Design, synthesis and antibacterial activity of novel pleuromutilin derivatives with thieno[2,3-d]pyrimidine substitution

BackgroundAcinetobacter baumannii possess inherent and acquired antibiotic resistance mechanisms that have rendered most antibiotics, including carbapenems, inactive. Colistin (COL) has risen as salvage therapy against these organisms due to its retained activity against A. baumannii. However, COL monotherapy is often met with suboptimal outcomes. Recently, combination therapy with COL and meropenem (MEM) or tigecycline (TGC) has been shown to be effective in eradicating multi-drug-resistant A. baumannii infections. The objective of this study was to further evaluate the efficacy of COL in combination with MEM or TGC against 50 multi-drug-resistant A. baumannii strains.MethodsFifty carbapenem-resistant A. baumannii strains were evaluated using combination minimum inhibitory concentration (MIC) testing and time-kill analysis (TKA). Single-drug MIC testing was performed for each strain by broth microdilution. Combination MIC testing was performed for COL+MEM and COL+TGC. Each strain was evaluated via 24-hour TKA to assess the synergistic capabilities of COL+MEM, and COL+TGC. Synergy was defined as a ≥ 2-log reduction CFU/mL in either combination from the most active single agent, while bactericidal activity was defined as a ≥ 3-log reduction CFU/mL of either combination from the initial inoculum.ResultsAll 50 strains were resistant to MEM and TGC with MICs ≥ 64 µg/mL and ≥ 4 µg/mL respectively; while 3 strains were resistant to COL, MICs ≥ 2 µg/mL. MEM and TGC MIC values were reduced as much as 128-fold (median 2-fold) and 32-fold (median 2-fold),, respectively, in the presence of subinhibitory COL. COL MIC values were reduced as much as 512-fold (median 4-fold) from baseline in the presence of subinhibitory MEM, and as high as 16-fold (median 2-fold) in the presence of TGC. In TKAs, COL+MEM was synergistic in 45/50 (90%) strains and bactericidal against 43/50 (86%) strains. COL+TGC TKAs revealed synergy in 32/50 (64%) strains, and bactericidal activity against 28/50 (56%) strains.ConclusionThe combinations of COL+MEM and COL+TGC demonstrate promise in combating highly resistant A. baumannii. Further research is mandated to explore other combinations that are capable of eradicating multi-drug-resistant A. baumannii.DisclosuresAll authors: No reported disclosures.

1281. An Evaluation of Tebipenem In Vitro Activity Against a Panel of Pseudomonas aeruginosa Isolates with Efflux, AmpC, and OprD Mutations

Background: Propolis consists of a complex mixture of resinous substances collected by honeybees from different plant sources. The objective of this study was to investigate the chemical composition, biological activities, and synergistic properties with antibiotics of propolis samples collected from various geographic origins (Germany, Ireland, and Czech Republic). Methods: The chemical composition of the propolis was analyzed by Gas Liquid Chromatography-Mass Spectrometry (GLC-MS) and High-performance liquid chromatography (HPLC). The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were evaluated by the standard broth microdilution method, while synergistic interactions were assessed by checkerboard dilution and time-kill curve assays. Results: HPLC and GLC-MS analyses revealed that ethanol extract of propolis (EEP) and water extracts of propolis (WEP) contained more than 100 different phytochemicals. The most abundant compounds were aromatic alcohols, aromatic acids, cinnamic acid and its esters, fatty acids, and flavanone (chrysin). Czech propolis showed the highest phenolic content (129.83 ± 5.9 mg CAE/g) followed by Irish propolis and German propolis. Furthermore, Irish propolis exhibited the highest value of total flavonoid content (2.86 ± 0.2 mg QE/g) and antioxidant activity (IC50 = 26.45 µg/mL). All propolis samples showed moderate antibacterial effect against Gram-positive microorganisms with MIC ranging from 0.08 mg/mL to 2.5 mg/mL. Moreover, EEP exhibited moderate activity against Gram-negative bacteria with MIC between 0.6 mg/mL to 5 mg/mL. In addition, EEP displayed moderate antifungal activity (MIC values between 0.6–2.5 mg/mL). The results obtained from time kill-kinetic assay and checkerboard dilution test of two-drug combinations between EEP and antibiotics such as vancomycin, oxacillin, and levofloxacin indicate mainly synergistic interactions against drug-resistant microbial pathogens including MRSA and VRE. Conclusions: The propolis extract synergistically enhanced the efficacy of antibiotics, especially those acting on cell wall synthesis (vancomycin and oxacillin) against drug-resistant microorganisms.

Trovafloxacin susceptibility was studied in aerobic clinical isolates of bacterial pathogens from 5 microbiology laboratories in Sweden. Trovafloxacin and ciprofloxacin minimum inhibitory concentration (MIC) determinations were performed on 474 clinical isolates. Disk diffusion tests using trovafloxacin and ciprofloxacin 10 microg disks were performed on a total of 7142 clinical isolates (trovafloxacin). Susceptibility interpretations for trovafloxacin and ciprofloxacin were determined from MIC values and disk diffusion tests using species-related MIC-limits and zone diameter breakpoints. Eight of 12 gram-positive species groups were fully susceptible to trovafloxacin as judged by MIC tests. Trovafloxacin gave MIC50 values of 0.032 mg/l for S. aureus, 1.0 mg/l for MRSA, 0.064 mg/l for coagulase negative staphylococci, 1.0 mg/l for MRSE, 0.064 mg/l for S. saprophyticus, 0.125 mg/l for group A and group B streptococci, 0.064 mg/l for group C and G streptococci and S. pneumoniae, 0.25 mg/l for E. faecalis, and 16.0 mg/l for E. faecium. These MIC values were 4-16-fold lower than those of ciprofloxacin. Both MIC and disk tests showed similar levels of susceptibility among gram-negative isolates for trovafloxacin and ciprofloxacin. For most gram-negative species the trovafloxacin MIC50 values were similar to or slightly higher than those for ciprofloxacin. Trovafloxacin MIC values were much lower for Acinetobacter strains, but higher for P. mirabilis compared with ciprofloxacin. The favourable susceptibility levels of Swedish aerobic pathogens to trovafloxacin emphasize the potential of this drug for the treatment of serious infections.

Multidrug-resistant bacterial pathogen P. aeruginosa has emerged as a significant global health challenge, underscoring the urgent need to identify and develop alternative therapeutic agents including plant natural products. In this study, the extract from Clidemia hirta plant extract was analyzed for antibacterial properties against Pseudomonas aeruginosa and component composition. The plant extract was obtained from leaves of C. hirta and its antibacterial activity against P. aeruginosa was determined in Kirby-Bauer disc diffusion assay. In this assay, the activity of the extract was tested at two different concentrations of 50 and 100μg/mL. The minimum inhibitory concentration (MIC) of the extract against P. aeruginosa was used with its MIC values against Vero cells to determine the selectivity index. GC-MS determined the phytochemical composition of the plant extract. The property of different extract components to bind the target receptor Penicillin Binding Protein 2a (7KIS) was assessed in silico studies including docking and molecular dynamics (MD) analyses. In these analyses, the stability and interaction dynamics of the Penicillin Binding Protein 2a (7KIS) protein complexed with selected extract components. The plant extracts had antibacterial activity against P. aeruginosa, with inhibition zones measuring 13mm and 19mm for 50 and 100μg/mL concentrations, respectively. The MIC of the plant extract was determined to be 20μg/mL, while its selectivity index was 4.54, indicating its antibiotic potential. One extract component, 2, 4-di-tert-butylphenol compound holds a binding affinity of -6.2kcal/mol in molecular docking studies. MD simulations revealed stable binding interactions between the 7KIS protein and the tested ligands, characterized by reduced atomic fluctuations and energetically favorable binding profiles. This study showed that C. hirta extract has a robust antibacterial potential against P. aeruginosa. Furthermore, GC-MS profiling molecular docking, and dynamic simulation data showed that such antibacterial potential might be attributed to its one component, 2, 4-di-tert-butylphenol. Further, in vivo and in vitro studies are needed to show the applicability of bioactive compounds from C. hirta in combating resistant bacterial pathogens.

Objectives: The aim of the study was to prepare a series of piperazine sulfonamide analogs (7a-l) and to perform in silico and in vitro antibacterial studies to determine their antibacterial activity. Methods: All the synthesized sulfonamides are characterized by different spectroscopic techniques. Further, the antibacterial screening results revealed that the synthesized sulfonamides exhibit good antibacterial activities. Results: Among the synthesized compounds, 7c and 7f displayed noteworthy antibacterial activity. The piperazine sulfonamide 7c exhibited superior inhibition of Enterobacter aerogenes and Bacillus subtilis pathogens with minimum inhibitory concentration (MIC) values of 81±0.78 and 49±1.02 μg/mL, respectively. The molecule 7f is most effective against E. aerogenes and B. subtilis with consecutive MIC’s of 86±0.58 μg/mL and 67±0.76 μg/mL. Moreover, the molecular docking studies were performed to comprehend the compounds binding interactions. Using in silico studies, the designed molecules were effectively screened as Escherichia coli deoxyribonucleic acid gyrase enzyme (PDB: 4BAE) inhibitors. The molecular docking studies for all the synthesized piperazine sulfonamide analogs (7a-l) were carried out using Maestro 11.2 and geometry optimized by Macro model program v9.1 (GLIDE, Schrodinger, LLC). In addition, to categorize the ligands accountable for the anti-bacterial activity, the molecular docking simulations were performed with software AutoDock Vina of PyRx and the Discovery studio. The obtained piperazine sulfonamide hybrids 7c and 7f gained superior molecular docking scores of −5.62 and −5.70, respectively. The structure activity relationships of the target sulfonamides were established. Conclusion: The in vitro antibacterial screening outcomes revealed that the molecules 7f and 7c showed potent anti-bacterial activity and good binding energy in docking analysis.

The World Health Organization notes that some bacteria have been demonstrated to possess significant public health risks; they have antibiotic resistance, and there are fewer alternatives for control. The n-hexane extract and cinaguaiacin obtained from Artemisia cina show promising antibacterial activity, including against multidrug-resistant bacteria that affect animal and human health. Objective: The aim of this study was to determine the antibacterial activity of the n-hexane extract of A. cina and cinaguaiacin against multidrug-resistant bacteria. Methods:A. cina was collected in the pre-flowering period, the n-hexane extract was obtained, and chromatographic techniques and structure were used to separate the lignans, which were elucidated with nuclear magnetic resonance techniques. Four ATCC strains were used, and four strains were isolated from clinical cases with different resistance profiles. The antibacterial activity was determined by calculating the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), the time-kill kinetics assay, and the cell membrane integrity and DNA release assay. Molecular docking studies of lignans demonstrated the binding mode involved in the active site of DNA gyrase B. Results: The n-hexane extract inhibited growth against 87.5% of the strains tested (MIC 5.31 to 42.5 mg/mL) and showed bactericidal activity against 25% of the strains tested (MBC 0.62 to 85 mg/mL). Cinaguaiacin inhibited growth against 100% of the strains tested (MIC, 0.56 to 2.25 mg/mL) and exhibited bactericidal activity against 25% of the strains tested (MBC, 0.62 to 85 mg/mL). Conclusions: The mechanism of cinaguaiacin’s action may be associated with damage to the plasma membrane, as the protein and DNA levels were higher than those of the positive control. The n-hexane extract and cinaguaiacin obtained from A. cina showed a bacteriostatic or bactericidal effect, depending on the strain evaluated.

The development of innovative antifungal medications to address the issues of indiscriminate antifungal use contributes to certain antifungal drug resistance. To tackle this issue, we have designed and synthesized novel amino acids naphthalene scaffolds ( 6 a – 6 i ) (Scheme 1) by acid amine coupling between compound 5 and various amino acids. Moreover, we evaluated the antifungal, anti‐bacterial and antimalarial activities of synthesized derivatives. Among them, compounds Met ( 6 a ), Phe ( 6 c ), Lys ( 6 d ), Ser ( 6 f ), and Tyr ( 6 i ) expressed excellent antifungal activity at a minimum inhibitory concentration (MIC) value of 250 μg/mL against Candida albicans compared to standard drug griseofulvin (500 μg/mL). The antibacterial assay results showed that compound Met ( 6 a ) exhibited effective antibacterial activity at MIC value at 50 and 62.5 μg/mL against Streptococcus pyogenes and Pseudomonas aeruginosa respectively, and compound Trp ( 6 g ) showed very good antibacterial activity at MIC 62.5 μg/mL against Staphylococcus aureus . The antimalarial activity of synthesized compoundsVal ( 6 b ) and Lys ( 6 d ) showed moderately active with mean IC 50 of 0.69 and 0.47 μg/mL, respectively compared with standard drug quinine (IC 50 =0.26 μg/mL). Also, a molecular docking study was performed to demonstrate the binding energy of synthesized scaffoldswith effective interaction with various proteins. The compound Met ( 6 a ) showed that the highest binding affinity (binding energy: −7.1 kcal/mol) which interacted more effectively with VAL 120 (2.90 Å).

Essential oils (EOs) from Citrus are not only economic, eco-friendly and natural alternatives to chemical preservatives but also have other biological applications. This study aimed to investigate the chemical composition of Citrus species (EOs from C. limonia, C. latifolia, C. sinensis and C. deliciosa fruit peel) to evaluate their in vitro antibacterial activity against Listeria monocytogenes, Yersinia enterocolitica, Staphylococcus aureus, Clostridium botulinum and Bacillus cereus. The chemotaxis model, which was used for evaluating their anti-inflammatory activity, showed that EOs exhibited effective results when the dose was 100 µg/mL. Regarding all antimicrobial activities, minimum inhibitory concentration (MIC) values of EOs were calculated by the broth microdilution method on 96-well microplates. EOs showed satisfactory antifungal activity against Malassezia furfur (MIC values between 32.5 and 62.5 µg/mL). Citrus deliciosa, whose MIC = 95.8 µg/mL, inhibited acetylcholinesterase (AChE) more selectively. All EOs from Citrus spp. fruit peel showed good antibacterial activity against Yersinia enterocolitica (MIC = 62.5 µg/mL) and Staphylococcus aureus (MIC = 62.5 µg/mL), mainly the EO from C. deliciosa whose MIC values were 50 µg/mL for both. EOs were moderately active against Clostridium botulinum, Bacillus cereus and Listeria monocytogenes since MIC values ranged from 100 μg/mL to 400 μg/mL. Both GC-FID and GC-MS analyses revealed that the single major constituent determined in EOs is the terpene limonene. EOs from Citrus may be important active ingredients of several products to prevent bacterial growth in food, to attack the fungus that causes seborrheic dermatitis and to treat inflammatory processes. In short, the promising antiacetylcholinesterase activity of EOs under evaluation was attributed to the high concentration of the monoterpene limonene

The goal of this research work was to prepare and evaluate the antitubercular (anti-TB) activity of ethionamide (ETH) and prothionamide (PTH) based coumarinyl-thiazole derivatives. ETH and PTH were reacted with coumarin intermediates (3a-3e) to provide the target compounds (4a-4e and 4f-4j, respectively). Spectral studies confirmed the assigned structures of 4a-4j. The Microplate Alamar Blue Assay was utilized to evaluate the anti-TB activity of compounds 4a-4j against Mycobacterium tuberculosis H37Rv strain in comparison to ETH, PTH, isoniazid (INH), and pyrazinamide (PYZ) as standard drugs. The cytotoxicity studies were carried out versus HepG2 and Vero cell lines. In addition. molecular docking studies of 4a-4j concerning the DprE1 enzyme and the in-silico evaluation of physicochemical and pharmacokinetic parameters were performed. Compounds 4a, 4b, 4f, and 4g displayed equal minimum inhibitory concentration (MIC) values in comparison to INH (3.125 μg/ml) and PYZ (3.125 μg/ml), whereas 4c-4e and 4h-4j displayed better MIC values (1.562 μg/mL) than INH and PYZ. All compounds presented better anti-TB potential than ETH (6.25 μg/mL) and PTH (6.25 μg/mL). The studies of toxicity revealed that 4a-4j were safe up to 300 μg/mL concentration versus Vero and HepG2 cell lines. The molecular docking studies suggested that 4a-4j could possess anti-TB activity through the inhibition of the DprE1 enzyme. The in silico studies showed that 4a-4j followed Lipinski's rule (drug-likeliness) and exhibited better gastrointestinal absorption than BTZ043 and macozinone. In conclusion, the ETH and PTH-based coumarinyl-thiazole template can help developing selective DprE1 enzyme inhibitors as potent anti-TB agents.

This study aimed to determine the antibacterial and antioxidant activities of the newly synthesized Schiff base and to support the laboratory results with molecular modeling studies. Antibacterial activity of schiff bases was demonstrated using Gram (-) Pseudomonas aeruginosa and Acinetobacter baumannii bacterial strains. Minimum Inhibition Concentration (MIC) values were determined to evaluate their antimicrobial activity against Gram-negative P. aeruginosa and A.baumanni bacterial strains. In antioxidant experiments, the responses to DPPH and ABTS radicals were calculated at certain concentration ranges and graphs were drawn. For the molecular modeling study, Autodock Vina and Discovery Studio 2020 package programs were used. The observed bacterial inhibition activity was variable depending on the clinical isolate and the concentration of the tested samples. The highest inhibition activity was achieved at concentration of 75 μl -100 μl. N,N'-(ethane-1,2-diyl)bis(1-(9H-fluoren-2-yl)methanimine) samples. Molecular docking results show that N,N'-(ethane-1,2-diyl)bis(1(9H-fluoren-2-yl) methanimine) binds strongly to the 4ZIY and 4ZHU structures. It has been proven by molecular docking study that the synthesized Schiff base ligand has antibiotic resistance properties. N, N'-(ethane-1,2-diyl)bis(1-(9Hfluoren-2-yl) methanimine) synthesis compound showed moderate activity against A. baumannii and P. aeruginosa strains. It is known that schiff bases have strong biological activities and show antibacterial activity. In this study, it can be said that the synthesis schiff base showed antibacterial and antioxidant activity. In addition, our results were supported by molecular modeling. Our findings can be taken to a higher level with in vivo and in vitro studies.

Novel 2-arylbenzothiazole DNA gyrase inhibitors: Synthesis, antimicrobial evaluation, QSAR and molecular docking studies

Background: The rise of multidrug-resistant (MDR) bacteria poses a significant challenge to global public health, contributing to increased morbidity and mortality rates. In this context, the repurposing of existing drugs has emerged as a promising strategy. In this study, hydralazine (HDZ), a vasodilator used as an antihypertensive since 1952, demonstrated antibacterial and antibiofilm activity against both Gram-positive and Gram-negative bacteria. Methods: In this study, the antibacterial activity of the antihypertensive hydralazine (HDZ) was evaluated against Gram-positive and Gram-negative strains through minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), growth curve with MIC and sub-MIC doses, combinatorial effect with gentamicin, scanning electron microscopy (SEM), molecular docking, and antibiofilm activity. Results: The MIC and MBC values ranged from 39.5 to 1.250 μg/mL, respectively. A change in the growth kinetics of the strains was observed when exposed to MIC and 1/2 MIC values, with a delay in the phases of up to 12 h. The combinatorial effect with gentamicin demonstrated an additive and indifferent potential when combined with HDZ. Conclusions: Furthermore, hydralazine showed antibiofilm activity against the tested strains, including MRSA. Electron microscopy analysis revealed significant changes in bacterial morphology when exposed to the MIC dose of HDZ for 4 h. The overall results of the study indicate hydralazine as a potential agent in the fight against bacterial infections.

One of the widely used microbiological methods to determine the toxicity of chemicals, catalysts, and other types of materials is the minimum inhibitory concentration (MIC) test. The present study aims to investigate the influence of composition of composite materials based on TiO2 and their particle size as well as bacterial type and shape based on the MIC values reported in the literature. The results show that among the 36 articles selected, most of the studies used Escherichia coli (E. coli) (26) and Staphylococcus aureus (S. aureus) (19) bacteria to determine MIC values. This study revealed that the MIC in values below 70 µg ml−1 for S. aureus was lower than that for E. coli bacteria (below 200 µg ml−1). Importantly, MIC value decreased from 60.6 to 7.66 µg ml−1 with decrease in the size of nanoparticles. It follows from the increased surface area for smaller-sized particles, thus increased interaction with bacteria during MIC test.

Introduction: Glucosamine-6-phosphate (GlcN6P) synthase biosynthetic pathway has been identified as potential targets for the development of new antimicrobial agents. Aim: A series of 2-chloro-N-(42-phenylthiazol-25-yl)acetamide derivatives (3a-r) was synthesized and evaluated their antimicrobial activity. Materials and Methods: The 2-chloro-N-(Para substituted phenylthiazol-25-yl) acetamide (2a-c) were synthesized by stirring intermediates (1a-c) with 2-chloroacetylchloride in dichloromethane in the presence of K2CO3. The intermediate (2a-c) were further reacted with different secondary amine such as pyrrolidine, N-methyl piperazine, N-ethyl piperazine, thiomorpholine, morpholine, piperidine etc in ethanol in presence of TEA Triethylamine (TEA) to get desired compounds (3a-r). Compounds were characterized by a spectroscopic technique such as Fourier transform infraredFTIR, 1 H-NMR, 13 C-NMR, and mass spectrometry. The synthesized thiazole derivatives (3a-r) were screened for anti-bacterial and anti-fungal activity against Escherichia coli, Staphylococcus aureus NCTC 6571, Pseudomonas aeruginosa NCTC 10662, CandidaC. albicans (MTCC-183), AspergillusA. niger (MTCC 281) NCTC 10418 and AspergillusA. flavus (MTCC 277). Result and Conclusion: The results of anti-bacterial screening revealed that among all the screened compounds, eight compounds viz. 3b, 3c, 3d, 3e, 3i, 3j, 3k, and 3p showed moderate to good anti-bacterial and antifungal activity having minimum inhibitory concentration (MIC) between 6.25- and 25 µg/ml. While compound 3d showed the most promising antibacterial activity against E. coli and S. aureus, while the compound 3j showed promising antifungal activity with MIC value 6.25 µg/ml against C. albicans, A. niger and A. flavus. In addition, all these eight potential molecules were also examined for possible binding on enzyme GlcN6Pglucosamine-6-phosphate synthase by molecular docking studies on (PDB ID 1JXA).