Mefloquine enhances the activity of colistin against antibiotic-resistant Enterobacterales in vitro and in an in vivo animal study

Coexistence of blaNDM-1, mcr-1 and blaCTX-M-199 in an ST499 multidrug resistant Klebsiella pneumoniae iIsolate

The coexistence of multiple resistance genes within a single bacterial strain presents a significant public health challenge, as it complicates treatment options and accelerates the spread of multidrug resistance. While the co-occurrence of blaNDM-1 and mcr-1 genes in Klebsiella pneumoniae (KP) is uncommon, this study reports the biological characterization of a K. pneumoniae isolate, L5151, derived from a patient with diarrhea. This strain carries blaNDM-1, mcr-1, and blaCTX-M-199 resistance genes simultaneously. Multilocus sequence typing (MLST) analysis identified the L5151 strain as an ST499 type. Antimicrobial susceptibility testing (AST) was conducted via agar dilution and the broth microdilution procedure. The AST results revealed that L5151 is resistant to a variety of antibiotics. Whole-genome sequencing (WGS) and bioinformatics analysis were performed to determine the genetic composition of the strain, including the presence and characteristics of resistance genes. The results of S1 nuclease-pulsed field gel electrophoresis (S1-PFGE) and Southern blotting confirmed that the L5151 strain harbors three plasmids and that the plasmid carrying mcr-1 (pL5151_MCR_CTX) is of the IncI2(Delta) type, whereas the plasmid carrying blaNDM-1 (pL5151_NDM) is of the IncN type. The combination of these plasmids in recipient strains conferred enhanced resistance to carbapenems and colistin, highlighting the potential for increased treatment challenges. This study emphasizes the importance of ongoing surveillance of multidrug-resistant strains to prevent their spread and outbreaks. These findings provide critical insights for clinical treatment strategies and infection prevention and control measures. Enhanced surveillance and targeted interventions are essential to manage the public health risks posed by multidrug-resistant strains.

In vitro synergistic effects of mefloquine combined with other antimicrobial agents on carbapenem-resistant Enterobacterales

PURPOSE

Human health is seriously threatened by carbapenem-resistant Enterobacterales (CRE) due to the lack of effective treatment. The purpose of this study is to examine the efficacy of mefloquine (MEF) together with multiple drugs against 96 clinical CRE isolates including 94 Klebsiella pneumoniae carbapenemase (KPC)-producers or Metallo-β-lactamases (MBLs)-producers and 2 colistin antibiotic resistance enzyme MCR-1-producers.

METHODS

Using the broth microdilution method, MICs of MEF in combination with multiple antimicrobial agents, including colistin (COL), imipenem, aztreonam-avibactam (ATM-AVI), ceftazidime-avibactam (CAZ-AVI) for 96 CRE isolates were determined. Time-kill assays were implemented for 3 colistin-resistant (COL-R) isolates to analyze in vitro synergistic impacts of COL combined with MEF.

RESULTS

MEF alone showed little antibacterial activity with MICs greater than 128 µg/mL for all the 96 clinical CRE isolates. The addition of MEF (32 µg/mL) increased the sensitivity of almost all strains (98.9%, 95/96) to COL, reducing the MICs range of COL from ≤ 0.0625->8 µg/mL to ≤ 0.004-0.5 µg/mL. In particular, we observed that COL-MEF combination therapy had a significant effect on COL-R isolates, reducing their MICs from resistance to susceptibility. Moreover, the MIC50 and MIC90 of imipenem were both reduced by 2-fold in almost all strains with the addition of MEF (32 µg/mL), and in single MBL-producers, the MIC50 (from 16 to 4 µg/mL) and MIC90 (from 128 to 32 µg/mL) were both reduced by 4-fold. In addition, the MIC50 and MIC90 values of 96 CRE isolates of CAZ-AVI and ATM-AVI did not decrease significantly after combined with MEF (32 µg/mL). For the time-kill assays of 3 COL-R isolates, COL or MEF alone had almost no killing effect, however, when MEF was combined with COL, the isolates were completely killed within 4 h, and NDM-5-producing Klebsiella pneumoniae did not regenerate within 24 h.

CONCLUSIONS

According to our study, COL-MEF may offer a potential alternative for treating CRE infections, especially COL-R Gram-negative bacterial infections.

Mefloquine reduces the bacterial membrane fluidity of Acinetobacter baumannii and distorts the bacterial membrane when combined with polymyxin B

Acinetobacter baumannii is a high-priority organism for the development of new antibacterial treatments. We found that the antimalarial medication mefloquine (MFQ) permeabilized the bacterial cell membrane of A. baumannii, decreased membrane fluidity, and caused physical injury to the membrane. MFQ also maintained activity across different pH conditions (pH range: 5-8). Structure-activity relationship analysis using MFQ analogs demonstrated that piperidin-2-yl methanol is required for antibacterial activity. Scanning and transmission electron microscopy demonstrated the compromised morphological and membrane integrity in MFQ-treated cells. MFQ synergized with the membrane permeabilizers polymyxin B and colistin and the MFQ + polymyxin B combination killed bacterial cells more effectively than either treatment alone. MFQ + polymyxin B was effective against other gram-negative bacteria including Escherichia coli, Burkholderia pseudomallei, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Bodipy-cadaverine displacement assays confirmed the active interaction of MFQ with other membrane lipid components, such as lipopolysaccharide, lipid A, lipoteichoic acids, and fatty acids. In all-atom molecular dynamics simulations, lipid interactions facilitated the permeation of MFQ into the simulated Gram-negative membrane. Additionally, positively charged nitrogen in the piperidine group of MFQ seems to enhance interactions with the negatively charged components of the bacterial membrane. MFQ + polymyxin B caused significantly greater curvature in the simulated membrane, indicating greater damage than standalone drug treatment. Finally, in vivo assays showed that MFQ + polymyxin B rescued Galleria mellonella larvae infected with A. baumannii. In conclusion, membrane-active agents such as MFQ may warrant further investigation as a potential components of gram-negative infection treatment, particularly in combination with polymyxin B.

IMPORTANCE

Antimicrobial resistance is a threat globally, and new treatments are urgently needed to combat the rise of multidrug-resistant bacteria. However, the development of anti-infectives has declined over the last two decades due to regulatory, financial and long-term requirement related challenges. In this study, we examined the membrane interactions of the antiparasitic agent mefloquine (MFQ) in combination with polymyxin B, using both in vitro and in silico approaches to evaluate their potential efficacy against gram-negative bacterial infections. We investigated the interaction of MFQ with lipid bilayers to understand the mechanism through which antibacterial activity is exerted. The piperidine moiety of MFQ plays a critical role in its interaction with the lipid bilayer and facilitates membrane permeabilization. In contrast, the membrane permeabilizer polymyxin B is associated with significant neurotoxicity and nephrotoxicity. Our findings highlight the potential of membrane-acting compounds, such as MFQ, to enhance combinatorial activity while mitigating polymyxin B-associated toxicity.

Exploring the antibacterial and anti-biofilm properties of Diacerein against methicillin-resistant Staphylococcus aureus

Background

Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant clinical challenge due to its multidrug resistance. Diacerein (DIA), primarily used to treat degenerative joint diseases, has recently been found to exhibit antibacterial activity, though its specific antibacterial mechanisms remain unclear.

Methods

The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of DIA, as well as in - vitro combination susceptibility testing, were determined using the broth microdilution method. Additionally, resistance induction assays, time-growth curve measurements, membrane fluidity, intracellular protein levels, and reactive oxygen species (ROS) were assessed. The inhibition and clearance of MRSA biofilms by DIA were evaluated using the crystal violet staining method, with bacterial morphology and biofilms observed via scanning electron microscopy and confocal laser scanning microscopy. Finally, transcriptome analysis was conducted to identify gene expression changes in MRSA treated with DIA, and RT-qPCR verification was performed.

Results

The MIC and MBC of DIA against MRSA were 32 μg/mL and 128 μg/mL, respectively, and synergistic antibacterial effects when combined with ampicillin. DIA increased intracellular ROS levels and membrane fluidity in MRSA, decreased soluble protein synthesis, and altered bacterial morphology. Additionally, DIA significantly inhibited MRSA biofilm formation and disrupted pre - existing biofilms. Transcriptome analysis revealed 1,045 differentially expressed genes between the DIA-treated group and the control group, primarily involving pathways such as the tricarboxylic acid cycle, phosphorylation, ribosome metabolism, and nucleotide metabolism.

Conclusion

In summary, DIA has antibacterial and anti-biofilm activities against MRSA and does not easily induce resistance. Its antibacterial mechanisms may involve multiple aspects, including bacterial protein synthesis, energy metabolism.

Mefloquine reduces the bacterial membrane fluidity of Acinetobacter baumannii and distorts the bacterial membrane when combined with polymyxin B

Acinetobacter baumannii is a high-priority organism for the development of new antibacterial treatments. We found that the antimalarial medication mefloquine (MFQ) permeabilized the bacterial cell membrane of A. baumannii , decreased membrane fluidity, and caused physical injury to the membrane. MFQ also maintained activity across different pH conditions (PH range 5-8). Structure-activity relationship analysis using MFQ analogs demonstrated that piperidin-2-yl methanol is required for antibacterial activity. Scanning and transmission electron microscopy demonstrated the compromised morphological and membrane integrity in MFQ treated cells. MFQ synergized with the membrane permeabilizers polymyxin B and colistin and the MFQ+polymyxin B combination killed bacterial cells more effectively than either treatment alone. MFQ+polymyxin B was effective against other Gram-negative bacteria including Escherisia coli, Burkholderia pseudomallei, Klebsiella pneumoniae, and Pseudomonas auroginosa . Bodipy-cadaverine displacement assays confirmed the active interaction of MFQ with other membrane lipid components, such as lipopolysaccharide, lipid A, lipoteichoic acids, and fatty acids. In all-atom molecular dynamics simulations, lipid interactions facilitated the permeation of MFQ into the simulated Gram-negative membrane. Additionally, positively charged nitrogen in the piperidine group of MFQ seems to enhance interactions with the negatively charged components of the bacterial membrane. MFQ+polymyxin B caused significantly greater curvature in the simulated membrane, indicating greater damage than standalone drug treatment. Finally, in vivo assays showed that MFQ+polymyxin B rescued Galleria mellonella larvae infected with A. baumannii . In conclusion, membrane-active agents such as MFQ may warrant further investigation as potential component of Gram-negative infection treatment, particularly in combination with polymyxin B.

Importance

Antimicrobial resistance is a threat globally, and new treatments are urgently needed to combat the rise of multidrug-resistant bacteria. However, the development of anti-infectives has declined over the last two decades due to regulatory, financial and long-term requirement related challenges. In this study, we examined the membrane interactions of the antiparasitic agent mefloquine in combination with polymyxin B, using both in vitro and in silico approaches to evaluate their potential efficacy against Gram-negative bacterial infections. We investigated the interaction of MFQ with lipid bilayers to understand the mechanism through which antibacterial activity is exerted. The piperidine moiety of MFQ plays a critical role in its interaction with the lipid bilayer and facilitates membrane permeabilization. In contrast, the membrane permeabilizer polymyxin B is associated with significant neurotoxicity and nephrotoxicity. Our findings highlight the potential of membrane-acting compounds, such as MFQ, to enhance combinatorial activity while mitigating polymyxin B-associated toxicity.

Progress in the study of mefloquine as an antibiotic adjuvant for combination bacterial inhibition treatment

Antimicrobial resistance is among the greatest threats to public health globally, and drug repurposing strategies may be advantageous to addressing this problem. Mefloquine, a drug traditionally used to treat malaria, has emerged as a promising antibiotic adjuvant, due to its ability to enhance the effectiveness of conventional antibiotics against resistant bacterial strains. In this paper, we first outline the enhancement properties of mefloquine and its mechanisms of action as an adjuvant antibiotic against multidrug-resistant bacteria. Mefloquine exhibits synergistic bacteriostatic effects when combined with colistin, β-lactams, antituberculosis drugs, quinolones, and linezolid. Potential mechanisms underlying its synergistic effects include inhibition of antibiotic efflux, disruption of bacterial cell membrane integrity, and disturbance of biofilm formation. In addition, we explore the bacteriostatic effects of several mefloquine derivatives against Mycobacterium tuberculosis and some fungi. Further, we summarize the findings of recent studies on other aspects of mefloquine activity, including its antiviral and antitumor effects. Finally, the advantages and challenges of mefloquine use as an antibiotic adjuvant in combination with antibiotics for bacterial inhibition are discussed. Overall, mefloquine shows excellent potential as an antibiotic adjuvant therapy against multidrug-resistant bacteria and is a promising candidate for combination therapy; however, further studies are needed to fully elucidate its mechanism of action and address the challenges associated with its clinical application.

Bacteria carrying mobile colistin resistance genes and their control measures, an updated review

The plasmid encoded mobile colistin resistance (MCRs) enzyme poses a significant challenge to the clinical efficacy of colistin, which is frequently employed as a last resort antibiotic for treating infections caused by multidrug resistant bacteria. This transferase catalyzes the addition of positively charged phosphoethanolamine to lipid A of the outer membrane of gram-negative bacteria, thereby facilitating the acquired colistin resistance. This review aims to summarize and critically discuss recent advancements in the distribution and pathogenesis of mcr-positive bacteria, as well as the various control measures available for treating these infections. In addition, the ecology of mcr genes, colistin-resistance mechanism, co-existence with other antibiotic resistant genes, and their impact on clinical treatment are also analyzed to address the colistin resistance crisis. These insights provide a comprehensive perspective on MCRs and serve as a valuable reference for future therapeutic approaches to effectively combat mcr-positive bacterial infections.

Combination of AS101 and Mefloquine Inhibits Carbapenem-Resistant Pseudomonas aeruginosa in vitro and in vivo

Background

In recent years, carbapenem-resistant Pseudomonas aeruginosa (CRPA) has spread around the world, leading to a high mortality and close attention of medical community. In this study, we aim to find a new strategy of treatment for CRPA infections.

Methods

Eight strains of CRPA were collected, and PCR detected the multi-locus sequence typing (MLST). The antimicrobial susceptibility test was conducted using the VITEK@2 compact system. The minimum inhibitory concentration (MIC) for AS101 and mefloquine was determined using the broth dilution method. Antibacterial activity was tested in vitro and in vivo through the chessboard assay, time killing assay, and a mouse model. The mechanism of AS101 combined with mefloquine against CRPA was assessed through the biofilm formation inhibition assay, electron microscopy, and detection of reactive oxygen species (ROS).

Results

The results demonstrated that all tested CRPA strains exhibited multidrug resistance. Moreover, our investigation revealed a substantial synergistic antibacterial effect of AS101-mefloquine in vitro. The assay for inhibiting biofilm formation indicated that AS101-mefloquine effectively suppressed the biofilm formation of CRPA-5 and CRPA-6. Furthermore, AS101-mefloquine were observed to disrupt the bacterial cell wall and enhance the permeability of the cell membrane. This effect was achieved by stimulating the production of ROS, which in turn hindered the growth of CRPA-3. To evaluate the therapeutic potential, a murine model of CRPA-3 peritoneal infection was established. Notably, AS101-mefloquine administration resulted in a significant reduction in bacterial load within the liver, kidney, and spleen of mice after 72 hours of treatment.

Conclusion

The present study showed that the combination of AS101 and mefloquine yielded a notable synergistic bacteriostatic effect both in vitro and in vivo, suggesting a potential clinical application of this combination in the treatment of CRPA.

AADB: A Manually Collected Database for Combinations of Antibiotics With Adjuvants

Antimicrobial resistance is a global public health concern. The lack of innovations in antibiotic development has led to renewed interest in antibiotic adjuvants. However, there is no database to collect antibiotic adjuvants. Herein, we build a comprehensive database named Antibiotic Adjuvant DataBase (AADB) by manually collecting relevant literature. Specifically, AADB includes 3,035 combinations of antibiotics with adjuvants, covering 83 antibiotics, 226 adjuvants, and 325 bacterial strains. AADB provides user-friendly interfaces for searching and downloading. Users can easily obtain these datasets for further analysis. In addition, we also collected related datasets (e.g., chemogenomic and metabolomic data) and proposed a computational strategy to dissect these datasets. As a test case, we identified 10 candidates for minocycline, and 6 of 10 candidates are the known adjuvants that synergize with minocycline to inhibit the growth of E. coli BW25113. We hope that AADB can help users to identify effective antibiotic adjuvants. AADB is freely available at http://www.acdb.plus/AADB.

Combined With Mefloquine, Resurrect Colistin Active in Colistin-Resistant Pseudomonas aeruginosa in vitro and in vivo

Colistin is a polymyxin antibiotic that is widely used for the treatment of multidrug resistant (MDR) Pseudomonas aeruginosa infections, as the last resort. Over the past few years, unreasonable use of antibiotics has resulted in an increase in MDR strains, including colistin-resistant P. aeruginosa. The present study aimed to explore the synergistic effects of mefloquine in combination with colistin for the treatment of colistin-resistant P. aeruginosa in vivo and in vitro. The synergistic effect of the combination of mefloquine and colistin was investigated in vitro using checkerboard method, time-killing assay, biofilm formation inhibition test, and biofilm eradication test. The study also explored the synergistic effects of this combination of drugs in vivo, using a Galleria mellonella infection model. The results for checkerboard method and time killing curve indicated that mefloquine in combination with colistin showed a good antibacterial activity. Furthermore, the combination of these two drugs inhibited biofilm formation and eradicated pre-formed mature biofilms. This synergistic effect was visualized using scanning electron microscopy (SEM), wherein the results showed that the combination of mefloquine and colistin reduced biofilm formation significantly. Further, the application of this combination of drugs to in vivo infection model significantly increased the survival rate of G. mellonella larvae. Altogether, the combination of mefloquine and colistin showed a good synergistic effect in vitro and in vivo, and highlighted its potential to be used as an alternative therapy for the treatment of colistin-resistant P. aeruginosa infection.