Better living through chemistry: Addressing emerging antibiotic resistance

The Phytochemical Tactics for Battling Antibiotic Resistance in Microbes: Secondary Metabolites and Nano Antibiotics Methods

One of the most serious threats to human health is antibiotic resistance, which has left the world without effective antibiotics. While continuous research and inventions for new antibiotics are going on, especially those with new modes of action, it is unlikely that this alone would be sufficient to win the battle. Furthermore, it is also important to investigate additional approaches. One such strategy for improving the efficacy of existing antibiotics is the discovery of adjuvants. This review has collected data from various studies on the current crisis and approaches for combating multi-drug resistance in microbial pathogens using phytochemicals. In addition, the nano antibiotic approaches, are discussed, highlighting the high potentials of essential oils, alkaloids, phenolic compounds, and nano antibiotics in combating antibiotic resistance.

Hydrogen Peroxide-Activated Nitric Oxide-Releasing Vancomycin-Loaded Electrostatic Complexation for Efficient Elimination of Methicillin-Resistant Staphylococcus aureus Abscesses

The treatment of subcutaneous abscesses has been greatly hindered due to the spread of drug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). Thus, alternative strategies are highly desired to complement conventional antibiotic therapies and surgical intervention. As one of such strategies, applications of nitric oxide (NO) have shown great potential in the treatment of bacteria-induced subcutaneous abscesses by improving the efficacy of many therapeutic methods. However, it is extremely challenging to achieve precise delivery and controlled release because of its gaseous nature. In the present study, an effective strategy was reported in which on demand hydrogen peroxide (H₂O₂)-activated nitric oxide-releasing vancomycin (Van)-loaded electrostatic complexation (Lipo/Van@Arg) was fabricated. In this system, Van was encapsulated into a negative-charged DSPG/Chol liposome (Lipo/Van) and electrostatically bound with the positive-charged l-arginine (l-Arg). As expected, Lipo/Van@Arg exhibited superior bacterial binding and biofilm penetration abilities. After being in the interior of the biofilms, Lipo/Van@Arg could be triggered by the endogenous H₂O₂ and effectively release NO. The released NO could exhibit combined antibacterial and biofilm eradication effects with Van. Moreover, an in vivo evaluation using a BALB/c mouse model of subcutaneous abscesses indicated that the combination treatment of NO and Van based on Lipo/Van@Arg could effectively eliminate MRSA from the abscesses, thereby preventing abscess recurrence. In summary, the Lipo/Van@Arg system developed in this study realized controlled delivery and precise release of NO, which had significant clinical implications in the efficient treatment of abscesses.

Photoactivated Indium Phosphide Quantum Dots Treat Multidrug-Resistant Bacterial Abscesses In Vivo

The increasing prevalence of drug-resistant bacterial strains is causing illness and death in an unprecedented number of people around the globe. Currently implemented small-molecule antibiotics are both increasingly less efficacious and perpetuating the evolution of resistance. Here, we propose a new treatment for drug-resistant bacterial infection in the form of indium phosphide quantum dots (InP QDs), semiconductor nanoparticles that are activated by light to produce superoxide. We show that the superoxide generated by InP QDs is able to effectively kill drug-resistant bacteria in vivo to reduce subcutaneous abscess infection in mice without being toxic to the animal. Our InP QDs are activated by near-infrared wavelengths with high transmission through skin and tissues and are composed of biocompatible materials. Body weight and organ tissue histology show that the QDs are nontoxic at a macroscale. Inflammation and oxidative stress markers in serum demonstrate that the InP QD treatment did not result in measurable effects on mouse health at concentrations that reduce drug-resistant bacterial viability in subcutaneous abscesses. The InP QD treatment decreased bacterial viability by over 3 orders of magnitude in subcutaneous abscesses formed in mice. These InP QDs thus provide a promising alternative to traditional small-molecule antibiotics, with the potential to be applied to a wide variety of infection types, including wound, respiratory, and urinary tract infections.

Molecular Insights into an Antibiotic Enhancer Action of New Morpholine-Containing 5-Arylideneimidazolones in the Fight against MDR Bacteria

In the search for an effective strategy to overcome antimicrobial resistance, a series of new morpholine-containing 5-arylideneimidazolones differing within either the amine moiety or at position five of imidazolones was explored as potential antibiotic adjuvants against Gram-positive and Gram-negative bacteria. Compounds (7–23) were tested for oxacillin adjuvant properties in the Methicillin-susceptible S. aureus (MSSA) strain ATCC 25923 and Methicillin-resistant S. aureus MRSA 19449. Compounds 14–16 were tested additionally in combination with various antibiotics. Molecular modelling was performed to assess potential mechanism of action. Microdilution and real-time efflux (RTE) assays were carried out in strains of K. aerogenes to determine the potential of compounds 7–23 to block the multidrug efflux pump AcrAB-TolC. Drug-like properties were determined experimentally. Two compounds (10, 15) containing non-condensed aromatic rings, significantly reduced oxacillin MICs in MRSA 19449, while 15 additionally enhanced the effectiveness of ampicillin. Results of molecular modelling confirmed the interaction with the allosteric site of PBP2a as a probable MDR-reversing mechanism. In RTE, the compounds inhibited AcrAB-TolC even to 90% (19). The 4-phenylbenzylidene derivative (15) demonstrated significant MDR-reversal “dual action” for β-lactam antibiotics in MRSA and inhibited AcrAB-TolC in K. aerogenes. 15 displayed also satisfied solubility and safety towards CYP3A4 in vitro.

New approach to address antibiotic resistance: Miss loading of functional membrane microdomains (FMM) of methicillin-resistant Staphylococcus aureus (MRSA)

The synthesized potent piperazine analog ChDiPiCa was characterised by various spectroscopic techniques and for the first time evaluated functional membrane microdomain (FMM) disassembly in methicillin-resistant Staphylococcus aureus (MRSA). The ChDiPiCa showed excellent in vitro biocidal activity against MRSA at 26 μg/mL compared to the antibiotic streptomycin and bacitracin 14 μg/mL and 13 μg/mL at 10 μg concentration respectively. The membrane damaging property was confirmed by the SEM analysis. Further, we addressed the new approach for the first time to overcome antibiotic resistance of MRSA through membrane microdomain miss loading to lipids. By which, the ChDiPiCa confirms the significant activity in miss loading of FMM of MRSA which is validated by the fatty acid profile and lipid analysis. The result shows that, altered saturated (Lauric acid and Myristic acid), mono unsaturated (Oleic acid), and poly unsaturated (Linoleic acid and Linolenic acid) fatty acids and hypothesises, altered the membrane functional lipids. For the better understanding of miss loading of FMM by the ChDiPiCa, the in-silico molecular docking studies was analyzed and confirmed the predicted role. This suggests the way to develop ChDiPiCa in medicinal chemistry as anti-MRSA candidates and also this report opens up new window to treat microbial pathogens and infections.