Effective Bactericidal Activity Research Articles

Killing Streptococcus mutans in mature biofilm with a combination of antimicrobial and antibiofilm peptides.

Biofilm poses a serious challenge for the treatment of bacterial infections, as it endows bacteria a pronounced resistance to traditional antibiotics. Antimicrobial peptides (AMPs) are considered potential substitutes for antibiotics. Combinational use of AMPs with other compounds to exert antibiofilm effects has been proved to be an effective means to reduce their toxicity and maximize their antimicrobial activity. However, the combination of various AMPs with different action mechanisms is rarely investigated. A newly designed lytic AMP ZXR-2.3 combined with antibiofilm peptide IDR-1018 or KT2 was tested for the antibiofilm effect on mature Streptococcus mutans biofilms. In general, the combination of ZXR-2.3 + IDR-1018 displayed synergistic effect on both biofilm eradication and bacterial killing, while ZXR-2.3 + KT2 showed no obvious synergism. The confocal images of preformed S. mutans biofilms confirmed the effective bactericidal activity of ZXR-2.3 + IDR-1018. A tube system was applied to investigate the biofilm infection under a flow of medium and SEM images indicated the biofilm disruption and bacterial killing effects of ZXR-2.3 + IDR-1018. Quantitative RT-PCR analysis showed that IDR-1018 induced dramatic changes in the mRNA expressions of the quorum sensing (QS) related genes comC, comD, vicR, and vicK of S. mutans in mature biofilms, whereas the other peptides and ciprofloxacin did not cause obvious changes in these genes. This might explain the better synergism of ZXR-2.3 and IDR-1018. The results of this study provide a potential application using the combination of different AMPs in the treatment of mature biofilm infection.

Shape-dependent significant physical mutilation and antibacterial mechanisms of gold nanoparticles against foodborne bacterial pathogens (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) at lower concentrations.

Gold nanoparticles (AuNPs) have been reported for their most desirable properties as compared to any other noble metal-based nanoparticles, which wider their applications in various fields including catalysis, bio-imaging, biosensors, medicine, biology, and material chemistry. In this study, the shape-dependent antibacterial activity of AuNPs: nanospheres (AuNSps), nanostars (AuNSts), and nanocubes (AuNCs) were investigated against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus at lower concentrations. The optical, crystallographic and morphological characterization of AuNPs was analyzed by UV-visible spectroscopy, X-ray diffraction spectroscopy, and transmission electron microscopy (TEM). Shape-dependent antibacterial qualitative and quantitative analyses revealed an effective bactericidal activity of AuNCs against the tested bacteria, followed by AuNSps and AuNSts. The study revealed that the AuNCs are effective bactericidal agents with 100% inactivation rate. The visual analysis confirmed the antibacterial activity of AuNCs and AuNSps by showing physical mutilated bacterial cells which involved cell loss, loosening of the cell wall, loss of flagella and cellular matrix. Finally, released nucleic acid was measured for the treated bacterial cells which support the physical mutilation by releasing 38 μg/mL (Pseudomonas aeruginosa) of cellular material after treating with AuNCs. It is concluded from this study that AuNPs showed the significant antibacterial property at lower concentrations. More applications can be explored including anti-infections, decontamination, and food safety.

Quercetin potentiates meropenem activity among pathogenic carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter baumannii.

Global spread of carbapenem-resistant Pseudomonas aeruginosa (CRPsA) and Acinetobacter baumannii (CRAB) is an emerging clinical problem. Since, quercetin is a well-known antibacterial agent; it would be relevant to demonstrate synergy between quercetin and meropenem and elucidate molecular basis of effective bactericidal activity of quercetin-meropenem against CRPsA and CRAB. Hence, minimum inhibitory concentration (MIC), checkerboard, time-kill and Baclight assays were performed to determine the antibacterial and synergistic activity of quercetin with meropenem against CRPsA and CRAB. To corroborate synergism, fractional inhibitory concentration index, combination index calculation and isobologram analysis were performed on selected isolates. Finally, to elucidate molecular basis of effective bactericidal activity of quercetin-meropenem against CRPsA and CRAB, effect of meropenem, quercetin and their combinations on cellular morphology and levels of blaNDM , mexB and adeB expressions were evaluated on selected isolates by scanning electron microscope and qRT-PCR. Quercetin exhibited synergy with meropenem. It inhibited blaNDM and AdeB expression. Half-MIC combination of quercetin-meropenem exerted bactericidal activity by disrupting cell wall/membrane integrity and altering cellular morphology. Quercetin could potentiate meropenem activity against CRPsA and CRAB. This study had demonstrated bactericidal and synergistic activity of quercetin with meropenem against CRPsA and CRAB.

Antibacterial Activity of combinatorial treatments composed of transition-metal/antibiotics against Mycobacterium tuberculosis

Notwithstanding evidence that tuberculosis (TB) is declining, one of the greatest concerns to public health is the emergence and spread of multi-drug resistant strains of Mycobacterium tuberculosis (MDR-TB). MDR-TB are defined as strains which are resistant to at least isoniazid (INH) and rifampicin, the two most potent TB drugs, and their increasing incidence is a serious concern. Recently, notable efforts have been spent on research to pursue novel treatments against MDR-TB, especially on synergistic drug combinations as they have the potential to improve TB treatment. Our research group has previously reported promising synergistic antimicrobial effects between transition-metal compounds and antibiotics in Gram-negative and Gram-positive bacteria. In this work, we evaluated antimycobacterial activity of transition-metals/antibiotics combinatorial treatments against first-line drug resistant strains of Mycobacterium tuberculosis. Our data showed that INH/AgNO3 combinatorial treatment had an additive effect (bactericidal activity) in an isoniazid-resistant clinical strain of Mycobacterium tuberculosis. Moreover, in vitro evaluation of cytotoxicity induced by both, the individual tratments of AgNO3 and INH and the combinatorial treatment of INH/AgNO3 in murine RAW 264.7 macrophages and human A549 lung cells; showed no toxic effects. Together, this data suggests that the INH/AgNO3 combinatorial treatment could be used in the development of new strategies to treat resistant strains of Mycobacterium tuberculosis.

Extraction and Antistaphylococcal Study of the Essential Oil of Origanum vulgare L. (Guelma-Algeria)

Antimicrobial properties of plant essential oils (EO) have been investigated through several observations and clinical studies which purpose them as potential tools to overcome the microbial drug resistance (MDR) problem. The aim of this research was to study the antibacterial effect of a traditional plant EO, Oraginum vulgare L., against clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) through disk diffusion and agar dilution methods. The EO showed very effective bactericidal activity towards the majority of the tested bacterial strains with inhibition zone diameters in the range of 9.9-31.9 mm and a minimum inhibitory concentration (MIC) ranging from 0.314 to 0.628 mg/ml. These results suggest that the essential oil of Origanum vulgare L. may be a useful alternative to antibiotics for the control of the infections caused by Staphylococcus aureus.

Structural and Functional Assessment of mBjAMP1, an Antimicrobial Peptide from Branchiostoma japonicum, Revealed a Novel α-Hairpinin-like Scaffold with Membrane Permeable and DNA Binding Activity

Here we describe the three-dimensional structure and antimicrobial mechanism of mBjAMP1, an antimicrobial peptide (AMP) isolated from Branchiostoma japonicum. The structure of mBjAMP1 was determined by 2D solution NMR spectroscopy and revealed a novel α-hairpinin-like scaffold stabilized by an intramolecular disulfide bond. mBjAMP1 showed effective growth inhibition and bactericidal activities against pathogenic bacteria but was not cytotoxic to mammalian cells. Antimicrobial mechanism studies using fluorescence-based experiments demonstrated that mBjAMP1 did not disrupt membrane integrity. Laser-scanning confocal microscopy indicated that mBjAMP1 is able to penetrate the bacterial cell membrane without causing membrane disruption. Moreover, gel retardation assay suggested that mBjAMP1 directly binds to bacterial DNA as an intracellular target. Collectively, mBjAMP1 may inhibit biological functions by binding to DNA or RNA after penetrating the bacterial cell membrane, thereby causing cell death. These results suggest that mBjAMP1 may present a promising template for the development of peptide-based antibiotics.

Photothermally Active Reduced Graphene Oxide/Bacterial Nanocellulose Composites as Biofouling-Resistant Ultrafiltration Membranes.

Biofouling poses one of the most serious challenges to membrane technologies by severely decreasing water flux and driving up operational costs. Here, we introduce a novel anti-biofouling ultrafiltration membrane based on reduced graphene oxide (RGO) and bacterial nanocellulose (BNC), which incoporates GO flakes into BNC in situ during its growth. In contrast to previously reported GO-based membranes for water treatment, the RGO/BNC membrane exhibited excellent aqueous stability under environmentally relevant pH conditions, vigorous mechanical agitation/sonication, and even high pressure. Importantly, due to its excellent photothermal property, under light illumination, the membrane exhibited effective bactericidal activity, obviating the need for any treatment of the feedwater or external energy. The novel design and in situ incorporation of the membranes developed in this study present a proof-of-concept for realizing new, highly efficient, and environmental-friendly anti-biofouling membranes for water purification.

Unveiling the Multifaceted Mechanisms of Antibacterial Activity of Buforin II and Frenatin 2.3S Peptides from Skin Micro-Organs of the Orinoco Lime Treefrog (Sphaenorhynchus lacteus).

Amphibian skin is a rich source of natural compounds with diverse antimicrobial and immune defense properties. Our previous studies showed that the frog skin secretions obtained by skin micro-organs from various species of Colombian anurans have antimicrobial activities against bacteria and viruses. We purified for the first time two antimicrobial peptides from the skin micro-organs of the Orinoco lime treefrog (Sphaenorhynchus lacteus) that correspond to Buforin II (BF2) and Frenatin 2.3S (F2.3S). Here, we have synthesized the two peptides and tested them against Gram-negative and Gram-positive bacteria, observing an effective bactericidal activity at micromolar concentrations. Evaluation of BF2 and F2.3S membrane destabilization activity on bacterial cell cultures and synthetic lipid bilayers reveals a distinct membrane interaction mechanism. BF2 agglutinates E. coli cells and synthetic vesicles, whereas F2.3S shows a high depolarization and membrane destabilization activities. Interestingly, we found that F2.3S is able to internalize within bacterial cells and can bind nucleic acids, as previously reported for BF2. Moreover, bacterial exposure to both peptides alters the expression profile of genes related to stress and resistance response. Overall, these results show the multifaceted mechanism of action of both antimicrobial peptides that can provide alternative tools in the fight against bacterial resistance.

Integration of pharmacokinetic-pharmacodynamic for dose optimization of doxycycline against Haemophilus parasuis in pigs.

The aims of this study were to establish optimal doses of doxycycline (dox) against Haemophilus parasuis on the basis of pharmacokinetic-pharmacodynamic (PK-PD) integration modeling. The infected model was established by intranasal inoculation of organism in pigs and confirmed by clinical signs, blood biochemistry, and microscopic examinations. The recommended dose (20mg/kg b.w.) was administered in pigs through intramuscular routes for PK studies. The area under the concentration 0- to 24-hr curve (AUC0-24 ), elimination half-life (T½ke ), and mean residence time (MRT) of dox in healthy and H.parasuis-infected pigs were 55.51±5.72 versus 57.10±4.89μg·hr/ml, 8.28±0.91 versus 9.80±2.38hr, and 8.43±0.27 versus 8.79±0.18hr, respectively. The minimal inhibitory concentration (MIC) of dox against 40 H.parasuis isolates was conducted through broth microdilution method, the corresponding MIC50 and MIC90 were 0.25 and 1μg/ml, respectively. The Ex vivo growth inhibition data suggested that dox exhibited a concentration-dependent killing mechanism. Based on the observed AUC24hr /MIC values by modeling PK-PD data in H.parasuis-infected pigs, the doses predicted to obtain bacteriostatic, bactericidal, and elimination effects for H.parasuis over 24hr were 5.25, 8.55, and 10.37mg/kg for the 50% target attainment rate (TAR), and 7.26, 13.82, and 18.17mg/kg for 90% TAR, respectively. This study provided a more optimized alternative for clinical use and demonstrated that the dosage 20mg/kg of dox by intramuscular administration could have an effective bactericidal activity against H.parasuis.

In Vitro Bactericidal and Virucidal Efficacy of Povidone-Iodine Gargle/Mouthwash Against Respiratory and Oral Tract Pathogens.

IntroductionRecent virus epidemics and rising antibiotic resistance highlight the importance of hygiene measures to prevent and control outbreaks. We investigated the in vitro bactericidal and virucidal efficacy of povidone-iodine (PVP-I) 7% gargle/mouthwash at defined dilution against oral and respiratory tract pathogens.MethodsPVP-I was tested against Klebsiella pneumoniae and Streptococcus pneumoniae according to bactericidal quantitative suspension test EN13727 and against severe acute respiratory syndrome and Middle East respiratory syndrome coronaviruses (SARS-CoV and MERS-CoV), rotavirus strain Wa and influenza virus A subtype H1N1 according to virucidal quantitative suspension test EN14476. PVP-I 7% gargle/mouthwash was diluted 1:30 with water to a concentration of 0.23% (the recommended concentration for “real-life” use in Japan) and tested at room temperature under clean conditions [0.3 g/l bovine serum albumin (BSA), viruses only] and dirty conditions (3.0 g/l BSA + 3.0 ml/l erythrocytes) as an interfering substance for defined contact times (minimum 15 s). Rotavirus was tested without protein load. A ≥ 5 log10 (99.999%) decrease of bacteria and ≥ 4 log10 (99.99%) reduction in viral titre represented effective bactericidal and virucidal activity, respectively, per European standards.ResultsPVP-I gargle/mouthwash diluted 1:30 (equivalent to a concentration of 0.23% PVP-I) showed effective bactericidal activity against Klebsiella pneumoniae and Streptococcus pneumoniae and rapidly inactivated SARS-CoV, MERS-CoV, influenza virus A (H1N1) and rotavirus after 15 s of exposure.ConclusionPVP-I 7% gargle/mouthwash showed rapid bactericidal activity and virucidal efficacy in vitro at a concentration of 0.23% PVP-I and may provide a protective oropharyngeal hygiene measure for individuals at high risk of exposure to oral and respiratory pathogens.FundingMundipharma Research GmbH & Co. KG (MRG).

Ultrasonic assisted synthesis with enhanced visible-light photocatalytic activity of NiO/Ag3VO4 nanocomposite and its antibacterial activity

The NiO/Ag3VO4 nanocomposite photocatalysts were developed by ultrasonic assisted preparation method to study the photocatalytic activity under visible light irradiation. The samples were characterized by UV-DRS, XRD, FT-IR, XPS, SEM, EDX, TEM, EIS and BET analysis. The photocatalytic activity of NiO/Ag3VO4 nanocomposite for the photodegradation of 4-Nitro Phenol (4-NP) and Rose Bengal (RB) under visible light irradiation was studied and it is observed that the activity has been much higher than that of the pure Ag3VO4. DRS spectrum shows the absorption edge of NiO-Ag3VO4 in visible region of spectrum. The formation of cubic structured NiO and orthorhombic structured Ag3VO4 was confirmed by powder X-ray diffraction analysis. The results of XPS analysis confirmed the coexistence of NiO and Ag3VO4 in the NiO/Ag3VO4 composite. The specific surface area and pore structure of the prepared samples were measured by BET. Enhanced charge separation efficiency was confirmed by electrochemical impedance spectroscopy (EIS) measurements. The kinetics of the NiO/Ag3VO4 nanocomposite was proposed to investigate the intervened effects of NiO to Ag3VO4 on the promotion of photocatalytic property. NiO/Ag3VO4 was found to be stable and reusable without appreciable loss of catalytic activity up to four consecutive cycles. A possible electron-hole transfer mechanism at the NiO/Ag3VO4 interface is proposed. It also showed effective and efficient bactericidal activities against Staphylococcus aureus, Streptococcus, Proteus and Escherichia coli bacteria. Our results provide some new insights on the performance of visible light photocatalysts on environmental remediation.

Silver nanoparticles have lethal and sublethal adverse effects on development and longevity by inducing ROS-mediated stress responses

Silver nanoparticles (AgNPs) are widely used in the household, medical and industrial sectors due to their effective bactericidal activities and unique plasmonic properties. Despite the promising advantages, safety concerns have been raised over the usage of AgNPs because they pose potential hazards. However, the mechanistic basis behind AgNPs toxicity, particularly the sublethal effects at the organismal level, has remained unclear. In this study, we used a powerful in vivo platform Drosophila melanogaster to explore a wide spectrum of adverse effects exerted by dietary AgNPs at the organismal, cellular and molecular levels. Lethal doses of dietary AgNPs caused developmental delays and profound lethality in developing animals and young adults. In contrast, exposure to sublethal doses, while not deadly to developing animals, shortened the adult lifespan and compromised their tolerance to oxidative stress. Importantly, AgNPs mechanistically resulted in tissue-wide accumulation of reactive oxygen species (ROS) and activated the Nrf2-dependent antioxidant pathway, as demonstrated by an Nrf2 activity reporter in vivo. Finally, dietary AgNPs caused a variety of ROS-mediated stress responses, including apoptosis, DNA damage, and autophagy. Altogether, our study suggests that lethal and sublethal doses of AgNPs, have acute and chronic effects, respectively, on development and longevity by inducing ROS-mediated stress responses.

Enzymatic activity of bromelain isolated pineapple (Ananas comosus) hump and its antibacterial effect on Enterococcus faecalis

Background: Enterococcus faecalis is the frequent cause of oral infections, such as periodontitis, infected root canals, and peri-radicular abscesses. Pineapple ( Ananas comosus ) fruit contains bromelain, one of proteolytic enzymes associated with several health benefits. Bromelain has been shown to promote healthy digestion, stimulate the immune system, improve cardiovascular conditions, and accelerate wound healing. Bromelain compounds possess anti-inflammatory and anticancer properties and exhibit antibacterial activity. Objective: To analyze the enzymatic activity of bromelain extracted from pineapple hump and investigate the antibacterial effect of bromelain against E. faecalis. Methods: Pineapple hump was dried and extracted with maceration technique. Further purification was obtained by ammonium sulfate fractionation, dialysis and ion exchange chromatography. Minimum inhibitory concentration (MIC) tests using diffusion and dilution techniques tested the antibacterial activity of the bromelain extract on E. faecalis. A one-way analysis of variance (ANOVA) test analyzed the significance of the differences in the E. faecalis inhibition zones after treatment with a range of bromelain extract concentrations. Differences were considered statistically significant if p < 0.05. Results: The specific activity of bromelain in the crude extract was 62.89 U/mg. Furthermore, bromelain activity using ammonium sulfate fractionation was 50.99 U/mg, dialysis was 54.59 U/mg, and ion exchange chromatography was 152.38 U/mg. The bromelain extract showed effective inhibitory and bactericidal activity against E. faecalis. The results of the inhibition test using a bromelain extract purified by ion exchange chromatography demonstrated that a concentration as small as 12.5% was effective in inhibiting the growth of E. faecalis (p < 0.05). Conclusion: The highest enzymatic activity of bromelain was found after purification with ion exchange chromatography. Bromelain exerted an antibacterial effect against a potent endodontic pathogen, but further studies are needed to explore this effect.

Assessment of synergistic antibacterial activity of combined biosurfactants revealed by bacterial cell envelop damage

Besides potential surface activity and some beneficial physical properties, biosurfactants express antibacterial activity. Bacterial cell membrane disrupting ability of rhamnolipid produced by Pseudomonas aeruginosa C2 and a lipopeptide type biosurfactant, BS15 produced by Bacillus stratosphericus A15 was examined against Staphylococcus aureus ATCC 25923 and Escherichia coli K8813. Broth dilution technique was followed to examine minimum inhibitory concentration (MIC) of both the biosurfactants. The combined effect of rhamnolipid and BS15 against S. aureus and E. coli showed synergistic activity by expressing fractional inhibitory concentration (FIC) index of 0.43 and 0.5. Survival curve of both the bacteria showed bactericidal activity after treating with biosurfactants at their MIC obtained from FIC index study as it killed >90% of initial population. The lesser value of MIC than minimum bactericidal concentration (MBC) of the biosurfactants also supported their bactericidal activity against both the bacteria. Membrane permeability against both the bacteria was supported by amplifying protein release, increasing of cell surface hydrophobicity, withholding capacity of crystal violet dye and leakage of intracellular materials. Finally cell membrane disruption was confirmed by scanning electron microscopy (SEM). All these experiments expressed synergism and effective bactericidal activity of the combination of rhamnolipid and BS15 by enhancing the bacterial cell membrane permeability. Such effect of the combination of rhamnolipid and BS15 could make them promising alternatives to traditional antibiotic in near future.

Antioxidant and Antibacterial Activities of the Essential Oil of Origanum vulgare L. Against Escherichia coli Strains

The aim of this study is to investigate the antioxidant activity and the antibacterial efficiency of the essential oil extracted by hydrodistillation from leaves of Origanum vulgare against ten (10) clinical strains of Escherichia coli and a reference strain E. coli ATCC provided by the laboratory of microbiology, faculty of medicine, University of Badji Mokhtar (Annaba, Algeria). The chemical composition of the essential oil was characterized by gas chromatography-Mass spectroscopy (GC-MS). Antioxidant activity was evaluated by radical scavenging ability (DPPH method). The antibacterial activity was detected by using disc-diffusion method and the agar dilution method which used for microbial growth inhibition at various concentrations of oil (calculating the minimum inhibitory concentration). The yield of essential oil of O.vulgare was 1.15 % and the major compounds were thymol (32.58 %), γ-terpinen (18.76 %), durenol (17.92 %) and durene (11.40 %). The essential oil showed an antioxidant activity (IC50 = 1.28±0.07 mg/ml) which was lower than the standard antioxidants (ascorbic acid and BHT). It showed a very effective bactericidal activity towards all tested bacterial strains with maximal inhibition zones in the range of 21.3-32.6 mm and a minimum inhibitory concentration (MIC) ranging from 0.314 to 0.628 mg/ ml.

A novel method to generate Salmonella Typhi Ty21a ghosts exploiting the λ phage holin-endolysin system.

Human typhoid fever caused by Salmonella Typhi still poses a severe global disease burden in developing countries despite the availability of commercial vaccines. In this study, we constructed a non-living S. Typhi Ty21a vaccine candidate by employing a lambda (λ) phage-derived holin-endolysin system to efficiently construct bacterial ghosts. The lysis plasmid pJHL464 harbors an R lysis cassette that is stringently regulated by dual promoters containing cI857/λPR and ParaBAD/araC components. The plasmid was introduced into an asd gene-deleted S. Typhi Ty21a strain designated JOL1675. The in vitro expression of endolysin (~17.76 kDa) in the subsequent JOL1675 vaccine construct when grown under lysis inducible conditions was validated by immunoblotting. In scanning electron microscopy analysis, surface transmembrane tunnels and a collapsed body were visualized in the ghosts. Following 48 h of lysis, no viable JOL1675 cells remained, indicating that lysis of all cells was achieved. Subcutaneous immunizations of mice with the JOL1675 ghosts produced significantly increasing titers of serum IgG and vaginal wash secretory IgA antibodies against JOL1675 outer membrane proteins during the observational period. Further, serum collected at 6 weeks post-immunization of rabbits exhibited effective bactericidal activity against wild type S. Typhi in the presence of complement. These data showed that JOL1675 ghosts are highly immunogenic and elicit humoral and mucosal responses expected to correlate with protective immunity against S. typhi. Collectively, our findings support the conclusion that incorporating a λ phage holin-endolysin-mediated lysis construct into S. Typhi is an efficient strategy for developing a novel and safe non-living typhoid vaccine candidate.

Characterization of three autolysins with activity against cereulide-producing Bacillus isolates in food matrices

Bacillus cereus is a pathogen related with diarrhoeal or emetic food poisoning cases, of which the latter caused by the cereulide-producing isolates are more severe with several reported lethal cases. It is therefore necessary to develop an effective strategy to prevent the propagation of B. cereus in the food supply. In this study, three autolysins from the cereulide-producing B. cereus group isolates, LysIS075, LysF8819.1 and LysCER057, were identified and characterized. The results showed that the three autolysins were highly lytic and bactericidal to the tested cereulide-producing B. cereus group strains and cross-lytic against other tested B. cereus group strains, and they could inhibit the spore germination and propagation of their tested derived emetic strains. Physical and chemical characterization showed that all the three autolysins were alkalophilic with the optimal activity at pH9.0 or 9.5 with one exception of LysF8819.1 also having significant lytic activity at pH5.0, and they all had relative strong lytic activity at 37–50°C during the 30minute assay. However, LysCER057 showed relative susceptibility to thermo-condition. Remarkably, the separate or cock-tail addition of the three autolysins in food matrices (milk and rice porridge) showed effective bactericidal activity within the tested 2h. All the results revealed that the three autolysins might be potential candidates to control emetic B. cereus strains in different applications.

Novel, facile, and fast technique for synthesis of AgCl nanorods loaded on activated carbon for removal of methylene blue dye

This article introduces a novel, facile, and simple technique for synthesis of AgCl nanorods modified activated carbon (AgCl-NRs-AC) for the first time as a new sorbent for removal of hazardous methylene blue (MB) dye from aqueous solution. Different characterization methods including field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and response surface methodology (RSM) were applied to examine the removal of MB by AgCl nanorods loaded on activated carbon as a new sorbent. A quadratic model was used to predict the variables. Central composite design (CCD) was used for the evaluation of adsorption parameters effect such as pH, adsorption dose, initial dye concentration, and contact time on the percentage removal of MB dye from aqueous solution. Analysis of variance (ANOVA) exhibited a high R2 value of 0.9900, high F-value (105.79), very low P-value, and non-significant lack of fit demonstrating good correlation between experimental and predicted values of the response. The optimum conditions were determined to be pH=7, adsorbent dose=15mg, initial dye concentration 25mgL−1, and contact time of 16min. Under the optimum conditions, the maximum removal of MB dye was 96.01670% with satisfactory desirability of 0.978. The effect of variables were examined and discussed by depicting three dimensional (3D) and contour (2D) plots to analyze the changes and the predicted responses. Results revealed that Langmuir and pseudo-second-order models were the best models for describing the adsorption process. Antibacterial activity of the synthesized nanorods were also evaluated by testing against some Gram-negative and Gram-positive bacteria. The synthesized nanorods showed effective bactericidal activity.

A biodegradable antibiotic-eluting PLGA nanofiber-loaded deproteinized bone for treatment of infected rabbit bone defects.

We fabricated a biodegradable antibiotic-eluting poly(d,l)-lactide-co-glycolide nanofiber-loaded deproteinized bone (ANDB) scaffold that provided sustained delivery of vancomycin to repair methicillin-resistant Staphylococcus aureus bone defects. To fabricate the biodegradable ANDB, poly(d,l)-lactide-co-glycolide and vancomycin were first dissolved in 1,1,1,3,3,3-hexafluoro-2-propano. The solution was then electrospun to produce biodegradable antibiotic-eluting membranes that were deposited on the surface of bovine deproteinized cancellous bone. We used scanning electron microscopy to determine the properties of the scaffold. Both elution and high-performance liquid chromatography assays were used to evaluate the invitro vancomycin release rate from the ANDB scaffold. Three types of scaffolds were co-cultured with bacteria to confirm the invitro antibacterial activity. The infected bone defect rabbit model was induced by injecting 10(7) colony forming units of a methicillin-resistant Staphylococcus aureus strain into the radial defect of rabbits. Animals were then separated into treatment groups and implanted according to the following scheme: ANDB scaffold in group A, poly(d,l)-lactide-co-glycolide nanofiber-loaded deproteinized bone (NDB) scaffold with intravenous (i.v.) vancomycin in group B, and NDB scaffold alone in group C. Treatment efficacy was evaluated after eight weeks using radiological, microbiological, and histological examinations. Invitro results revealed that biodegradable ANDB scaffolds released concentrations of vancomycin that were greater than the minimum inhibitory concentration for more than four weeks. Bacterial inhibition tests also confirmed antibacterial efficacy lasted for approximately four weeks. Radiological and histological scores obtained invivo revealed significant differences between groups A, B and C. Importantly, group A had significantly lower bacterial load and better bone regeneration when compared to either group B or C. Collectively, these results show that our fabricated ANDB scaffolds possess: (1) effective bactericidal activity against methicillin-resistant Staphylococcus aureus, (2) the ability to promote site-specific bone regeneration, and (3) the potential for use in the treatment of infected bone defects.

Chemical Composition and Antibacterial Activity of the Essential of Cedrus atlantica (Cedarwood oil)

The purpose of this study was to determine the chemical composition and antibacterial activity of the Moroccan Cedarwood essential oil. The sawdust samples of Cedrus atlantica were collected from Azrou, located in the heart of The Middle Atlas region of Morocco. The plant samples were subjected to hydrodistillation for eight hours. The oils were then analysed by Gas Chromatography equipped with flame ionization detector (GC-FID) and Gas chromatography coupled with Mass spectrometry (GC-MS). The antimicrobial activities were tested in vitro on gram-negative bacteria Escherichia coli and Salmonella, as well as gram-positive Staphylococcus aureus, Bacillus subtilis and Bacillus cereus using the agar diffusion assay/aromatogramme and minimum inhibitory concentration (MIC). Three bacterial strains (Escherichia coli, Bacillus subtilis and Bacillus cereus) were found to be sensitive to cedarwood essential oil and showed effective bactericidal activity with a Minimum Inhibitory Concentration of 0,4 μl/ml for Escherichia coli and Bacillus cereus, and 0,2 μl/ml for Bacillus subtilis.