Influence of efflux pump inhibitors on the multidrug resistance of Helicobacter pylori

An all-in-one therapeutic platform for the treatment of resistant Helicobacter pylori infection

Helicobacter pylori (H. pylori) infection is a major cause of gastric diseases. Currently, bismuth-based quadruple therapy is widely adopted for eradicating H. pylori infection. However, this first-line strategy faces several challenges such as drug resistance, intestinal dysbacteriosis, and patients' poor compliance. To overcome these problems, an all-in-one therapeutic platform (CLA-Bi-ZnO2@Lipo) that composed of liposomes loading clarithromycin (CLA), Bi, and ZnO2 hybrid nanoparticles was developed for eradicating multidrug-resistant (MDR) H. pylori. The in vitro and in vivo results showed that CLA-Bi-ZnO2@Lipo could target the infection-induced inflammatory mucosa through liposome mediated nanoparticle-tissue surface charge interaction and quickly respond to the gastric acid environment to release CLA, Bi3+, Zn2+, and H2O2. By oral administration per day, the acid triggered decomposition of CLA-Bi-ZnO2@Lipo could significantly increase intragastric pH to 6 within 30 min; The released CLA, Zn2+, and H2O2 further exerted synergistical anti-bacterial effects in which a ∼2 order higher efficacy in reducing MDR H. pylori burden was achieved in comparison with standard quadruple therapy (p < 0.05); The released Zn2+ and Bi3+ could also alleviate mucosal inflammation. Most importantly, the CLA-Bi-ZnO2@Lipo exhibited superior biosafety and nearly no side effects on intestinal flora. Overall, this study developed a highly integrated and safe anti-MDR H. pylori agent which had great potential to be used as an alternative treatment for MDR H. pylori eradication.

Antibiotic Resistance of Helicobacter pylori: Mechanisms and Clinical Implications

Helicobacter pylori is a pathogenic bacterium associated with various gastrointestinal diseases, including chronic gastritis, peptic ulcers, mucosa-associated lymphoid tissue lymphoma, and gastric cancer. The increasing rates of H. pylori antibiotic resistance and the emergence of multidrug-resistant strains pose significant challenges to its treatment. This comprehensive review explores the mechanisms underlying the resistance of H. pylori to commonly used antibiotics and the clinical implications of antibiotic resistance. Additionally, potential strategies for overcoming antibiotic resistance are discussed. These approaches aim to improve the treatment outcomes of H. pylori infections while minimizing the development of antibiotic resistance. The continuous evolution of treatment perspectives and ongoing research in this field are crucial for effectively combating this challenging infection.

Co-administration of amoxicillin-loaded chitosan nanoparticles and inulin: A novel strategy for mitigating antibiotic resistance and preserving microbiota balance in Helicobacter pylori treatment

Helicobacter pylori (H. pylori) is a causative agent of various gastrointestinal diseases and eradication mainly relies on antibiotic treatment, with (AMX) being a key component. However, rising antibiotic resistance in H. pylori necessitates the use of antibiotics combination therapy, often disrupting gut microbiota equilibrium leading to further health complications. This study investigates a novel strategy utilizing AMX-loaded chitosan nanoparticles (AMX-CS NPs), co-administered with prebiotic inulin to counteract H. pylori infection while preserving microbiota health. Following microbroth dilution method, AMX displayed efficacy against H. pylori, with a MIC50 of 48.34 ± 3.3 ng/mL, albeit with a detrimental impact on Lactobacillus casei (L. casei). The co-administration of inulin (500 μg/mL) with AMX restored L. casei viability while retaining the lethal effect on H. pylori. Encapsulation of AMX in CS-NPs via ionic gelation method, resulted in particles of 157.8 ± 3.85 nm in size and an entrapment efficiency (EE) of 86.44 ± 2.19 %. Moreover, AMX-CS NPs showed a sustained drug release pattern over 72 h with no detectable toxicity on human dermal fibroblasts cell lines. Encapsulation of AMX into CS NPs also reduced its MIC50 against H. pylori, while its co-administration with inulin maintained L. casei viability. Interestingly, treatment with AMX-CS NPs also reduced the expression of the efflux pump gene hefA in H. pylori. This dual treatment strategy offers a promising approach for more selective antimicrobial treatment, minimizing disruption to healthy microbial communities while effectively addressing pathogenic threats.

Current paradigms in the management of refractory Helicobacter pylori infection

Helicobacter pylori is the most prevalent chronic bacterial infection, with approximately half of the world's population estimated to be colonized. The World Health Organization (WHO) has classified Helicobacter pylori as a class-I carcinogen. All main society guidelines recommend its eradication in infected individuals. The global trend indicates that eradication rates are decreasing annually and the likelihood of eradication decreases with each unsuccessful therapeutic attempt. Resistance to antibiotics in H. pylori strains is the leading cause for eradication failure. Still, drug resistance and treatment failure may be complex, multi-dimensional and associated with several other factors. Knowledge of these factors can aid in optimizing eradication rates. This review will focus on the factors associated with refractory H. pylori, with a particular emphasis on antibiotic resistance mechanisms and their clinical implications. Also, the most recent literature and recommendations available for determining an appropriate regimen after the failure of the first attempt at eradication will be discussed.

Advances in the pharmacological and regulatory management of multidrug resistant Helicobacter pylori

INTRODUCTION

Antibiotic resistance of Helicobacter pylori (H. pylori) hampers the success of eradication and in recent years multidrug resistance (MDR) shows an increase worldwide.

AREAS COVERED

This review covers current aspects of pharmacological and regulatory management of MDR-resistant H. pylori infection.

EXPERT OPINION

MDR H. pylori is increasing worldwide and its prevalence varies both between continents and countries. High consumption and misuse of antibiotics, H. pylori treatment failures and bacterial factors such as mutations, efflux pumps and biofilms are among the factors associated with MDR. Important steps for confronting the rise of MDR H. pylori strains should follow the principles of antibiotic stewardship, i.e. eradication regimens should be optimized with regard to all aspects of therapy, including drugs, doses, formulation, frequency of administration, administration in relation to meals and duration of therapy that reliably achieve at least 90% (preferably >95%) cure rates in adherent patients with susceptible infections.

Proton Pump Inhibitors, Kidney Damage, and Mortality: An Updated Narrative Review

Since their approval by the Food and Drug Administration (FDA) in 1989, proton pump inhibitors (PPIs) have become one of the most highly utilized drugs in the United States, assuming a position as one of the top 10 most prescribed medications in the country. The purpose of PPIs is to limit the amount of gastric acid secreted by the parietal cells via irreversible inhibition of the H+/K+-ATPase pump, therefore maintaining an elevated gastric acid pH of greater than 4 for 15-21 h. Even though PPIs have many clinical uses, they are not without their adverse effects, mimicking achlorhydria. Besides electrolyte abnormalities and vitamin deficiencies, long-term use of PPIs has been linked to acute interstitial nephritis, bone fractures, poor COVID-19 infection outcomes, pneumonia, and possibly an increase in all-cause mortality. The causality between PPI use and increased mortality and disease risk can be questioned since most studies are observational. Confounding variables can greatly affect an observational study and explain the wide-ranging associations with the use of PPIs. Patients on PPIs are generally older, obese, sicker with a higher number of baseline morbidities, and on more medications than the compared PPI non-users. These findings suggest that PPI users are at a higher risk of mortality and complications based on pre-existing conditions. This narrative review aims to update readers on the concerning effects that proton pump inhibitor use can have on patients and give providers a resource to create informed decisions on appropriate PPI use.

Revealing the novel effect of Jinghua Weikang capsule against the antibiotic resistance of Helicobacter pylori

Background

Helicobacter pylori (H. pylori) infects half of the human population globally. Eradication rates with triple or quadruple therapy have decreased owing to the increasing rate of antibiotic resistance. Jinghua Weikang capsule (JWC) is the first and most popular Chinese patent medicine approved by the state for the treatment of gastritis and peptic ulcers caused by H. pylori infection in China. Previous studies have found that JWC has a certain bactericidal effect on drug-resistant H. pylori and its major component, Chenopodium ambrosioides L. inhibits biofilm formation, but the mechanism remains unclear. This study focused on drug-resistant H. pylori and explored whether JWC could reverse drug resistance and its related mechanisms.

Method

The agar plate dilution method, E-test method, and killing kinetics assay were used to evaluate the bactericidal effect of JWC on antibiotic-resistant H. pylori and its effect on antibiotic resistance. Sanger sequencing was used to detect mutations in drug resistance genes. The crystal violet method, scanning electron microscopy, and confocal laser scanning microscopy were used to evaluate the effects of JWC on biofilms. qPCR was performed to evaluate the effect of JWC on the expression of efflux pump-related genes. qPCR and immunofluorescence were used to evaluate the effects of JWC on H. pylori adhesion.

Results

JWC showed considerable antibacterial activity against drug-resistant H. pylori strains, with minimum inhibitory concentration (MIC) values ranging from 64 to 1,024 μg/ml. The MIC of metronidazole (MTZ) against H. pylori 26,695–16R decreased from 64 to 6 μg/ml after treatment with 1/2 MIC of JWC. The resistance of H. pylori 26,695–16R to MTZ was reversed by JWC, and its effect was better than that of PaβN and CCCP. H. pylori 26,695–16R is a moderate biofilm-forming strain, and JWC (16–64 μg/ml) can inhibit the formation of biofilms in H. pylori 26,695–16R. JWC reduced the expression of HP0605-HP0607 (hefABC), HP0971-HP0969 (hefDEF), HP1327-HP1329 (hefGHI), and HP1489-HP1487. JWC reduced the adhesion of H. pylori to GES-1 cells and the expression of adhesives NapA, SabA, and BabA.

Conclusion

The reversal of MTZ resistance by JWC may be achieved through the adhesin/efflux pump-biofilm pathway.

Nanocluster-mediated photothermia improves eradication efficiency and antibiotic sensitivity of Helicobacter pylori

Background

Helicobacter pylori (H. pylori) eradication plays a crucial role in gastric cancer prevention, but the antimicrobial resistance of H. pylori is obstructing this elimination process. In this study, we developed nanoclusters (NCs) from Zn0.3Fe2.7O4 nanoparticles using a poly(ethylene glycol)-b-poly(ε-caprolactone)-based nanocarrier as an innovative antibiotic-independent H. pylori management.

Results

The nanocluster showed minimal toxicity and maximal biocompatibility. With a low concentration (50 µg/mL) of NCs under a short time period (~ 2 min) of near-infrared (808 nm) irradiation, we kept the culture medium temperature to 41 °C for 20 min with continuous irradiation. The heated NCs exhibited efficient photothermal effects and resulted in an excellent inhibition of H. pylori growth, adhesion and ability to induce vacuolization in eukaryotic cells in in vitro investigation. Transmission electron microscopy showed a dramatic morphologic change after NCs photothermia on H. pylori, including cell wall and membrane rupture, as well as ribosome damage. Besides, levofloxacin and clarithromycin resistance was decreased after photothermal treatment in H. pylori NCTC 11637 and/or clinical strains, however metronidazole resistance was unchanged. We also discovered a significant decrease in the biofilm formation of H. pylori under the NCs-based photothermal application, while efflux pump function was unchanged.

Conclusions

Based on this novel NCs-based photothermal approach, we were able to demonstrate in vitro a significant inhibition of both H. pylori growth and molecular toxicity, and its improvement in antibiotic sensitivity alone with the eradication of H. pylori biofilms previously believed to be tolerant to conventional antibiotics.

Exploration of the molecular mechanisms underlying the antibiotic resistance of Helicobacter pylori: A whole-genome sequencing-based study in Southern China

BACKGROUND

Although antimicrobial resistance (AMR) in Helicobacter pylori is a global threat to human health and the underlying molecular mechanisms have been explored previously, only a few of them are fully elucidated.

MATERIALS AND METHODS

In the present study, we isolated 54 Helicobacter pylori strains from Southern China and assessed their susceptibility to five antibiotics using the agar dilution assay. Whole-genome sequencing was performed to screen the AMR genotypes of the Helicobacter pylori isolates.

RESULTS

Our study revealed a high prevalence of resistance to clarithromycin (CLR), levofloxacin (LVX), and metronidazole (MTZ) in the Chinese isolates, 55.56% of which showed multidrug-resistant phenotypes. We screened for the 94 types of previously reported AMR mutations in 12 genes, but only a few of them were related to the AMR phenotype. Furthermore, we discovered four new mutations in the 23S rRNA gene and one mutation in infB related to CLR resistance. Another three mutations in gyrA and one in gyrB were closely correlated with the AMR pattern against LVX. We also demonstrated that the mutations R16C/H in rdxA, V56I in rpsU, and D54A in sodB might contribute to resistance to MTZ, which were previously reported in laboratory experiments but not found in clinical strains. We examined the concordance between the genotype and phenotype of AMR and identified several potential molecular biomarkers for predicting CLR and LVX resistance.

CONCLUSIONS

Our study explored the molecular mechanisms underlying the antibiotic resistance of Helicobacter pylori isolates from Southern China. We propose further epidemiologic investigations in China.

Clinical Factors Implicated in Antibiotic Resistance in Helicobacter pylori Patients

Helicobacter pylori is a common gastric pathogen associated with multiple clinical syndromes, including cancer. Eradication rates of H. pylori remain suboptimal despite the progress made in the past few decades in improving treatment strategies. The low eradication rates are mainly driven by antibiotic resistance of H. pylori. Non-invasive molecular testing to identify patients with antibiotic-resistant H. pylori represents a promising therapeutic avenue, however this technology currently remains limited by availability, costs, and lack of robust validation. Moreover, there is insufficient evidence to demonstrate that resistance-testing-based treatment approaches are superior to appropriately designed empiric strategies. Consensus guidelines recommend use of proven locally effective regimens; however, eradication data are inconsistently generated in several regions of the world. In this review, we describe several clinical factors associated with increased rates of antibiotic resistant H. pylori, including history of previous antibiotic exposure, increasing age, female gender, ethnicity/race, extent of alcohol use, and non-ulcer dyspepsia. Assessment of these factors may aid the clinician in choosing the most appropriate empiric treatment strategy for each patient. Future study should aim to identify locally effective therapies and further explore the clinical factors associated with antibiotic resistance.

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.

Helicobacter pylori infection and antibiotic resistance - from biology to clinical implications

Helicobacter pylori is a major human pathogen for which increasing antibiotic resistance constitutes a serious threat to human health. Molecular mechanisms underlying this resistance have been intensively studied and are discussed in this Review. Three profiles of resistance - single drug resistance, multidrug resistance and heteroresistance - seem to occur, probably with overlapping fundamental mechanisms and clinical implications. The mechanisms that have been most studied are related to mutational changes encoded chromosomally and disrupt the cellular activity of antibiotics through target-mediated mechanisms. Other biological attributes driving drug resistance in H. pylori have been less explored and this could imply more complex physiological changes (such as impaired regulation of drug uptake and/or efflux, or biofilm and coccoid formation) that remain largely elusive. Resistance-related attributes deployed by the pathogen cause treatment failures, diagnostic difficulties and ambiguity in clinical interpretation of therapeutic outcomes. Subsequent to the increasing antibiotic resistance, a substantial drop in H. pylori treatment efficacy has been noted globally. In the absence of an efficient vaccine, enhanced efforts are needed for setting new treatment strategies and for a better understanding of the emergence and spread of drug-resistant bacteria, as well as for improving diagnostic tools that can help optimize current antimicrobial regimens.

The Action of Efflux Pump Genes in Conferring Drug Resistance to Klebsiella Species and Their Inhibition

Nosocomial infections caused by Klebsiella species are characterized by high rates of morbidity and mortality. The emergence of the multidrug-resistant (MDR) and extensive drug-resistant (XDR) Gram-negative bacteria reduces the antibiotic efficacy in the treatment of infections caused by the microorganisms. Management of these infections is often difficult, due to the high frequency of strains resistant to multiple antimicrobial agents. Multidrug efflux pumps play a major role as a mechanism of antimicrobial resistance in Gram-negative pathogens. Efflux systems are significant in conferring intrinsic and acquired resistance to the bacteria. The emergence of increasing drug resistance among Klebsiella pneumoniae nosocomial isolates has limited the therapeutic options for treatment of these infections and hence there is a constant quest for an alternative. In this review, we discuss various resistance mechanisms, focusing on efflux pumps and related genes in conferring resistance to Klebsiella. The role of various efflux pump inhibitors (EPIs) in restoring the antibacterial activity has also been discussed. In specific, antisense oligonucleotides as alternative therapeutics in combatting efflux-mediated resistance in Klebsiella species have focused upon.

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.

Propranolol, chlorpromazine and diclofenac restore susceptibility of extensively drug-resistant (XDR)-Acinetobacter baumannii to fluoroquinolones

Nosocomial infections caused by extensively drug-resistant (XDR) or Pan-Drug resistant (PDR) Acinetobacter (A.) baumannii have recently increased dramatically creating a medical challenge as therapeutic options became very limited. The aim of our study was to investigate the antibiotic-resistance profiles and evaluate the various combinations of ciprofloxacin (CIP) or levofloxacin (LEV) with antimicrobial agents and non-antimicrobial agents to combat antimicrobial resistance of XDR A. baumannii. A total of 100 (6.25%) A. baumannii clinical isolates were recovered from 1600 clinical specimens collected from hospitalized patients of two major university hospitals in Upper Egypt. Antimicrobial susceptibility tests were carried out according to CLSI guidelines. Antimicrobial susceptibility testing of the respective isolates showed a high percentage of bacterial resistance to 19 antimicrobial agents ranging from 76 to99%. However, a lower percentage of resistance was observed for only colistin (5%) and doxycycline (57%). The isolates were categorized as PDR (2; 2%), XDR (68; 68%), and multi-drug resistant (MDR) (30; 30%). Genotypic analysis using ERIC-PCR on 2 PDR and 32 selected XDR isolates showed that they were not clonal. Combinations of CIP or LEV with antibiotics (including, ampicillin, ceftriaxone, amikacin, or doxycycline) were tested on these A. baumannii non-clonal isolates using standard protocols where fractional inhibitory concentrations (-FICs) were calculated. Results of the respective combinations showed synergism in 23.5%, 17.65%, 32.35%, 17.65% and 26.47%, 8.28%, 14.71%, 26.47%, of the tested isolates, respectively. CIP or LEV combinations with either chlorpromazine (CPZ) 200 μg/ml, propranolol (PR) in two concentrations, 0.5 mg/ml and 1.0 mg/ml or diclofenac (DIC) 4 mg/ml were carried out and the MIC decrease factor (MDF) of each isolate was calculated and results showed synergism in 44%, 50%, 100%, 100% and 94%, 85%, 100%, 100%, of the tested isolates, respectively. In conclusion, combinations of CIP or LEV with CPZ, PR, or DIC showed synergism in most of the selected PDR and XDR A. baumannii clinical isolates. However, these combinations have to be re-evaluated in vivo using appropriate animal models infected by XDR- or PDR- A. baumannii.

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.

Helicobacter pylori: Multiple resistance in patients from Bogotá, Colombia

Introduction: The main cause for Helicobacter pylori infection treatment failure is antibiotic resistance, where clarithromycin and metronidazole play the main role. In Colombia, primary resistance as a consequence of the use of these two antibiotics and excessive levofloxacin use is above the accepted limit (13.6%, 83%, and 16%, respectively). Despite this fact, empirical therapies that include the combination of these antibiotics are used in patients with previous therapeutic failure. Objective: To determine antibiotic resistance in patients previously treated for H. pylori in Bogotá, Colombia. Materials and methods: We conducted a descriptive study that included ten isolates obtained from five patients with three or four previous failed treatments for H. pylori. Antibiotic resistance to amoxicillin, clarithromycin, levofloxacin, and metronidazole was investigated by agar dilution and confirmed by DNA sequencing (Magrogen, Korea). Results: Eight isolates were resistant to two or more antibiotics. All isolates were resistant to levofloxacin. Susceptibility patterns in isolates from the gastric antrum and the body of the stomach were different in three patients. Conclusion: As far as we know, this is the first evidence of multiple H. pylori resistance in Colombia in previously treated patients. Results demonstrated the consequences of using an ineffective antibiotic scheme and the need to assess antibiotic susceptibility in different anatomical sites of the stomach. The consequences of multiple resistance decrease possible antibiotic effectiveness to eradicate H. pylori in the future.

Effects of Omeprazole and Caffeine Alone and in Combination with Gentamicin and Ciprofloxacin Against Antibiotic Resistant Staphylococcus Aureus and Escherichia Coli Strains

Objective

Antibiotic resistance is a global health problem and threatens health of societies. These problems have led to a search for alternative approaches such as combination therapy. The aim of the present study was to investigate the effect of caffeine and omeprazole in combination with gentamicin or ciprofloxacin against standard and clinically resistant isolates of Staphylococcus aureus and Escherichia coli.

Methods

The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of different agents against bacterial strains were determined. The interaction of non- antibiotic drugs with gentamicin and ciprofloxacin was studied in vitro using a checkerboard method and calculating fraction inhibitory concentration index (FICI). Verapamil as efflux pump inhibitor was used to evaluate the possible mechanism of bacterial resistance to antibiotics.

Results

The MIC and MBC values of gentamicin against bacterial strains were in the range of 20- 80 μg/ml and 40-200 μg/ml, respectively. Caffeine and omeprazole had no intrinsic inhibitory activity against tested microorganisms. However, upon combination of caffeine with antibiotics, the synergistic effects were observed. Verapamil was able to reduce the MIC values of gentamicin (4 folds) only in some bacterial strains.

Conclusion

These findings indicated that caffeine was effective in removing bacterial infection caused by S. aureus and E. coli. The relevant mechanisms of antibiotic resistance were not related to the drug efflux.

Effective antimicrobial activity of rifabutin against multidrug-resistant Helicobacter pylori

BACKGROUND

Helicobacter pylori resistance to more than one antibiotic is the main reason for failure in bacterial eradication in a considerable number of patients. Rifabutin (RFB) with a broad-spectrum of antimicrobial therapy has been suggested for treatment of refractory multidrug-resistant infections.

METHODS

Helicobacter pylori isolates from 104 patients were examined for resistance to 5 currently used antibiotics and RFB, using agar dilution method. Twofold serial dilutions of antibiotics were used and MICs (μg/mL) determined as metronidazole (MTZ 8), clarithromycin (CLR 2), amoxicillin (AMX 1), tetracycline (TET 0.5), furazolidone (FRZ 0.5), and RFB (0.06).

RESULTS

Of 104 H. pylori isolates, only 7 (6.7%) were sensitive to all the 6 antibiotics. However, 30 (28.8%) were resistant to one antibiotic, 28 (26.9%) to two, 19 (18.2%) to three, 14 (13.4%) to four, and 6 (5.7%) to five currently used antibiotics. Overall, 67(64.4%) of isolates were resistant to 2-5 currently used antibiotics and considered as multidrug-resistant (MDR), with 59 (88.1%) showing sensitivity to RFB and 8 (11.9%) resistance (P < 0.05). Of 33 isolates resistant to both MTZ and CLR, 25 (75.7%) were sensitive to RFB and 8 (24.3%) resistant (P < 0.05).

DISCUSSION

In vitro antimicrobial effectiveness of RFB on MDR H. pylori including those with resistance to both MTZ and CLR was demonstrated. However, RFB efficacy decreased as the number of antibiotics responsible for MDR increased. Considering that RFB inhibits both extra- and intracellular H. pylori, it can be suggested as an effective antibiotic against of MDR H. pylori.

Bifunctional Enzyme SpoT Is Involved in Biofilm Formation of Helicobacter pylori with Multidrug Resistance by Upregulating Efflux Pump Hp1174 (gluP)

The drug resistance of Helicobacter pylori is gradually becoming a serious problem. Biofilm formation is an important factor that leads to multidrug resistance (MDR) in bacteria.

The drug resistance of Helicobacter pylori is gradually becoming a serious problem. Biofilm formation is an important factor that leads to multidrug resistance (MDR) in bacteria. The ability of H. pylori to form biofilms on the gastric mucosa is known. However, there are few studies on the regulatory mechanisms of H. pylori biofilm formation and multidrug resistance. Guanosine 3′-diphosphate 5′-triphosphate and guanosine 3′,5′-bispyrophosphate [(p)ppGpp] are global regulatory factors and are synthesized in H. pylori by the bifunctional enzyme SpoT. It has been reported that (p)ppGpp is involved in the biofilm formation and multidrug resistance of various bacteria. In this study, we found that SpoT also plays an important role in H. pylori biofilm formation and multidrug resistance. Therefore, it was necessary to carry out some further studies regarding its regulatory mechanism. Considering that efflux pumps are of great importance in the biofilm formation and multidrug resistance of bacteria, we tried to determine whether efflux pumps controlled by SpoT participate in these activities. We found that Hp1174 (glucose/galactose transporter [gluP]), an efflux pump of the major facilitator superfamily (MFS), is highly expressed in biofilm-forming and multidrug-resistant (MDR) H. pylori strains and is upregulated by SpoT. Through further research, we determined that gluP is involved in H. pylori biofilm formation and multidrug resistance. Furthermore, the average expression level of gluP in the clinical MDR strains (C-MDR) was considerably higher than that in the clinical drug-sensitive strains (C-DSS). Taken together, our results revealed a novel molecular mechanism of H. pylori resistance to multidrug exposure.

Overcoming problems of poor drug penetration into bacteria: challenges and strategies for medicinal chemists

INTRODUCTION

Bacterial cell walls and membranes provide essential protection for bacteria against environmental influences. Different bacteria possess different cell envelopes and understanding each of these structures is crucial for the design of effective antibacterial drugs whose targets are intracellular. Optimal properties of drugs that are required for their entry into bacteria are still hard to predict. The guidelines that are suitable and well established for the penetration of a drug into eukaryotic cells are poorly adaptable to the complex world of pathogens. Areas covered: The factors that govern the penetration of anti-infection drugs into bacteria are examined and the available strategies to overcome this therapeutically very important barrier are reviewed. The areas covered include optimization of the physicochemical properties of compounds, utilization of iron-chelating compounds, i.e. siderophores, the use of efflux pump inhibitors, and of carriers such as liposomes. Expert opinion: Although several rules governing permeation have recently been proposed for effective antibacterial drugs, none of them has been so far established as the 'golden' rule. Thus, new research is needed to find a more general approach on how to increase the concentration of antibacterial compounds in bacterial cells.

rdxA, frxA, and efflux pump in metronidazole-resistant Helicobacter pylori: Their relation to clinical outcomes

BACKGROUND AND AIM

rdxA and frxA mutations and enhancement of efflux pump have been suggested as the cause of metronidazole resistance in Helicobacter pylori. This study was performed to investigate the resistance mechanisms related to clinical eradication outcome, and to examine direct involvement of hefA in metronidazole-resistant isolates with intact rdxA and frxA.

METHODS

A total of 53 H. pylori-positive patients who were treated with metronidazole-containing sequential or quadruple therapy from 2011 to 2015 were enrolled. The metronidazole susceptibility of H. pylori isolates was examined by agar dilution test. Mutations in rdxA and frxA, were analyzed with DNA sequencing, and impact of hefA on metronidazole resistance was examined with quantitative real-time reverse transcription polymerase chain reaction, knockout and genetic complementation test for hefA.

RESULTS

Seven mutation types of rdxA and/or frxA were found in H. pylori isolated from non-eradicated subjects. rdxA mutation was associated with eradication failure (P = 0.002), and nonsense mutation in rdxA reduced eradication efficacy (P = 0.009). hefA expression was significantly higher in resistant isolates (P < 0.001), especially in rdxA(-)frxA(-) as compared to rdxA(+)frxA(+) (P = 0.027). Resistant isolates with no mutation in rdxA and frxA became susceptible after hefA knockout. Genetic complementation for hefA recovered metronidazole resistance in all of three hefA knockout mutants.

CONCLUSIONS

These results suggest that rdxA mutations play a critical role in metronidazole resistance as well as the outcomes of eradication therapy. In addition, hefA seems to be directly involved in metronidazole resistance, which explains the resistance in clinical isolates with intact rdxA and frxA.

Primary Helicobacter pylori resistance in elderly patients over 20 years: A Bulgarian study

We evaluated the antibiotic susceptibility of 233 Helicobacter pylori strains isolated in the period 2011-2016, involving 62 strains from elderly patients aged 66-93years and 171 strains from younger adults. To assess resistance evolution, primary resistance rates in 92 strains from as many patients aged ≥60years in 1996-2003 were compared with those in 85 strains from infected patients in the same age group in 2011-2016. In the patients aged >65years evaluated during the last 6 years, amoxicillin resistance according to EUCAST and prior breakpoints was 1.6 and 0%, respectively. Resistance rates were the same by both breakpoint systems to metronidazole (35.5%), clarithromycin (22.6%), tetracycline (1.6%) and levofloxacin (32.3%). In 2011-2016, there were no significant differences between resistance rates in the subjects aged >65years and the younger adults. Notably, during the last 6 years, double/triple resistance was found in 21.0% of the subjects aged >65years. Moreover, the prevalence of quinolone primary resistance (30.0%) was significantly (3.4-fold) higher than that (8.9%) observed in 1996-2003. Briefly, the presence of both combined resistance and a strikingly high primary levofloxacin resistance in the elderly implies a cautious antibiotic choice for H. pylori eradication. In vitro susceptibility testing of the strains is highly important in this age group. The results can be linked to more frequent comorbidities and co-infection treatment in older compared with younger patients and, additionally, to the national antibiotic consumption. The high prevalence of quinolone resistance in the elderly patients is an alarming finding.

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.

A Review of the Novel Application and Potential Adverse Effects of Proton Pump Inhibitors

Proton pump inhibitors (PPIs) are known as a class of pharmaceutical agents that target H⁺/K⁺-ATPase, which is located in gastric parietal cells. PPIs are widely used in the treatment of gastric acid-related diseases including peptic ulcer disease, erosive esophagitis and gastroesophageal reflux disease, and so on. These drugs present an excellent safety profile and have become one of the most commonly prescribed drugs in primary and specialty care. Except for gastric acid-related diseases, PPIs can also be used in the treatment of Helicobacter pylori infection, viral infections, respiratory system diseases, cancer and so on. Although PPIs are mainly used short term in patients with peptic ulcer disease, nowadays these drugs are increasingly used long term, and frequently for a lifetime, for instance in patients with typical or atypical symptoms of gastroesophageal reflux disease and in NSAID or aspirin users at risk of gastrotoxicity and related complications including hemorrhage, perforation and gastric outlet obstruction. Long-term use of PPIs may lead to potential adverse effects, such as osteoporotic fracture, renal damage, infection (pneumonia and clostridium difficile infection), rhabdomyolysis, nutritional deficiencies (vitamin B12, magnesium and iron), anemia and thrombocytopenia. In this article, we will review some novel uses of PPIs in other fields and summarize the underlying adverse reactions.

Effect of biofilm formation by clinical isolates of Helicobacter pylori on the efflux-mediated resistance to commonly used antibiotics

AIM

To evaluate the role of biofilm formation on the resistance of Helicobacter pylori (H. pylori) to commonly prescribed antibiotics, the expression rates of resistance genes in biofilm-forming and planktonic cells were compared.

METHODS

A collection of 33 H. pylori isolates from children and adult patients with chronic infection were taken for the present study. The isolates were screened for biofilm formation ability, as well as for polymerase chain reaction (PCR) reaction with HP1165 and hp1165 efflux pump genes. Susceptibilities of the selected strains to antibiotic and differences between susceptibilities of planktonic and biofilm-forming cell populations were determined. Quantitative real-time PCR (qPCR) analysis was performed using 16S rRNA gene as a H. pylori-specific primer, and two efflux pumps-specific primers, hp1165 and hefA.

RESULTS

The strains were resistant to amoxicillin, metronidazole, and erythromycin, except for one strain, but they were all susceptible to tetracycline. Minimum bactericidal concentrations of antibiotics in the biofilm-forming cells were significantly higher than those of planktonic cells. qPCR demonstrated that the expression of efflux pump genes was significantly higher in the biofilm-forming cells as compared to the planktonic ones.

CONCLUSION

The present work demonstrated an association between H. pylori biofilm formation and decreased susceptibility to all the antibiotics tested. This decreased susceptibility to antibiotics was associated with enhanced functional activity of two efflux pumps: hp1165 and hefA.

Possibilities for optimization of eradication therapy for Helicobacter pylori infection in modern clinical practice

A steady decline in the effectiveness of standard eradication therapy (ET) regimens for Helicobacter pylori infection necessitates a search for ways of their optimization, by enhancing the efficiency of treatment protocols and by improving their safety and tolerability. The review systematizes the data available in the literature on main accessible methods for optimizing ET regimens. Among the optimization methods that can considerably enhance the efficiency of ET regimens, one may identify their addition of a bismuth agent (by 10—20%), the use of rebamipide (by 11.9%), adjuvant therapy with probiotics (by 8.1—13%), or double-dose proton pump inhibitors (by 8%). Only adjuvant therapy with probiotics results in a significant decrease in the incidence of side effects from ET. In posteradication period, rebamipide should be used to potentiate gastric mucosal repair and to regress inflammatory processes.

Current status of Helicobacter pylori infection and evolution of treatment strategy in China

Infection with Helicobacter pylori (H. pylori) has become a common digestive disease and the prevalence of H. pylori infection remains high in the Chinese population. Recently, the Kyoto global consensus report on H. pylori gastritis and the Toronto consensus for the treatment of H. pylori infection in adults were issued. Therefore, it is essential to discuss the prevention and control of H. pylori infection in China. Due to severe resistance to antibiotics, toxic and host factors, the eradication rate in China has currently became lower than before. Therefore, whether to intervene H. pylori infection in the asymptomatic population and enlarge the indication for eradication and the cost-effect for this new strategy should be discussed. In addition, the implementation of the "test and treat" policy or not in China is debatable. Developing optimal treatment strategy has become a major challenge that clinicians face. This review focuses on the current H. pylori infection situation and the evolution of treatment strategies in China.

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.

Detection of Helicobacter pylori resistance to clarithromycin and fluoroquinolones in Brazil: A national survey

AIM

To evaluate bacterial resistance to clarithromycin and fluoroquinolones in Brazil using molecular methods.

METHODS

The primary antibiotic resistance rates of Helicobacter pylori (H. pylori) were determined from November 2012 to March 2015 in the Southern, South-Eastern, Northern, North-Eastern, and Central-Western regions of Brazil. Four hundred ninety H. pylori patients [66% female, mean age 43 years (range: 18-79)] who had never been previously treated for this infection were enrolled. All patients underwent gastroscopy with antrum and corpus biopsies and molecular testing using GenoType HelicoDR (Hain Life Science, Germany). This test was performed to detect the presence of H. pylori and to identify point mutations in the genes responsible for clarithromycin and fluoroquinolone resistance. The molecular procedure was divided into three steps: DNA extraction from the biopsies, multiplex amplification, and reverse hybridization.

RESULTS

Clarithromycin resistance was found in 83 (16.9%) patients, and fluoroquinolone resistance was found in 66 (13.5%) patients. There was no statistical difference in resistance to either clarithromycin or fluoroquinolones (P = 0.55 and P = 0.06, respectively) among the different regions of Brazil. Dual resistance to clarithromycin and fluoroquinolones was found in 4.3% (21/490) of patients. The A2147G mutation was present in 90.4% (75/83), A2146G in 16.9% (14/83) and A2146C in 3.6% (3/83) of clarithromycin-resistant patients. In 10.8% (9/83) of clarithromycin-resistant samples, more than 01 mutation in the 23S rRNA gene was noticed. In fluoroquinolone-resistant samples, 37.9% (25/66) showed mutations not specified by the GenoType HelicoDR test. D91N mutation was observed in 34.8% (23/66), D91G in 18.1% (12/66), N87K in 16.6% (11/66) and D91Y in 13.6% (9/66) of cases. Among fluoroquinolone-resistant samples, 37.9% (25/66) showed mutations not specified by the GenoType HelicoDR test.

CONCLUSION

The H. pylori clarithromycin resistance rate in Brazil is at the borderline (15%-20%) for applying the standard triple therapy. The fluoroquinolone resistance rate (13.5%) is equally concerning.

Occurrence of Mutations in the Antimicrobial Target Genes Related to Levofloxacin, Clarithromycin, and Amoxicillin Resistance in Helicobacter pylori Isolates from Buenos Aires City

Domain V of 23S rRNA, gyrA and gyrB Quinolones Resistance-Determining Region (QRDR), and pbp-1A gene point mutations were investigated in Helicobacter pylori-resistant isolates from three centres of Buenos Aires. Minimal inhibitory concentrations (MICs) were performed in 197 isolates from 52 H. pylori-positive naive patients by agar dilution method. Point mutations were achieved by amplification and sequencing of the target genes, and their association with resistance was determined by natural transformation assays. Resistance rates were as follows: metronidazole 28.8%, clarithromycin (CLA) 26.9%, levofloxacin (LEV) 32.7%, and amoxicillin (AMX) 7.6%. Nearly one-third of patients carried multidrug-resistant isolates. A2143G or A2142G in domain V of 23S-rRNA was found in all isolates showing high level of resistance to CLA (MIC >2 mg/L), accounting for 76.0% (38/50) of those with the resistant phenotype. The mutations A2267G or T1861C carried by 8/12 isolates with MIC 1-2 mg/L (low level) did not confer resistance by transformation. Substitutions at GyrA position 87 or 91, mainly N87K and D91G, were found in 92.8% (52/56) of the LEV-resistant isolates: 48 isolates with MIC 4-64 mg/L and 4/8 isolates with MIC 2 mg/L. The remaining four harboured K133N, also present in susceptible isolates. None of the substitutions in GyrB demonstrated to confer resistance. Transformation proved that PBP-1A N562Y and/or T556S substitutions confer the AMX resistance in our isolates, showing an additive effect. In conclusion, the usually reported mutations related to CLA, LEV, and AMX resistance were found in our isolates. However, low-level CLA resistance seems not to be due to mutations in Domain V of 23S rRNA gene.

Clarithromycin resistance and prevalence of Helicobacter pylori virulent genotypes in patients from Southern México with chronic gastritis

In developing countries, clarithromycin resistance and frequency of re-infection are factors that contribute to high prevalence of Helicobacter pylori infection. The aim of this research was determine the prevalence of clarithromycin resistance and its relation with A2142G, A2142C and A2143G mutations in the domain V of the 23S rRNA gene of H. pylori isolates in patients from Southern Mexico with chronic gastritis. Another purpose of this work was to study the prevalence of virulent genotypes and distribution of resistant strains according to the vacA/cagA/babA2 H. pylori genotypes. One hundred forty-four patients with chronic gastritis were studied. Forty-five H. pylori strains were isolated and clarithromycin susceptibility was determined by the disk-diffusion method. The 82.2% of the strains had the combination of alleles vacA s1 m1 and the cagA gene was detected in 77.8% and 40% of the strains were babA2 positive. The vacA s1 m1 genotype was detected more frequently in cagA(+) strains, vacA s1m1/cagA(+)/babA2(-) genotype was more frequent than vacA s1m1/cagA(+)/babA2(+), 37.8% and 33.3%, respectively. Eight strains were clarithromycin resistant, in three of these, point mutations were identified, but only in one strain the A2143G mutation associated with clarithromycin resistance was found. Other point mutations (A1821G, G1826A, T1830C, A2089G, T1600C, C1601T, C1602T, T1610C, A1611C and T1633G) that have not been associated with clarithromycin resistance were identified. The highest proportion of resistant strains was vacA s1m1/cagA(+) (62.5%). In patients from southern Mexico with chronic gastritis, the prevalence of clarithromycin resistance is within internationally accepted range (17.8%) and allows continued use of triple therapy for H. pylori eradication. However, it is necessary to monitor the evolution of clarithromycin resistance in this area. The largest proportion of resistant H. pylori strains is not harboring the A2142G, A2142C and A2143G mutations in the 23S rRNA gene (87.5%). The vacA s1m1/cagA(+) genotype was the most prevalent and among clarithromycin-resistant strains, this was the predominant.

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.

Antimicrobial activities of ethanol and butanol fractions of white rose petal extract

White rose (Rosa hybrida) petals were extracted with ethanol (EtOH) or butanol (BuOH), and tested for their antimicrobial activities against two species of Gram-positive bacteria, six species of Gram-negative bacteria, and two species of fungi. On in vitro antimicrobial assays, Helicobacter pylori and Propionibacterium acnes were highly susceptible to white rose petal extract (WRPE)-EtOH and WRPE-BuOH, leading to minimal inhibitory concentrations of 100 and 10 μg/mL for H. pylori and 400 and 40 μg/mL for P. acnes, respectively. In in vivo experiments, C57BL/6 mice were infected with H. pylori by intragastric inoculation (1 × 10(8) CFU/mouse) 3 times, and orally treated twice a day for 14 days with WRPE-EtOH and WRPE-BuOH. On a CLO kit assay, 200 mg/kg of WRPE-EtOH fully eliminated the bacteria from the gastric mucosa, and the effect of 100 mg/kg of ethanol fraction was similar to pantoprazole (30 mg/kg), displaying 75% elimination. WRPE-BuOH was more effective, exhibiting 75% elimination at 20 mg/kg. The CLO test results were confirmed by bacterial identification. WRPE-EtOH and WRPE-BuOH inhibited the growth of various bacteria and fungi, and in particular, they effectively killed H. pylori and eliminated the bacteria from the mouse stomach. The results indicate that WRPE-EtOH and WRPE-BuOH could be good candidates for the elimination of H. pylori.

High antibiotic resistance rate: A difficult issue for Helicobacter pylori eradication treatment

Helicobacter pylori (H. pylori) infection is associated with a variety of upper gastrointestinal diseases, including gastric cancer. With the wide application of antibiotics in H. pylori eradication treatment, drug-resistant strains of H. pylori are increasing. H. pylori eradication treatment failure affects the outcome of a variety of diseases of the upper gastrointestinal tract. Therefore, antibiotic resistance that affects H. pylori eradication treatment is a challenging situation for clinicians. The ideal H. pylori eradication therapy should be safe, effective, simple, and economical. The eradication rate of triple antibiotic therapy is currently less than 80% in most parts of the world. Antibiotic resistance is the main reason for treatment failure, therefore the standard triple regimen is no longer suitable as a first-line treatment in most regions. H. pylori eradication treatment may fail for a number of reasons, including H. pylori strain factors, host factors, environmental factors, and inappropriate treatment.

High Efficacy of Finafloxacin on Helicobacter pylori Isolates at pH 5.0 Compared with That of Other Fluoroquinolones

Finafloxacin is a novel fluoroquinolone with improved antimicrobial efficacy, especially in an acidic environment. The efficacy of finafloxacin for the inhibition of Helicobacter pylori infection was compared with the efficacies of levofloxacin and moxifloxacin at neutral and acidic pH. The impacts of gyrA point mutation on the efficacy of those three fluoroquinolones were also investigated. A total of 128 clinical H. pylori strains were utilized. MICs of levofloxacin, moxifloxacin, and finafloxacin were determined at pH 5.0 and pH 7.0 by the agar dilution method. The impact of gyrA point mutations that are responsible for fluoroquinolone resistance was analyzed; the results showed 50 strains with an Asn-87 point mutation, 48 strains with an Asp-91 point mutation, and the remaining 30 strains with no gyrA mutations. The use of finafloxacin led to MIC values at pH 5.0 that were lower than the values seen at pH 7.0 for 112 strains (112/128, 87.5%), and this proportion was higher than that seen with moxifloxacin (21/128, 16.4%, P < 0.001). Finafloxacin also demonstrated a rate of susceptibility (MIC, <1 μg/ml) (37.5%, 48/128) at pH 5.0 that was higher than that seen with moxifloxacin (2.3%, 3/128) (P < 0.001). The trends were similar regardless of which of the Asn-87, Asp-91, and A2143 point mutations were present. In conclusion, the superior antimicrobial efficacy of finafloxacin against H. pylori in an acidic environment suggests the possible use of finafloxacin for treatment of H. pylori infection, as has been proposed by its developer, Merlion Pharma.

Multidrug Efflux Systems in Microaerobic and Anaerobic Bacteria

Active drug efflux constitutes an important mechanism of antibiotic and multidrug resistance in bacteria. Understanding the distribution, expression, and physiological functions of multidrug efflux pumps, especially under physiologically and clinically relevant conditions of the pathogens, is the key to combat drug resistance. In animal hosts, most wounded, infected and inflamed tissues display low oxygen tensions. In this article, we summarize research development on multidrug efflux pumps in the medicinally relevant microaerobic and anaerobic pathogens and their implications in the effort to combat drug-resistant infections.

Inhibitory effects of emodin, baicalin, schizandrin and berberine on hefA gene: treatment of Helicobacter pylori-induced multidrug resistance

AIM

To investigate the inhibitory effects of emodin, baicalin, etc. on the hefA gene of multidrug resistance (MDR) in Helicobacter pylori (H. pylori).

METHODS

The double dilution method was used to screen MDR H. pylori strains and determine the minimum inhibitory concentrations (MICs) of emodin, baicalin, schizandrin, berberine, clarithromycin, metronidazole, tetracycline, amoxicillin and levofloxacin against H. pylori strains. After the screened MDR stains were treated with emodin, baicalin, schizandrin or berberine at a 1/2 MIC concentration for 48 h, changes in MICs of amoxicillin, tetracycline, levofloxacin, metronidazole and clarithromycin were determined. MDR strains with reduced MICs of amoxicillin were selected to detect the hefA mRNA expression by real-time quantitative PCR.

RESULTS

A total of four MDR H. pylori strains were screened. Treatment with emodin, baicalin, schizandrin and berberine significantly decreased the MICs of amoxicillin and tetracycline against some strains, decreased by 1 to 2 times, but did not significantly change the MICs of clarithromycin, levofloxacin, and metronidazole against MDR strains. In the majority of strains with reduced MICs of amoxicillin, hefA mRNA expression was decreased; one-way ANOVA (SPSS 12.0) used for comparative analysis, P < 0.05.

CONCLUSION

Emodin, baicalin, schizandrin and berberine significantly decreased the MICs of amoxicillin and tetracycline against some H. pylori strains, possibly by mechanisms associated with decreasing hefA mRNA expression.

Comparative analysis of anti-Helicobacter pylori activities of FEMY-R7 composed of Laminaria japonica and Oenothera biennis extracts in mice and humans

Helicobacter pylori-eliminating effects of FEMY-R7, composed of Laminaria japonica and Oenothera biennis extracts, were investigated in mice and humans. Male C57BL/6 mice were infected with the bacteria by intragastric inoculation (1×10⁹ CFU/mouse) 3 times at 2-day intervals, and simultaneously, orally treated twice a day with total 20, 64 or 200 mg/kg/day FEMY-R7 for 2 weeks. In Campylobcter-like organism (CLO)-detection tests on gastric mucosa and feces, FEMY-R7 reduced the urease-positive reactivity in a dose-dependent manner; i.e., the positivity ratios were decreased to 70, 20, and 10% for gastric mocosa and to 80, 50, and 20% for feces. In a clinical sudy, human subjects, confirmed to be infected with Helicobacter pylori, were orally administered twice a day with capsules containing total 100, 320 or 1,000 mg/man/day FEMY-R7 (matching doses for 20, 64 or 200 mg/kg/day, respectively, in mice from a body surface area-based dose translation) for 8 weeks. FEMY-R7 decreased the positivity ratios in feces to 70, 40, and 30%, respectively. In bacterial culture, H. pylori was identified from the CLO-positive stools of mice and humans. The bacterial identification ratios exhibited a good correlation between the matching doses in mice and humans. It is suggested that FEMY-R7 could be a promising functional food without tolerance as an adjunct to reduce the dosage of antibiotics for the treatment of recurrent H. pylori infection.

Multidrug efflux pumps from Enterobacteriaceae, Vibrio cholerae and Staphylococcus aureus bacterial food pathogens

Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a serious public health concern. In particular, microorganisms belonging to the Enterobacteriaceae and Vibrionaceae families of Gram-negative bacteria, and to the Staphylococcus genus of Gram-positive bacteria are important causative agents of food poisoning and infection in the gastrointestinal tract of humans. Recently, variants of these bacteria have developed resistance to medically important chemotherapeutic agents. Multidrug resistant Escherichia coli, Salmonella enterica, Vibrio cholerae, Enterobacter spp., and Staphylococcus aureus are becoming increasingly recalcitrant to clinical treatment in human patients. Of the various bacterial resistance mechanisms against antimicrobial agents, multidrug efflux pumps comprise a major cause of multiple drug resistance. These multidrug efflux pump systems reside in the biological membrane of the bacteria and actively extrude antimicrobial agents from bacterial cells. This review article summarizes the evolution of these bacterial drug efflux pump systems from a molecular biological standpoint and provides a framework for future work aimed at reducing the conditions that foster dissemination of these multidrug resistant causative agents through human populations.

Anti-Helicobacter pylori activities of FEMY-R7 composed of fucoidan and evening primrose extract in mice and humans

Helicobacter pylori-eliminating effects of FEMY-R7, composed of fucoidan and evening primrose extract, were investigated in mice and humans. Male C57BL/6 mice were infected with the bacteria by intragastric inoculation (1×10(9) CFU/mouse) 3 times at 2-day intervals, and simultaneously, orally treated twice a day with 10 or 100 mg/kg FEMY-R7 for 2 weeks. In Campylobcter-like organism-detection test, FEMY-R7 markedly reduced the urease-positive reactivity. In a clinical sudy, human subjects, confirmed to be infected with Helicobacter pylori, were orally administered twice a day with a capsule containing 150 mg FEMY-R7 for 8 weeks. FEMY-R7 significantly decreased both the Delta over baseline-value in urea breath test and the serum pepsinogens I and II levels. The results indicate that FEMY-R7 not only eliminates H. pylori from gastric mucosa of animals and humans, but also improves gastric function.

GenoType HelicoDR test in the determination of antimicrobial resistance of Helicobacter pylori in Korea

OBJECTIVE

Antimicrobial resistance of Helicobacter pylori is most important factor in eradication success. GenoType HelicoDR test has been developed for rapid detection of antimicrobial resistance. The present study evaluated the clinical usefulness of GenoType HelicoDR test in Korea.

MATERIALS AND METHODS

To detect 23S rRNA for clarithromycin resistance and gyrA mutations for fluoroquinolone resistance, both DNA sequencing after minimal inhibitory test (MIC) and GenoType HelicoDR test were performed in H. pylori isolates from the gastric mucosa of 101 patients. The eradication results of clarithromycin and moxifloxacin-containing triple therapy were evaluated by the 23S rRNA and gyrA mutations.

RESULTS

For 42 isolates with A2143G mutation by GenoType HelicoDR, 83.3% (35/42) of concordance rate was estimated with DNA sequencing method and 85.7% (36/42) for MIC test. For 43 isolates with N87K mutation by GenoType HelicoDR, 71.1% (31/43) of concordance rate was estimated with DNA sequencing and 88.4% (38/43) for MIC test. The sensitivity and specificity of GenoType HelicoDR test in determination of 23S rRNA mutation were 94.9% and 87.1%, and those of gyrA 98.2% and 80.0%. The sensitivity and specificity of GenoType HelicoDR test in determination of clarithromycin resistance based on MIC test were 55.0% and 80.0%, for fluoroquinolone 74.4% and 70.0%.

CONCLUSION

GenoType HelicoDR test is useful to determine mutations responsible for clarithromycin or fluoroquinolone-containing eradication failure but has a limitation for the clinical applicability in determination of resistance.

Identification of natural compound inhibitors for multidrug efflux pumps of Escherichia coli and Pseudomonas aeruginosa using in silico high-throughput virtual screening and in vitro validation

Pseudomonas aeruginosa and Escherichia coli are resistant to wide range of antibiotics rendering the treatment of infections very difficult. A main mechanism attributed to the resistance is the function of efflux pumps. MexAB-OprM and AcrAB-TolC are the tripartite efflux pump assemblies, responsible for multidrug resistance in P. aeruginosa and E. coli respectively. Substrates that are more susceptible for efflux are predicted to have a common pharmacophore feature map. In this study, a new criterion of excluding compounds with efflux substrate-like features was used, thereby refining the selection process and enriching the inhibitor identification process. An in-house database of phytochemicals was created and screened using high-throughput virtual screening against AcrB and MexB proteins and filtered by matching with the common pharmacophore models (AADHR, ADHNR, AAHNR, AADHN, AADNR, AAADN, AAADR, AAANR, AAAHN, AAADD and AAADH) generated using known efflux substrates. Phytochemical hits that matched with any one or more of the efflux substrate models were excluded from the study. Hits that do not have features similar to the efflux substrate models were docked using XP docking against the AcrB and MexB proteins. The best hits of the XP docking were validated by checkerboard synergy assay and ethidium bromide accumulation assay for their efflux inhibition potency. Lanatoside C and diadzein were filtered based on the synergistic potential and validated for their efflux inhibition potency using ethidium bromide accumulation study. These compounds exhibited the ability to increase the accumulation of ethidium bromide inside the bacterial cell as evidenced by these increase in fluorescence in the presence of the compounds. With this good correlation between in silico screening and positive efflux inhibitory activity in vitro, the two compounds, lanatoside C and diadzein could be promising efflux pump inhibitors and effective to use in combination therapy against drug resistant strains of P. aeruginosa and E. coli.

In vitro and in vivo anti-Helicobacter pylori activities of FEMY-R7 composed of fucoidan and evening primrose extract

Effects of FEMY-R7, composed of fucoidan and evening primrose extract, on the bacterial growth and intragastric infection of Helicobacter pylori as well as gastric secretion were investigated in comparison with a proton-pump inhibitor pantoprazole. For in vitro anti-bacterial activity test, H. pylori (1×10(8) CFU/mL) was incubated with a serially-diluted FEMY-R7 for 3 days. As a result, FEMY-R7 fully inhibited the bacterial growth at 100 µg/mL, which was determined to be a minimal inhibitory concentration. In addition, 6-hour incubation with H. pylori, FEMY-R7 inhibited urease activity in a concentration-dependent manner, showing a median inhibitory concentration of 1,500 µg/mL. In vivo elimination study, male C57BL/6 mice were infected with the bacteria by intragastric inoculation (5×10(9) CFU/mouse) 3 times at 2-day intervals, and simultaneously, orally treated twice a day with 10, 30 or 100 mg/kg FEMY-R7 for 7 days. In Campylobcter-like organism-detection test and bacterial identification, FEMY-R7 exerted a high bacteria-eliminating capacity at 30-100 mg/kg, comparably to 30 mg/kg pantoprazole. In contrast to a strong antacid activity of pantoprazole in a pylorus-ligation study, FEMY-R7 did not significantly affect gastric pH, free HCl, and total acidity, although it significantly decreased fluid volume at a low dose (10 mg/kg). The results indicate that FEMY-R7 eliminate H. pylori from gastric mucosa by directly killing the bacteria and preventing their adhesion and invasion, rather than by inhibiting gastric secretion or mucosal damage.

Progress in research of Helicobacter pylori efflux pumps

The wide use and abuse of antibiotics have led to serious drug resistance of Helicobacter pylori (H. pylori), and strains simultaneously resistant to metronidazole, clarithromycin and amoxicillin have appeared. As a result, the rate of H. pylori eradication declines clinically. The presence of bacterial efflux pumps is an important mechanism responsible for bacterial resistance to most antibiotics, especially multiple drug resistance (MDR). In recent years, much attention has been paid to the research of efflux pumps and their inhibitors to solve the problem of drug resistance of H. pylori. In this paper we will introduce main efflux pumps and efflux pump inhibitors in H. pylori.

Prevalence of primary and secondary antimicrobial resistance of Helicobacter pylori in Korea from 2003 through 2012

BACKGROUND

Antimicrobial resistance of Helicobacter pylori (H. pylori) affects the efficacy of eradication therapy. The aim of this study was to estimate the prevalence of primary and secondary resistance of H. pylori isolates to antibiotics and to characterize the risk factors associated with antimicrobial resistance in Korea.

MATERIALS AND METHODS

This study was performed during the period of 2003-2012. Primary resistance was evaluated from 347 patients without any history of eradication, and secondary resistance was evaluated in 86 patients from whom H. pylori was cultured after failure of eradication. Minimal inhibitory concentration test was performed for amoxicillin, clarithromycin, metronidazole, tetracycline, azithromycin, levofloxacin, and moxifloxacin using agar dilution method. Primary and secondary resistance rates of H. pylori to 7 antibiotics were evaluated and risk factors for the antibiotic resistance were analyzed.

RESULTS

Increase in the primary resistance rate was found in amoxicillin (6.3-14.9%, p = .051), clarithromycin (17.2-23.7%, p = .323), and both of levofloxacin and moxifloxacin (4.7-28.1%, p = .002) during the study period. Secondary resistance rate significantly increased in metronidazole, levofloxacin, and moxifloxacin. Increase of resistance occurred after initial failure of eradication therapy in case of clarithromycin (p < .001), azithromycin (p < .001), levofloxacin (p = .011), and moxifloxacin (p = .020). Multivariable analyses showed that clarithromycin, azithromycin, levofloxacin, and moxifloxacin resistance was associated with previous eradication treatment history.

CONCLUSIONS

The increased primary and secondary antibiotic resistance of H. pylori in Korea is ongoing, and it will become a significant limitation for effective eradication of H. pylori in the future.

Sensitization of Staphylococcus aureus to methicillin and other antibiotics in vitro and in vivo in the presence of HAMLET

HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a protein-lipid complex from human milk with both tumoricidal and bactericidal activities. HAMLET exerts a rather specific bactericidal activity against some respiratory pathogens, with highest activity against Streptococcus pneumoniae, but lacks activity against most other bacterial pathogens, including Staphylococci. Still, ion transport associated with death in S. pneumoniae is also detected to a lower degree in insensitive organisms. In this study we demonstrate that HAMLET acts as an antimicrobial adjuvant that can increase the activity of a broad spectrum of antibiotics (methicillin, vancomycin, gentamicin and erythromycin) against multi-drug resistant Staphylococcus aureus, to a degree where they become sensitive to those same antibiotics, both in antimicrobial assays against planktonic and biofilm bacteria and in an in vivo model of nasopharyngeal colonization. We show that HAMLET exerts these effects specifically by dissipating the proton gradient and inducing a sodium-dependent calcium influx that partially depolarizes the plasma membrane, the same mechanism induced during pneumococcal death. These effects results in an increased cell associated binding and/or uptake of penicillin, gentamicin and vancomycin, especially in resistant stains. Finally, HAMLET inhibits the increased resistance of methicillin seen under antibiotic pressure and the bacteria do not become resistant to the adjuvant, which is a major advantageous feature of the molecule. These results highlight HAMLET as a novel antimicrobial adjuvant with the potential to increase the clinical usefulness of antibiotics against drug resistant strains of S. aureus.

The strongest resistance of Staphylococcus aureus to erythromycin is caused by decreasing uptake of the antibiotic into the cells

The consequence of excessive use of macrolides is a high occurrence of mechanisms responsible for resistance to these drugs. Of 97 erythromycin-resistant bacterial strains gathered in the Wrocław area in Poland, 60% exhibited very high resistance, and those with the inducible MLS_B (macrolide-lincosamide-streptogramin B) resistance phenotype predominated. Direct genetic investigation revealed that the erm genes coding for ribosomal methylases are the most frequently occurring erythromycin resistance-determining genes. No genetic resistance determinant was detected in 13% of the erythromycin-resistant strains. The efflux mechanism occurs in strains isolated from the nasopharyngeal cavity twice as often as in those isolated from other material, where the mechanism connected with target site modification predominates. Measurements of radiolabelled antibiotic accumulation inside bacterial cells revealed that in highly resistant strains (MIC > 1024 μg/ml), an important factor responsible for the resistance is the permeability barrier at the cell wall level. This would be a hitherto unknown mechanism of resistance to erythromycin in Staphylococcus aureus.