina trichantha. All compounds exhibited antibacterial activity against Helicobacter pylori strains with MIC values ranging from 8 to 64 μg mL⁻¹.

Orally administrated chitosan microspheres bind Helicobacter pylori and decrease gastric infection in mice

Persistent Helicobacter pylori (H. pylori) infection is related to 90% of gastric cancers. With bacterial resistance rising and treatment inefficiency affecting 15% of the patients, alternative treatments urge. Chitosan microspheres (ChMics) have been proposed as an H. pylori-binding system. This work evaluates ChMics biocompatibility, mucopenetration and capacity to treat H. pylori infection in mice after oral administration. ChMics of different size (XL, ∼120 µm and XS, ∼40 µm) and degree of acetylation (6% and 16%) were developed and revealed to be able to adhere both human and mouse-adapted H. pylori strains without cytotoxicity towards human gastric cells. Ex vivo studies showed that smaller (XS) microspheres penetrate further within the gastric foveolae, suggesting their ability to reach deeply adherent bacteria. In vivo assays showed 88% reduction of infection when H. pylori-infected mice (C57BL/6) were treated with more mucoadhesive XL6 and XS6 ChMics. Overall, ChMics clearly demonstrate ability to reduce H. pylori gastric infection in mice, with chitosan degree of acetylation being a dominant factor over microspheres' size on H. pylori removal efficiency. These results evidence the strong potential of this strategy as an antibiotic-free approach to fight H. pylori infection, where microspheres are orally administered, bind H. pylori in the stomach, and remove them through the gastrointestinal tract. STATEMENT OF SIGNIFICANCE: Approximately 90% of gastric cancers are caused by the carcinogenic agent Helicobacter pylori, which infects >50% of the world population. Bacterial resistance, reduced antibiotic bioavailability, and the intricate distribution of bacteria in mucus and within gastric foveolae hamper the success of most strategies to fight H. pylori. We demonstrate that an antibiotic-free therapy based on bare chitosan microspheres that bind and remove H. pylori from stomach can achieve 88% reduction of infection from H. pylori-infected mice. Changing size and mucoadhesive properties, microspheres can reach different areas of gastric mucosa: smaller and less mucoadhesive can penetrate deeper into the foveolae. This promising, simple and inexpensive strategy paves the way for a faster bench-to-bedside transition, therefore holding great potential for clinical application.

Flavodoxins as Novel Therapeutic Targets against Helicobacter pylori and Other Gastric Pathogens

Flavodoxins are small soluble electron transfer proteins widely present in bacteria and absent in vertebrates. Flavodoxins participate in different metabolic pathways and, in some bacteria, they have been shown to be essential proteins representing promising therapeutic targets to fight bacterial infections. Using purified flavodoxin and chemical libraries, leads can be identified that block flavodoxin function and act as bactericidal molecules, as it has been demonstrated for Helicobacter pylori (Hp), the most prevalent human gastric pathogen. Increasing antimicrobial resistance by this bacterium has led current therapies to lose effectiveness, so alternative treatments are urgently required. Here, we summarize, with a focus on flavodoxin, opportunities for pharmacological intervention offered by the potential protein targets described for this bacterium and provide information on other gastrointestinal pathogens and also on bacteria from the gut microbiota that contain flavodoxin. The process of discovery and development of novel antimicrobials specific for Hp flavodoxin that is being carried out in our group is explained, as it can be extrapolated to the discovery of inhibitors specific for other gastric pathogens. The high specificity for Hp of the antimicrobials developed may be of help to reduce damage to the gut microbiota and to slow down the development of resistant Hp mutants.

Recent progress in Helicobacter pylori treatment

The main challenge in the field of Helicobacter pylori (H. pylori) infection is antibiotic resistance, which influences the efficacy of eradication regimens. Bismuth-containing quadruple therapy has been confirmed as an effective regimen for eradicating H. pylori, especially in strains with antibiotic resistance. High-dose proton-pump inhibitor-amoxicillin dual therapy could decrease the use of unnecessary antibiotics, which is a promising alternative approach. Adjuvant therapy (specific probiotic or vitamin) also showed good results, although more evidence is needed. Novel anti-H. pylori drugs are needed, and the establishment of the H. pylori database is an effective way to acknowledge the real-time information of H. pylori management. This review provides the recent progress of H. pylori treatment, and further studies are needed to address the role of different regimens in improving H. pylori eradication rate, especially in strains with antibiotics resistance.

Repurposing Dihydropyridines for Treatment of Helicobacter pylori Infection

Antibiotic resistance is a major cause of the increasing failures in the current eradication therapies against Helicobacter pylori. In this scenario, repurposing drugs could be a valuable strategy to fast-track novel antimicrobial agents. In the present study, we analyzed the inhibitory capability of 1,4-dihydropyridine (DHP) antihypertensive drugs on the essential function of the H. pylori response regulator HsrA and investigated both the in vitro antimicrobial activities and the in vivo efficacy of DHP treatments against H. pylori. Six different commercially available and highly prescribed DHP drugs-namely, Nifedipine, Nicardipine, Nisoldipine, Nimodipine, Nitrendipine, and Lercanidipine-noticeably inhibited the DNA binding activity of HsrA and exhibited potent bactericidal activities against both metronidazole- and clarithromycin-resistant strains of H. pylori, with minimal inhibitory concentration (MIC) values in the range of 4 to 32 mg/L. The dynamics of the decline in the bacterial counts at 2 × MIC appeared to be correlated with the lipophilicity of the drugs, suggesting different translocation efficiencies of DHPs across the bacterial membrane. Oral treatments with 100 mg/kg/day of marketed formulations of Nimodipine or Nitrendipine in combination with omeprazole significantly reduced the H. pylori gastric colonization in mice. The results presented here support a novel therapeutic solution for treatment of antibiotic-resistant H. pylori infections.

Helicobacter pylori and gastrointestinal and neurological diseases: Study protocol of an umbrella review of systematic reviews and meta-analyses

BACKGROUND

Systematic reviews showed that Helicobacter pylori (HP) infection is a major risk for developing gastric cancer and gastric ulcer and that it might be the cause of inflammatory bowel diseases, functional gastrointestinal disorders, and neurological diseases like Alzheimer disease. However, the robustness of the evidence was not tested. We will perform an umbrella review to systematically evaluate current evidence on the correlation between HP infection and gastrointestinal and neurological diseases.

METHODS

We will search OVID MEDLINE, EMBASE, and the Cochrane library for systematic reviews that evaluate the correlation of HP with gastrointestinal and neurological diseases, from inception to 1 July, 2019. Two reviewers will independently screen titles and abstracts of retrieved articles for eligible studies, and they will extract information for data analysis. We will assess heterogeneity between studies using I statistics and evaluate small-study effect in each systematic review through Egger test. Excess significance bias will be evaluated by compared the expected number of clinical studies with positive findings with the observed number. Quality of each systematic review will be assessed by using AMSTAR2 checklist.

ETHICS AND DISSEMINATION

This umbrella review is anticipated to be finished in December 2019, and the results will be published in a peer-reviewed journal and disseminated through conference presentation or poster. Because all of the data used in this systematic review and meta-analysis has been published, this review does not require ethical approval.Registration: PROSPERO CRD42019137226.

Multidrug resistance in Helicobacter pylori: current state and future directions

Introduction: Helicobacter pylori antibiotic resistance has increased worldwide and multidrug resistance (MDR), which seriously hampers eradication success of the frequent chronic infection, has often been reported. Areas covered: H. pylori MDR rates are discussed, mostly from recent articles published since 2015. Present approaches and future directions to counteract the MDR are outlined. Expert opinion: Alarming presence of triple, quadruple and, in some studies, quintuple and sextuple resistance was detected. Primary MDR rates ranged from <10% in most European countries to >40% in Peru. Post-treatment or overall MDR rates were >23-36% in about half of the studies. MDR prevalence has varied both among and within the countries. Factors linked to the MDR are national antibiotic consumption, antibiotic misuse, treatment failures and bacterial factors such as mutations, efflux pumps, and biofilms. Important directions to counteract the MDR increase can be optimization of present and new eradication regimens, wider use of bismuth-containing regimens, assessment of benefit of vonoprazan, new antibiotics such as newer fluoroquinolones and oxazolidinone analogues, adjuvants involving N-acetylcysteine and probiotics, anti-biofilm approaches using anti-biofilm peptides and rhamnolipid and development of vaccines and non-invasive tests for resistance detection. However, more efforts and studies are required. Strain susceptibility testing is increasingly important.