Minimum Inhibitory Concentration Values Research Articles

Antibacterial Activity of Clindamycin/BPO in Combination With Adapalene

Introduction: Acne guidelines recommend the addition of benzoyl peroxide (BPO) to antibiotics to reduce resistance in Cutibacterium acnes (C. acnes). Pairing the antibiotic/BPO combination with a retinoid, such as adapalene, may further increase treatment efficacy, although research on adapalene’s antibacterial activity is limited. To determine if adapalene improves antimicrobial activity, this in vitro study evaluated minimum inhibitory concentration (MIC) of clindamycin, adapalene, and BPO alone or in combination against both susceptible and resistant C. acnes isolates. Methods: Part 1a: C. acnes sensitivity to clindamycin, adapalene, or BPO was assessed via MIC values obtained by the broth microdilution method, with lower MIC indicating higher susceptibility. Part 1b: The effect (synergistic, additive, antagonistic, or indifferent [no interaction]) of combining adapalene with clindamycin or BPO on C. acnes inhibition was evaluated using a checkerboard assay, wherein two test compounds are combined in varying concentrations. Part 2: Susceptibility to single formulations of clindamycin, adapalene, and BPO, and fixed-dose combination formulations of an antibiotic (clindamycin or erythromycin) with BPO was determined by measuring antibacterial zone of inhibition using agar diffusion method, with larger diameter indicating increased bacterial inhibition. Results: Part 1a: Clindamycin demonstrated strain-dependent activity (MIC range: <0.125-64 μg/ml), while BPO and adapalene had no/low activity as indicated by high MIC (>512 and >64, respectively) against the 6 acne-associated strains tested. Part 1b: The combination of adapalene with clindamycin resulted in an additive effect for 3 and no interaction for 1 strain, whereas adapalene with BPO did not result in any interaction against the 4 acne-associated strains tested. Part 2: Activity of single formulations varied, with adapalene 0.1% having no activity (zone of inhibition: 0 cm) against any of the 8 acne-associated C. acnes strains tested. The fixed-dose combination formulations had generally similar activity against all strains tested (range: 0.9-5 cm). Conclusions: In these in vitro analyses, adapalene and BPO had no/low activity against C. acnes, whereas clindamycin alone or in combination formulations demonstrated strain-dependent activity. The relatively high MIC of BPO is not unexpected and aligns with previous studies in which the in vitro activity of BPO was low compared to its high in vivo antimicrobial activity. Further, addition of the retinoid adapalene had an additive effect on the antimicrobial activity of clindamycin against 3 out of 4 C. acnes strains tested, but no effect on the activity of BPO in vitro. Taken together, these data suggest that when combined with clindamycin/BPO, adapalene may enhance antimicrobial activity, while also bringing its own, unique retinoid mechanism of action to the triple combination, adding to clindamycin's bacteriostatic and anti-inflammatory properties. Funding: Ortho Dermatologics

Antibacterial, Antioxidant and Cytotoxicity Assessment of Crassocephalum crepidioides Leaf Extract

The goal of the present investigation was to demonstrate the antibacterial activity of different solvent extracts (methanol, ethanol, cold aqueous and hot aqueous) of Crassocephalum crepidioides against ATCC bacterial cultures of Staphylococcus aureus, Escherichia coli, Methicillin resistant Staphylococcus aureus, Pseudomonas aeruginosa and its antioxidant potential. Furthermore, the chemical constituents present in the extract was perused by Gas chromatography-mass spectroscopy (GC-MS), along with in vitro cytotoxicity assessment. All the extracts were shown to be sensitive against S. aureus, MRSA and P. aeruginosa except for the ethanolic extract which was resistant to P. aeruginosa. Of all the extracts, hot aqueous extract found to be the most effective. It was found that Minimum inhibitory concentration (MIC) value of hot aqueous extract against S. aureus, MRSA and P. aeruginosa were 5 mg/mL, 5 mg/mL and 40 mg/mL, respectively. DPPH results showed that C. crepidioides leaf extract has potent antioxidant activity with IC50 value of 57.9 µg/mL. 22 compounds were detected in hot aqueous extract through Gas chromatography-mass spectroscopy. The results of the cytotoxicity evaluation displayed that the IC50 value of the hot aqueous extract of C. crepidioides on Vero cell lines was 292 µg/mL. This study concludes that C. crepidioides leaf extract is non-toxic, has various bioactive components and strong antibacterial and antioxidant activities, thus making it a promising therapeutic agent for various biomedical applications.

Exploring the Antibacterial Properties and Chemical Profiles of Essential Oils from Syzygium aromaticum and Nigella sativa Against MDR Bacteria

For centuries, plants have been studied for their healing properties. Recently, the rise of antibiotic resistance in bacteria has prompted scientists to explore herbal remedies. Syzygium aromaticum, from the Myrtaceae family, has been utilized as a histological clearing agent. In contrast, Nigella sativa (black cumin), a member of the Ranunculaceae family, has long been utilized in traditional medicine dating back to ancient times. The current study investigates the chemical composition and antibacterial activity of essential oils from Syzygium aromaticum (clove) and Nigella sativa (black cumin) against multidrug-resistant (MDR) bacteria. Using the agar well diffusion method, Syzygium aromaticum exhibited significant antibacterial activity, particularly against Salmonella typhi (30.66 mm inhibition zone), while Nigella sativa was effective only against Staphylococcus aureus (19 mm). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for Syzygium aromaticum ranged from 3.53 to 7.06 mg/mL, indicating stronger antibacterial properties than Nigella sativa (MIC: 12.7 mg/mL, MBC: 22.5 mg/mL). GC-MS analysis revealed that Syzygium aromaticum contained bioactive compounds like Diglycolic acid (76.59%) and Eugenol (2.06%), while Nigella sativa was dominated by Heptasiloxane (80.83%) and Thymoquinone (2.66%). These findings suggest that Syzygium aromaticum essential oil could serve as a potent natural antimicrobial agent against MDR pathogens.

ANTIOXIDANT, INHIBITION OF ADVANCED GLYCATION END-PRODUCT FORMATION AND ANTIMICROBIAL ACTIVITIES OF OCIMUM GRATISSIMUM (SCENT LEAF) METHANOLIC LEAF EXTRACT AGAINST Escherichia coli AND Bacillus SPP

The study investigates the antioxidant, inhibition of advanced glycation end-product formation and antimicrobial activities of methanolic leaf extract of Ocimum gratissimum. GC-MS, qualitative, antioxidant scavenging and antiglycation activities of the extract of Ocimum gratissimum were determined using standard procedures. The antimicrobial activity was evaluated by agar well diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using standard methods. The GC-MS analysis of Ocimum gratissimum leaf revealed the presence of 49 compounds with P –cymene been the most abundant. The phytochemical screening of the extract shows the presence of alkaloids, tannins, phenolic, flavonoids, saponins etc. The in-vitro antioxidant assay of the extract was found to have ?-carotene, lycopene, total phenolic compounds, total flavonoid compounds, reducing power and DPPH scavenging activities. The extract showed significant inhibitory effects on the formation of compounds containing two carbonyl groups and Advanced Glycated End products formation with IC50 of 75.85 ±4.87 µg/mL. Agar well diffusion assay was characterized by inhibition zones of 21.0 ± 0.30, 19.66 ± 0.20, 33.78± 0.30 and 33.25 ± 0.40 mm for Escherichia coli and Bacillus spp respectively at 250 mg/ml for Ocimum gratissimum and 25 mg/ml for tetracycline solution. The MIC values for E.coli and Bacillus spp were 33.33, 66.67, 0.78 and 0.78 for both extract and tetracycline while their MBC values were 66.67, 133.00, 1.56 and 1.56 respectively. MBC/ MIC values showed that Ocimum gratissimum extract and tetracycline had bactericidal effects. These results indicated that Ocimum gratissimum possesses antioxidant, prevents glycation and has antimicrobial activities.

The antimicrobial and antibiofilm effects of gentamicin, imipenem, and fucoidan combinations against dual-species biofilms of Staphylococcus aureus and Acinetobacter baumannii isolated from diabetic foot ulcers.

Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia due to impaired insulin production or utilization, leading to severe health complications. Diabetic foot ulcers (DFUs) represent a major complication, often exacerbated by polymicrobial infections involving Staphylococcus aureus and Acinetobacter baumannii. These pathogens, notorious for their resistance to antibiotics, complicate treatment efforts, especially due to biofilm formation, which enhances bacterial survival and resistance. This study explores the synergistic effects of combining gentamicin, imipenem, and fucoidan, a sulfated polysaccharide with antimicrobial properties, against both planktonic and biofilm forms of S. aureus and A. baumannii. Isolates of S. aureus and A. baumannii were collected from DFUs and genetically confirmed. Methicillin resistance in S. aureus was identified through disk diffusion and PCR. Biofilm formation, including dual-species biofilms, was analyzed using the microtiter plate method. The antimicrobial efficacy of gentamicin, imipenem, and fucoidan was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC). Synergistic interactions were evaluated using the fractional inhibitory concentration index (FICi) and fractional bactericidal concentration index (FBCi). The expression of biofilm-associated genes (icaA in S. aureus and bap in A. baumannii) was analyzed, and the cytotoxicity of fucoidan was assessed. The study revealed that 77.4% of S. aureus and all A. baumannii isolates showed multidrug resistance. Among 837 tested conditions for dual-species biofilm formation, 72 resulted in strong biofilm formation and 67 in moderate biofilm formation. The geometric mean MIC values for gentamicin were 12.2µg/mL for S. aureus, 22.62µg/mL for A. baumannii, and 5.87µg/mL for their co-culture; for imipenem, they were 19.84, 9.18, and 3.70µg/mL, respectively, and for fucoidan, 48.50, 31.20, and 19.65µg/mL, respectively. The MBC values for gentamicin were 119.42, 128, and 11.75µg/mL; for imipenem, they were 48.50, 14.92, and 8µg/mL; and for fucoidan, they were 88.37, 62.62, and 42.48µg/mL. The MBIC values were 55.71, 119.42, and 18.66µg/mL for gentamicin; 68.59, 48.50, and 25.39µg/mL for imipenem; and 153.89, 101.49, and 53.53µg/mL for fucoidan. The MBEC values were 315.17, 362.03, and 59.25µg/mL for gentamicin; 207.93, 157.58, and 74.65µg/mL for imipenem; and 353.55, 189.46, and 99.19µg/mL for fucoidan. When cultured in planktonic form, the geometric mean FICi and FBCi values indicated additive effects, while co-culture showed FICi values of ≤ 0.5, suggesting a synergistic interaction. Treatment with gentamicin and fucoidan led to significant downregulation of the icaA and bap genes in both single-species and dual-species biofilms of S. aureus and A. baumannii. The reductions in gene expression were more pronounced in dual-species biofilms compared to single-species biofilms. Additionally, treatment with imipenem and fucoidan also resulted in significant downregulation of these genes in both biofilm types. Cytotoxicity assessments indicated that higher concentrations of fucoidan were toxic, yet no harmful effects were noted at the optimal synergistic concentrations used with antibiotics. In our investigation, we found that combining gentamicin, imipenem, and fucoidan had a synergistic effect on dual-species biofilms of S. aureus and A. baumannii, suggesting potential benefits for treating such infections effectively. This underscores the importance of understanding microbial interactions, antibiotic susceptibility, and biofilm formation in DFUs.

AdeABC, AdeFGH, and AdeIJK efflux pumps as key factors in tigecycline resistance of Acinetobacter baumannii: a study from Western Balkan hospitals.

The present study investigated the role of resistance-nodulation-cell division (RND) efflux pumps in tigecycline resistance of Acinetobacter baumannii clinical isolates recovered from three Western Balkan countries (Serbia, Bosnia and Herzegovina and Montenegro). A total of 37 A. baumannii isolates recovered from seven tertiary care hospitals in 2016 and 2022 were tested against tigecycline using broth microdilution method. Then, efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP) was used to determine the involvement of efflux pumps in tigecycline resistance. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE) and multiplex PCR-based determination of clonal lineage. Regulators of efflux pumps were analyzed for amino acid substitutions, while reverse transcription-quantitative PCR (RT-qPCR) enabled quantification of RND efflux pumps expression. All tested isolates were interpreted as resistant to tigecycline and showed reduced tigecycline minimum inhibitory concentration (MIC) values in the presence of CCCP. PFGE analysis showed significant diversity among isolates grouped in cluster I including IC2 (n = 32) and IC3 (n = 1) isolates, while cluster II was comprised of four IC1 isolates. The most prevalent substitutions in AdeR were V120I and A136V and in AdeS G186V and N268H (n = 33). The Q262R substitution was detected in AdeL proteins of IC1 isolates, whereas no alterations were observed within AdeN. The expression of the adeB, adeG, and adeJ genes in selected isolates was upregulated in five (1.16- to 3-fold), sixteen (1.35- to 2.82-fold), and twelve isolates (1.62- to 4-fold) compared to ATCC19606, respectively. This study revealed that overexpression of RND efflux pumps underlies tigecycline resistance in A. baumannii clinical isolates from the Western Balkans.

Enhancing Antibacterial Efficacy: Combining Novel Bacterial Topoisomerase Inhibitors with Efflux Pump Inhibitors and Other Agents Against Gram-Negative Bacteria

Background: The novel bacterial topoisomerase inhibitors (NBTIs) developed in our laboratory show potent on-target enzyme inhibition but suffer from low activity against Gram-negative bacteria. Methods: With the aim of improving the antibacterial activity of our compounds against Gram-negative bacteria, we tested them in combination with different efflux pump inhibitors (EPIs), a strategy that showed promise in several other classes of antimicrobials. We also investigated the combined effect of NBTIs with ATP-competitive inhibitors of bacterial type II topoisomerases (ACIs), as well as the antibiofilm properties of our compounds and the combination with EPIs against early and mature Acietobacter baumannii biofilm. Results: Our results demonstrate that combinations of NBTIs with EPI Phenylalanine-arginyl-β-naphthylamide significantly reduce the corresponding NBTIs’ minimal inhibitory concentration values and show potentiation of A. baumannii biofilm inhibition as compared to NBTIs alone. Although combinations of NBITs and ACIs did not show synergistic effects, the FIC index value calculations revealed additive effects for all the combinations of a selected NBTI in combination with three ACIs in all the assayed Gram-negative bacteria from the ESKAPE group. Conclusions: These results show for the first time that combinations of NBTIs with either EPIs or a different class of the topoisomerase inhibitors may be a beneficial strategy to combat difficult-to-treat bacterial infections.

Systematic screening of 42 vancomycin-resistant Enterococcus faecium strains for resistance, biofilm, and desiccation in simulated microgravity.

Vancomycin-resistant Enterococcus faecium (VRE) presents significant challenges in healthcare, particularly for hospitalized and immunocompromised patients, including astronauts with dysregulated immune function. We investigated 42 clinical E. faecium isolates in simulated microgravity (sim. µg) using a 2-D Clinostat, with standard gravity conditions (1 g) as a control. Isolates were tested against 22 antibiotics and characterized for biofilm formation and desiccation tolerance. Results showed varied responses in minimum inhibitory concentration (MIC) values for seven antibiotics after sim. µg exposure. Additionally, 55% of isolates showed a trend of increased biofilm production, and 59% improved desiccation tolerance. This investigation provides initial insights into E. faecium's changes in response to simulated spaceflight, revealing shifts in antibiotic resistance, biofilm formation, and desiccation tolerance. The observed adaptability emphasizes the need to further understand VRE's resilience to microgravity, which is crucial for preventing infections and ensuring crew health on future long-duration space missions.

Design, Synthesis, and Anti-Mycobacterial Evaluation of Triclosan-Isoniazid Hybrids.

A series of Triclosan-based hybrids and their Schiff base derivatives with isoniazid were designed through in silico modelling and synthesized using copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction. These compounds were then evaluated against both Mycobacterium tuberculosis (Mtb) and Mycobacterium abscessus (Mab). However, none of the synthesized hybrids exhibited significant growth inhibition, with minimum inhibitory concentration (MIC) values consistently exceeding 100 µg/mL. To further investigate these findings, we conducted mechanistic studies including thermogravimetric analysis (TGA) and UV-Vis stability tests. TGA demonstrated thermal stability of the Schiff bases up to 270 °C, while UV-Vis analysis confirmed their chemical resilience across a wide pH spectrum, showing resistance to hydrolysis under acidic and basic conditions. The lack of observed antimicrobial activity may be attributed to the high lipophilicity of these molecules, as indicated by LogP values exceeding 5, which could limit their bioavailability. These findings suggest that although combining triclosan and isoniazid holds potential, further optimization of this hybrid strategy is necessary to improve efficacy.

Development of novel reduced graphene oxide/metalloporphyrin nanocomposite with photocatalytic and antimicrobial activity for potential wastewater treatment and medical applications.

This research investigates a novel nanocomposite material composed of reduced graphene oxide (rGO) and nickel-5,15-bisdodecylporphyrin (Ni-BDP) nanoparticles for the effective removal of methyl orange (MO), a harmful synthetic dye, from water. The structure and composition of the synthesized rGO/Ni-BDP nanocomposite were characterized using high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and ultraviolet-visible (UV-Vis) spectroscopy. The study demonstrates the material's efficacy as both a catalyst and adsorbent for MO removal. Optimal performance was observed at pH 3.0, where the positively charged nanocomposite surface facilitated strong interactions with negatively charged MO molecules, leading to enhanced photocatalytic activity. Under these conditions, 0.01g of the nanocomposite achieved an impressive 86.2% MO removal efficiency. Furthermore, the study explored the reusability of the rGO/Ni-BDP nanocomposite in repeated cycles of photocatalytic MO degradation under visible light irradiation. While exhibiting some decrease in efficiency over five cycles, the nanocomposite maintained a respectable degradation rate even after multiple uses. Finally, the antimicrobial properties of the nanocomposite were evaluated against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria exhibiting a zone of inhibition measuring 23mm and 26, respectively. The minimum inhibitory concentration (MIC) values of 2.50µg/ml and 1.25µg/ml for Escherichia coli and Staphylococcus aureus, respectively. The results revealed significant antibacterial activity, demonstrating the broad-spectrum efficacy of the rGO/Ni-BDP nanocomposite. This research underscores the potential of the rGO/Ni-BDP nanocomposite as a versatile material for environmental remediation and antibacterial applications.

Antibacterial Effects of Silica Nanoparticles Loading Nano-silver and Chlorhexidine in Root Canals Infected by Enterococcus faecalis.

The persistence of microbial infection can lead to endodontic failure. Enterococcus faecalis (E. faecalis) is acknowledged to be a closely associated bacterium. This study investigated the antimicrobial effects of mesoporous silica nanoparticles (nMS) carrying nano-silver and chlorhexidine (nMS-nAg-Chx) on E. faecalis. Analyses were conducted to assess the antimicrobial efficacy of nMS-nAg-Chx towards planktonic E. faecalis, including the zone of inhibition, minimal inhibitory concentration (MIC), and growth curves. The measurement of lactic acid, scanning electron microscopy (SEM), live-dead bacteria staining, and quantitative real-time PCR (qRT-PCR) were done to further investigate its anti-biofilm effect. Colony forming unit (CFU) and SEM were used to assess its efficacy in infected root canals. The growth of planktonic E. faecalis was suppressed with a MIC value of 25 μg/mL (P＜0.05). nMS-nAg-Chx concentration-dependently inhibited biofilm formation of E. faecalis with the reduction of lactic acid (P < 0.05), sparse biofilm structure, reduced percentage of viable bacteria (P < 0.05), and suppressed expression of ebpR, gelE, ace, and efa genes (P < 0.05). The seven-day sealing of nMS-nAg-Chx resulted in a notable reduction in bacterial counts compared to the saline control group in the E. faecalis infected root canals (P < 0.05). NMS-nAg-Chx effectively inhibits E. faecalis and removes its biofilm from infected human root canals. It may be used for endodontic treatments in the control of E. faecalis bacteria as an intracanal medication.

Identification of IspD as a novel target for tuberculosis treatment using compound M6

IntroductionTuberculosis (TB) is a serious infectious disease that endangers human health, and TB becomes more difficult in eradiation due to its multidrug resistance (MDR). The objective of this research was to identify novel targets for treating TB.MethodsA 2-fold serial dilution method was used to determine minimal inhibitory concentrations (MIC) of compound M6 against Mycobacterium smegmatis (M. smegmatis). Compound M6 was subjected to reverse molecular docking with seven Mycobacterium tuberculosis proteins, and the best binding protein with the highest LibDock score was evaluated. The target protein with the highest score was purified through prokaryotic expression. Isolated target proteins were investigated for the enzyme activities and for the kinetic effect of compound M6 by absorbance detection. Subsequently, the CRISPR/Cas9 technology was employed to inhibit target gene expression for detecting MIC changes. Finally, potential targets were evaluated for the effect of the compound M6 in bacteria.ResultsThe MIC values of compound M6 against M. smegmatis were 32 μg/mL. The results from reverse molecular docking show that IspD has the highest LibDock score of 142.50, followed by Rv0674, IspF, and Dxr, with docking scores of 110.762, 71.6955, and 57.7446, respectively. IspD is a key enzyme in the 2-C-methyl-D-erythritol 4-phosphate pathway of MTB. The aKi and Ki values of M6 for the substrate MEP are 609.58 μM and 81.33 μM. For CTP, the aKi and Ki values are 657.89 μM and 40.07 μM. With tetracycline inducing CRISPR/Cas9 to suppress the expression of IspD, the MIC value of M6 against IspD went down significantly from 32 μg/mL to 4 μg/mL.ConclusionIspD is a novel target of the compound M6 for treating TB.

Doxifluridine effectively kills antibiotic-resistant Staphylococcus aureus in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality globally, often exacerbated by infections such as methicillin-resistant Staphylococcus aureus (MRSA). The rise in antibiotic-resistant strains complicates treatment and underscores the need for novel therapeutic drugs. In this paper, we further investigated the antimicrobial potential of a fluoropyrimidine anticancer drug doxifluridine against multidrug-resistant S. aureus. Determination of minimum inhibitory concentration (MIC) or minimum bactericidal concentration (MBC), monitoring of growth curve, time-kill assays, biofilm bactericidal assays, and chequerboard studies were conducted to evaluate the antibacterial efficacy of doxifluridine. Safety was assessed via hemolysis and cytotoxicity assays, and an in vivo Galleria mellonella larvae model was employed to test protective effects. Doxifluridine demonstrated significant antibacterial activity against clinical multidrug resistance (MDR) S. aureus isolates, with MIC and MBC values ranging from 0.5 to 2 µg/mL and 1 to 4 µg/mL, respectively. The results revealed doxifluridine's potent bactericidal effects within 8 hours. Moreover, doxifluridine-treated bacteria showed a substantial reduction in biofilm mass and viability. Furthermore, chequerboard assays indicated synergistic interactions between doxifluridine and other antibiotics, reducing MIC values by two- to eightfold. More importantly, safety evaluations confirmed that doxifluridine did not exhibit hemolytic toxicity or cytotoxicity. Finally, doxifluridine significantly increased the survival rate of MRSA-infected G. mellonella larvae in vivo. In brief, doxifluridine exhibited promising in vitro and in vivo antibacterial activity against MRSA, suggesting its potential as a repurposed drug for treating resistant bacterial infections in COPD patients.IMPORTANCEThe study provides robust evidence for the antibacterial efficacy of doxifluridine against Methicillin-resistant Staphylococcus aureus in chronic obstructive pulmonary disease (COPD) patients. Its rapid action, ability to disrupt biofilms, and synergistic effects with other antibiotics, combined with a favorable safety profile, highlight its potential as a repurposed therapeutic agent. Future clinical trials will be essential to confirm these findings and pave the way for its integration into clinical practice. This work not only provides candidate for tackling the management of bacterial infections in COPD but also exemplifies the potential of drug repurposing in combating antibiotic-resistant infections.

Photodynamic inactivation strategies for maximizing antifungal effect against Sporothrix spp. and Candida albicans in an in vitro investigation.

Sporotrichosis is a zoonotic disease caused by the dimorphic fungus Sporothrix spp., leading to skin lesions that can, in some cases, progress and result in the death of infected individuals. Candida albicans is another fungus involved in several skin, oral, and vaginal mucosal infections. Fungal diseases are concerning due to increasing incidence and the limited variety of antifungal classes available for treatment. Furthermore, antifungal medications can cause various side effects, exacerbated by their prolonged use during infection treatment. There is a need to explore alternatives to conventional drugs that are effective, fast, and safe in combating sporotrichosis. This study aimed to achieve in vitro elimination of the fungi Sporothrix brasiliensis and Sporothrix schenckii through Photodynamic Inactivation (PDI), using curcumin as a photosensitizer and in combination with antifungal agents used in the treatment of sporotrichosis. Yeasts of Candida albicans, Sporothrix brasiliensis, and Sporothrix schenckii were subjected to Photodynamic Inactivation (PDI) using light at a wavelength of 450 ± 10 nm, irradiance of 35 mW/cm2, delivering a fluence of 31.5 J/cm2, with curcumin as the photosensitizer at doses ranging from 0.75 to 150 μg/mL. After determining the Minimum Inhibitory Concentration (MIC) values of the antifungal drugs itraconazole, ketoconazole, and potassium iodide, sub-MIC doses of these antifungals were combined with sub-MIC doses of curcumin in a new PDI session. Photodynamic inactivation is a promising technique in the treatment of sporotrichosis, as well as its combination with antifungals. The combination of curcumin in concentrations ranging from 0.75 g/mL a 7.5 g/mL with sub-MIC concentrations of itraconazole, ketoconazole, and potassium iodide was able to completely inactivate the fungi C. albicans, S. brasiliensis and S. schenckii, indicating that PDI may increase the effectiveness of antifungals. However, further studies are needed to establish protocols for future clinical applications.

The in vitro Study of the Synergistic Antibacterial Effect of Hydroalcoholic Mentha Extract with Alum on the Growth of Streptococcus mutans

: Antimicrobial resistance poses a significant global health challenge, necessitating the search for novel therapeutic approaches. Streptococcus mutans, a key etiological agent in dental caries, requires innovative strategies due to its biofilm-forming ability and resistance to conventional antibiotics. Natural plant-derived compounds have garnered attention as potential antimicrobial agents with a low risk of resistance development. In this study, we investigated the synergistic antibacterial effect of a hydroalcoholic Mentha extract combined with alum against Streptococcus mutans (PTCC 16836). The well diffusion assay demonstrated that alum exhibited a larger inhibition zone diameter (12.04 ± 2.02 mm) compared to the hydroalcoholic Mentha extract (10.33 ± 1.53 mm). However, the minimum inhibitory concentration (MIC) values for the hydroalcoholic Mentha extract (8.20 ± 5.57 mg/mL) and alum (0.35 ± 0.20 mg/mL) were comparable. The minimum bactericidal concentration (MBC) for the hydroalcoholic Mentha extract was 10 mg/mL, while the MBC for alum was 0.625 ± 0.006 mg/mL. The combination of these substances demonstrated a synergistic effect, indicating enhanced antibacterial activity against Streptococcus mutans. The study's findings suggest potential applications in dentistry, offering a natural and effective adjunctive treatment for dental caries management. The underlying mechanisms of this synergistic effect warrant further exploration. To translate these promising findings into clinical applications, further in vivo investigations and rigorously designed clinical trials are necessary to establish the safety and efficacy of this combination therapy. The natural origin of these substances may provide an environmentally sustainable and cost-effective approach in the fight against antimicrobial resistance.

Pyrazole Amides Towards Trailblazing Antimicrobial Research: Bridging in Vivo Insights and Molecular Docking Studies

Antimicrobial resistance presents a significant threat to contemporary healthcare systems, making it increasingly difficult to treat infections that were once easily managed. This study aims to assess the efficacy of pyrazole benzamide derivatives (M5a–M5o), which were synthesized for their antimicrobial and antifungal activities. These compounds were tested against methicillin resistant staphylococcus aureus (MRSA), vancomycin resistant staphylococcus aureus (VRSA), mycobacterium tuberculosis H37Rv and other resistant species. The minimum inhibitory concentrations (MIC) were determined using standardized protocols to evaluate their potency and effectiveness. Molecular docking studies were also conducted to explore potential interactions and binding affinities at the molecular level, providing further insights into their antimicrobial and anti-tubercular mechanisms. Compounds M5i, M5k, and M5b emerged as the most potent, displaying MIC value of 3.12 μg/ml. These compounds show great potential as new agents in addressing the growing problem of antimicrobial resistance. Molecular docking studies against Enoyl-[acyl-carrier-protein] reductase (4DRE), revealed key interactions, with compound M5n showing a docking energy of -9.8 kcal/mol and compound M5g at -9.6 kcal/mol. These compounds formed important hydrogen bonds and π-interactions with residues like Lys165, Gly14, Ser94, and Ile21. Overall, the findings indicate that specific pyrazole-benzamide derivatives exhibit promising antimicrobial and antifungal activities, underscoring their potential as therapeutic agents. Additionally, the integration of molecular docking studies proves valuable in guiding the development and optimization of these compounds for future therapeutic applications.

Development of Cyclometalated Iridium(III) Complexes of 2-Phenylbenzimidazole and Bipyridine Ligands for Selective Elimination of Gram-Positive Bacteria.

Herein, we have reported a series of cationic aggregation-induced emission (AIE) active iridium(III) complexes (Ir1-Ir5) of the type [Ir(C^N)2(N^N)]Cl, wherein C^N is a cyclometalating 2-phenylbenzimidazole ligand with varying alkyl chain lengths and N^N is a 2,2'-bipyridine ligand attached to bis-polyethylene glycol chains, for the treatment of bacterial infections. The AIE phenomenon of the complexes leveraged for detecting bacteria by fluorescence microscopy imaging that displayed a strong red emission in Gram-positive bacteria. The antibacterial activity of the complexes assessed against Gram-positive methicillin-sensitive S. aureus, methicillin-resistant S. aureus, E.faecium and E.faecalis and Gram-negative E. coli and P.aeruginosa bacteria of clinical interest. The complexes Ir2-Ir4 exerted potent antibacterial activity towards Gram-positive strains with low minimum inhibitory concentrations (MICs) values in the range of 1-9 μM, which is comparable to clinically approved antibiotic vancomycin. In contrast, these complexes were found to be inactive towards Gram-negative bacterial strains (MICs > 100 µM). The mechanism of antibacterial activity of the complexes implies that ROS generation, membrane depolarization and rupture are responsible for bacterial cell death. Further, the complexes Ir1-Ir3 were found to be low-toxic against human red blood cells and human embryonic kidney (HEK293) cells, indicating their potential for use as antibacterial agents.

Dual role of ramR mutation in enhancing immune activation and elevating eravacycline resistance in Klebsiella pneumoniae

AbstractThe rise of Klebsiella pneumoniae resistant to last‐resort antimicrobials poses an urgent threat to global health. The ramR‐ramA regulatory system critically influences drug resistance by regulating the AcrAB‐TolC efflux pump, which also plays a crucial role in the pathogenicity of K. pneumoniae. However, the mechanism of the ramR‐ramA system on bacteria‐host interaction remains unclear. To determine how specific mutations in ramR influence eravacycline (ERV) resistance and their impact on the immune activation capabilities of K. pneumoniae, thereby highlighting potential targets for therapeutic intervention, we performed genetic sequencing to identify mutations in ramR. Then, the CRISPR‐Cas9 technology was employed to construct specific ramR mutations into K. pneumoniae, which were then subjected to phenotypic and functional assays in both in vitro and in vivo (mouse models, macrophage, and blood‐killing experiment) settings. ramR L58P and F165L genetic alterations disrupt the binding affinity of RamR to the ramA promoter, thereby upregulating the efflux pump expression and increasing ERV minimum inhibitory concentration values up to 64‐fold compared to the wild‐type. Concurrently, these mutations modulate lipid A structure by increasing 2‐hydroxy fatty acid chain abundance. In mouse models, ramR L58P and F165L mutants showed lower bacterial burden in organs (spleen, lung, and kidney) 6 h post‐infection, and are fast cleared in 48 h. Furthermore, despite lower intracellular bacterial loads, ramR L58P and F165L mutants induce heightened pro‐inflammatory cytokine responses in macrophages and elevate systemic cytokine levels (interleukin [IL]2, IL4, IL6, IL12, interferon‐α, and interferon‐γ) in human blood co‐culture experiments. This study illuminates the critical role of ramR mutations in conferring ERV resistance and enhancing immune responses in K. pneumoniae. The dual impact of these mutations on both antimicrobial resistance and immune activation not only underscores the challenges in treating infections but also advocates for heightened surveillance and innovative strategies to counteract the emerging threat of antimicrobial‐resistant K. pneumoniae.

Synthesis of antibiofilm (1R,4S)-(-)-fenchone derivatives to control Pseudomonas syringae pv. tomato.

Biofilm plays a crucial role in Pseudomonas syringae pv. tomato (Pst) infection. We identified (1R,4S)-(-)-fenchone (FCH) as the most potent antibiofilm agent against Pst among 39 essential oil compounds. Subsequently, we synthesized a series of FCH oxime ester and acylhydrazine derivatives to explore more potent derivatives. II3 was screened out as the most potent derivative, exhibiting a minimal biofilm inhibitory concentration of 60 μg mL-1 and a lowest concentration with maximal biofilm inhibition (LCMBI) of 200 μg mL-1, lower than those of FCH (80 and 500 μg mL-1, respectively). II3 and FCH showed minimum inhibitory concentration values >1000 μg mL-1 and similar maximal biofilm inhibition extents of 48.7% and 49.5% at their respective LCMBIs, respectively. Meanwhile, neither of them influenced cell viability or the activity of metabolic enzymes at their respective LCMBIs. II3 at its LCMBI significantly reduced biofilm thickness, extracellular polysaccharide content, and pectinase and cellulase production indices. In vivo assay results indicated that II3 could preventatively reduce the bacterial contents in tomato leaves at its LCMBI, and when combined with kasugamycin (KSG) (10 μg mL-1), II3 achieved the same level of bacterial reduction as the sole application of KSG (70 μg mL-1), thereby reducing the required dosage of KSG. Mechanistic studies demonstrated that II3 can down-regulate biofilm-related genes and inhibit PsyR/PsyI quorum sensing system, which differs from the bactericidal mechanisms. These results underscore the potential of II3 as an antibiofilm agent for the control of Pst or FCH as a promising natural candidate for future in-depth optimization. © 2024 Society of Chemical Industry.

Potent Antimicrobial Azoles: Synthesis, In Vitro and In Silico Study

Background/Objectives: The increase in fungal infections, both systemic and invasive, is a major source of morbidity and mortality, particularly among immunocompromised people such as cancer patients and organ transplant recipients. Because of their strong therapeutic activity and excellent safety profiles, azole antifungals are currently the most extensively used systemic antifungal drugs. Antibacterial properties of various topical antifungals, such as oxiconazole, which features oxime ether functionality, were discovered, indicating an exciting prospect in antimicrobial chemotherapy. Methods: In this study, eleven new oxime ether derivatives with the azole scaffold (5a–k) were synthesized and tested for their antimicrobial effects using the microdilution method to obtain broad-spectrum hits. Results: Although the title compounds showed limited efficacy against Candida species, they proved highly effective against dermatophytes. Compounds 5c and 5h were the most potent derivatives against Trichophyton mentagrophytes and Arthroderma quadrifidum, with minimum inhibitory concentration (MIC) values lower than those of the reference drug, griseofulvin. The MIC of 5c and 5h were 0.491 μg/mL and 0.619 μg/mL against T. mentagrophytes (MIC of griseofulvin: 2.52 μg/mL). The compounds were also tested against Gram-positive and Gram-negative bacteria. Briefly, 5c was the most active against Escherichia coli and Bacillus subtilis, with MIC values much better than that of ciprofloxacin (MIC of 5c = 1.56 μg/mL and 1.23 μg/mL, MIC of ciprofloxacin = 31.49 and 125.99 μg/mL, respectively). Molecular docking suggested a good fit in the active site of fungal lanosterol 14α-demethylase (CYP51) and bacterial FtsZ (Filamenting temperature-sensitive mutant Z) protein. Conclusions: As a result, the title compounds emerged as promising entities with broad antifungal and antibacterial effects, highlighting the utility of oxime ether function in the azole scaffold.