Gallic Acid Restores the Sulfonamide Sensitivity of Multidrug-Resistant Streptococcus suis via Polypharmaceology Mechanism

Guanosine enhances the bactericidal effect of ceftiofur sodium on Streptococcus suis by activating bacterial metabolism

The emergence and rapid development of antibiotic resistance poses a serious threat to global public health. Streptococcus suis (S. suis) is an important zoonotic pathogen, and the development of its antibiotic resistance has made the infections difficult to treat. The combination of non-antibiotic compounds with antibiotics is considered a promising strategy against multidrug-resistant bacteria. However, the mechanism by which metabolites act as antibiotic adjuvant remains unclear. Here, we found that guanosine metabolism was repressed in multidrug-resistant S. suis. Exogenous guanosine promoted the antibacterial effects of ceftiofur sodium (CEF) in vitro and in vivo. Furthermore, we demonstrated that exogenous guanosine promoted the biosynthesis of purine pathway, TCA cycle and bacterial respiration, which make bacteria more sensitive to the killing effect of antibacterial. In addition, the function of the cell membrane is affected by guanosine and the accumulation of antimicrobials in the bacteria increased. Bacterial-oxidative stress and DNA damage induced by guanosine is also one of the mechanisms by which the antibacterial effect is enhanced. These results suggest that guanosine is a promising adjuvant for antibacterial drugs and provide new theoretical basis for the clinical treatment of S. suis infection.

Glabridin restore the sensitivity of colistin against mcr-1-positive Escherichia coli by polypharmacology mechanism

The clinical effectiveness of colistin against multidrug-resistant Gram-negative pathogen infections has been threatened by the emergence of the plasmid-mediated colistin-resistant gene mcr-1. This development underscores the urgent need for innovative therapeutic strategies that target resistance mechanisms. In this study, we demonstrated that glabridin can restore the sensitivity of colistin to mcr-1-positive Escherichia coli (E. coli) and exhibits a reduced propensity for resistance development. Our investigation into the underlying mechanisms revealed that glabridin may re-sensitize E. coli to colistin by targeting MCR-1 to inhibit its activity, regulating the expression of mcr-1, and restoring the Zeta potential at the cell membrane surface. Furthermore, the combination of glabridin and colistin increased bacterial membrane permeability, decreased membrane fluidity, disrupted transmembrane proton motive force (PMF), reduced the ratios of NAD+/NADH and FAD/FADH2, facilitated the tricarboxylic acid (TCA) cycle, and led to the accumulation of reactive oxygen species (ROS) in E. coli cells, ultimately resulting in bacterial death. In animal models, glabridin significantly enhanced the efficacy of colistin in treating E. coli infections. Our findings suggest that glabridin is a promising polypharmacological antibiotic adjuvant for addressing infections associated with colistin-resistant E. coli.

Targeting membrane integrity and imidazoleglycerol-phosphate dehydratase: Sanguinarine multifaceted approach against Staphylococcus aureus biofilms

BACKGROUND

Staphylococcus aureus is an opportunistic pathogen capable of readily forming biofilms, which can result in life-threatening infections involving different organs. Sanguinarine are benzo[c]phenanthridine alkaloids extracted from the Sanguinaria canadensis L. (Papaveraceae), which have a wide range of biological activities. Previous reports have shown that sanguinarine is able to induce an elevation of ROS to exert an anti-S. aureus effect. Nevertheless, the specific mechanism of action of sanguinarine against S. aureus biofilms remains unexplored.

PURPOSE

The objective of this study was to elucidate the target site of sanguinarine in S. aureus, as well as to investigate its mechanism of antimicrobial action and its interference with biofilm formation. Additionally, the study aimed to provide further evidence supporting the use of sanguinarine as an alternative to traditional antibiotics.

METHODS

Initially, we assessed the in vitro anti-S. aureus properties of sanguinarine through a series of methodologies, including MIC assays, time-dependent assays, and resistance development studies. Secondly, we explored the antimicrobial mechanism of sanguinarine using TEM, membrane permeability assays, and membrane fluidity assays. Subsequently, the mechanism by which sanguinarine interferes with S. aureus biofilm formation was preliminarily analyzed in vitro. Additionally, the interaction between sanguinarine and imidazoleglycerol-phosphate dehydratase (IGPD) was investigated using bio-layer interferometry assays, circular dichroism spectroscopy, molecular docking, and site-directed mutagenesis to further elucidate the role of sanguinarine in biofilm disruption. Finally, the therapeutic efficacy of sanguinarine was evaluated in vivo using mouse models of biofilm and bacteremia.

RESULTS

Herein, sanguinarine demonstrated notable antimicrobial properties and interfering effects on biofilm formation. Mechanistic investigations revealed that sanguinarine exerts its antimicrobial action by dissipating the proton motive force in bacteria and compromising the integrity and functionality of the cytoplasmic membrane. Furthermore, sanguinarine was found to regulate IGPD expression and inhibit L-histidine synthesis, thereby interfering S. aureus biofilm formation. Consequently, due to its polypharmacological effect, sanguinarine significantly reduced the S. aureus load in mouse organs and the formation of biofilm on the surface of implants in vivo without any resistance.

CONCLUSIONS

In this study, we demonstrated that sanguinarine can exert antibacterial and interfere with biofilm formation by disrupting the cell membrane of S. aureus and targeting IGPD. These findings suggest that sanguinarine holds potential for further development as a novel antibiotic to combat biofilm-associated infections.

Antibacterial activity of gallic acid and methyl gallate against emerging non-fermenting bacilli

Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and Burkholderia cenocepacia are considered emerging pathogens classified as a public health problem due to extensive antimicrobial resistance. Therefore, the discovery of new therapeutic strategies has become crucial. This study aimed to evaluate the antimicrobial activity of gallic acid and methyl gallate against non-fermenting bacteria. The study included five clinical isolates of Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and Burkholderia cenocepacia. The minimum inhibitory concentrations of gallic acid and methyl gallate were determined by the broth microdilution method. Growth curves, metabolic activity, and biofilm formation of each bacterial strain in the presence or absence of phenolic compounds were performed. Finally, the therapeutic efficacy of the compounds was evaluated using an in vivo model. Gallic acid and methyl gallate showed antibacterial activity against bacterial strains in a concentration range of 64 to 256 µg/mL, both compounds reduced bacterial growth and metabolic activity of the strains, even at subinhibitory concentrations. Only, methyl gallate exhibited activity to inhibit the formation of bacterial biofilms. Moreover, gallic acid and methyl gallate increased larval survival by up to 60% compared to 30% survival of untreated larvae in a bacterial infection model in Galleria mellonella. Our results highlight the potential of gallic acid and methyl gallate as therapeutic alternatives for infections by emerging non-fermentative bacteria.

Rosmarinic Acid Restores the Ceftiofur Antibacterial Activity against Methicillin-Resistant Staphylococcus aureus by Inhibiting Sortase A

Methicillin-resistant Staphylococcus aureus (MRSA), one of the most important zoonotic bacterial pathogens, necessitates innovative antibacterial strategies. Rosmarinic acid (RA) possesses various biological functions, including antibacterial and anti-inflammatory effects. This study aimed to explore the synergistic effects and mechanism of RA in conjunction with ceftiofur (CF) against MRSA. Results showed that the combination of RA and CF demonstrated synergistic anti-MRSA activity, conferring protective effects in an MRSA bacteremia mouse model. Mechanistic investigations further established that RA interacts with sortase A (SrtA) through hydrogen bonds, electrostatic, and van der Waals forces at critical sites, leading to the reversible inhibition of SrtA activity. Consequently, this inhibition impeded the ability of MRSA to invade cells and form biofilms. Conclusively, RA directly inhibits SrtA activity, thus enhancing the synergistic anti-MRSA effect of CF. These findings provide a theoretical foundation for the use of RA in combination with CF as a therapeutic strategy for MRSA infections.

Preparation and characterization of nano-emulsion formulations of Asparagus densiflorus root and aerial parts extracts: evaluation of in-vitro antibacterial and anticancer activities of nano-emulsion versus pure plant extract

OBJECTIVE

Preparation and characterization of nano-emulsion formulations for Asparagus densiflorus aerial and root parts extracts.

SIGNIFICANCE

Genus Asparagus is known for its antimicrobial and anticancer activities, however, freeze dried powder of aqueous - alcoholic extract prepared in this study, exhibited a limited water solubility, limiting its therapeutic application. Thus, encapsulation of its phytochemicals into nano-emulsion is proposed as a solution to improve water solubility, and facilitate its clinical translation.

METHODS

the composition of extracts for both aerial and root parts of Asparagus densiflorus was identified by HPLC and LC-MS analysis. Nano-emulsion was prepared via homogenization where a mixture of Castor oil: phosphate buffered saline (10 mM, pH 7.4): Tween 80: PEG 600 in a ratio of 10: 5: 2.5: 2.5, respectively. Nano-emulsion formulations were characterized for particle size, polydispersity index (PDI), zeta potential, TEM, viscosity and pH. Then, the antibacterial and anticancer activities of nano-emulsion formulations versus their pure plant counterparts was assessed.

RESULTS

The analysis of extracts identified several flavonoids, phenolics, and saponins which were reported to have antimicrobial and anticancer activities. Nano-emulsion formulations were monodispersed with droplet sizes ranging from 80.27 ± 2.05 to 111.16 ± 1.97 nm, and polydispersity index ≤0.3. Nano-emulsion formulations enhanced significantly the antibacterial (multidrug resistant bacteria causing skin and dental soft tissues infections) and anticancer (HuH7, HEPG2, H460 and HCT116) activities compared to their pure plant extract counterparts.

CONCLUSION

Employing a nano-delivery system as a carrier for phytochemicals might be an effective strategy to enhance their pharmacological activity, overcome their limitations, and ultimately increase their potential for clinical applications.

Exogenous methionine contributes to reversing the resistance of Streptococcus suis to macrolides

Streptococcus suis (S. suis) has been increasingly recognized as a porcine zoonotic pathogen that threatens the health of both pigs and humans. Multidrug-resistant Streptococcus suis is becoming increasingly prevalent, and novel strategies to treat bacterial infections caused by these organisms are desperately needed. In the present study, an untargeted metabolomics analysis showed that the significant decrease in methionine content and the methionine biosynthetic pathway were significantly affected by the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis in drug-resistant S. suis. The addition of L-methionine restored the bactericidal activity of macrolides, doxycycline, and ciprofloxacin on S. suis in vivo and in vitro. Further studies showed that the exogenous addition of methionine affects methionine metabolism by reducing S-adenosylmethionine synthetase activity and the contents of S-adenosylmethionine, S-adenosyl homocysteine, and S-ribose homocysteine. Methionine can decrease the total methylation level and methylesterase activity in multidrug resistant S. suis. The drug transport proteins and efflux pump genes were significantly downregulated in S. suis by exogenous L-methionine. Moreover, the exogenous addition of methionine can reduce the survival of S. suis by affecting oxidative stress and metal starvation in bacteria. Thus, L-methionine may influence the development of resistance in S. suis through methyl metabolism and metal starvation. This study provides a new perspective on the mitigation of drug resistance in S. suis.IMPORTANCEBacterial antibiotic resistance has become a severe threat to human and animal health. Increasing the efficacy of existing antibiotics is a promising strategy against antibiotic resistance. Here, we report that L-methionine enhances the efficacy of macrolides, doxycycline, and ciprofloxacin antibiotics in killing Streptococcus suis, including multidrug-resistant pathogens. We investigated the mechanism of action of exogenous methionine supplementation in restoring macrolides in Streptococcus suis and the role of the methionine cycle pathway on methylation levels, efflux pump genes, oxidative stress, and metal starvation in Streptococcus suis. It provides a theoretical basis for the rational use of macrolides in clinical practice and also identifies a possible target for restoring drug resistance in Streptococcus suis.