Efflux pumps and microbial biofilm formation

Intestinal biofilms: pathophysiological relevance, host defense, and therapeutic opportunities

SUMMARYThe human intestinal tract harbors a profound variety of microorganisms that live in symbiosis with the host and each other. It is a complex and highly dynamic environment whose homeostasis directly relates to human health. Dysbiosis of the gut microbiota and polymicrobial biofilms have been associated with gastrointestinal diseases, including irritable bowel syndrome, inflammatory bowel diseases, and colorectal cancers. This review covers the molecular composition and organization of intestinal biofilms, mechanistic aspects of biofilm signaling networks for bacterial communication and behavior, and synergistic effects in polymicrobial biofilms. It further describes the clinical relevance and diseases associated with gut biofilms, the role of biofilms in antimicrobial resistance, and the intestinal host defense system and therapeutic strategies counteracting biofilms. Taken together, this review summarizes the latest knowledge and research on intestinal biofilms and their role in gut disorders and provides directions toward the development of biofilm-specific treatments.

A review of chemical signaling mechanisms underlying quorum sensing and its inhibition in Staphylococcus aureus

Staphylococcus aureus is a significant bacterium responsible for multiple infections and is a primary cause of fatalities among patients in hospital environments. The advent of pathogenic bacteria such as methicillin-resistant S. aureus revealed the shortcomings of employing antibiotics to treat bacterial infectious diseases. Quorum sensing enhances S. aureus's survivability through signaling processes. Targeting the key components of quorum sensing has drawn much interest nowadays as a promising strategy for combating infections caused by bacteria. Concentrating on the accessory gene regulator quorum-sensing mechanism is the most commonly suggested anti-virulence approach for S.aureus. Quorum quenching is a common strategy for controlling illnesses triggered by microorganisms since it reduces the pathogenicity of bacteria and improves bacterial biofilm susceptibility to antibiotics, thus providing an intriguing prospect for drug discovery. Quorum sensing inhibition reduces selective stresses and constrains the emergence of antibiotic resistance while limiting bacterial pathogenicity. This review examines the quorum sensing mechanisms involved in S. aureus, quorum sensing targets and gene regulation, environmental factors affecting quorum sensing, quorum sensing inhibition, natural products as quorum sensing inhibitory agents and novel therapeutical strategies to target quorum sensing in S. aureus as drug developing technique to augment conventional antibiotic approaches.

Inhibition of polymorphic MexXY-OprM efflux system in Pseudomonas aeruginosa clinical isolates by Berberine derivatives

The MexXY-OprM multidrug efflux pump (EP) in aminoglycosides resistant Pseudomonas aeruginosa is one of the major resistance mechanisms, which is often overexpressed in strains isolated from pulmonary chronic disease such as cystic fibrosis.[1-3] In this research, we focused on the design of potential efflux pumps inhibitors, targeting MexY, the inner membrane component, in an allosteric site. Berberine[4] has been considered as lead molecule since we previously demonstrated its effectiveness in targeting MexY in laboratory reference strains.[5,6] Since this protein is often present in polymorphic variants in clinical strains, we sequenced and modeled all the mutated forms and we synthesized and evaluated by computational techniques, some berberine derivatives carrying an aromatic functionalization in its 13-C ring position. These compounds were tested in vitro against clinical P. aeruginosa strains for antimicrobial and antibiofilm activity. In conclusion, the results demonstrated the importance of the aromatic moiety functionalization in exerting the EP inhibitory activity in synergy with the aminoglycoside tobramycin. More, we found that aminoacidic composition of MexY in different strains must be considered for predicting potential binding site and affects the different activity of berberine derivatives. Finally, the antibiofilm effect of these new EPIs is promising, particularly for o-CH3-berberine derivative.

In Vitro and In Vivo Antileishmanial Activity of Thioridazine

INTRODUCTION

Leishmaniasis is a neglected disease with high prevalence and incidence in tropical and subtropical areas. Existing drugs are limited due to cost, toxicity, declining efficacy and unavailability in endemic places. Drug repurposing has established as an efficient way for the discovery of drugs for a variety of diseases.

PURPOSE

The objective of the present work was testing the antileishmanial activity of thioridazine, an antipsychotic agent with demonstrated effect against other intracellular pathogens.

METHODS

The cytotoxicity for mouse peritoneal macrophages as well as the activity against Leishmania amazonensis, Leishmania mexicana and Leishmania major promastigotes and intracellular amastigotes, as well as in a mouse model of cutaneous leishmaniasis, were assessed.

RESULTS

Thioridazine inhibited the in vitro proliferation of promastigotes (50% inhibitory concentration-IC50-values in the range of 0.73 µM to 3.8 µM against L. amazonensis, L. mexicana and L. major) and intracellular amastigotes (IC50 values of 1.27 µM to 4.4 µM for the same species). In contrast, in mouse peritoneal macrophages, the 50% cytotoxic concentration was 24.0 ± 1.89 µM. Thioridazine inhibited the growth of cutaneous lesions and reduced the number of parasites in the infected tissue of mice. The dose of thioridazine that inhibited lesion development by 50% compared to controls was 23.3 ± 3.1 mg/kg and in terms of parasite load, it was 11.1 ± 0.97 mg/kg.

CONCLUSIONS

Thioridazine was effective against the promastigote and intracellular amastigote stages of three Leishmania species and in a mouse model of cutaneous leishmaniasis, supporting the potential repurposing of this drug as an antileishmanial agent.

Combating antimicrobial resistance: the silent war

Once hailed as miraculous solutions, antibiotics no longer hold that status. The excessive use of antibiotics across human healthcare, agriculture, and animal husbandry has given rise to a broad array of multidrug-resistant (MDR) pathogens, posing formidable treatment challenges. Antimicrobial resistance (AMR) has evolved into a pressing global health crisis, linked to elevated mortality rates in the modern medical era. Additionally, the absence of effective antibiotics introduces substantial risks to medical and surgical procedures. The dwindling interest of pharmaceutical industries in developing new antibiotics against MDR pathogens has aggravated the scarcity issue, resulting in an exceedingly limited pipeline of new antibiotics. Given these circumstances, the imperative to devise novel strategies to combat perilous MDR pathogens has become paramount. Contemporary research has unveiled several promising avenues for addressing this challenge. The article provides a comprehensive overview of these innovative therapeutic approaches, highlighting their mechanisms of action, benefits, and drawbacks.

Advances in the Discovery of Efflux Pump Inhibitors as Novel Potentiators to Control Antimicrobial-Resistant Pathogens

The excessive use of antibiotics has led to the emergence of multidrug-resistant (MDR) pathogens in clinical settings and food-producing animals, posing significant challenges to clinical management and food control. Over the past few decades, the discovery of antimicrobials has slowed down, leading to a lack of treatment options for clinical infectious diseases and foodborne illnesses. Given the increasing prevalence of antibiotic resistance and the limited availability of effective antibiotics, the discovery of novel antibiotic potentiators may prove useful for the treatment of bacterial infections. The application of antibiotics combined with antibiotic potentiators has demonstrated successful outcomes in bench-scale experiments and clinical settings. For instance, the use of efflux pump inhibitors (EPIs) in combination with antibiotics showed effective inhibition of MDR pathogens. Thus, this review aims to enable the possibility of using novel EPIs as potential adjuvants to effectively control MDR pathogens. Specifically, it provides a comprehensive summary of the advances in novel EPI discovery and the underlying mechanisms that restore antimicrobial activity. In addition, we also characterize plant-derived EPIs as novel potentiators. This review provides insights into current challenges and potential strategies for future advancements in fighting antibiotic resistance.

The Isolate Pseudomonas multiresinivorans QL-9a Quenches the Quorum Sensing Signal and Suppresses Plant Soft Rot Disease

Quorum sensing (QS) is a communication mechanism used among microorganisms that regulate the population density and behavior by sensing the concentration of signaling molecules. Quorum quenching (QQ), a novel, eco-friendly, and efficient method for disease control, interferes with QS by disturbing the production and enzymatic degradation of signaling molecules, blocking communication among microorganisms, and thus has deep potential for use in plant disease control. Pectobacterium carotovorum can cause bacterial soft rot, resulting in yield reduction in a variety of crops worldwide, and can be mediated and regulated by the N-acyl homoserine lactones (AHLs), which are typical signaling molecules. In this study, a novel quenching strain of Pseudomonas multiresinivorans QL-9a was isolated and characterized, and it showed excellent degradation ability against AHLs, degrading 98.20% of N-(-3-oxohexanoyl)-L-homoserine lactone (OHHL) within 48 h. Based on the results of the gas chromatography-mass spectrometer (GC-MS) analysis, a possible pathway was proposed to decompose OHHL into fatty acids and homoserine lactone, in which AHL acylase was involved. Additionally, it has been demonstrated that the QL-9a strain and its crude enzyme are promising biocontrol agents that can considerably reduce the severity of the soft rot disease brought on by P. carotovorum, consequently preventing the maceration of a variety of host plant tissues. All of these results suggest promising applications of the QL-9a strain and its crude enzyme in the control of various plant diseases mediated by AHLs.