Trans-Cinnamaldehyde-Driven Silver Nanoparticles: Dual Role in Targeting Biofilm Disruption and Control of Biofilm‑Forming Pathogens via Impairing Ferrous Ion Uptake

Jellein-I-conjugated gold nanoparticles: Insights into the antibacterial, antibiofilm activities against MRSA, and anticancer properties

Synergistic effect of curcumin-Cu and curcumin-Ag nanoparticle loaded niosome: Enhanced antibacterial and anti-biofilm activities

Background and objectivesKlebsiella pneumoniae is a multidrug-resistant pathogen implicated in severe community- and hospital-acquired infections such as bacteremia, urinary tract infections, sepsis, and pneumonia. Biofilm formation, driven by extracellular polymeric substances (EPS), enhances its persistence and resistance to antibiotics. This study evaluated the anti-biofilm, antibacterial, and quorum-quenching activities of a novel α-amylase B. cereus-derived α-amylase against clinical isolates of K. pneumoniae. MethodsThe anti-biofilm activity of the enzyme was assessed via minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC) assays. Biofilm architecture and viability were analyzed using confocal laser scanning microscopy (CLSM) with live/dead staining. Antibacterial efficacy was determined through minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Quorum-quenching effects were evaluated using qRT-PCR to assess the expression of biofilm-associated genes (fimH and mrkD), normalized to rpoB.ResultsB. cereus-derived α-amylase exhibited MBIC and MBEC values of 64 µg/ml and 128 µg/ml, respectively; MIC and MBC ranged from 32 to 128 µg/ml. The B. cereus-derived α-amylase enzyme inhibited biofilm formation by approximately 79% ± 0.69, compared to 58% ± 2.06 by commercial α-amylase. Biofilm thickness was reduced from 179 μm to ~ 39 μm and ~ 73 μm following treatment with B. cereus-derived and commercial α-amylase, respectively. Live/dead ratios shifted significantly from 97/3% (untreated) to ~ 54/46% and 73/27% after treatment with B. cereus-derived and commercial α-amylase enzymes, respectively. Quorum-sensing gene expression was markedly downregulated following treatment with ½ MIC of B. cereus-derived α-amylase: fimH to 0.247 ± 0.045 (75.3% reduction) and mrkD to 0.187 ± 0.035 (81.3% reduction).ConclusionB. cereus-derived α-amylase exhibited potent anti-biofilm, antibacterial, and quorum-quenching activities against K. pneumoniae clinical isolates. These findings highlight its potential as a novel therapeutic agent for managing biofilm-associated infections, either alone or as an adjunct to conventional treatments.

Introduction: The primary aetiology of chronic periapical abscesses, including E. faecalis, S. mutans, S. sanguinis, and P. gingivalis, can be eliminated using intracanal medicaments such as calcium hydroxide. The purpose of this study was to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) value of calcium hydroxide paste in the vulnerable initial 7-day of treatment against E. faecalis ATCC 29212, S. mutans ATCC 25175, S. sanguinis ATCC 10556, and P. gingivalis ATCC 33277. Methods: An in-vitro laboratory experiment using a spectrophotometer as a microdilution method was conducted to determine bacteria's MIC and MBC values on calcium hydroxide paste. The sample used in this study was four bacteria using intracanal medicament of calcium hydroxide (Ca(OH)2), incubated for seven days at 37°C, and then bacterial growth was observed. The cell inhibition percentage was calculated using optical density measurements to determine the MIC value. The low MIC and MBC were defined as sensitive bacteria to calcium hydroxide. Results: Calcium hydroxide paste against E. faecalis (ATCC 29212) with MIC values at a concentration of 750 μg/ml and MBC values at a concentration of 96,000 μg ml; S. mutans (ATCC 25175) with MIC value at a concentration of 3,000 ug/ml and MBC value at a concentration of 48,000 ug/ml; S. sanguinis (ATCC 10556) with MIC value at a concentration of 3,000 ug/ml and MBC value at a concentration of 6,000 ug/ml; P. gingivalis (ATCC 33277) with MIC value at a concentration of 6,000 ug/ml and MBC value at a concentration of 48,000 ug ml. Conclusions: Calcium hydroxide can inhibit bacterial growth activity. E. faecalis (ATCC 29212) and S. sanguinis (ATCC 10556) are more sensitive to calcium hydroxide paste than other bacteria, with the lowest MIC and MBC on seven days of incubation since the maximum calcium and hydroxyl ions are released.

Swietenia macrophylla is known to possess several medicinal uses, however, its antibacterial and antibiofilm activities against foodborne pathogens remain not well investigated. The present work was performed to examine the phytochemical compounds, antibacterial and antibiofilm activities of S. macrophylla ethanolic extract (SMEE) against four foodborne pathogens namely, Salmonella typhimurium ATCC 14028, Escherichia coli ATCC 25922, Shigella sonnei ATCC 33862 and Pseudomonas aeruginosa ATCC 10145. The phytochemical analysis of SMEE was performed using gas chromatography-mass spectrometry while the antibacterial activities of SMEE were determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. On the other hand, the antibiofilm and time-killing activities of SMME were evaluated using a crystal violet assay. The result demonstrated that SMEE contained major phytochemical compounds such as olean-12-ene (27.37%), resorcinol (16.45%), 24-noroleana-3,12-diene (13.4%), and germanicol (11.50%). The MIC values of SMEE ranged from 31.25 to 500 µg/mL, while all the MBC values were found to be greater than 1000 µg/mL. At the 12 h exposure to SMEE, all the biofilms were inhibited by 50% except E. coli. Biofilm inhibitory concentration (BIC50) values of SMEE ranged between 5.19 and 42.47 µg/mL. In conclusion, S. macrophylla is a promising source of natural antibacterial and antibiofilm agents to treat foodborne diseases.

BackgroundConventional antibacterial compounds can inhibit the growth of microorganisms, but their adverse effects and the development of drug limit their widespread use. The current study aimed to synthesize PEG-coated UIO-66-NH2 nanoparticles loaded with vancomycin and amikacin (VAN/AMK-UIO-66-NH2@PEG) and evaluate their antibacterial and anti-biofilm activities against vancomycin-resistant Staphylococcus aureus (VRSA) clinical isolates.MethodsThe VAN/AMK-UIO-66-NH2@PEG were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) to determine their size, polydispersity index (PDI), encapsulation efficiency (EE%), zeta-potential, drug release profile, and physical stability. Antibacterial activity was evaluated using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill assays. Biofilm formation by VRSA was assessed using the crystal violet (CV) and minimum biofilm eradication concentration (MBEC) assays. The effect of sub-MIC concentrations of the formulations on the expression of biofilm-related genes (icaA, icaD) and resistance-related genes (mecA, vanA) was investigated using quantitative real-time polymerase chain reaction (RT-qPCR).ResultsAs demonstrated by MIC, MBC and time-kill assay, the VAN/AMK-UIO-66-NH2@PEG nanoparticles exhibited enhanced antibacterial activity against VRSA isolates compared to free drugs and prepared formulations. Furthermore, CV and MBEC tests indicated that the VAN/AMK-UIO-66@NH2/PEG can reduce biofilm formation dramatically compared to VAN/AMK and VAN/AMK-UIO-66@NH2, due to its great drug release properties. This study also found that the expression level of the mecA, vanA, icaA, and icaD genes in VAN/AMK-UIO-66@NH2/PEG treated VRSA isolates was substantially decreased compared to other groups.ConclusionsThese findings highlighted the efficiency of VAN/AMK-UIO-66@NH2/PEG in combating antimicrobial resistance and biofilm formation in VRSA isolates. Future studies, particularly in vivo models, are necessary to evaluate the safety, efficacy, and clinical applicability of these nanoparticles for the treatment of bacterial infections.

To evaluate the effects of herbal extracts derived from plants commonly prescribed by traditional practitioners for the treatment of typhoid fever. A cross sectional study. Departments of Life Sciences and Chemistry, University of Buea, Cameroon. Methanol extracts of plant parts commonly used in Cameroon for the treatment of typhoid fever. Antimicrobial activity was tested using the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) assays. Methanol extracts of plant parts commonly used in Cameroon for the treatment of typhoid fever were tested for antibacterial activity against Salmonella typhi, S. paratyphi and S. typhimurium. The formulations used were: 1) Formulation A comprising Cymbogogon citratus leaves, Carica papaya leaves, and Zea mays silk. 2) Formulation B comprising C. papaya roots, Mangifera indica leaves, Citrus limon fruit and C. citratus leaves. 3) C. papaya leaves. 4) Emilia coccinea whole plant. 5) Comelina bengalensis leaves. 6) Telfaria occidentalis leaves. 7) Gossypium arboreum whole plant. Antimicrobial activity was tested using the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) assays. Generally, Formulation A elicited inhibitory activity at a lower range of 0.02 to 0.06 mg/ml. Similarly, Formulation B elicited bacterial activity at the lowest range of 0.06 to 0.25 mg/ml. C. bengalensis leaves on the other hand, showed the lowest activity with a concentration range of 0.132 to 2.0 mg/ml and 1 to 4 mg/ml in MIC and MBC assays respectively. S. paratyphi was most sensitive to the formulations (concentration range of 0.02 to 1 mg/ml in both MIC and MBC assays) while S. typhimurium was the least sensitive and concentrations of up to 4 mg/ml were required to be bactericidal. It is concluded that plant extracts with low MIC and MBC values (1 mg/ml and lower) may contain compounds with therapeutic activity.

Background: Antimicrobial resistance (AMR) has become precarious, warranting investments in antimicrobial discovery. Aim: To investigate the antibacterial activity of rosemary essential oil (REO), alone and in combination with selected conventional antibiotics. Methods: REO was subjected to antimicrobial susceptibility testing (including minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) determination) and investigation of anti-pre-biofilm and antibiofilm activities. Results: The phytochemical composition of the REO was eucalyptol (42.68%), bornanone (33.20%), endo-borneol (9.37%), α-terpeneol (7.95%), linalool (2.10%), bornyl acetate (1.81%), caryophyllene (1.09%), 4-terpeneol (0.94%), and anethole (0.87%). The antibacterial inhibition zones generally increased with increasing REO concentration (i.e., 10, 20, 50, 100, and 200 mg/mL). The MIC and MBC ranges of REO for all bacteria were 3.13-6.25 mg/mL and 3.12-12.5 mg/mL, respectively. The MICs (in µg/mL) of ciprofloxacin, chloramphenicol, streptomycin, tetracycline, and ampicillin, respectively, were Escherichia coli (0.98, 3.92, 1.96, 7.81, and 250), Klebsiella pneumoniae (1.25, 7.81, 125, 7.81, and 1000), MRSA (62.5, 7.81, 3.91, 7.81, and 250), Streptococcus mutans and Bacillus subtilis (125, 15.68, 250, 31.25, and 1000), Pseudomonas aeruginosa (125, 31.25, 500, 31.25, and 1000), and Salmonella Typhi (0.98, 15.68, 125, 1.96, and 1000). The MBC-MIC ratios of REO against all bacteria were in the range 1-2, indicating bactericidal effects. Mainly synergy (FICI = 0.16-0.37) was observed between REO and the conventional antibiotics. The IC50 values (in µg/mL) of REO against the bacteria, pre-biofilm vs. biofilm formation, were E. coli (1342.00 vs. 4.00), K. pneumoniae (106.00 vs. 3.00), MRSA (134.00 vs. 6.00), S. mutans (7259.00 vs. 7.00), B. subtilis (120.00 vs. 7.00), P. aeruginosa (4989.00 vs. 7.00), and S. Typhi (10.00 vs. 2.00). Conclusions: Rosemary essential oil had significant bactericidal effects on the bacteria tested, and its MIC and MBC values were low. Overall, it was synergistic with known conventional antibiotics and, thus, has encouraging prospects in combination therapy involving conventional antibiotics, even in the treatment of infections with multidrug-resistant bacteria, including biofilm-forming ones.

The effect of sulphur on the antibacterial properties of succinic acid-Cu(II) and mercaptosuccinic acid-Cu(II) MOFs

Background and Aim:Staphylococcus pseudintermedius is an opportunistic zoonotic pathogen frequently implicated in skin and wound infections in companion animals. Its ability to form biofilms complicates treatment by increasing antibiotic resistance. Rhodomyrtone, a potent acylphloroglucinol isolated from Rhodomyrtus tomentosa, exhibits promising antibacterial activity against Gram-positive bacteria. This study aimed to develop rhodomyrtone-rich fractions and evaluate their antibacterial and antibiofilm activities against S. pseudintermedius.Materials and Methods:Ethanolic extracts of R. tomentosa leaves were subjected to acetone partitioning followed by quick column chromatography, yielding fractions F1–F15. Fractions F3–F7 were selected based on thin-layer chromatography and 1H nuclear magnetic resonance for rhodomyrtone content and quantified by high-performance liquid chromatography. Antibacterial activity against Staphylococcus aureus American Type Culture Collection (ATCC) 25923, S. pseudintermedius ATCC 49444, and 10 clinical S. pseudintermedius isolates was assessed using broth microdilution to determine minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values. Fraction F4, with the highest rhodomyrtone content, was further investigated using time-kill kinetics, scanning electron microscopy (SEM), and a crystal violet assay for biofilm inhibition.Results:Fraction F4 contained the highest rhodomyrtone concentration (489.08 mg/g) and demonstrated the most potent antibacterial activity, with MIC and MBC values ranging from 0.5 to 2 µg/mL and 2 to 8 µg/mL, respectively, against clinical isolates. The time-kill study revealed a 4-log reduction (99.99%) in bacterial load within 8 h at 2× MIC. Biofilm formation by all tested S. pseudintermedius isolates was significantly inhibited at sub-MIC concentrations of F4 (p < 0.05). SEM analysis showed notable morphological disruptions in bacterial cells treated with F4, suggesting membrane damage as a possible mechanism of action.Conclusion:Fraction F4 from R. tomentosa leaf extract exhibited strong antibacterial and antibiofilm activity against S. pseudintermedius, comparable to that of pure rhodomyrtone and superior to doxycycline. These findings support the potential use of rhodomyrtone-rich fractions as standardized herbal antibacterial agents in veterinary medicine, providing an effective alternative for treating drug-resistant staphylococcal infections.

The increasing incidence of hospital-acquired infections caused by multi-drug resistant pathogens, such as Acinetobacter baumannii, coupled with the low efficacy of drugs and rising treatment costs has created interest in the potential antimicrobial properties of natural products. The main objective of this work was to determine the effect of coriander essential oil on Acinetobacter baumannii in different growth phases, as well as its ability to inhibit the formation or eradication of biofilms. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of coriander oil using a microdilution broth susceptibility assay was determined. The effects of different concentrations of coriander oil (ranging from 0.125 to 4×MIC) on biofilm formation and on established biofilm were tested using 96-well microtiter plates. Crystal violet assay was used as indicator of total biofilm biomass and the biofilm viability was assessed with a XTT staining method. It was found that coriander oil presented significant antibacterial activity against all tested strains of A. baumannii, with MIC values between 1 and 4 μL/mL. The MBC values were the same as the MIC, being an indicator of the bactericidal activity of this essential oil. In what concerns the effect of this essential oil on biofilm formation inhibition was observed of at least 85% of biomass formation by all A. baumannii strains using 2×MIC of coriander oil, in addition to a decrease in the metabolic activity of the cells. After exposure to coriander oil, a decrease in 24 h and 48 h-old biofilm biomass and metabolism was seen for all tested concentrations, even with sub-inhibitory concentrations. Coriander essential oil proved to have a significant antibacterial and anti-biofilm activity and should be considered in the development of future disinfectants to control A. baumannii dissemination.

Environmental resistance is an important factor for understanding the epidemiology of leptospirosis. Recently, new Leptospira hosts were identified, including also marine mammals. Moreover, halotolerant Leptospira strain, isolated from the environment and animals, highlighted the capability of this microorganism to persist in the seawater. The aim of this research was to investigate the bacteriostatic and bactericidal effect of salt on Leptospira strains belonging to 16 different serovars. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were verified through the microdilutions method starting from a 20% sodium chloride concentration. MIC values obtained were between 0.3125% and 10% of salt, while MBC values between 0.625% and >20%. Icterohaemorrhagiae (MIC: 0.3125%; MBC: 0.625%) resulted the most inhibited serovar, while the most resistant was Tarassovi (MIC: 10%; MBC: >20%). Interestingly, trends were reported for Pomona (MIC: 1.25%; MBC: >20%) and Bratislava (MIC: 0.625%; MBC: 20%), highlighting low MIC values but high MBC values. This is the first investigation aimed at the in vitro effect of salt on the growth of Leptospira spp. reference strains.

Antimicrobial resistance (AMR) presents a global challenge as microorganisms evolve to withstand the effects of antibiotics. In addition, the improper use of antibiotics significantly contributes to the AMR acceleration. Essential oils have garnered attention for their antimicrobial potential. Indeed, essential oils extracted from plants contain compounds that exhibit antibacterial activity, including against resistant microorganisms. Hence, this study aimed to evaluate the antimicrobial and antibiofilm activity of the essential oil (EO) extracted from Lippia grata and its combination with ampicillin against Staphylococcus aureus strains (ATCC 25923, ATCC 700698, and JKD6008). The plant material (leaves) was gathered in Mossoro, RN, and the EO was obtained using the hydrodistillation method with the Clevenger apparatus. The antimicrobial activity of the EO was assessed through minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Antibiofilm activity was evaluated by measuring biomass using crystal violet (CV) staining, viable cell counting, and analysis of preformed biofilms. In addition, the synergistic effects of the EO in combination with ampicillin were examined by scanning electron and confocal microscopy. The EO displayed a MIC value of 2.5mg/mL against all tested S. aureus strains and an MBC only against S. aureus JKD6008 at 2.5mg/mL. L. grata EO caused complete biofilm inhibition at concentrations ranging from 10 to 0.312mg/mL against S. aureus ATCC 25923 and 10 to 1.25mg/mL against S. aureus ATCC 700698 and S. aureus JKD6008. In the viable cell quantification assay, there was a reduction in CFU ranging from 1.0 to 8.0 logs. The combination of EO with ampicillin exhibited a synergistic effect against all strains. Moreover, the combination showed a significantly inhibiting biofilm formation and eradicating preformed biofilms. Furthermore, the EO and ampicillin (individually and in combination) altered the cellular morphology of S. aureus cells. Regarding the mechanism, the results revealed that L. grata EO increased membrane permeability and caused significant membrane damage. Concerning the synergy mechanism, the results revealed that the combination of EO and ampicillin increases membrane permeability and causes considerable membrane damage, further inhibiting bacteria synergistically. The findings obtained here suggest that L. grata EO in combination with ampicillin could be a viable treatment option against S. aureus infections, including MRSA strain.

Risks for development of local and/or systemic infections are the most important complications of catheters that are widely used during hospitalization process. The aims of this study were to investigate and compare the antibiotic susceptibilities of methicillin-resistant staphylococci isolated from catheters, in planktonic and biofilm forms, and to evaluate the antimicrobial effects of antibiotics on those forms alone and in combinations. A total of 30 strains [15 methicillin-resistant Staphylococcus aureus (MRSA) and 15 methicillin-resistant coagulase-negative staphylococci (MR-CNS)] isolated from catheter cultures of patients hospitalized in different clinics and intensive care units in Baskent University Medical School Hospital between 2006-2009, were included in the study. The antibiotic sensitivities of MRSA and MR-CNS isolates were investigated in vitro in planktonic phase and on sessile cells after biofilm was formed. Vancomycin, ciprofloxacin, rifampicin, gentamicin, meropenem, tigecycline, linezolid, ceftazidime and cephazolin were used for antibiotic susceptibility testing. The sensitivity of planktonic cells to antibiotics was primarily investigated, so that minimal inhibitor concentration (MIC) and minimal bactericidal concentration (MBC) values were determined by broth microdilution method. Afterwards, each strain was transformed to sessile cell in a biofilm environment, and MIC and MBC values were also determined for sessile cells. Double and triple antibiotic combinations were prepared, the effectiveness of combinations were studied on both planktonic and biofilm cells with multiple-combination bactericidal testing (MCBT) method. The data set obtained from planktonic and biofilm cells for each antibiotic analyzed via two proportion z test. Statistically significant decreases were found in the sensitivities of sessile cells when compared to planktonic cells (p< 0.01). The tests performed with the use of double and triple antibiotic combinations also showed the susceptibility decrease between planktonic and biofilm forms to be significant in most of the combinations (p< 0.01). The comparison of double and triple antibiotic combinations against planktonic and sessile cells as determined by the inhibition of more than 90% of the strains, revealed no significant difference . Vancomycin and tigecycline were the most effective antibiotics for all isolates in planktonic and sessile cells. Combinations containing vancomycin and rifampicin showed the best activity both double and triple antibiotic combinations against biofilm. In conclusion, our data indicated that combination therapy, especially double combinations of antibiotics seem to be a rational approach for biofilm-related infections.

Purpose This study aimed to evaluate the antimicrobial efficacy of fluoride-free mouthwashes against Scardovia wiggsiae, a key bacterium associated with fluoride-resistant dental caries. The investigation focused on bacterial growth inhibition, planktonic cell viability, and biofilm formation. Methods Twelve commercially available fluoride-free mouthwashes with various active ingredients, including hydrogen peroxide, cetylpyridinium chloride (CPC), essential oils, and organic extracts, were tested. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays were conducted to determine bacterial growth inhibition and killing potential. Planktonic cell viability and biofilm formation assays were performed at three dilutions (1:3, 1:6, and 1:12) using a 16-h culture of S. wiggsiae. Optical density (OD) values were measured at 595 nm for planktonic cells and 490 nm for biofilms. Results Significant variability was observed in bacterial inhibition among mouthwashes. Hydrogen peroxide- and CPC-based formulations demonstrated the strongest antimicrobial activity, significantly reducing bacterial growth, planktonic viability, and biofilm formation. Essential oil-based formulations exhibited moderate antimicrobial effects, with reduced efficacy at higher dilutions. Organic-based mouthwashes showed limited inhibition, while formulations containing zinc chloride and stabilised chlorine dioxide demonstrated the weakest effects. Conclusion Hydrogen peroxide- and CPC-containing mouthwashes exhibited the highest antimicrobial potential against S. wiggsiae and may serve as effective fluoride-free alternatives for high-risk populations. Essential oil-based formulations provided moderate benefits, whereas zinc chloride and chlorine dioxide showed minimal efficacy. These findings underscore the importance of selecting appropriate antimicrobial agents for biofilm control and caries prevention. Further in vivo studies are necessary to validate long-term effectiveness in clinical settings.