Steroid Derivatives as Potential Antimicrobial Agents Against Staphylococcus aureus Planktonic Cells

Antibacterial activity of Shallots (Allium xwakegi Araki.) cultivars in Palu Valley against Salmonella Typhi ATCC 27870 through in vitro and in silico evaluation

Background and Objectives

Shallots, recognized for their minimal toxicity, cost-effectiveness, and widespread availability, are increasingly considered a viable source of biological activity. This study evaluates the antibacterial efficacy of a specific shallot cultivar from Palu Valley, Indonesia, against Salmonella typhi, the pathogen responsible for typhoid fever.

Materials and Methods

Utilizing thin-layer chromatography (TLC-bioautography) and gas chromatography-mass spectroscopy (GC-MS), the study identifies active compounds in shallot ethanol extract and employs molecular docking to assess interactions between receptors and ligands.

Results

Findings indicate significant antibacterial activity, with a notable inhibition zone diameter of 31.5 mm at spot Rf 0.28 in TLC bioautography and an optimum concentration of 2% yielding an average clear zone diameter of 28.27 mm in the agar diffusion test. GC-MS analysis reveals 41 compounds, predominantly dodecanoic acid and 1,2,3-propanetriyl ester. Additionally, molecular docking reveals the lowest binding affinity (-7.3 kcal/mol) for Ergost-8-En-3-Ol, 14-Methyl-, (3.Beta,5. Alpha.) against DNA gyrase.

Conclusion

This study confirms Palu Valley shallot extract's potent antibacterial effect against Salmonella typhi, highlighting its therapeutic potential.

Selection of Mexican Medicinal Plants by Identification of Potential Phytochemicals with Anti-Aging, Anti-Inflammatory, and Anti-Oxidant Properties through Network Analysis and Chemoinformatic Screening

Many natural products have been acquired from plants for their helpful properties. Medicinal plants are used for treating a variety of pathologies or symptoms. The axes of many pathological processes are inflammation, oxidative stress, and senescence. This work is focused on identifying Mexican medicinal plants with potential anti-oxidant, anti-inflammatory, anti-aging, and anti-senescence effects through network analysis and chemoinformatic screening of their phytochemicals. We used computational methods to analyze drug-like phytochemicals in Mexican medicinal plants, multi-target compounds, and signaling pathways related to anti-oxidant, anti-inflammatory, anti-aging, and anti-senescence mechanisms. A total of 1373 phytochemicals are found in 1025 Mexican medicinal plants, and 148 compounds showed no harmful functionalities. These compounds displayed comparable structures with reference molecules. Based on their capacity to interact with pharmacological targets, three clusters of Mexican medicinal plants have been established. Curatella americana, Ximenia americana, Malvastrum coromandelianum, and Manilkara zapota all have anti-oxidant, anti-inflammatory, anti-aging, and anti-senescence effects. Plumeria rubra, Lonchocarpus yucatanensis, and Salvia polystachya contained phytochemicals with anti-oxidant, anti-inflammatory, anti-aging, and anti-senescence reported activity. Lonchocarpus guatemalensis, Vallesia glabra, Erythrina oaxacana, and Erythrina sousae have drug-like phytochemicals with potential anti-oxidant, anti-inflammatory, anti-aging, and anti-senescence effects. Between the drug-like phytochemicals, lonchocarpin, vallesine, and erysotrine exhibit potential anti-oxidant, anti-inflammatory, anti-aging, and anti-senescence effects. For the first time, we conducted an initial virtual screening of selected Mexican medicinal plants, which was subsequently confirmed in vivo, evaluating the anti-inflammatory activity of Lonchocarpus guatemalensis Benth in mice.

PYED-1 Overcomes Colistin Resistance in Acinetobacter baumannii

Antibiotic resistance has become more and more widespread over the recent decades, becoming a major global health problem and causing colistin to be increasingly used as an antibiotic of last resort. Acinetobacter baumannii, an opportunistic pathogen that has rapidly evolved into a superbug exhibiting multidrug-resistant phenotypes, is responsible for a large number of hospital infection outbreaks. With the intensive use of colistin, A. baumannii resistance to colistin has been found to increase significantly. In previous work, we identified a deflazacort derivative, PYED-1 (pregnadiene-11-hydroxy-16,17-epoxy-3,20-dione-1), which exhibits either direct-acting or synergistic activity against Gram-positive and Gram-negative species and Candida spp., including A. baumannii. The aim of this study was to evaluate the antibacterial activity of PYED-1 in combination with colistin against both A. baumannii planktonic and sessile cells. Furthermore, the cytotoxicity of PYED-1 with and without colistin was assessed. Our results show that PYED-1 and colistin can act synergistically to produce a strong antimicrobial effect against multidrug-resistant populations of A. baumannii. Interestingly, our data reveal that PYED-1 is able to restore the efficacy of colistin against all colistin-resistant A. baumannii isolates. This drug combination could achieve a much stronger antimicrobial effect than colistin while using a much smaller dosage of the drugs, additionally eliminating the toxicity and resistance issues associated with the use of colistin.

Delving into the Mechanisms of Sponge-Associated Enterobacter against Staphylococcal Biofilms

Staphylococci are one of the most common causes of biofilm-related infections. Such infections are hard to treat with conventional antimicrobials, which often lead to bacterial resistance, thus being associated with higher mortality rates while imposing a heavy economic burden on the healthcare system. Investigating antibiofilm strategies is an area of interest in the fight against biofilm-associated infections. Previously, a cell-free supernatant from marine-sponge-associated Enterobacter sp. inhibited staphylococcal biofilm formation and dissociated the mature biofilm. This study aimed to identify the chemical components responsible for the antibiofilm activity of Enterobacter sp. Scanning electron microscopy confirmed that the aqueous extract at the concentration of 32 μg/mL could dissociate the mature biofilm. Liquid chromatography coupled with high-resolution mass spectrometry revealed seven potential compounds in the aqueous extract, including alkaloids, macrolides, steroids, and triterpenes. This study also suggests a possible mode of action on staphylococcal biofilms and supports the potential of sponge-derived Enterobacter as a source of antibiofilm compounds.

6-Polyaminosteroid Squalamine Analogues Display Antibacterial Activity against Resistant Pathogens

A series of 6-polyaminosteroid analogues of squalamine were synthesized with moderate to good yields and evaluated for their in vitro antimicrobial properties against both susceptible and resistant Gram-positive (vancomycin-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus) and Gram-negative (carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa) bacterial strains. Minimum inhibitory concentrations against Gram-positive bacteria ranged from 4 to 16 µg/mL for the most effective compounds, 4k and 4n, and showed an additive or synergistic effect with vancomycin or oxacillin. On the other hand, the derivative 4f, which carries a spermine moiety like that of the natural trodusquemine molecule, was found to be the most active derivative against all the resistant Gram-negative bacteria tested, with an MIC value of 16 µg/mL. Our results suggest that 6-polyaminosteroid analogues of squalamine are interesting candidates for Gram-positive bacterial infection treatments, as well as potent adjuvants to fight Gram-negative bacterial resistance.

Hormonal drugs: Influence on growth, biofilm formation, and adherence of selected gut microbiota

Many studies have reported the influence of hormonal drugs on gut microbiota composition. However, the underlying mechanism of this interaction is still under study. Therefore, this study aimed to evaluate the possible in vitro changes in selected members of gut bacteria exposed to oral hormonal drugs used for years. Selected members of gut bacteria were Bifidobacterium longum, Limosilactobacillus reuteri, Bacteroides fragilis, and Escherichia coli representing the four main phyla in the gut. Selected hormonal drugs used for a long time were estradiol, progesterone, and thyroxine. The effect of intestinal concentrations of these drugs on the selected bacterial growth, biofilm formation, and adherence to Caco-2/HT-29 cell line was assessed. Short-chain fatty acids (SCFAs) have been included in host functions including the gut, immune and nervous functions; thus, the drug’s effects on their production were assayed using High- Performance Liquid Chromatography. Sex steroids significantly increased the growth of all tested bacteria except B. longum, similarly, thyroxine increased the growth of tested Gram-negative bacteria however reducing that of tested Gram-positive bacteria. The effect of drugs on biofilm formation and bacterial adherence to cell lines cocultures was variable. Progesterone decreased the biofilm formation of tested Gram-positive bacteria, it nevertheless increased L. reuteri adherence to Caco-2/HT-29 cell line cell lines coculture. By contrast, progesterone increased biofilm formation by Gram-negative bacteria and increased adherence of B. fragilis to the cell lines coculture. Moreover, thyroxine and estradiol exhibited antibiofilm activity against L. reuteri, while thyroxine increased the ability of E. coli to form a biofilm. Moreover, hormones affected bacterial adherence to cell lines independently of their effect on hydrophobicity suggesting other specific binding factors might contribute to this effect. Tested drugs affected SCFAs production variably, mostly independent of their effect on bacterial growth. In conclusion, our results showed that the microbiota signature associated with some hormonal drug consumption could be the result of the direct effect of these drugs on bacterial growth, and adherence to enterocytes besides the effect of these drugs on the host tissue targets. Additionally, these drugs affect the production of SCFAs which could contribute to some of the side effects of these drugs.

The Potential of 24-Propylcholestrol as Antibacterial Oral Bacteria of Enterococcus faecalis ATCC 29212 and Inhibitor Biofilms Formation: in vitro and in silico Study

Introduction

Uncontrolled biofilm can cause several diseases such as dental caries, gingivitis, and periodontitis. Dental caries is a disease caused by the accumulation of plaque-containing pathogenic bacteria, including Enterococcus faecalis. These bacteria infect the root canals of teeth and colonize to form biofilms. Biofilm inhibition is carried out by interfering with cell wall formation metabolism. MurA enzyme has a role in peptidoglycan biosynthesis of cell walls. Enterococcal surface protein (Esp) is the main contributor of E. faecalis to form biofilms. In addition, inhibition of biofilms by interfering with the quorum sensing (QS) system, suppressing gelatinase virulence factors by blocking autoinducers gelatinase biosynthesis-activating pheromone (GBAP).

Purpose

Knowing the potential of Piper betel Linn. compounds as antibacterial in vitro and antibiofilm agents against E. faecalis in silico.

Patients and Methods

The compounds were purified by a bioactivity-guided chromatographic method. Antibacterial activity was tested by disc diffusion method, in vitro studies. In silico study, compound P. betel L. was used as the test ligand and compared with positive control fosfomycin, ambuic acid, quercetin, and taxifolin. The proteins used MurA, Esp, GBAP, and gelatinase were docking with the Autodock Vina PyRx 0.8 followed by the PYMOL program and visualized with the Discovery Studio 2020 program.

Results

An antibacterial compound was identified 24-propylcholesterol which can inhibit the activity of E. faecalis ATCC 29212 with MIC value of 78.1 µg/mL and MBC value of 156.3 µg/mL. Molecular docking results showed the binding affinity of 24-propylcholesterol with MurA, ESP, GBAP, and gelatinase enzymes was -7.6, -8.7, -5.3, and -7.9 kcal/mol.

Conclusion

24-propylcholesterol has potential as an antibacterial against E. faecalis and as an antibiofilm through in silico inhibition of QS. However, further research is needed in vitro and in vivo to determine the effectiveness of these compounds as antibacterial and antibiofilm.

Antimicrobial and Antibiofilm Effect of 4,4'-Dihydroxy-azobenzene against Clinically Resistant Staphylococci

The spread of antibiotic resistance among human and animal pathogens is one of the more significant public health concerns. Moreover, the restrictions on the use of particular antibiotics can limit the options for the treatment of infections in veterinary clinical practice. In this context, searching for alternative antimicrobial substances is crucial nowadays. In this study, 4,4'-dihydroxy-azobenzene (DHAB) was tested for its potential in vitro as an antimicrobial agent against two relevant human and animal pathogens, namely Staphylococcus aureus and Staphylococcus pseudintermedius. The values of minimal inhibitory concentration (MIC) were 64 and 32 mg/L respectively, and they comparable to other azo compounds of probed antimicrobial activity. In addition, the minimal bactericidal concentrations (MCB) were 256 and 64 mg/L. The mechanism by which DHAB produces toxicity in staphylococci has been investigated. DHAB caused membrane damage as revealed by the increase in thiobarbituric acid reactive substances (TBARS) such as malondialdehyde. Furthermore, differential induction of the enzymes peroxidases and superoxide dismutase in S. aureus and S. pseudintermedius suggested their prevalent role in ROS-scavenging due to the oxidative burst induced by this compound in either species. In addition, this substance was able to inhibit the formation of biofilms by both bacteria as observed by colorimetric tests and scanning electron microscopy. In order to assess the relevance of DHAB against clinical strains of MRSA, 10 clinical isolates resistant to either methicillin or daptomycin were assayed; 80% of them gave values of CMI and CMB similar to those of the control S. aureus strain. Finally, cutaneous plasters containing a composite formed by an agar base supplemented with DHAB were designed. These plasters were able to inhibit in vitro the growth of S. aureus and S. pseudintermedius, particularly the later, and this suggests that this substance could be a promising candidate as an alternative to antibiotics in the treatment of animal skin infections, as it has been proven that the toxicity of this substance is very low particularly at a dermal level.

Attenuating the virulence of the resistant superbug Staphylococcus aureus bacteria isolated from neonatal sepsis by ascorbic acid, dexamethasone, and sodium bicarbonate

Background

Infections affecting neonates caused by Staphylococcus aureus are widespread in healthcare facilities; hence, novel strategies are needed to fight this pathogen. In this study, we aimed to investigate the effectiveness of the FDA-approved medications ascorbic acid, dexamethasone, and sodium bicarbonate to reduce the virulence of the resistant Staphylococcus aureus bacteria that causes neonatal sepsis and seek out suitable alternatives to the problem of multi-drug resistance.

Methods

Tested drugs were assessed phenotypically and genotypically for their effects on virulence factors and virulence-encoding genes in Staphylococcus aureus. Furthermore, drugs were tested in vivo for their ability to reduce Staphylococcus aureus pathogenesis.

Results

Sub-inhibitory concentrations (1/8 MIC) of ascorbic acid, dexamethasone, and sodium bicarbonate reduced the production of Staphylococcus aureus virulence factors, including biofilm formation, staphyloxanthin, proteases, and hemolysin production, as well as resistance to oxidative stress. At the molecular level, qRT-PCR was used to assess the relative expression levels of crtM, sigB, sarA, agrA, hla, fnbA, and icaA genes regulating virulence factors production and showed a significant reduction in the relative expression levels of all the tested genes.

Conclusions

The current findings reveal that ascorbic acid, dexamethasone, and sodium bicarbonate have strong anti-virulence effects against Staphylococcus aureus. Thus, suggesting that they might be used as adjuvants to treat infections caused by Staphylococcus aureus in combination with conventional antimicrobials or as alternative therapies.

The inhibitory effect of some pyrazole ligands and their Cu(II) complexes on the growth of Escherichia coli, Klebsiella–Enterobacter spp., and Staphylococcus aureus

The aim of this study was to evaluate the inhibitory activity of chemistry products against the growth of Escherichia coli, Klebsiella–Enterobacter spp., and Staphylococcus aureus. Pyrazole derivatives (4-bromo-2-(1H-pyrazol-3-yl)phenol, 4-nitro-3-pyrazolecarboxylic acid, N-(benzyloxycarbonyl)-1H-pyrazole-1-carboxamidine), 3-amino-5-hydroxypyrazole, 3,5-pyrazoledicarboxylic acid monohydrate, and selected complexes of Cu(II) with the mentioned pyrazoles as ligands were used as chemistry bioactives for antibacterial activity. The testing method was carried out according to the disc diffusion method. Some compounds have shown inhibitory effects against the growth of E. coli. A small number of compounds have shown inhibitory effects against the growth of Klebsiella–Enterobacter spp. but did not show inhibitory effects on Staphylococcus aureus compared to amoxicillin as a standard.

The Glucocorticoid PYED-1 Disrupts Mature Biofilms of Candida spp. and Inhibits Hyphal Development in Candida albicans

Invasive Candida infections have become a global public health problem due to the increase of Candida species resistant against antifungal therapeutics. The glucocorticoid PYED-1 (pregnadiene-11-hydroxy-16α,17α-epoxy-3,20-dione-1) has antimicrobial activity against various bacterial taxa. Consequently, it might be considered for the treatment of Candida infections. The antifungal activity of PYED-1 was evaluated against several fungal strains that were representative of the five species that causes the majority of Candida infections-namely, Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei. PYED-1 exhibited a weak antifungal activity and a fungistatic effect on all five Candida species. On the other hand, PYED-1 exhibited a good anti-biofilm activity, and was able to eradicate the preformed biofilms of all Candida species analyzed. Moreover, PYED-1 inhibited germ tube and hyphae formation of C. albicans and reduced adhesion of C. albicans to abiotic surfaces by up to 30%.

N-Nonyloxypentyl-l-Deoxynojirimycin Inhibits Growth, Biofilm Formation and Virulence Factors Expression of Staphylococcus aureus

Staphylococcus aureus is one of the major causes of hospital- and community-associated bacterial infections throughout the world, which are difficult to treat due to the rising number of drug-resistant strains. New molecules displaying potent activity against this bacterium are urgently needed. In this study, d- and l-deoxynojirimycin (DNJ) and a small library of their N-alkyl derivatives were screened against S. aureus ATCC 29213, with the aim to identify novel candidates with inhibitory potential. Among them, N-nonyloxypentyl-l-DNJ (l-NPDNJ) proved to be the most active compound against S. aureus ATCC 29213 and its clinical isolates, with the minimum inhibitory concentration (MIC) value of 128 μg/mL. l-NPDNJ also displayed an additive effect with gentamicin and oxacillin against the gentamicin- and methicillin-resistant S. aureus isolate 00717. Sub-MIC values of l-NPDNJ affected S. aureus biofilm development in a dose-dependent manner, inducing a strong reduction in biofilm biomass. Moreover, real-time reverse transcriptase PCR analysis revealed that l-NPDNJ effectively inhibited at sub-MIC values the transcription of the spa, hla, hlb and sea virulence genes, as well as the agrA and saeR response regulator genes.

PYED-1 Inhibits Biofilm Formation and Disrupts the Preformed Biofilm of Staphylococcus aureus

Pregnadiene-11-hydroxy-16α,17α-epoxy-3,20-dione-1 (PYED-1), a heterocyclic corticosteroid derivative of deflazacort, exhibits broad-spectrum antibacterial activity against Gram-negative and Gram-positive bacteria. Here, we investigated the effect of PYED-1 on the biofilms of Staphylococcus aureus, an etiological agent of biofilm-based chronic infections such as osteomyelitis, indwelling medical device infections, periodontitis, chronic wound infections, and endocarditis. PYED-1 caused a strong reduction in biofilm formation in a concentration dependent manner. Furthermore, it was also able to completely remove the preformed biofilm. Transcriptional analysis performed on the established biofilm revealed that PYED-1 downregulates the expression of genes related to quorum sensing (agrA, RNAIII, hld, psm, and sarA), surface proteins (clfB and fnbB), secreted toxins (hla, hlb, and lukD), and capsular polysaccharides (capC). The expression of genes that encode two main global regulators, sigB and saeR, was also significantly inhibited after treatment with PYED-1. In conclusion, PYED-1 not only effectively inhibited biofilm formation, but also eradicated preformed biofilms of S. aureus, modulating the expression of genes related to quorum sensing, surface and secreted proteins, and capsular polysaccharides. These results indicated that PYED-1 may have great potential as an effective antibiofilm agent to prevent S. aureus biofilm-associated infections.