Search Results (153)

The increasing number of antibiotic-resistant pathogens forces us to accelerate the search for new antimicrobial agents. Based on this, we chose to synthesize a library of 1-(2-hydroxy-5-methylphenyl)-5-oxopyrrolidine-3-carboxylic acid derivatives and evaluate their antibacterial activity against various pathogens. A series of (2-hydroxy-5-methylphenyl)-5-oxopyrrolidine-3-carboxylic acid and its hydrazide derivatives were prepared and identified by the methods of IR, ¹H, and ¹³C NMR spectroscopy and a microanalysis technique. The resulting compounds were evaluated in vitro for their efficacy against the Gram-positive Staphylococcus aureus (ATCC 9144), Listeria monocytogenes (ATCC 7644), and Bacillus cereus (ATCC 11778) bacterial strains as well as the Gram-negative Escherichia coli (ATCC 8739) bacteria. Oxacillin, ampicillin, and cefuroxime were used as control antibiotics. Among the obtained compounds, hydrazone with a 5-nitrothien-2-yl fragment surpassed the control cefuroxime (7.8 μg/mL) against almost all strains tested. Hydrazone with a 5-nitrofuran-2-yl moiety showed a slightly lower but also potent effect on all bacterial strains. Moreover, hydrazone with a benzylidene moiety demonstrated very strong inhibition of S. aureus (3.9 μg/mL) in comparison with the antibacterial drug cefuroxime (7.8 μg/mL). In addition, some of these compounds exhibited remarkable bactericidal properties. In a complete biofilm disruption study, 5-nitrothienylhydrazone showed excellent results in disrupting S. aureus and E. coli biofilms. The test results show the potential of the newly obtained derivatives as a source of antibacterial agents. Therefore, further studies on the molecular optimization of these compounds are necessary for the development of new antibacterial drugs. Full article

Background/Objectives: The current need for new antibacterial compounds that target non-classical pathways is highlighted by the emergence of multidrug-resistant Klebsiella pneumoniae. In the development of antibiotics, DNA adenine methyltransferase (Dam), a key regulator of bacterial gene expression and pathogenicity, is still underutilized. Epoxy-functionalized analogues of isatin derivatives have not been adequately investigated for their antibacterial activity, particularly as Dam inhibitors. In the pursuit of antimicrobial agents, this study synthesized an epoxy-functionalized isatin derivative (L3) using a one-pot reaction. The compound was characterized using FT-IR, ¹H-NMR, ¹³C-NMR, HR-MS, and UV–Vis spectroscopy. Methods: In silico evaluation performed by using ADMETlab3 and SwissADME. While molecular docking studies were achieved by AutoDock and Vina to find L3’s interaction with potential antibacterial target (Dam protein in K. pneumoniae). In addition, the antibacterial potential of L3 was evaluated using minimum inhibitory concentration (MIC) assays against Bacillus cereus, Bacillus pumilus, Escherichia coli, and K. pneumoniae. Results: Among these, L3 exhibited potential inhibitory activity against K. pneumoniae, with a MIC value of 93.75 μg/mL. In silico evaluations confirmed L3’s favorable drug-like properties, including potential oral bioavailability, blood–brain barrier (BBB) permeability, and low plasma protein binding (PPB). The compound satisfied Lipinski’s and other drug-likeness rules as well as getting a quantitative estimate of drug-likeness (QED) score of 0.52. Here, a homology model of Dam protein in K. pneumoniae was generated using the SWISS-MODEL server and validated using computational tools. Targeted docking analysis revealed that L3 exhibited significant potential binding affinity against Dam protein, with binding energies of −6.4 kcal/mol and −4.85 kcal/mol, as determined by Vina and AutoDock, respectively. The associated inhibition constant was calculated as 280.35 µM. Further interaction analysis identified the formation of hydrogen bonds with TRP7 and PHE32, along with Van der Waals’ interactions involving GLY9, ASP51, and ASP179. Conclusions: These findings highlight L3 as a promising scaffold for antimicrobial drug development, particularly in targeting Dam protein in K. pneumoniae. Furthermore, the ADMET profiling and physicochemical properties of L3 support its potential as a drug-like candidate. Full article

Background/Objectives: Bacterial contamination leads to foodborne illnesses, and new antibiotics are required to combat these pathogens. Interest has increased in medicinal plants as targets for new antibiotics. Methods: This study evaluated the antibacterial activity of leaf extracts from Terminalia citrina (Gaertn.) Roxb. ex Fleming against four bacterial pathogens (including a methicillin-resistant Staphylococcus aureus (MRSA) strain) using disc diffusion and liquid microdilution assays. The phytochemical composition of the extracts were determined using ultra-high-performance liquid chromatography–mass spectrometry (UPLC-MS). Results: Both the aqueous and methanol extracts demonstrated noteworthy antibacterial activity against Bacillus cereus (MICs of 468.8 µg/mL and 562.5 µg/mL, respectively). Additionally, the extracts were effective against MRSA (MICs = 625 µg/mL). Strong antibacterial effects were also observed against S. aureus, with MICs of 625 µg/mL (aqueous extract) and 833.3 µg/mL (methanol extract). Twelve combinations of extracts and conventional antibiotics were synergistic against B. cereus and S. flexneri. UPLC-MS analysis revealed two flavonoids, orientin 2″-O-gallate and astragalin, exclusive to the aqueous extract, whilst pinocembrin and gallic acid were only detected in the methanol extract. Both extracts contained vitexin 2″-O-p-coumarate, ellagic acid, orientin, rutin, chebulic acid, terminalin, and quercetin-3β-D-glucoside. Both extracts were determined to be nontoxic. Conclusions: The abundance and diversity of polyphenols in the extracts may contribute to their strong antibacterial properties. Further research is required to investigate the antibacterial effects of the individual extract compounds, including their effects when combined with conventional antibiotics, and the potential mechanisms of action against foodborne pathogens. Full article

Endophytic bacteria in Sphagnum palustre have a growth-promoting effect on plants. In this study, the endophytic bacterium strain J11 in S. palustre was isolated and identified as Bacillus cereus, and its growth cycle, functional characteristics, and effects on maize growth were analyzed. The results indicate that as B. cereus, the growth cycle of J11 consists of four phases, and the logarithmic phase lasts 2~24 h, with the abilities of phosphorus solubilization, protease, IAA, siderophore, and NH₃ production. The phosphorus solubilization ability of J11 ranges from 1.66 ± 0.07 to 1.98 ± 0.07 mg/L, and the IAA production varies from 1.51 ± 0.07 to 8.67 ± 0.16 mg/L. It has a growth-promoting effect on maize by increasing the seed germination rate by 29.27%, plant height by 4.21%, leaf length by 17.12%, leaf width by 29.51%, above-ground fresh weight by 50.79%, below-ground fresh weight by 46.30%, and chlorophyll content by 56.81%. This study represents the first report on the isolation and identification of B. cereus from S. palustre. Furthermore, this study systematically investigated its multiple plant growth-promoting traits and functional characteristics. These findings provide valuable resources and a theoretical foundation for the development and functional exploration of microbial resources in agricultural applications. Full article

With the increasing occurrence of bacterial resistance, it is now essential to look for new alternatives to protect the curative utilization of antibiotics within the One Health concept. Here, we adapt and optimize a broth microdilution method and compare it against the broth macrodilution method for evaluating the antibacterial activity of a complex essential oils mix (EO mix) against four livestock pathogens: Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa, and Staphylococcus aureus. Microdilution method performance (final volume well: 300 µL; inoculum: 1.0 × 10⁶ CFU/mL) was evaluated following CLSI recommendations, by comparing the MIC of each of the four strains with the MICs obtained with the macrodilution method (final volume tube: 2 mL; inoculum 1.0 × 10⁶ CFU/mL). Microdilution analysis was performed with an automated plate reader (Bioscreen C), and three bacterial growth parameters (OD max, lag phase, and growth rate) were calculated (DMFit curve-fitting software (v2.1; courtesy of the Institute of Food Research, Norwich, UK)). EO mix MICs were determined for E. coli, S. aureus, and B. cereus. Our results emphasize the importance of ensuring the accuracy of MIC results by performing three technical and three biological replicates, and combining OD max, lag phase, and growth rate to assess the impact of an EO mix at sub-MIC levels. Full article

Pleurotus tuoliensis is a valuable edible mushroom native to Xinjiang in northwest China. It colonizes the roots and stems of Ferula plants. Field inoculation in its natural habitat has been shown to significantly enhance the colonization rate of P. tuoliensis hyphae in Ferula plants. However, the effects of field inoculation on P. tuoliensis hyphal colonization, soil properties, and microbial communities remain underexplored. In this study, we examined the characteristics of rhizosphere soil and microbial communities under four conditions: natural environments with and without hyphal colonization, and field inoculation with and without colonization. High-throughput sequencing results revealed that field inoculation markedly increased the relative abundance of Pleurotus species (57.98%) compared to natural colonization (14.11%). However, field inoculation also resulted in a reduction in microbial community diversity compared to hyphal colonization. Concurrently, the relative abundance of Pseudomonadota, Bacteroidota, and Bacillota significantly increased following field inoculation. LEfSe analysis suggested that the identified potential biomarkers were most likely associated with the Bacillus genus within Bacillota. Furthermore, mushroom growth-promoting bacteria were successfully isolated and identified as members of the Bacillus cereus group (L5) and Bacillus safensis (S16). This finding suggests that field inoculation with P. tuoliensis in its natural habitat promotes microbial communities that enhance its growth. This study offers new insights into conserving wild edible fungi and their interactions with soil microbiota. Full article

In this work, OP- and OC-degrading bacteria were isolated from agricultural soil samples taken in the department of Bolivar, Colombia. The objective of this research was to degrade organochlorine and organophosphorus pesticides using bacterial colonies native to agricultural soils. Two bacterial colonies were isolated from the soil samples, which showed a higher degree of adaptation to media contaminated with the pesticide mixtures. They were identified by biochemical tests using BBL Crystal kits, and, subsequently, their 16S rDNA was sequenced using the PCR technique. Bacterial growth was studied by the OD index, taking absorbance readings on a UV-VIS spectrophotometer at 600 nm, at the 0.5 McFarland scale, and quantification of pesticide degradation was studied by GC–MS. The colonies identified were Bacillus cereus and Paenibacillus lautus. B. cereus isolates were exposed to the OPs malathion, chlorpyrifos, and coumaphos [80 mg·L⁻¹], degrading at rates of 52.4%, 78.8% and 79.5%, respectively, after 12 days of incubation in liquid medium at pH = 7.0 ± 0.2 and 37 °C. Furthermore, P. lautus isolates exposed to the OCs lindane, metolachlor, endrin, and p,p′-DDT [80 mg·L⁻¹] degraded at rates of 64.0%, 60.8%, 55.7% and 65.1% under the same conditions of temperature, pH, and incubation time. These results show that B. cereus and P. lautus might be useful for cleaning up environments that have been polluted by OPs and OCs. Full article

Buccal drug delivery systems often struggle with poor drug solubility, limited adhesion, and rapid clearance, leading to suboptimal therapeutic outcomes. To address these limitations, we developed a novel hybrid eutectogel composed of xanthan gum (XTG), hyaluronic acid (HA), and a Natural Deep Eutectic Solvent (NADES) system (choline chloride, sorbitol, and glycerol in 2:1:1 mole ratio), incorporating 2.5% ibuprofen (IBU) as a model drug. The formulation was optimized using a face-centered central composite design to enhance the rheological, textural, and drug release properties. The optimized eutectogels exhibited shear-thinning behavior (flow behavior index, n = 0.26 ± 0.01), high mucoadhesion (adhesiveness: 2.297 ± 0.142 N·s), and sustained drug release over 24 h, governed by Higuchi kinetics (release rate: 237.34 ± 13.61 μg/cm²/min^1/2). The ex vivo residence time increased substantially with NADES incorporation, reaching up to 176.7 ± 23.1 min. An in vivo anti-inflammatory evaluation showed that the eutectogel reduced λ-carrageenan-induced paw edema within 1 h and that its efficacy was sustained in the kaolin model up to 24 h (p < 0.05), achieving comparable efficacy to a commercial 5% IBU gel, despite a lower drug concentration. Additionally, the eutectogel presented a minimum inhibitory concentration for Gram-positive bacteria of 25 mg/mL, and through direct contact, it reduced microbial viability by up to 100%. Its efficacy against Bacillus cereus, Enterococcus faecium, and Klebsiella pneumoniae, combined with its significant anti-inflammatory properties, positions the NADES-based eutectogel as a promising multifunctional platform for buccal drug delivery, particularly for inflammatory conditions complicated by bacterial infections. Full article

Bacillus cereus sensu lato (B. cereus s.l.) are significant spoilage and pathogenic microorganisms found in various foodstuffs. They are responsible for defects like sweet curdling in milk, which impacts dairy product storage and distribution. Nevertheless, the genetic mechanisms underlying B. cereus-induced sweet curdling remain poorly characterized. In this study, we investigated the genetic and functional basis underlying this phenomenon through whole genome sequencing of the newly isolated B. cereus strain BC46 and transcriptome sequencing at two phases of its growth in milk. Hybrid assembly of Illumina and Nanopore reads resulted in a 5.6 Mb genome with 35.1% GC content, classifying BC46 as B. cereus sensu stricto (B. cereus s.s.) within the panC group IV. Several virulence factors, antimicrobial resistance genes, and cold shock proteins were identified in the genome. A distinct functional profile of BC46 was observed before and after the development of sweet curdling in milk. Genes associated with sporulation, toxin production, hydrolysis, and proteolysis were upregulated in sweet-curdled samples. Our findings highlight potential gene targets that may play an important role in the BC46-induced sweet curdling in milk, enhancing our understanding of its molecular basis and supporting the development of new genetic approaches for early spoilage detection. Full article

Sulfamethazine (SM2), a prevalent sulfonamide antibiotic, is commonly detected as an environmental pollutant. Microbial degradation serves as an important approach to treating SM2 contamination. In this study, an SM2-degrading strain, identified as Bacillus cereus J2, was isolated from the activated sludge that had been cultured using SM2 as the exclusive carbon source, which demonstrated exceptional degradation capabilities. Under optimized conditions (30 °C, initial OD600 = 0.1, pH = 8), strain J2 completely degraded 50 mg/L SM2 within 36 h. The strain also showed high degradation efficiency for other sulfonamides, such as sulfamethoxazole and sulfadiazine, and could grow normally in a mixed system containing these compounds. The growth kinetics with SM2 as the exclusive carbon source conformed well to the Haldane model (R² = 0.925), revealing that the strain’s maximum specific growth rate was determined to be 0.066 h⁻¹ (µ_max) at an initial SM2 concentration of 51.35 mg/L. Seven intermediate degradation products were identified using TQ-LCMS analysis, suggesting three potential degradation pathways for SM2. These findings suggest that Bacillus cereus J2 holds significant promise for the bioremediation of SM2-contaminated environments. Full article

The co-contamination of nitrate nitrogen (NO₃⁻-N) and tetracycline (TC) in aquaculture water has caused serious environmental and health problems. Bioremediation is a promising approach for the removal of NO₃⁻-N and TC. However, free bacteria are sensitive to environmental variation, limiting its application. In this study, a bacterial strain with high NO₃⁻-N and TC degradation ability, Bacillus cereus W2, was isolated and immobilized on wheat straw biochar by an adsorption method. The effect of immobilization conditions, including biochar dosage, inoculum amount, and immobilization time on NO₃⁻-N and TC removal was explored. The degradation abilities of the biochar-immobilized Bacillus cereus W2 under different nitrate and TC concentrations was investigated. Results showed that the prepared biochar had abundant functional groups such as -COOH, -OH, -C=C-OH, etc., which have good affinity for microbial cell membranes and are conducive to the adhesion and proliferation of microbial cells. The highest NO₃⁻-N and TC removal efficiencies of 99.50% and 78.60% after 24 h were obtained under a biochar dosage of 4 mg·mL⁻¹, microbe inoculation amount of 40%, and immobilization time of 24 h. The immobilized Bacillus cereus W2 performed better NO₃⁻-N and TC removal than the free cells under different initial NO₃⁻-N and TC concentrations. The enhanced removal of NO₃⁻-N by the biochar-immobilized Bacillus cereus W2 may be attributed to the promoted expression level of functional genes involved in denitrification (nirS, norB, and nosZ). The biochar-immobilized Bacillus cereus W2 demonstrates potential for treating various nitrate-antibiotic co-contaminated wastewaters, including those from livestock farming, aquaculture systems, and pharmaceutical industries. Full article

Multidrug-resistant Pseudomonas aeruginosa infections pose a critical challenge to healthcare systems, particularly in nosocomial settings. This drug-resistant bacterium forms biofilms and produces an array of virulent factors regulated by quorum sensing. In this study, metal-tolerant bacteria were isolated from a metal-contaminated site and screened for their ability to synthesize multifunctional nanocomposites (NCs). Rapid color changes in the reaction solution evidenced the biotransformation process. The potent isolated Bacillus cereus SASAK, identified via 16S rRNA sequencing and deposited in GenBank under accession number MH885570, facilitated the microbial-mediated synthesis of ZnO nanoparticles and silver-doped ZnO NCs. These biogenic nanocomposites were characterized using UV-VIS-NIR spectroscopy, FTIR, XRD, zeta potential, HRTEM, FESEM, and EDX analyses. At a sub-MIC concentration of 100 µg/mL, 2% Ag-ZnO NCs effectively inhibited virulent factor production and biofilm formation in P. aeruginosa without affecting bacterial growth. Notably, there was a significant reduction in violacein pigment (96.25%), swarming motility, and pyocyanin concentration (1.87 µg/mL). Additionally, biofilm formation (81.1%) and EPS production (83.9%) using P. aeruginosa were substantially hindered, along with reduced extracellular protease activity, as indicated by zone formation (from 2.3 to 1.8 cm). This study underscores the potential of Ag-ZnO NCs as promising agents for combating quorum sensing-mediated virulence in chronic infections caused by multidrug-resistant P. aeruginosa. Full article

Terminalia bellirica (Gaertn) Roxb. and Terminalia chebula Retz. are significant botanicals in ancient Ayurvedic medicine. They are renowned for their therapeutic properties, notably in addressing gastrointestinal (GI) diseases. These plants have undergone thorough examination related to their antibacterial, anti-inflammatory, and antioxidant properties, which make them highly efficient natural treatments for controlling gastrointestinal infections. The current research demonstrated the antibacterial efficacy of fruit extracts of Terminalia bellirica and Terminalia chebula against Bacillus cereus, Shigella sonnei, Shigella flexneri, and Salmonella typhimurium. We performed disc diffusion and liquid microdilution experiments to evaluate the antibacterial efficacy. All extracts of Terminalia bellirica and Terminalia chebula showed good antibacterial effects against B. cereus and S. flexneri. The minimum inhibitory concentration (MIC) values ranged from 94 µg/mL to 556 µg/mL. The methanolic extracts from both plants also showed noteworthy antibacterial activity against S. sonnei and S. typhimurium, with MIC values of 755 µg/mL for both. Fractional inhibitory concentration studies revealed additive interactions between some conventional antibiotics and the plant extracts when used concurrently. Liquid chromatography–mass spectrometry (LC-MS) analyses revealed that the T. bellirica and T. chebula extracts contained various tannins including methyl gallate, propyl gallate, gallic acid, and ellagic acid. Lethality assays conducted using Artemia franciscana Kellogg nauplii indicated that all the plant extracts are non-toxic. The antibacterial properties and absence of toxicity in T. bellirica and T. chebula fruit extracts indicate their potential for antibiotic development, warranting additional mechanistic and phytochemical studies. Full article

Bacillus cereus sensu lato (B. cereus s.l.) comprises mesophilic and psychrotolerant bacteria commonly found in natural environments as well as in organic and conventional milk. Due to their potential toxigenicity and antibiotic resistance, these bacteria pose a significant threat to consumer health. Organic milk production, which prohibits the use of antibiotics and artificial additives, may influence the composition of microbiota between milk types. This study aimed to compare the antibiotic resistance profiles and enterotoxic potential of B. cereus s.l. isolates from organic and conventional milk. The results indicate that, although conventional milk contains on average 3 times fewer B. cereus s.l. isolates, it has 10–15% more resistant isolates to selected beta-lactams, macrolides, and aminoglycosides. Regarding drug resistance, 21% of B. cereus s.l. isolates were multidrug-resistant, and as many as 42% were non-susceptible to two classes of antibiotics. Even among the sensitive isolates, bacteria from conventional milk exhibited on average 2.05 times higher MICs (minimal inhibitory concentrations) for beta-lactams, 1.49 times higher for erythromycin, 1.38 times higher for vancomycin, and 1.38 times higher for azithromycin. Antibiotic resistance was mostly associated with the origin of the isolates. These findings underscore the need for ongoing monitoring of antibiotic resistance and enterotoxicity among opportunistic B. cereus s.l. strains, which may pose challenges for public health and veterinary medicine. The results highlight that selective pressure associated with antibiotic use can drive resistance development in bacteria that are not the primary targets of antimicrobial therapy. Full article

The biosynthesis of silver nanoparticles using plant extracts is a promising field of research because of the useful biomedical applications of metal nanoparticles. In this study, the antibacterial and antioxidant properties of silver nanoparticles biosynthesized with the aqueous leaf extract of Pergularia tomentosa were defined using a simple, eco-friendly, consistent, and cost-effective method. The leaf extract of Pergularia tomentosa (PT) served as a capping and reducing agent to biosynthesize silver nanoparticles. The effects of several parameters, such as the concentration of AgNO₃, ratio of AgNO₃ to extract, pH, and incubation time, were examined to optimize the synthesis process. In total, 5 mM of AgNO₃, a 1:0.06 ratio of AgNO₃ to Pergularia tomentosa extract, pH 9.0, and reaction mixture incubation for 24 h were found to be the ideal parameters for biosynthesizing silver nanoparticles (AgNPs). UV–visible spectroscopy, X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and scanning electron microscopy were used to characterize the biosynthesized Pergularia tomentosa silver nanoparticles (PT-AgNPs). Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) and Gram-negative bacteria (Salmonella enteritides and Escherichia coli) were used to test the PT-AgNPs’ antibacterial activity. The presence of different functional groups was determined using FTIR. The AgNPs were hexagon shaped. The nanoparticles were more toxic against S. enteritides than both B. cereus and E. coli. In antioxidant analyses, the AgNPs were found to be as strong at free radical scavenging as gallic acid (standard), with IC₅₀ values of 0.69 and 22.30 μg/mL for DPPH and ABTS radicals, respectively. Interestingly, the PT-AgNPs displayed increased anti-inflammatory activity compared with the P. tomentosa leaf extract (79% vs. 59% at 500 µg/mL). The PT-AgNPs did not display any cytotoxicity against the MCF-7 cell line at the MIC. In conclusion, silver nanoparticles fortified with Pergularia tomentosa extract exhibited potential as effective antibacterial, anti-inflammatory, and antioxidant agents, suggesting their viability as alternatives to commercially available products. Full article