Coli Inhibition Research Articles

Synergistic adsorption-photocatalytic degradation of tetracycline by S-scheme InVO4/ZnIn2S4 heterojunction: mechanism, toxicity assessment, and potential applications

The development of materials with dual adsorption/photocatalytic functions for the removal of difficult-to-degrade organics is a very promising and challenging strategy. In this paper, a novel S-scheme heterojunction photocatalyst, InVO4/ZnIn2S4, was successfully synthesized with a unique hierarchical structure, which provides plenty of accessible adsorption/photocatalytic sites with a high light-harvesting rate (by multiple reflections). The experimental results show that optimized InVO4/ZnIn2S4 (5-IV/ZIS) has superior removal performance, whose adsorption-photocatalytic synergistic removal of tetracycline (TET) can reach 69.31 % after 15 min and 90.69 % after 45 min. Based on the analysis of the mechanism, the excellent removal performance can be attributed to the adsorption of the target onto the material by hydrogen bonding, followed by the degradation of the adsorbed target by active substances (h+ > O2•− > e- >1O2 >•OH) generated by the S-scheme heterojunction. In addition, the possible pathways for the photocatalytic removal of TET on 5-IV/ZIS were investigated by HPLC-MS analysis. T.E.S.T. and E. coli inhibition experiments demonstrated a significant reduction in the toxicity of TET after the photocatalytic reaction. In conclusion, the novel multifunctional photocatalyst 5-IV/ZIS prepared in this study can be used for the efficient treatment of organic compounds in wastewater with a bright application prospect.

A multifunctional integrated coating reinforced with exfoliated boron nitride towards superior decorative, antibacterial, durable, and flame-retardant performances

To solve the problems of traditional transparent fireproof coatings with a single-function nature and susceptibility to environmental aging, a novel functionalized exfoliated boron nitride (h-BN) with organophosphate (PPB) was synthesized and applied in an amino resin, preparing an integrated coating with decorative, fire-resistant, antibacterial, and weathering functions. The results indicate that the introduction of h-BN not only maintains the coating's high transparency but also enhances its hardness and adhesion capabilities. Furthermore, the presence of h-BN positively influences the flame retardance and smoke suppression of MBPPB coatings. Notably, when the mass ratio of PPB to h-BN is 98:2, the resulting MBPPB4 coating reduces the flame spread rate (FSR) by 45.7% and the smoke density rating by 62.6% compared to MBPPB0 coating without h-BN. Thermogravimetric analyses indicate that coatings containing h-BN exhibit superior char formation and thermal stability, where the MBPPB3 coating, with a PPB to h-BN ratio of 98.5:1.5, shows a 49.8% higher char yield at 800 °C than MBPPB0. The accelerated aging test demonstrates that the incorporation of h-BN also reduces the incidence of coatings blistering and cracking, thereby exhibiting outstanding weatherability. Additionally, h-BN significantly enhances the coating's antibacterial efficacy, with an E. coli inhibition rate of up to 99.0% for MBPPB3 coating.

Platinum and gold activated ZnFe2O4 nanomaterials for boosting photocatalytic inhibition of bacteria under visible light

We successfully synthesized visible-light-activated magnetic photocatalysts, namely PtAu/ZnFe2O4, by modified hydrothermal process in which ascorbic acid was used as a reducing and stabilizing agent for the reduction of Pt and Au nanoparticles. These photocatalysts have the ability to use visible light for photocatalytic reactions and also exhibits magnetic properties. Photocatalytic tests conducted in this study showed that PtAu/ZnFe2O4 composites have greater photocatalytic performance under visible light. These composites, obviously improved have shown effectiveness against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, the analysis of charge carrier density presented that the addition of Pt and Au to ZnFe2O4 resulted in an increased fragmentation of the photogenerated charge carriers. This finding suggests that the said metals introduced enhance the overall photocatalysis performance by significantly facilitating charge carrier separation Application. Trapping experiments indicating reactive species such as •O2− (superoxide) ions and h+ (pores) in PtAu/ZnFe2O4 performs a key role in the photocatalytic process. Furthermore, the as-prepared PtAu/ZnFe2O4 composite can be efficiently separated through external magnetic field after the photocatalytic reaction. Additionally, the hybrid materials displayed extremely effectual photocatalytic antibacterial property. The antibacterial activity was much proficient in light (E. coli inhibition zone= 17, and S. aureus inhibition zone = 19) than in dark (E. coli inhibition zone= 09, and S. aureus inhibition zone = 11). Taken together, these findings highlight the promising potential of the PtAu/ZnFe2O4 photocatalyst as a magnetic photocatalyst with antibacterial properties for practical applications in wastewater treatment. This research opens up avenues for the future development and implementation of photocatalysis in addressing environmental challenges associated with wastewater treatment.

Ru and MWCNTs-OH co-modified copper foam as high-performance electrode materials for electrocatalytic degradation of doxycycline

In this study, an efficient composite electrode for the degradation of doxycycline (DC), i.e., the ruthenium/hydroxylated multi-walled carbon nanotube/copper foam composite electrode (Ru/MWCNTs-OH/CF), was prepared by the constant current deposition method. The composite electrode was characterized by SEM, XRD and XPS. Impedance testing, polarization curve analysis, and linear voltammetry analysis were conducted on the composite electrode, confirming that the combination of MWCNTs-OH and Ru can reduce the charge transfer resistance of the electrode and significantly improve catalytic activity. Under optimal conditions, the degradation efficiency of the Ru/MWCNTs-OH/CF composite electrode for 10 mg/L DC reached 77.20 % at 60 min. The degradation reaction followed the proposed primary reaction kinetics. The degradation efficiency only decreased by 2.23 % after ten cycles of the experiment, indicating the excellent stability of the electrode. The reaction mechanism was investigated by LSV and quenching experiments. The results showed that DC was degraded under the synergistic action of ·OH, H* and active chlorine species. The degradation path of DC was deduced by LC-MS. The E. coli inhibition experiment and toxicological assessment based on ecological conformational relationships confirmed that the toxicity of the product organisms generated by DC degradation at the Ru/MWCNTs-OH/CF electrode was significantly reduced. The results indicate that the Ru/MWCNTs-OH/CF electrode has high activity and stability and is a promising material for practical applications in the removal of antibiotics from water.

Effects of methoxy polyethylene glycol‐polycaprolactone block copolymers and silica nanoparticles on the mechanical, tissue affinity and antibacterial properties of n‐butyl cyanoacrylate adhesive

AbstractCyanoacrylates are widely used as surgical tissue adhesives because of their high biodegradability, but they are brittle and have poor tissue affinity. In this study, methoxy polyethylene glycol‐polycaprolactone block copolymers (MPEG‐co‐PCLs) with different PCL chain lengths were synthesized by ring‐opening polymerization. Then, a new tissue adhesive with excellent mechanical properties, tissue affinity, antibacterial properties, and coagulation performances was prepared by incorporating MPEG‐co‐PCL and silica nanoparticles (SNPs) into n‐butyl cyanoacrylate (BCA). The optimal MPEG: PCL ratio is 1:4 (MP‐3), and the optimal mass ratio of MPEG‐co‐PCL and SNPs (0.5SNPs/0.5MP‐3) is 0.5 wt.%. Compared to BCA, the adhesion strength and flexibility of 0.5SNPs/0.5MP‐3 are dramatically improved by 110% and 244%, respectively. MPEG‐co‐PCL can fully exploit the advantages of homopolymers, and therefore, improve the tissue affinity and adhesion strength of the adhesive and avoid BCA polymerization initiated by MPEG and poor compatibility of PCL with BCA. SNPs can also compensate for the lack of antibacterial properties of BCA against Gram‐negative bacteria. The E. coli inhibition circle of 0.5SNPs/0.5MP‐3 is twice as large as BCA. SNPs can also improve coagulation by promoting platelet aggregation. This work provides an effective strategy for developing adhesives with potential clinical applications.

Preparation and characterization of glycerol plasticized yam starch-based films reinforced with titanium dioxide nanofiller

In this study, yam starch was extracted from yam tubers using water and used for preparation of glycerol plasticized and titanium dioxide (TiO2) nanofiller reinforced films. The effects of TiO2 nanofiller concentration on the properties of the film were studied. Concentration of TiO2 nanofiller affects the mechanical and morphological properties of the film. The tensile strength and percent elongation were modeled and optimized by a three-variable, three-level Box-Behnken Design (BBD) using Response Surface Methodology (RSM). An optimal tensile strength (4.68 MPa) and elongation percentage (32.96%) were observed with the model at starch (3.60 g), glycerol (1.40 mL) and TiO2 nanofiller concentration (0.35 g) for the reinforced starch film. The experimental tensile strength and elongation percentage at break were 4.45 MPa and 37.77%, respectively. This shows the model can reasonably predict the optimum tensile strength and elongation of the current biofilms. Moreover, the biodegradability and antimicrobial properties of biofilms prepared at optimum tensile strength and elongation percentage were conducted. About 29% of the initial weight of the film was decomposed in the soil in the first 15 days. Moreover, an E. Coli inhibition zone of 3.25 mm was observed for the TiO2 reinforced films.

Electrospun nanofibrous membranes with asymmetric wettability for unidirectional moisture transport, efficient PM capture and bacteria inhibition

The performance of moisture management, PM capture, and bacteria inhibition are significant for air cleaning materials. Herein, a nanofiber composite PVDF/PAN-CTAB membrane with multiple functions was constructed via a facile electrospinning strategy. Incorporating cetyltrimethyl ammonium bromide (CTAB) in the windward PAN layer simultaneously improved membrane moisture transport rate, antibacterial performance, and PM capture ability. The enhanced moisture management performance was achieved by regulating the microstructure of the nanofibers and the thickness ratio of the asymmetric wetting layers. Hydrophobic-hydrophilic interface superimposed force on water droplets was measured to thoroughly investigate directional water transport behavior. Consequently, the prepared PVDF/PAN-CTAB membrane possesses a water vapor transport rate of >13 kg m−2 d−1, PM0.3 removal efficiency of ≥99% with a low pressure drop of ∼84 Pa, and an E. coli inhibition rate of 99.99%. This work would pave the way for engineering asymmetric wettability structure to improve the moisture management performance of antibacterial air cleaning membrane, and provides a novel scientific sight on directional water transport phenomenon based on force test and analysis.

Preparation and properties of antibacterial PVDF composite thin films

As medical dressings, polyvinylidene fluoride (PVDF) thin films loaded with antimicrobial agents offer excellent wound infection control. In this study, PVDF/tea polyphenol (TPs) and PVDF/TPs/Ag composite thin films were prepared by electrically assisted three-dimensional (3D) printing method. The surface morphology, hydrophilicity, and antibacterial properties of the composite thin films were studied. The results showed that the presence of appropriate amount of TPs promoted the crystallinity and β-phase content of the PVDF thin films, and TPs played an important role in the formation of abundant holes on the surface of PVDF films. It facilitated the deposition of silver nanoparticles on the surface of PVDF thin film and improved the uniformity of their distribution. The Escherichia coli (E. coli) inhibition rate of the PVDF/TPs composite thin film reached 97.22%. The antibacterial activity of this composite thin film improved significantly after the deposition of silver nanoparticles, and the E. coli inhibition rate of the PVDF/TPs/Ag composite thin film was 99.58%.

In Vitro Effect of Plant Parts Extract of Senecio glaucus L. on Pathogenic Bacteria

Senecio glaucus L. is an annual herb that grows in several Egyptian desert habitats. The diversity of habitats inhabited by this species, as well as its distribution, chemical composition, and biological activity, are all unknown. This research aimed to examine the chemical composition of S. glaucus from various environments in Egypt, as well as the antioxidant and antimicrobial activities. The general assessment of the analytical results for different parts of S. glaucus showed that the capitula and leaves in both inland and coastal samples were rich in bioactive constituents than the other parts as following (capitula > leaf > root > stem). Based on the results of IC50, the antioxidant properties of the eight parts of two samples follows the sequence capitula ˃ root ˃ leaf ˃ stem for the coastal sample, and capitula ˃ leaf ˃ stem ˃ root for the inland sample. The IC50 values ranged from 25.94 to 41.20 mg/ml in coastal sample, where the IC50 values ranged from 28.02 to 42.83 mg/ml in desert sample, compared to ascorbic acid (IC50 = 13.30 mg/ml). The antimicrobial potential of MeOH extracts of S. glaucus parts collected from different habitats exhibited different inhibitory spectrum behavior with varying degrees of inhibition against six Gram-positive bacteria and four Gram-negative bacteria. In both coastal and inland samples, the E. coli inhibition zone was the most susceptible bacterium. Whereas, in the case of the coastal sample, the inhibition zone of B. subtilis was the most sensitive bacterium. The results of the antibacterial test were compared with 3 standard antibiotics.

Temperature-Switchable Glycopolymers and Their Conformation-Dependent Binding to Receptor Targets.

The temperature-dependent binding of copolymers from poly(N-isopropylacrylamide) (PNIPAM) and mannose ligands to Escherichia coli and concanavalin A (ConA) is determined. Through polymer analogous reactions using poly(N-acryloxysuccinimide) and amine-linked mannose residues with different linkers, glycopolymers are prepared with the variation of the mannose density. Quantitative adhesion inhibition assays show the inhibitory potential of the glycopolymers as a function of the mannose/NIPAM ratio and linker type above and below their lower critical solution temperature (LCST). Intriguingly, opposite temperature effects on the binding to E. coli and ConA are observed. While the E. coli inhibition is stronger above the LCST, the ConA inhibition is, in overall, weaker at elevated temperatures. When going beyond the LCST, the polymers undergo a coil-to-globule transition, forming microphases with surface-enriched hydrophilic sugar moieties exhibiting increased E. coli inhibition through steric shielding. However, the formation of such microphases above the LCST renders a fraction of carbohydrate ligands inaccessible,and the polymers remaining in the solution phase then have coil sizes below the minimum binding site spacing of the ConA receptor, explaining reduced ConA inhibition. Overall, these results suggest that the coil-to-globule transition of glycopolymers may induce lower or higher inhibitory potentials due to the adverse effects of steric shielding and carbohydrate ligand accessibility.

Antioxidant and Antimicrobial Activities of Melissa officinalis L. (Lemon Balm) Extracts

Family lamiaceae is an important plant family, its includes 236 genera and 250 spicies in which Melissa officinalis (M. officinalis) is the most common one Plants of this genus contain many chemical compounds like essential oils, terepenes, flavonoids, glucasinolates, anthocyanins and alkaloids. Also it exhibited different biological activities as antioxidant and antibacterial. Methanolic extract of plant was prepared where total phenolic content (TPC) and total flavonoid content (TFC) were estimated by colorimetrically. Antioxidant activity was estimated by DPPH radical scavenging activity. Also, six microbial species were used to estimate the antimicrobial activity of M. officinalis .Total phenolic and flavonoids of M. officinalis ethyl acetate extract are 143.50 mg GAE/g (dw) and 124.96 mg QE/g dw, respectively. These results confirm the antioxidant effect of the plant sample under study.The effect of M. officinalis methanolic extract on Staphylococcus aureus ranged between 9.0 and 14 mm with concentration varied between 30 and 100 μl, respectively, while, E. Coli inhibition zone was fluctuated between 10.0 and 11.0 mm for the same concentration. This plant extract was considered sensitive agent against Staphylococcus aureus and E. Coli . Moreover, the stronger effect of M. officinalis extracts was detected on Saccharomyces cerevisiae with a diameter of 16.0 mm when a concentration of 100 μl was used

Facile and rapid synthesis of efficient epoxy-novolac acrylate / MWCNTs-APTES-ZnO hybrid coating films by UV irradiation: Thermo-mechanical, shape stability, swelling, hydrophobicity and antibacterial properties

The focus of this investigation is based on the absence of previous study on shape stability, swelling and hydrophobicity in polar and non-polar solvents and antibacterial properties of epoxy-novolac acrylate (ENA)/multi-walled carbon nanotubes (MWCNTs)-3-aminopropyl triethoxysilane (APTES)-ZnO (ENA-MWCNT-A-ZnO) hybrid coating films. Hybrid coating films were prepared by mixing of ENA with photo-initiator (2-hydroxy 2-methyl phenyl propane 1-one), Trimethylolpropane triacrylate (TMPTA) and multi-walled carbon nanotubes-APTES-ZnO (MWCNTs-A-ZnO) concentration (1 and 2 wt %). The hybrid films were characterized by electron microscopy to study surface and bulk morphologies. Spectroscopy studies were carried out to determine the effect of MWCNTs-A-ZnO incorporation on intermolecular interactions, degree of crystallinity and extent of crosslinking, respectively. The extent of MWCNTs-A-ZnO loading on the morphological structure, melt viscosity, glasstransition temperature, tensilestrength and antibacterial performance of the coating films was evaluated. The glass transition temperature, tensile strength and young's modulus of the ENA are significantly increased with increasing MWCNTs-A-ZnO concentration. Resilient shape stability was observed in water as well as in various organic solvents. The S. aureus bacteria shows higher degree of inhibition compared to E. coli inhibition zone and increasing of E. coli inhibition zone with increasing concentration of MWCNT-A-ZnO nanoparticles.

Antibacterial casein-based ZnO nanocomposite coatings with improved water resistance crafted via double in situ route

Neat casein film often suffers from poor water resistance and unexpected antibacterial activity. In this study, casein-based ZnO nanocomposite were prepared via double in situ polymerization, where y-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) was used as silane coupling agent. Morphology, structure and size distribution of the composite latexes were characterized by TEM, FTIR, DLS, TG. Meantime, water absorption and antibacterial properties of the as-prepared composite coatings were also investigated. The results indicated that the average size of casein-based ZnO nanocomposite particles was approximately 259 nm. When dosage of ZnO precursor was increased to 3%, water resistance of the composite film was maximized in that water absorption rate was reduced to 49.9%. When dosage of KH560 was 3.5%, the E. coli inhibition zone of casein-based ZnO nanocomposite was expanded from 0 mm to 9.0 mm, suggesting obviously enhanced antibacterial performance than that prepared via single in situ method. The as-prepared composite is a good candidate for functional coatings in relative fields.

Longitudinal Assessment of Systemic and Genital Tract Inflammatory Markers and Endogenous Genital Tract E. coli Inhibitory Activity in HIV-Infected and Uninfected Women.

Stability over time of systemic and mucosal immunity and their associations with bacterial vaginosis (BV) and HIV-specific parameters were assessed. Immune mediators and HIV viral load in plasma and cervicovaginal lavage (CVL), E. coli inhibition, and Nugent score were measured at three semiannual visits among 94 participants in the Women's Interagency HIV Study. Mixed models identified the factors associated with immune mediators. There was higher E. coli inhibition and lower inflammation over time in the genital tract and systemically. BV was consistently associated with higher CVL inflammatory mediators and lower CVL E. coli inhibition. HIV-infected women with higher CD4 counts had lower systemic and genital inflammatory mediators, and genital HIV shedding was associated with higher CVL inflammatory mediators. Use of antiretroviral therapy (ART) was associated with lower plasma and CVL mediators, but higher E. coli inhibition. HIV and BV are linked to inflammation, and ART may be associated with improved vaginal health.

Anti-bacterial and in vivo tumor treatment by reactive oxygen species generated by magnetic nanoparticles.

Photodynamic therapy is widely used in clinics and for anti-bacterial applications. The major challenge is the limited depth of tissue penetration of light and poor targetability. In this study, magnetite nanoparticles were used as a highly sensitive T2-weighted MR imaging contrast agents to target the tumor and mimic horseradish peroxidase (HRP), which could catalyze the decomposition of hydrogen peroxide to generate reactive oxygen species (ROS) to inhibit the tumor in vivo. In these experiments, MNPs were demonstrated to possess the enzyme-mimicking activity in different pH values, and the activity was dependent on the size of the MNPs: the smaller the size, the higher the activity. We demonstrated that MNPs showed highly efficient anti-bacterial (E. coli) activity in presence of H2O2. The E. coli inhibition ratio reached nearly 100% at optimal concentration. The anti-tumor activity was evaluated through HeLa cell viability under treatment with MNPs and H2O2. Consequently, the cell viability was significantly decreased and more than 80% of HeLa cells were dead after treatment with MNPs and H2O2 under different pH values. MR imaging was used to demonstrate the tumor targetability of 13 nm MNPs in vitro and in vivo. Consequently, the relaxivity of the 13 nm MNPs was determined to be r2 = 104 s-1 mM-1. The MR signal was much more negative and the intensity was significantly diminished with the increase of the concentration of 13 nm MNPs in vitro. The tumor signal was clearly visualized and a 3-fold decrease of the MR signal intensity of the tumor site of the mice was observed after 24 h-post treatment with the 13 nm MNPs. Finally, the tumor inhibition in vivo was investigated using 6 nm MNPs in BALB/c nude female mice bearing subcutaneously implanted HeLa cells on the right flank. The results show statistically significant efficacy in delaying tumor growth from day 6, and an approximately 99% tumor inhibition ratio was shown by the combination of MNPs and H2O2 after treatment for 17 days. By leveraging the passive targeting and MR imaging properties, we expect that the enzyme-mimicking MNPs could be used for cancer theranostics and may open up a new avenue for the treatment of epidermal infections.

Expression and the clinical significance of Wnt10a and Wnt10b in endometrial cancer are associated with the Wnt/β-catenin pathway

To determine the role played by the Wnt/β-catenin signaling pathway in the development of endometrial cancer (EC), we examined the expression of Wnt10a and Wnt10b in EC tissues and the correlation between their expression. Furthermore, the associations between these two proteins and the clinicopathological characteristics and prognosis of EC were also evaluated. In our search of alternative mechanisms, we investigated the impact of Wnt10b on proliferation and apoptosis of EC cells. Western blotting, 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry were used to evaluate the expression of Wnt10b and some key proteins of the Wnt/β-catenin pathway, proliferation and apoptosis in EC. Our results showed that Wnt10b expression in EC tissues was significantly higher compared to that in hyperplastic and normal samples. The expression of Wnt10a in endometrioid cancer tissues was higher compared to that in other types of cancerous samples. The difference in Wnt10b levels was significant among subgroups for histological type, grade of differentiation, FIGO phase and lymphovascular metastasis. Furthermore, no correlation was observed between the expression of Wnt10a and Wnt10b. In the follow-up, Wnt10b gene expression was frequently upregulated in EC and associated with better prognostic clinicopathological markers in EC patients. Collectively, the in vitro data showed that the upregulated expression of Wnt10b in Ishikawa cells promoted proliferation and inhibited apoptosis through β-catenin and c-myc activation and adenomatous polyposis coli (APC) inhibition, which suggests that Wnt10b activates EC via the Wnt/β-catenin pathway. These results suggest that Wnt10b likely plays an important role in the development of EC. Furthermore, these results identify a role for Wnt10b in EC cells through promoting proliferation and inhibiting apoptosis, primarily through the activation of the Wnt/β-catenin pathway. The role played by Wnt10a in EC, however, still requires further investigation.

Avian lipocalin expression following E. coli infection and inhibition of bacterial growth in vitro

Avian lipocalin expression following E. coli infection and inhibition of bacterial growth in vitro

A new approach to chemically modified chitosan sulfates and study of their influences on the inhibition of Escherichia coli and Staphylococcus aureus growth

A new approach to prepared chemically modified chitosan sulfate derivatives was reported, from which chitosan sulfate was prepared from chitosan first. Then N-acyl or N,O-quaternary ammonium groups were introduced by the reaction of chitosan sulfate with caproic anhydride, propanoic anhydride, or 2,3-epoxypropyl trimethylammonium. The structures of the derivatives were characterized by elemental analysis, FT-IR, 13C NMR, 1H NMR and gel permeation chromatography. The antibacterial activities against Escherichia coli, which is a gram-negative bacterium, and Staphylococcus aureus, which is a gram-positive bacterium, have been investigated by optical density method. It was found that the chitosan sulfate showed no inhibition against E. coli, while at concentration below 10 2 μg/ml its inhibition against S. aureus was higher than phenic acid, a widely used biocide. The quaternized derivatives of the chitosan sulfate also showed S. aureus inhibition but no E. coli inhibition. The acylated chitosan sulfates were found to be not only increasing the S. aureus inhibition activities but also exhibiting some inhibition towards the growth of E. coli slightly. The activities of N-acyl chitosan sulfates seem to be related to the structures of the covalently bonded acyl moieties, among which the N-hexanoyl moiety was more effective in enhancing the E. coli inhibition activities. The antibacterial mechanism of the chitosan sulfate and its derivatives was also simply discussed.

Selection of Escherichia coli-inhibiting strains of Lactobacillus paracasei subsp. paracasei.

The aim of this study was to select Escherichia coli-inhibiting strains among lactic acid bacteria. On the basis of phenotypical and technological characteristics, 20 strains of lactic acid bacteria were screened from a total of 225 isolates, obtained from nine samples of artisanal Caprino d'Aspromonte cheese, made from raw goats' milk. The antagonistic activity of these 20 strains was detected in plates against three different strains of E. coli. Two strains of Lactobacillus paracasei subsp. paracasei showed a marked anti-E. coli activity against all three strains tested; the other lactic acid bacteria did not exhibit inhibiting activity. The E. coli inhibition can be ascribed to production of bacteriocin-like compounds. The use of L. paracasei subsp. paracasei strains to increase the safety of the cheeses made from raw milk is recommended because these cultures strongly inhibit E. coli, without foreseeable adverse sensory changes.

Inhibition of Enteropathogens by Lactobacilli Strains Used in Fermented Milk

The inhibitory effect of lactobacilli on the growth of different pathogens was studied. The degree of inhibition was measured by disc assay in different media, showing that the inhibitory substance(s) can be extracellular and diffusible. The associative cultures were performed with lactobacilli and Escherichia coli in a relationship of 1:1 or 103:1. In the first experiments, the E. coli inhibition began at 9 h after culturing. In the experiments with lower levels of different intestinal pathogens, associative cultures were incubated for 4–6 h obtaining different degrees of inhibition with the highest being for E. coli and Klebsiella pneumoniae. After a day of incubation, we did not recover viable pathogens from the mixed cultures, while lactobacilli grew to 108–109 microorganisms per ml. The inhibition of pathogens was not due to pH alone, because the addition of different organic acids to culture media did not inhibit their normal growth. Lactobacillus casei and Lactobacillus acidophilus in this study can be considered a potential biotherapeutic treatment in patients infected with certain intestinal pathogens.