Ultra violet-C pretreatment enhances the antimicrobial efficacy of unpeeled carrots against subsequent contamination with Listeria monocytogenes.

To our knowledge, this study is the first to elucidate the bactericidal efficacy of unpeeled carrots (hereafter referred to as carrots) pretreated with Ultra Violet-C (UV-C) against subsequent contamination with Listeria monocytogenes. Carrots pretreated with UV-C (240 mJ/cm2) exhibited a significant antilisterial effect within 2 h. In fact, the population of UV-C-pretreated carrots decreased from 7.94 log CFU/cm2 to levels below the limit of detection (LOD; <1.65 log CFU/cm2) within 24 h. For carrots that were not pretreated with UV-C, 3-4 log reductions were found after 24 h. Carrots pretreated with UV-C exhibited antimicrobial activity against another gram-positive pathogen, Staphylococcus aureus, but not against the gram-negative pathogens, E. coli O157:H7 and Salmonella enterica. Pretreatment with UV-C created a lasting antimicrobial effect as introducing L. monocytogenes on carrots, 72 h post-UV-C treatment, still maintained the antilisterial effect. Notably, all UV-C doses in the range of 48-240 mJ/cm2 induced a lasting antilisterial effect. The bactericidal effects against L. monocytogenes were confirmed in three varieties of washed and unwashed carrots (Danvers, Nantes, and Chantenay). Fluorescence microscopy confirmed the bactericidal effect of UV-C-pretreated carrots on the survival of L. monocytogenes. Conclusively, pretreating carrots with UV-C can reduce the population of L. monocytogenes to levels below the LOD and may further prevent pathogen growth during cold storage. Additional studies are necessary to discern the mechanism underlying the bactericidal efficacy of UV-C-pretreated carrots.

Bactericidal efficacy of mobile ultraviolet-C disinfection devices in reducing contamination in biosafety laboratories.

INTRODUCTION: Biosafety research requires a wide range of microorganisms and thorough disinfection to prevent laboratory infection is often required. Ultraviolet-C (UV-C) exposure reduces bacterial and viral concentrations. Therefore, in this study, we aimed to evaluate the efficacy of a mobile UV-C device as a non-contact disinfection strategy. METHODOLOGY: The bactericidal efficacy of the UV-C device was determined based on log10 decreases in the relative abundances of bacterial indicators, including Escherichia coli, Staphylococcus aureus, Staphylococcus albus, and Pseudomonas aeruginosa at 0.5 and 1.0 m after irradiation for 30, 60, and 90 min. Next, the reduction of natural bacteria in air and on surface as a result of the UV-C device exposure in the laboratory were determined. RESULTS: Exposure to the UV-C disinfection device resulted in mean log10 decreases in microbial contamination of 3.55 and 5.85 following irradiation for 30 and 90 min, respectively, at a distance of 0.5 m. Further, P. aeruginosa and E. coli were the most and least sensitive to UV-C exposure, respectively. The bacterial load in air decreased by 65.53% after 60 min of irradiation, while those on surfaces decreased by 44.19% and 78.23% after 30 and 60 min of irradiation, respectively. CONCLUSIONS: The UV-C device effectively reduced bacterial load after irradiation for over 60 min. Further studies are encouraged to determine the effectiveness of the UV-C disinfection device in frequently occupied institutions, such as primary medical, health, and nursery, and its efficiency in infection control.

Bactericidal Efficacy and Mechanisms of Non-Electrolytic Slightly Acidic Hypochlorous Water on Pseudomonas fragi and Pseudomonas fluorescens.

Chilled pork is frequently contaminated with Pseudomonas fragi and Pseudomonas fluorescens. In this study, the bactericidal efficacy and mechanisms of non-electrolytic slightly acidic hypochlorous water (NE-SAHW) against two strains of these two species were evaluated. The results showed that the antibacterial efficacy of NE-SAHW was positively correlated with the concentration level of NE-SAHW and negatively correlated with the initial populations of the strains. The strains of small populations were completely inhibited when provided with each level of NE-SAHW. The killed cells of P. fragi were 0.94, 1.39, 4.02, and 5.60 log10 CFU/mL, respectively, and of P. fluorescens they were 1.21, 1.52, 4.14, and 5.74 log10 CFU/mL, respectively, when the initial populations of the strains were at high levels (about 7 log10 CFU/mL). Both strains were completely killed within 12 s with the available chlorine concentration (ACC) of 50 mg/L of NE-SAHW. Morphological changes in both cells were observed by using a Scanning Electron Microscope (SEM) and it was discovered that the cell membranes were damaged, which led to the leakage of the intracellular substances, including K+, nucleic acid, and protein. In terms of the Fourier Transform Infrared Spectroscopy (FTIR) results, NE-SAHW destroyed the structures of membrane proteins and cell structure proteins, and influenced the composition of polysaccharides. The bacteria were definitely dead after treatment by NE-SAHW compared to the control according to the results of flow cytometry. These results demonstrated the potential bactericidal property of NE-SAHW when applied to the meat and other food sterilization industries.

In Vitro and In Vivo Studies of Antibacterial Coatings on Titanium Alloy Implants for Veterinary Application.

The aim of this work was the evaluation of biological properties of hybrid coatings modified with Ag, Cu, and Zn nanoparticles (NPs) applied on TPLO medical implants by the sol-gel process. The implant coatings enriched with various concentrations of metallic NPs were investigated in the in vitro bactericidal efficacy tests against Gram+ and Gram- bacteria and pathogenic yeast. Next, the designed materials were tested on human osteosarcoma cell lines. The cells adhesion, proliferation, viability, and differentiation were investigated. The cell growth wasevaluated using SEM, and the metallic ion release was measured. The results revealed that the NPs concentration in the hybrid layers decreased with the incubation time. In the last stage, the implants were tested in vivo on six canine patients. Three months after the operation, the radiological evaluation of the performed anastomosis was carried out as well as the histopathological evaluation of tissue regeneration. The strongest bactericidal efficacy was observed for the layers containing AgNPs. Along with an increased concentration of metallic additives, a growing toxic effect was clearly observed. The most pronounced toxic effect was especially evident with the AgNPs concentration exceeding 1 mol %. In all the operated patients, no deviations were found during the follow-up examinations in the postoperative period. The low dose of AgNPs in the hybrid layer facilitated the tissue healing process. It was proven that silver nanoparticles may accelerate the bone healing process. The correct tissue reparation was observed.

Evolving the EN 1500 test method for alcohol-based hand rub closer to clinical reality by reducing the organic load on hands and enabling product to be applied to dry hands.

BACKGROUND: The methods currently used in Europe and North America to evaluate the bactericidal efficacy of hand hygiene products have some limitations (e.g. selection of test organism, method of contamination), and none of the methods allow prediction of actual clinical efficacy. Therefore, the World Health Organization has proposed the development of methods that better reflect typical clinical reality. METHODS: In Experiment 1, two contamination methods (immersion method according to EN 1500 and low-volume method according to ASTM E2755) were tested with the EN 1500 test organism Escherichia coli using 60% v/v iso-propanol. Experiment 2 compared the two contamination methods with Enterococcus faecalis. Experiment 3 compared the two test organisms using the low-volume contamination method. Data within each experiment were compared using the Wilcoxon test for paired samples, and data from all experiments were combined and fit to linear mixed-effects models. RESULTS: Mixed-effects analysis confirmed that both the test organism and the contamination method impacted the pre-values, and all three factors influenced log10 reductions. Higher pre-values resulted in significantly higher log10 reductions, immersion contributed to significantly higher log10 reductions, and E. coli showed significantly lower log10 reductions. CONCLUSION: An efficacy evaluation against E. faecalis with a low-volume contamination method could be considered as an alternative to the EN 1500 standard. This could help to improve the clinical relevance of the test method by including a Gram-positive organism and reducing the soil load, allowing product application closer to reality.

The quality by design approach for optimization of slayer exciter based low power portable atmospheric plasma jet on bactericidal efficacy of Pseudomonas aeruginosa.

A simple, portable, economical low-temperature atmospheric plasma (LTAP) for bactericidal efficacy of Gram-negative bacteria (Pseudomonas aeruginosa) with different carrier gases (argon, helium, and nitrogen) using the quality by design (QbD) approach, design of experiments (DoE), and response surface graphs (RSG) is presented. Box-Behnken design was used as the DoE to narrow down and further optimize the experimental factors of LTAP. Plasma exposure time, input DC voltage, and carrier gas flow rate were varied to examine the bactericidal efficacy using the zone of inhibition (ZOI). A higher bactericidal efficacy was achieved under the optimal bactericidal factors having ZOI of 50.837 ± 2.418 mm2 with the plasma power density of 132 mW/cm3 for LTAP-Ar at 61.19 s, 14.8747 V, and 219.379 sccm than LTAP-He and LTAP-N2 . The LTAP-Ar was further evaluated at different frequencies and probe lengths to achieve a ZOI of 58.237 ± 4.01 mm2 .

In vitro bactericidal efficacy of a new triple antibiotic paste formulation against Enterococcus faecalis biofilm.

The aim of this study was to evaluate the bactericidal efficacy on Enterococcus faecalis biofilm of a novel, low-concentration triple-antibiotic paste (TAP-L2) in propylene glycol/carboxymethylcellulose vehicle (VEH-2), a ready-to-use prototype, compared with two currently used products; a low-concentration (TAP-L1) and a high-concentration paste (TAP-H1) mixed in macrogol/propylene glycol vehicle (VEH-1). Sixty-two root canals were infected with E. faecalis biofilm, medicated with (a) TAP-L1, (b) TAP-L2, (c) TAP-H1, (d) VEH-1 or (e) VEH-2 (n = 10) and incubated for 21 days. Live/dead assays were performed using confocal laser scanning microscopy (CLSM), and dead bacteria (%) were calculated. The TAP-H1 group demonstrated the highest dead bacteria (67.54 ± 2.38%), which was significantly higher than the TAP-L2 and TAP-L1 groups (56.85 ± 7.11% and 54.23 ± 10.19%) (p < 0.05). The TAP groups demonstrated significantly higher dead bacteria than the VEH-1 and VEH-2 groups (47.51 ± 6.41% and 45.14 ± 8.28%) (p < 0.05). The ready-to-use TAP-L2 had antibacterial activity comparable to TAP-L1, both of which were lower than TAP-H1.

Factors influencing bactericidal efficacy using atmospheric cold plasma (ACP) against Escherichia coli in wheat flour.

This study aimed to evaluate operating factors that influence the bactericidal efficacy of atmospheric cold plasma (ACP) using wheat flour contaminated with Escherichia coli. It also investigated how non-optimized operating factors of ACP could affect wheat flour properties. Five operating factors (container volume, flour weight, shaking RPM, treatment time, and gas flow rate) were evaluated for the bactericidal effect of ACP using the Box-Behnken design. In addition, thermal and pasting properties were measured to assess the effect of non-optimized ACP operating conditions on wheat flour quality. ACP operating factors (volume of the container, shaking RPM, and treatment time) had significant effects on reducing E. coli in wheat flour (p < 0.05). The bactericidal effect also depended on the distance and contact area between the plasma jet and sample. The temperature at the flour surface increased (max. 70 ℃) when ACP treatment didn't provide sufficient space and optimized duration. Thermal, pasting, and gelling properties of ACP treated-wheat flour in a 10 mL container increased significantly compared to untreated wheat flour. Large amounts of samples, long processing time, and insufficient space contributed to overheating which leads to denaturation or change of the wheat flour properties. The present study proposed important data for industrial sterilization of wheat flour using ACP.

TXH11106: A Third-Generation MreB Inhibitor with Enhanced Activity against a Broad Range of Gram-Negative Bacterial Pathogens.

The emergence of multi-drug-resistant Gram-negative pathogens highlights an urgent clinical need to explore and develop new antibiotics with novel antibacterial targets. MreB is a promising antibacterial target that functions as an essential elongasome protein in most Gram-negative bacterial rods. Here, we describe a third-generation MreB inhibitor (TXH11106) with enhanced bactericidal activity versus the Gram-negative pathogens Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa compared to the first- and second-generation compounds A22 and CBR-4830, respectively. Large inocula of these four pathogens are associated with a low frequency of resistance (FOR) to TXH11106. The enhanced bactericidal activity of TXH11106 relative to A22 and CBR-4830 correlates with a correspondingly enhanced capacity to inhibit E. coli MreB ATPase activity via a noncompetitive mechanism. Morphological changes induced by TXH11106 in E. coli, K. pneumoniae, A. baumannii, and P. aeruginosa provide further evidence supporting MreB as the bactericidal target of the compound. Taken together, our results highlight the potential of TXH11106 as an MreB inhibitor with activity against a broad spectrum of Gram-negative bacterial pathogens of acute clinical importance.

Bactericidal efficacy of a low concentration of vaporized hydrogen peroxide with validation in a BSL-3 laboratory.

BACKGROUND: Highly infective pathogens are cultured and studied in biosafety laboratories. It is critical to disinfect these laboratories thoroughly in order to prevent laboratory infection. A whole-room, non-contact, reduced corrosion disinfection strategy using hydrogen peroxide was proposed and evaluated. AIM: To evaluate the bactericidal efficacy of 8% and 10% vaporized hydrogen peroxide (VHP) in a laboratory setting, with spores and bacteria used as bioindicators. METHODS: Spores of Bacillus atrophaeus and Bacillus stearothermophilus, along with Escherichia coli, Staphylococcus aureus and Staphylococcus albus bacteria were placed in pre-selected locations in a sealed laboratory, and an OXY-PHARM NOCOSPRAY2 VHP generator was applied. Spore killing efficacy was evaluated qualitatively, bactericidal efficacy was analysed quantitatively, and the mean log10 reduction was determined. Finally, the optimized disinfection strategy was verified in a biosafety level 3 (BSL-3) laboratory. FINDINGS: Significant reductions in microbial load were obtained for each of the selected spores and bacteria when exposed to VHP 8% and 10% for 2-3 h. S. aureus was found to be more resistant than E. coli and S. albus. Tests with VHP 8% and exposure for >3 h showed a 100% kill rate for B. atrophaeus on surfaces and equipment in the BSL-3 laboratory. CONCLUSION: The VHP generator has good diffusivity and low corrosiveness, and is a time-saving method for removal of disinfectant residue. This study provides reference for the precise disinfection of air and the surfaces of objects in biosafety laboratories under various conditions.

In vitro evaluation of novel titania-containing borate bioactive glass scaffolds.

Titanium-containing borate bioactive glass scaffolds (0, 5, 15, and 20 mol %, identified as BRT0, BRT1, BRT3, and BRT4) with a microstructure similar to that of human trabecular bone were prepared and evaluated in vitro for potential bone loss applications in revision total knee arthroplasty (rTKA). Methyl thiazolyl tetrazolium (MTT) cell viability assays of scaffold ion release extracts revealed that BRT0 scaffolds (0 mol % titanium) inhibited cell proliferation and activity at day 14. At day 30, all scaffold extracts decreased cell proliferation and activity significantly. However, live/dead cell assay results demonstrated that degradation products from all the scaffolds had no inhibitory effect on cell viability. Significant bactericidal efficacies of BRT3 extracts against Escherishia coli (Gram-negative) and BRT1 extracts against Staphylococcus aureus and Staphylococcus epidermidis (both Gram-positive bacteria) were demonstrated. Finally, evaluation of the cell/bioactive glass surface interactions showed well-spread cells on the surface of the BRT3 glass discs and BRT1 and BRT3 scaffolds, when compared to BRT0 and BRT4 scaffolds. The results indicate that by changing the Ti4+ :B3+ ratio, the ion release and consequently cell proliferation could be improved. in vitro results in this study demonstrate that BRT3 scaffolds could be a promising candidate for addressing bone loss in rTKAs; however, in vivo studies would be required to evaluate the effect of a dynamic environment on the cell and tissue response to the fabricated scaffolds.

Cross-contamination by disinfectant towelettes varies by product chemistry and strain.

BACKGROUND: Disinfectant products are used frequently on environmental surfaces (e.g. medical equipment, countertops, patient beds) and patient care equipment within healthcare facilities. The purpose of this study was to assess the risk of cross-contamination of Staphylococcus aureus and Pseudomonas aeruginosa during and after disinfection of predetermined surface areas with ready-to-use (RTU) pre-wetted disinfectant towelettes. METHODS: This study tested six disinfectant towelette products against S. aureus ATCC CRM-6538 and P. aeruginosa strain ATCC-15442 on Formica surfaces. Each disinfectant was evaluated on a hard nonporous surface and efficacy was measured every 0.5 m2 using a modified version of EPA MLB SOP-MB-33 to study the risk of cross-contamination. RESULTS: We found that all of the wipes used in this study transferred S. aureus and P. aeruginosa from an inoculated surface to previously uncontaminated surfaces. Disinfectant towelettes with certain chemistries also retained a high level of viable bacteria after disinfection of the surface area. The cross-contamination risk also varied by product chemistry and bacterial strain. CONCLUSION: Disinfectant wipes can cross-contaminate hard nonporous surfaces and retain viable bacterial cells post-disinfection, especially over larger surface areas. This highlights a need to further investigate the risk disinfectant wipes pose during and post-disinfection and guidance on maximum surface areas treated with a single towelette.

Synergistic effect of methylene blue and biogenic gold nanoparticles against Enterococcus faecalis.

This study reports successful photodynamic inactivation of planktonic and biofilm cells of Enterococcus faecalis using Methylene Blue (MB) in combination with gold nanoparticles synthesized using the cell-free filtrate obtained from 3-day biomass of Trichoderma asperellum strain. Monodispersed colloidal gold nanoparticles were characterized by UV-vis absorption, TEM and DLS to be 13 ±â€¯3 nm spheres. Diode lasers with the peak-power wavelength ʎ = 660 nm (output power of 21, 41 and 68 mW; power density of 55, 108 and 179 mW∙cm-2, respectively, were used as a light source to study the effects of MB alone, the gold nanoparticles alone (AuNPs) and the MB + AuNPs mixture on the viability of E. faecalis cells. The lethal effect of planktonic cells was achieved for MB after 30 min of laser irradiation with energy fluence of 322 J∙cm-2. When MB + AuNPs mixture was used as photosensitizer, the lethal effect was achieved with energy fluence of 292 J∙cm-2. The biofilm culture was more resistant to photo-inactivation and the best bactericidal effect of MB as photosensitizer was found after light dose of 483 J∙cm-2. The bacterial cell viability was reduced by 99.92%. It was proved that MB + AuNPs mixture synergistically enhances the kill of the studied microorganism as the same light dose resulted in 99.991% kill.

Biological and Physicochemical Assessment of Middle Ear Prosthesis.

Polymers modified with bioactive nanoparticles are a promising solution for patients who need a tissue replacement. Modern implants, thanks to bioactive and bactericidal functions, facilitate the healing and regeneration process of the replaced tissue. The aim of this study was to assess whether silver nanoparticles (AgNPs) could support antibacterial function without cytotoxic effect and deterioration of biostability. This article describes biological and physiochemical aspects concerning a new polymeric middle ear implant (Otoimplant) enriched with silver nanoparticles. This kind of prosthesis is a promising implant for the reconstruction of ossicles in ossiculoplasty. We found that incorporation of silver nanoparticles into a polymeric matrix resulted in bactericidal efficacy against Gram-positive and Gram-negative bacteria, both resistant to antibiotics and basic strains. Our prostheses do not show cytotoxic effect and are a suitable biomaterial platform for effective culture of Saos2 and NHOst osteoblastic cells. The in vitro incubation of the samples in distilled water revealed that surface parameters, such as roughness, may slightly increase as a result of unveiling nanoparticles. However, the prolonged immersion does not change mechanical parameters. During one-year incubation, the prosthesis proved to retain stable values of Young's modulus, tensile strength, propagation of longitudinal ultrasonic waves, pH, and conductivity.

Interruption in membrane permeability of drug-resistant Staphylococcus aureus with cationic particles of nano­silver.

The increasing drug-resistance pathogens among gram-positive bacterial species are becoming a major health concern nowadays. Over the past few years, the bactericidal efficacy of nano­silver against some drug-resistant gram-positive bacteria has been established, however further investigation is needed to determine whether nano­silver could be an option for the treatment of drug-resistant gram-positive microbial infections. The purpose of the present study was to determine the bactericidal efficacy of nano­silver with its membrane destroying property using drug-resistant Staphylococcus aureus MTCC 3160. In the present study, bactericidal assessment of nano­silver with different antibiotics was determined by agar well diffusion method. Interaction of nano­silver towards bacterial membrane was carried to understand the probable bactericidal actions of nano­silver, which was further confirmed by respiratory chain dehydrogenase, zeta potential, Scanning Electron Microscopy (SEM) and Gas Chromatography-Mass Spectrometry (GC-MS). The effect of nano­silver on bacterial Deoxyribonucleic Acids (DNA) was evaluated by agarose gel electrophoresis. Bactericidal assessment of nano­silver showed a very strong bactericidal action compare to antibiotics. The binding affinity of nano­silver towards bacterial membrane induced loss of catalytic activity for respiratory chain dehydrogenases. Zeta potential, SEM and GC-MS analysis also revealed extensive damage to the bacterial cell membrane. Moreover, the analysis of agarose gel electrophoresis revealed that nano­silver can enhance the decomposability of bacterial DNA, which was directly attached to the bacterial cell membrane. The present findings suggested that nano­silver directly interact with the bacterial cell surface without the need to penetrate; and this distinctive property raises the hope that nano­silver will remain an important bactericide in bacteria than antibiotics.

From the laboratory concept to clinical trials: the journey of Otoimplant so far.

INTRODUCTION: Nowadays, the role of alloplastic prostheses has become more important in ossicular chain reconstruction. Especially, bioactive medical devices may be an alternative for those currently used on the market. Areas covered: Medical devices which are implanted for over 30 days in the body are required to fulfill strict requirements. It is crucial to ensure the proper level of biocompatibility, biological stability and lack of cytotoxicity of the implanted material. If a medical device is expected to play an additional role, e.g. act as a bioactive or bactericidal agent, supplementary tests should be conducted to assess the relevant qualities. The aim of this article is to present the sequence of procedures leading to the success of a middle ear prosthesis called Otoimplant - from a theoretical concept to the clinical trial. Expert commentary: However, to introduce a new prosthesis into the market, research such as, in vitro, in vivo and clinical trials are required to keep medical devices approved. This article describes a research path that medical device ought to negotiate before the clinical trials may start.

Bactericidal efficacy of molybdenum oxide nanoparticles against antimicrobial-resistant pathogens.

Multidrug-resistant bacteria pose a major threat to effective antibiotics and alternatives to fight multidrug-resistant pathogens are needed. We synthetized molybdenum oxide (MoO3) nanoparticles (NP) and determined their antibacterial activity against 39 isolates: (i) eight Staphylococcus aureus, including representatives of methicillin-resistant S. aureus epidemic clones; (ii) six enterococci, including vancomycin-resistant isolates; and (iii) 25 Gram-negative isolates (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae), including extended spectrum beta-lactamases and carbapenemases producers. All isolates showed a MoO3 NP MIC of 700-800 mg l-1. MoO3 NP produced a clear inhibition zone for S. aureus and all Gram-negative isolates at concentrations ≥25 mg ml-1 and ≥50 mg ml-1 for enterococci. When the NP solutions were adjusted to pH ~7, the biocidal activity was completely abolished. MoO3 NP create an acidic pH and show a universal antimicrobial activity against susceptible and resistant isolates belonging to the most relevant bacterial species responsible for hospital-acquired infections.

Efficient visible light induced synthesis of silver nanoparticles by Penicillium polonicum ARA 10 isolated from Chetomorpha antennina and its antibacterial efficacy against Salmonella enterica serovar Typhimurium.

The green synthesis of silver nanoparticles (AgNPs) using biological systems such as fungi has evolved to become an important area of nanobiotechnology. Herein, we report for the first time the light-induced extracellular synthesis of silver nanoparticles using algicolous endophytic fungus Penicillium polonicum ARA 10, isolated from the marine green alga Chetomorpha antennina. Parametric optimization, including the concentration of AgNO3, fungal biomass, ratio of cell filtrate and AgNO3, pH, reaction time and presence of light, was done for rapid AgNPs production. The obtained silver nanoparticles (AgNPs) were characterized by UV-Visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and Transmission electron microscopy (HRTEM-EDAX). The AgNPs showed a characteristic UV-visible peak at 430 nm with an average size of 10-15 nm. The NH stretches in FTIR indicate the presence of protein molecules. The Raman vibrational bands suggest that the molecules responsible for the reduction and stability of AgNPs were extracellular proteins produced by P.polonicum. Antibacterial evaluation of AgNPs against the major foodborne bacterial pathogen Salmonella enterica serovar Typhimurium MTCC 1251, was assessed by well diffusion, Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assay. Killing kinetic studies revealed complete killing of the bacterial cells within 4 h and the bactericidal nature of synthesized nanoparticles was confirmed by fluorescent microscopy and scanning electron microscopy. Furthermore, the bactericidal studies with Transmission electron microscopy (TEM) at different time intervals explored the presence of AgNPs in the cell wall of S.Typhimurium at about 30 min and the complete bacterial lysis was found at 24 h. The current research opens an insight into the green synthesis of AgNPs and the mechanism of bacterial lysis by direct damage to the cell wall.

Green synthesized silver nanoparticles by marine endophytic fungus Penicillium polonicum and its antibacterial efficacy against biofilm forming, multidrug-resistant Acinetobacter baumanii.

Acinetobacter baumanii, a gram-negative, non-motile, encapsulated coccobacillus which causes infections worldwide. The objective of this study was to find a fungal strain that could be utilized to biosynthesize antibacterial silver nanoparticles (AgNPs) against Acinetobacter baumanii. The present investigation explains rapid and extracellular biosynthesis of silver nanoparticles by the algicolous endophytic fungus, Penicillium polonicum, isolated from the marine green alga Chetomorpha antennina. The obtained silver nanoparticles were characterized by UV-Vis spectroscopy, Raman spectroscopy, Fourier transformation infrared (FTIR), and Transmission electron microscopy (TEM). The SNPs showed a characteristic UV- visible peak at 430 nm with an average size of 10-15 nm. As evident from the FTIR and Raman spectra, possibly the protein components of fungal extract have caused the reduction of silver nitrate. Parametric optimization, including the concentration of AgNO3, ratio of cell filtrate and AgNO3, fungal biomass, reaction time, pH, and presence of light, was done for rapid AgNPs production. The antibacterial efficacy of AgNPs against multi-drug-resistant, biofilm-forming Acinetobacter baumanii, was evaluated by well diffusion assay. The Minimum inhibitory concentration (MIC) of AgNP was 15.62 µgml-1 and the minimum bactericidal concentration (MBC) was 31.24 µgml-1. Killing kinetic assay revealed complete killing of the bacterial cells within 6 h. Log reduction and percent survival of bacterial cells were analyzed from killing kinetic study. Bactericidal nature of synthesized nanoparticles was confirmed by fluorescent microscopical analysis. The effect of AgNPs on the ultrastructure of bacterial pathogen was evaluated by Transmission electron microscopy.

Enhancement of photo-bactericidal effect of tetrasulfonated hydroxyaluminum phthalocyanine on Pseudomonas aeruginosa.

At the present time, photodynamic inactivation (PDI) is receiving considerable interest for its potential as an antimicrobial therapy. The results of our study indicate that enhancement of the phototoxic effect on Pseudomonas aeruginosa can be achieved by combination of tetrasulfonated hydroxyaluminum phthalocyanine (AlPcS4) and bimetallic gold/silver nanoparticles (Au/Ag-NPs) synthesized by the cell-free filtrate of Aureobasidium pullulans. The bimetallic nanoparticles were characterized by a number of techniques including UV-vis, XPS, TEM, and SEM-EDS to be 14 ± 3 nm spherical particles coated with proteins. The effect of diode lasers with the peak-power wavelength ʎ = 650 nm (output power of 10 and 40 mW; radiation intensity of 26 and 105 mW/cm2) in combination with the AlPcS4 and the bimetallic nanoparticles mixture on the viability of P. aeruginosa rods was shown. Particularly high efficiency of killing bacterial cells was obtained for the light intensity of 105 mW/cm2, after 20, 30, and 40 min of irradiation corresponding to 126, 189, and 252 J/cm2 energy fluences. For AlPcS4+Au/Ag-NPs treatment, the viable count reduction were equal to 99.90, 99.96, and 99.975%, respectively. These results were significantly better than those accomplished for irradiated separated assays of AlPcS4 and Au/Ag-NPs.