Antimicrobial Activity Research Articles

Comparative in vitro efficacy of antibiotics against the intracellular reservoir of Staphylococcus aureus.

We assessed antimicrobial activity at phagolysosome-mimicking pH, intracellular penetration, and SA eradication within KCs in vitro for clinically prescribed antistaphylococcal agents alone or in combination: vancomycin, daptomycin, ceftaroline, ceftobiprole, oritavancin, oxacillin, cefazolin; rifampin and fosfomycin. pH-adjusted broth microdilution assays, intracellular bioaccumulation assays, and intracellular killing assays against clinical bloodstream isolates were performed using a murine KC line with study agents. Rifampin and β-lactams exhibited enhanced activity [2- to 16-fold minimum inhibitory concentrations (MIC) decrease] at phagolysosomal pH while vancomycin, oritavancin, daptomycin and fosfomycin demonstrated reduced activity (2- to 32-fold MIC increase in order of least to greatest potency reduction). All agents evaluated had poor to modest intracellular to extracellular concentration ratios (0.024-7.8), with exceptions of rifampin and oritavancin (intracellular to extracellular ratios of 17.4 and 78.2, respectively). Finally, we showed that the first-line treatment for SA bacteraemia (SAB), vancomycin, performed worse than all other tested antibiotics in eradicating intracellular SA at human Cmax concentration (0.20 log cfu decrease), while oritavancin performed better than all other agents alone (2.05 versus 1.06-1.36 log cfu decrease). Our findings raise concerns about the efficacy of commonly prescribed antibiotics against intracellular SA reservoirs and emphasize the need to consider targeting pathogen eradication from the liver to achieve early control of SAB.

Effects of different washing and precipitating solutions on sugar content, cytotoxicity, chemical structure and prebiotic potential of pistachio hull polysaccharide

Pistachio hull contains water-soluble polysaccharides with prebiotic potential. In polysaccharide extraction, ethanol is commonly used to remove impurities and precipitate polysaccharides. This study compared the efficiency and safety of different washing and precipitating materials to identify a cost-effective method to produce polysaccharides. The extracted polysaccharides were ethanol washed and ethanol precipitated (EWEP), methanol washed and methanol precipitated (MWMP), chemical washed and ethanol precipitated (CWEP), and chemical washed and methanol precipitated (CWMP). Bases on our results, using chemical compounds in washing stage led to a 50 % decrease in the amount of extracted polysaccharide. The FT-IR analysis results, probiotic stimulation growth, and cytotoxicity assay showed no difference between the MWMP and EWEP polysaccharides (p > 0.05). The residual methanol, microstructure morphology, monosaccharide composition and antimicrobial activity of MWMP polysaccharide were also measured. We indicated that methanol is a safe, efficient and cost-effective agent for removing impurities and precipitating water-soluble polysaccharides. Further studies are required to explore the physical, chemical and functional characteristics of MWMP polysaccharide.

Green synthesis of copper and iron nanoparticles from extracts of eucalyptus with their antimicrobial activities

Green synthesis of copper and iron nanoparticles from extracts of eucalyptus with their antimicrobial activities

In vitro antifungal activity analysis of Streptomyces sp. strain 196 against Candida albicans and Aspergillus flavus.

Numerous bioactive compounds have been reported to be produced by the members of the genus Streptomyces. During our previous studies, Streptomyces sp. strain 196 was tested for its antimicrobial activity, and bioactive compounds produced by this strain were characterized LC-MS and 1H NMR. To examine the antifungal potential of strain 196 is the goal of the current investigation. Present investigation is focused on exploring antifungal activity of extract of strain 196 (196EA) on membrane disruption potential against two fungi Candida albicans ATCC 90028 and Aspergillus flavus ITCC 5599. Results revealed that the MIC value is higher for A. flavus than for C. albicans which is 450µg/mL and 250µg/mL, respectively. Disc diffusion and spot assay also correspond to the values of the MIC for their respective pathogen. In growth curve analysis, lag and log phase are significantly affected by the extract of strain 196. The effects of extract from strain 196 on plasma membrane disruption of Candida albicans and Aspergillus flavus were analyzed in terms of ergosterol quantification assay, cellular leakage, proton efflux measurement (PM-ATPase), plasma membrane integrity assay (PI), and DNA damage assay (DAPI). Results shown that the extract of strain 196 has the potential to inhibit the cell membrane of the both pathogenic fungi which was further confirmed with the help of scanning electron microscopic (SEM) studies.

In-situ growth of Ag nanoparticles embedded in chitosan coating for potent antimicrobial activity

Developing highly antimicrobial coatings is an important strategy to control the risk of pathogen colonization and biofilm formation, especially in indwelling and implantable medical devices. This work presents a facile and practical approach to preparing potent antimicrobial coatings based on the chitosan-silver composite. The synthesis is conducted by simply stirring a chitosan (CS) solution with different amounts of silver (Ag) at room temperature, and the composite is applied as a coating on a polystyrene (PS) surface. In-situ reduction of Ag+ ions to metallic Ag (Ago) during the coating process leads to silver nanoparticles (AgNPs) forming into Ag rods half-embedded into the chitosan film and half-exposed on the coating surface. This distinctive structure promotes effective antibacterial action through the Ag+ release and photocatalytic activity of AgNPs. The coatings exhibit potent antimicrobial activity with 99.89% efficiency against Escherichia coli after 90minutes and 100% against Staphylococcus epidermidis after 30minutes under LED light irradiation. These coatings also display high stability with an insignificant decrease in the antibacterial activity after three times of reutilization. The newly synthesized formulations can be considered a promising alternative for antimicrobial coatings to avoid biofilm formation and for coating materials with various applications, especially in the biomedical field.

Construction and Performance Study of a Dual-Network Hydrogel Dressing Mimicking Skin Pore Drainage for Photothermal Exudate Removal and On-Demand Dissolution.

In recent years, negative pressure wound dressings have garnered widespread attentions. However, it is challenging to drain the accumulated fluid under negative pressures for hydrogel dressings. To address this issue, this study prepared a chemical/physical duel-network PEG-CMCS/AG/MXene hydrogel composed by chemical disulfide crosslinked network of four-arm polyethylene glycol/carboxymethyl chitosan (4-Arm-PEG-SH/CMCS), and the physical network of hydrogen bond of agar (AG). Under near-infrared light (NIR) irradiation, the PEG-CMCS/AG/MXene hydrogel undergoes photothermal heating due to integrate of MXene, which destructs the hydrogen bond network and allows the removal of exudate through a mechanism mimicking the sweat gland-like effect of skin pores. The photothermal heating effect also enables the antimicrobial activity to prevent wound infections. The excellent electrical conductivity of PEG-CMCS/AG/MXene can promote cell proliferation under the external electrical stimulation (ES) in vitro. The animal experiments of full-thickness skin defect model further demonstrate its ability to accelerate wound healing. The conversion between thioester and thiol achieved with L-cysteine methyl ester hydrochloride (L-CME) can provides the on-demand dissolution of the dressing in situ. This study holds promises to provide a novel solution to the issue of fluid accumulations under hydrogel dressings and offers new approaches to alleviating or avoiding the significant secondary injuries caused by frequent dressing changes.

Anti-bacterial cyclic dipeptides from Hormonema dematioides, an endophytic fungus of Juniperus communis

Hormonema sp., an endophytic fungi found in the medicinal plant of Juniperus communis leaves, was reported to possess antimicrobial compounds from its unidentified species. In this study, 21 cyclic dipeptides (1–21) were isolated and identified from H. dematioides. All the 21 isolated cyclic dipeptides were reported for the first time from the genus Hormonema. The antimicrobial activity by the disc diffusion method showed that five compounds including cyclo(Pro-Gly) (9), cyclo(Phe-Ile) (11), cyclo(Ile-Val) (12), cyclo(Val-Ala) (17), and cyclo(Ala-Phe) (20) inhibited the growth of Staphylococcus aureus with inhibition zone diameters ranging from 12 to 30 mm. Further bioassay demonstrated that four cyclic dipeptides (9, 12, 17, and 20) showed significant antibacterial activity against S. aureus with MIC values of 0.04, 0.39, 0.01, and 0.10 µg/mL, respectively, as compared to the positive control (ciprofloxacin, MIC = 0.08 µg/mL). However, none of these cyclic dipeptides showed obvious anti-fungal activity against Candida albicans.

Molecular characterization and multifunctional evaluation of lactic acid bacteria isolated from traditional sourdough

The primary objective of this study was to characterize lactic acid bacteria (LAB) strains derived from sourdough for possible utilization as functional starters to produce sourdough and various cereal-based fermented foods. A total of 350 autochthonous LAB strains were isolated from 65 Type I sourdough samples and characterized using six random amplified polymorphic DNA (RAPD) primers at intra- and interspecific levels. Species identification of selected strains representing distinct clusters from RAPD analysis was performed based on the 16S rRNA region. The LAB strains were identified as Companilactobacillus crustorum (n = 135), Levilactobacillus brevis (n = 125), Latilactobacillus curvatus (n = 40), Companilactobacillus paralimentarius (n = 32), and Lactiplantibacillus plantarum (n = 18). A total of 66 LAB strains were selected for technological characterization along with two commercial strains. The characterization involved acidity development, EPS production potential, leavening activity, and growth abilities under harsh conditions. Principle component analysis (PCA) identified 2 Lp. plantarum and 14 Lev. brevis strains as the most relevant technologically. Among them, Lp. plantarum L35.1 and Lev. brevis L37.1 were resistant to tetracycline. Evaluation of probiotic characteristics (survival in pH 2.5 and bile presence, auto aggregation capacity, hydrophobic activity, antioxidant activity, antimicrobial activity) by PCA identified four strains with relevance to Lactobacillus rhamnosus GG (LGG), which were further selected for in vitro digestion assays. Lactiplantibacillus plantarum L7.8, Lev. brevis L55.1, and L62.2 demonstrated similar viability indices to LGG, along with increased auto aggregation capacity and antioxidant activity. These strains are promising as candidate starters for producing sourdough and sourdough-related fermented food products.

Diversity and potential functional role of phyllosphere-associated actinomycetota isolated from cupuassu (Theobroma grandiflorum) leaves: implications for ecosystem dynamics and plant defense strategies.

Exploring the intricate relationships between plants and their resident microorganisms is crucial not only for developing new methods to improve disease resistance and crop yields but also for understanding their co-evolutionary dynamics. Our research delves into the role of the phyllosphere-associated microbiome, especially Actinomycetota species, in enhancing pathogen resistance in Theobroma grandiflorum, or cupuassu, an agriculturally valuable Amazonian fruit tree vulnerable to witches' broom disease caused by Moniliophthora perniciosa. While breeding resistant cupuassu genotypes is a possible solution, the capacity of the Actinomycetota phylum to produce beneficial metabolites offers an alternative approach yet to be explored in this context. Utilizing advanced long-read sequencing and metagenomic analysis, we examined Actinomycetota from the phyllosphere of a disease-resistant cupuassu genotype, identifying 11 Metagenome-Assembled Genomes across eight genera. Our comparative genomic analysis uncovered 54 Biosynthetic Gene Clusters related to antitumor, antimicrobial, and plant growth-promoting activities, alongside cutinases and type VII secretion system-associated genes. These results indicate the potential of phyllosphere-associated Actinomycetota in cupuassu for inducing resistance or antagonism against pathogens. By integrating our genomic discoveries with the existing knowledge of cupuassu's defense mechanisms, we developed a model hypothesizing the synergistic or antagonistic interactions between plant and identified Actinomycetota during plant-pathogen interactions. This model offers a framework for understanding the intricate dynamics of microbial influence on plant health. In conclusion, this study underscores the significance of the phyllosphere microbiome, particularly Actinomycetota, in the broader context of harnessing microbial interactions for plant health. These findings offer valuable insights for enhancing agricultural productivity and sustainability.

Synthesis, biological properties, drug-likeness, In silico ADME studies and theoretical studies on 1,3,2λ5-diazaphosphinane derivatives: A DFT investigation

Under various reaction conditions, Tetraphosphorus decasulphide P4S10 and Lawesson's reagent LR interacted with 2-cyano-N-[(2-hydroxyphenyl) methylidene] acetohydrazide (1) to synthesize a new 1,3,2λ5-diazaphosphinane derivatives 2–4. The three novel compounds 2−4 have been synthesized and characterized by elemental and spectral analyses (UV–Vis, FT-IR, MS, and 1H–NMR) throughout the current inquiry. The ground state energies, harmonic vibrational wavenumbers, and ground state geometries of the investigated compounds 2−4 were optimized by applying the density functional theory (DFT) at the B3LYP level, utilizing 6–311++G (d, p) basis sets. The first principal study has been investigated for the electronic properties, molecular electrostatic potentials, and quantum chemical identities. There was a noticeable shift in intramolecular charge from the occupied to the empty molecular orbitals. Time-dependent density functional theory (TD-DFT) and the CAM-B3LYP/6–311++G (d, p) function was used to conduct the UV–Vis analysis. A few bacterial and fungal strains were used to test the antimicrobial activities. The stability of the molecule resulting from hyper conjugative interactions that cause its nonlinear optical activity and charge delocalization was investigated using a natural bond orbital approach. The Mullikan atomic charge and molecular electrostatic potential are also anticipated. The value of the HOMO-LUMO energy gap indicates the possibility of charge transfer within the molecule. Compound 4 is the most reactive, with an energy difference between the border orbital of ΔEgap = 2.97 eV, according to analysis of the global descriptors. In addition, compared to the other 2 and 3 compounds under study, compound 4 is the softest, least stable, and has the largest electronic exchange capacity. Examined the structure-activity relationship using DFT calculations (SAR) and compared the findings with real-world antimicrobial outcomes for compounds 2–4. Also, Drug-likeness and In silico ADME studies were performed.

Ferredoxin: a novel antimicrobial peptide derived from the black scraper (Thamnaconus modestus)

Ferredoxin (FDX) is a highly conserved iron-sulfur protein that participates in redox reactions and plays an important role as an electron transport protein in biological processes. However, its function in marine fish remains unclear. We identified two ferrodoxin proteins, FDX1 and FDX2, from black scraper (Thamnaconus modestus) to confirm their genetic structures and expression profiles and to investigate their antimicrobial activity properties by fabricating them with antimicrobial peptides based on sequences. The two TmFDXs mRNAs were most abundant in peripheral blood leukocytes of healthy T. modestus. After artificial infection with Vibrio anguillarum, a major pathogen of T. modestus, TmFDX1 mRNA was significantly upregulated in the gills, heart, intestines, kidneys, liver, and spleen, but was consistently downregulated in the brain. The expression levels of TmFDX2 mRNA were significantly upregulated in the heart, intestines, kidneys, liver, and spleen; however, no significant changes in expression were observed in the brain or gills. Based on the 2Fe-2S ferredoxin-type iron-sulfur-binding domain sequence, two peptides (pFDX1 and pFDX2) were synthesized. The bactericidal effect, biofilm formation inhibition, and gDNA-binding activity of these peptides were investigated. These findings highlight the potential as a natural peptide candidate for TmFDXs.

Sustained-release, antibacterial, adhesive gelatin composite hydrogel with AgNPs double-capped with curdlan derivatives

In this work, carboxymethylated curdlan (CMCD) was utilized as a capping and stabilizing agent for the green synthesis of silver nanoparticles. Subsequently, quaternized curdlan (QCD) was introduced as the second capping layer through electrostatic attraction, leading to the preparation of double-capped silver nanoparticles (AgNPs@CQ). The successful synthesis of silver nanoparticles was characterized using UV–vis, FTIR, XRD, TEM, and DLS. AgNPs@CQ were incorporated into gelatin and a AgNPs@CQ/Gel composite hydrogel was obtained. The incorporation of AgNPs@CQ imparts excellent antibacterial properties to the composite hydrogel, thereby enhancing its antimicrobial efficacy. The presence of double-capping layers significantly retards the release rate of silver, contributing to prolonged antimicrobial activity. The MTT and live/dead fluorescence staining results demonstrate that the gelatin hydrogel incorporating double-capped AgNPs exhibits enhanced cell viability compared to the one incorporating single-capped AgNPs. Additionally, the composite hydrogel exhibits remarkable mechanical strength and adhesive performance. The AgNPs@CQ/Gel composite hydrogel demonstrates a cost-effective and facile preparation, showing significant potential in the field of dressings.

Advancements of Porphyrin-Derived Nanomaterials for Antibacterial Photodynamic Therapy and Biofilm Eradication.

The threat posed by antibiotic-resistant bacteria and the challenge of biofilm formation has highlighted the inadequacies of conventional antibacterial therapies, leading to increased interest in antibacterial photodynamic therapy (aPDT) in recent years. This approach offers advantages such as minimal invasiveness, low systemic toxicity, and notable effectiveness against drug-resistant bacterial strains. Porphyrins and their derivatives, known for their high molar extinction coefficients and singlet oxygen quantum yields, have emerged as crucial photosensitizers in aPDT. However, their practical application is hindered by challenges such as poor water solubility and aggregation-induced quenching. To address these limitations, extensive research has focused on the development of porphyrin-based nanomaterials for aPDT, enhancing the efficacy of photodynamic sterilization and broadening the range of antimicrobial activity. This review provides an overview of various porphyrin-based nanomaterials utilized in aPDT and biofilm eradication in recent years, including porphyrin-loaded inorganic nanoparticles, porphyrin-based polymer assemblies, supramolecular assemblies, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Additionally, insights into the prospects of aPDT is offered, highlighting its potential for practical implementation.

A bacteriocin expression platform for targeting pathogenic bacterial species

Bacteriocins are antimicrobial peptides that are naturally produced by many bacteria. They hold great potential in the fight against antibiotic resistant bacteria, including ESKAPE pathogens. Engineered live biotherapeutic products (eLBPs) that secrete bacteriocins can be created to deliver targeted bacteriocin production. Here we develop a modular bacteriocin secretion platform that can be used to express and secrete multiple bacteriocins from non-pathogenic Escherichia coli host strains. As a proof of concept we create Enterocin A (EntA) and Enterocin B (EntB) secreting strains that show strong antimicrobial activity against Enterococcus faecalis and Enterococcus faecium in vitro, and characterise this activity in both solid culture and liquid co-culture. We then develop a Lotka-Volterra model that can be used to capture the interactions of these competitor strains. We show that simultaneous exposure to EntA and EntB can delay Enterococcus growth. Our system has the potential to be used as an eLBP to secrete additional bacteriocins for the targeted killing of pathogenic bacteria.

Enhancement of lemongrass essential oil physicochemical properties and antibacterial activity by encapsulation in zein-caseinate nanocomposite

Essential oils (EOs) represent a pivotal source for developing potent antimicrobial drugs. However, EOs have seldom found their way to the pharmaceutical market due to their instability and low bioavailability. Nanoencapsulation is an auspicious strategy that may circumvent these limitations. In the current study, lemongrass essential oil (LGO) was encapsulated in zein-sodium caseinate nanoparticles (Z-NaCAS NPs). The fabricated nanocomposite was characterized using dynamic light scattering, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and transmission electron microscopy. The antimicrobial activity of LGO loaded NPs was assessed in comparison to free LGO against Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli, and Klebsiella pneumoniae. Furthermore, their antibacterial mechanism was examined by alkaline phosphatase, lactate dehydrogenase, bacterial DNA and protein assays, and scanning electron microscopy. Results confirmed the successful encapsulation of LGO with particle size of 243 nm, zeta potential of – 32 mV, and encapsulation efficiency of 84.7%. Additionally, the encapsulated LGO showed an enhanced thermal stability and a sustained release pattern. Furthermore, LGO loaded NPs exhibited substantial antibacterial activity, with a significant 2 to 4 fold increase in cell wall permeability and intracellular enzymes leakage versus free LGO. Accordingly, nanoencapsulation in Z-NaCAS NPs improved LGO physicochemical and antimicrobial properties, expanding their scope of pharmaceutical applications.

Quantification of nisin concentration from fluorescence-based antimicrobial activity assay using Bayesian calibration.

Bacteriocins are ribosomally synthesized peptides with the innate ability to kill or inhibit growth of other bacteria. In recent years, bacteriocins have received increased interest, as their antimicrobial activity enhances food safety and shelf life by combatting pathogens such as Listeria monocytogenes. They also have application potential as an active pharmaceutical compound to combat multidrug-resistant pathogens. As new bacteriocins continue to be discovered, accelerated workflows for screening, identification, and process development have been developed. However, antimicrobial activity measurement is often still limited with regards to quantification and throughput. Here, we present the use of a non-linear calibration model to infer nisin concentrations in cultivation supernatants of Lactococcus lactis ssp. lactis B1629 using readouts of pHluorin2 fluorescence-based antimicrobial activity assays.

Antimicrobial Activities and Characterization of Bacteriocin-Like Substances Isolated from Lactic Acid Bacteria of Local Fermented Foods

Antimicrobial Activities and Characterization of Bacteriocin-Like Substances Isolated from Lactic Acid Bacteria of Local Fermented Foods

Gallic acid exerts antibiofilm activity by inhibiting methicillin-resistant Staphylococcus aureus adhesion

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious threat to patients with nosocomial infections, and infection is strongly associated with biofilm formation. Gallic acid (GA) is a natural bioactive compound found in traditional Chinese medicines that exerts potent antimicrobial activity. However, the anti-MRSA biofilm efficacy of GA remained to be determined. This study investigated the antimicrobial activities of GA against MRSA and the mechanisms involved. The results revealed the significant antibacterial and antibiofilm activities of GA. The minimal inhibitory concentration of GA against MRSA was 32 μg/mL and a growth curve assay confirmed the significant inhibitory effect of GA on planktonic MRSA. Crystal violet and XTT assays showed that 8 µg/mL GA effectively inhibited the formation of new biofilms and disrupted existing biofilms by reducing both biofilm biomass and metabolic activities. Alkaline phosphatase and β-galactosidase leakage assays and live/dead staining provided evidence that GA disrupted the integrity of bacterial cell walls and membranes within the biofilm. Scanning electron microscopy observations showed that GA significantly inhibited bacterial adhesion and aggregation, affecting the overall structure of the biofilm. Bacterial adhesion, polysaccharide intercellular adhesion (PIA) production and real-time quantitative PCR assay confirmed that GA inhibited bacterial adhesion, PIA synthesis, and the expression of icaAD and sarA. These results suggested that GA inhibited biofilm formation by inhibiting the expression of sarA, then downregulating the expression of icaA and icaD, thereby reducing the synthesis of PIA to attenuate the adhesion capacity of MRSA. GA is therefore a promising candidate for development as a pharmaceutical agent for the prevention and treatment of bacterial infections caused by MRSA.

Investigation of some probiotic and technological properties of lactic acid bacteria strains isolated from artisanal sheep milk cheese and their growth in goat milk

The objective of this study was to assess the probiotic and technological properties of lactic acid bacteria (LAB) isolated from artisanal sheep milk cheeses for potential use in dairy products made from goat milk. Strains studied were Lacticaseibacillus paracasei LC6, Lactiplantibacillus plantarum LP48, Lactococcus lactis subsp. hordniae LH69 and Leuconostoc mesenteroides LM99. The criteria studied were fermentative capacity, carbohydrate fermentation profile, β-galactosidase (lactase) activity, auto-aggregation capacity, hydrophobicity, antimicrobial activity, resistance to simulated gastric secretion, bile resistance, and resistance to different pH and salts concentrations, as well as growth and viability in goat milk. In general, the strains studied showed characteristics compatible with potential probiotic effects. However, according to criteria studied, L. plantarum LP498 best met the conditions; it was compatible with probiotic potential under all the conditions considered and showed noteworthy differences compared to the other micro-organisms studied, particularly in its capacity for self-aggregation and pH resistance. Therefore, L. plantarum LP48 could be adequate for the manufacture of artisanal goat milk products.

A new dynamic in vitro model for evaluating antimicrobial activity against bacterial biofilms on central venous catheters.

Central venous catheters (CVCs) are widely used for intravenous medication administration. However, biofilm formation along the catheter surface is the main most important cause of catheter-related bloodstream infections. Nowadays, several antimicrobial-coated catheters are available to prevent biofilm development. In this study, we introduced a new dynamic in vitro model to evaluate the antimicrobial activity against bacterial biofilms on CVCs. Rifampicin-minocycline-coated catheters and control catheters without antimicrobial component were assembled into the model to test the antimicrobial activity on external surface and internal surface. After 1 h irrigation of Staphylococcus epidermidis or Staphylococcus aureus preculture and 23 h irrigation of Trypticase Soy Broth, the viable adherent organism was collected and counted. The enumeration results showed that the number of bacteria attached to antibacterial catheter was significantly less than that of the control catheter, both on external surface (P < 0.05) and internal surface (P < 0.05). The results were further confirmed by the scanning electron microscopy. In conclusion, the dynamic in vitro model can be applied to evaluate the antimicrobial activity against bacterial biofilms grown on the external and internal surfaces of CVCs used in clinical practice.IMPORTANCEFor the first time, a new dynamic in vitro model was constructed to evaluate the antimicrobial activity against bacterial biofilms on central venous catheters (CVCs) on both external surface and internal surface. This model could be applied to evaluate the antimicrobial activity against bacterial biofilms not only on CVCs but also other types of catheters.