Effective Biocide Research Articles

Efficiency of Some Biocides as Safe Alternatives to Fungicides on Cercospora Leaf Spot Control, their Effect on Biochemical Constituent and Yield of Sugar Beet

Cercospora leaf spot incited by Cercospora beticola Sacc. is a very detrimental fungal disease affecting sugar beet crop production in Egypt as well as sugar yield. The efficacy of four selected commercial biocides i.e., Biobac, Bio-Arc, Bio-Zeid and Plant Guard, was investigated to control Cercospora leaf spot on sugar beet plants in comparison with the recommended fungicide Score as a check difenoconazole fungicide as well as untreated control under field conditions at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt. The biocides and fungicide were sprayed at different three spray regimes as two sprays, four sprays or six sprays with 15 days intervals between sprays for such treatment. All tested biocides and Score fungicide led to significant decrease in Cercospora leaf spot disease severity of the treated sugar beet plants in comparison with control treatment. Increasing spraying numbers of the tested biocides or Score fungicide from two times to six sprays per season caused increasing reduction of Cercospora leaf spot severity. Spraying Plant guard, Bio-Zeid and Biobac biocides six times achieved very comparable effectiveness to Score treatment at the same spray regime in the two growing seasons 2015/2016 and 2016/2017, whereas, Bio-Arc was the less effective biocide treatment particularly when sprayed two times per season. All tested biocides at different spraying regimes led to significant increase in values of phenolic compounds, total chlorophyll, (achieved higher quality traits at the end of the season), sucrose (%) and purity (%) and top, root as well as sugar yield quality of sugar beet were significantly increased. The impurities of produced sugar as sodium, potassium and α-amino nitrogen in the juice were significantly decreased in comparison with untreated control during the two growing seasons. Overall results clarified that spraying Score fungicide or Bio- Zeid, Plant guard and Biobac, respectively six times resulted the highest increase of quality traits as sucrose (%) and purity %) and top, root and sugar yields of sugar beet and significant decrease in total amino acid, juice impurities (Na, K and α-a N %), whereas Bio- Arc when applied two times recorded the least effective treatment close to the control during the two growing seasons 2015/2016 and 2016/2017. It was concluded that biocides, Bio-Zeid, Plant guard and Biobac could be sprayed six times/season at 15 days intervals as alternatives to fungicide applications to control Cercospora leaf spot of sugar beet and to produce higher yields of root and sugar with better quality.

Preliminary Investigation on the Resistance of Some Environmental Bacteria in Yola Metropolis, Adamawa State, Nigeria, to Biocides and Antibiotics

Background: Bacteria are capable of developing resistance against the effect of antibacterial agents used in eliminating them from their typical environment. This should be monitored to ensure an economic practice while eliminating or preventing bacteria in an environment. Objectives: The aim of this study was to isolate and identify environmental bacteria and investigate their ability to resist antibacterial effects of biocides and antibiotics. Methods: Environmental samples were collected and different bacterial isolates were obtained and characterized. Antimicrobial susceptibility testing was carried out on 6 of the obtained isolates. Results: Six different bacterial species were isolated and characterized from the environmental samples, including Staphylococcus aureus (32%), Klebsiella spp. (20%), Salmonella spp. (16%), Proteus spp. (15%), Staphylococcus spp. (11%), and Serratia spp. (6%). The most effective biocides were the Tiscol disinfectant and Dettol antiseptics while the most effective antibiotic was Tarivid. However, all the tested isolates showed different levels of resistance to all the antibacterials. Conclusions: Biocide and antibiotic resistant bacteria species were isolated from the environment and most of them showed some resistance to administered antibacterials; Staphylococcus aureus was the most resistant organism to antibiotics while Proteus spp. was the most resistant to the 3 biocides. The 3 biocides had different rates of inhibition, with Tiscol disinfectant and Dettol antiseptics having greater effectiveness against all the isolates.

Comparative Assessment of Biocidal Activity of Different RGO/Ceramic Oxide-Ag Nanocomposites

The aim of this study was to compare the bioactivity of RGO/ceramic oxide-Ag nanocomposites. Different ceramic oxides (MexOy) i.e.: Al2O3, TiO2, SiO2 and ZnO2 were in situ co-deposited with Ag nanoparticles on the surface of RGO resulting in the formation of a nanocomposite structure of stacked flakes. The results of our investigations indicate that it is possible to obtain the targeted biocidal properties of the RGO/Ag system by choosing the appropriate ceramic oxide as a modificator of Ag nanoparticles. The strongest antimicrobial properties against E. coli, S. aureus and Bacillus sp. strains were achieved for RGO/SiO2-Ag nanocomposite whereas for Sarcina sp. bacteria the most effective biocide was RGO/TiO2-Ag nanocomposite.

Efficacy of chlorine dioxide gas in reducing Escherichia coli and Salmonella from broiler house environments

Escherichia coli and Salmonella spp. are considered to be the major pathogens associated with human transmissible infectious diseases in the air of poultry houses. Chlorine dioxide (ClO2) is an effective biocide against a wide range of microorganisms. Accordingly, this study investigated the efficiency of gaseous ClO2 application for disinfecting broiler houses by collecting air samples before and after fumigation using a passive method. Fumigation was performed with 125 mL or 250 mL of ClO2 liquid (containing 2,000 ppm of ClO2) and 3 trials were conducted for each dose. A total of 27 petri dishes were used for each trial (for each type of bacteria: E. coli or Salmonella) and placed in 3 different locations (front, middle and back) and 3 different positions (top, middle and floor) of the broiler shed. Air samples were collected at 10 min, 1 h, 3 h, 6 h, and 12 h before and after fumigation to evaluate the air quality in terms of the concentration of E. coli and Salmonella. Both levels of ClO2 were capable of reducing the concentration of E. coli from broiler house air during all measuring periods except 10 min, with highest disinfection rate being observed at 6 h. With the exception of 1 h, the concentration of Salmonella was also reduced after fumigation with ClO2 in all measuring period; with the highest disinfection rate occurring at 6 h. Fumigation with ClO2 had no negative effect on birds’ health condition. Taken together, these results suggest that the application of gaseous ClO2 at the investigated levels can be an effective option for reducing bacterial load from broiler house environments.

Facile synthesis of novel soluble cellulose-grafted hyperbranched polymers as potential natural antimicrobial materials

A new class of soluble cellulose-grafted hyperbranched polymers has been synthesized by a facile “hypergrafting” reaction using bis(2-chloroethyl)amine and soluble cellulose tosylates. The molecular structures of the obtained new materials were characterized by 13C NMR, FTIR spectroscopy, and elemental analysis. The degree of substitution of the hyperbranched cellulose derivatives ranges between 0.13–0.53. The new cellulose-based materials were soluble in various polar aprotic organic solvents. The thermal properties of the new cellulose materials were investigated by thermal gravimetric analysis. Antibacterial activity of the new cellulose derivatives was evaluated by diffusion disk tests against various gram negative and positive bacteria. Our results suggested that the obtained natural cellulosic materials can act as effective polymeric biocides, and may have great potential in various antimicrobial materials applications.

Isolation and characterization of Lactobacillus paracasei LPC and phage ΦT25 from fermented milk

Infections by bacteriophages (phages) cause great economic losses in the dairy industry. Most dairy plants have encountered severe phage contamination, resulting in fermentation failure. This study was the first to isolate and characterize a lactic acid bacteria (LAB) phage from abnormal fermented milk in a Thailand factory. The results showed that only 1 LAB isolate was obtained. This LAB was identified by API 50 CHL, 16S rDNA sequence analysis and PCR using species-specific primers that were designed to differentiate the Lactobacillus casei group. From the above evidence, this isolate was identified as Lactobacillus paracasei. Small plaques were formed on double layer agar plates, and the Lb. paracasei phage was designated as ΦT25. Transmission electron micrographs showed that the phage ΦT25 had a hexagonal head (55 ± 4.6 nm in diameter) and a long noncontractile tail (184 ± 7.8 nm in length), indicating that it belongs to Bradley's group B or the Siphoviridae family. The one-step growth curve revealed a latent period of 55 min, with a burst size of approximately 38 phage particles per infected cell. Our host-range determination study demonstrated that this phage was incapable of cross-infecting with other genera or species of LAB tested. The genome size of the phage ΦT25 was estimated to be 41 kb. This phage did not survive heating to 72 and 90 °C and pH 2. The most effective chemical biocides were 75% ethanol, 800 ppm hypochlorite, 0.15%(v/v) peracetic acid, 1% (w/v) Virkon®, 5% Dettol® and 2-, 5% Decon® 90. This study has provided relevant information about the Lb. paracasei phage and recommendations for phage control in dairy plants.

Chemodenitrification in the cryoecosystem of Lake Vida, Victoria Valley, Antarctica.

Lake Vida, in the Victoria Valley of East Antarctica, is frozen, yet harbors liquid brine (~20% salt, >6 times seawater) intercalated in the ice below 16m. The brine has been isolated from the surface for several thousand years. The brine conditions (permanently dark, -13.4°C, lack of O2 , and pH of 6.2) and geochemistry are highly unusual. For example, nitrous oxide (N2 O) is present at a concentration among the highest reported for an aquatic environment. Only a minor 17 O anomaly was observed in N2 O, indicating that this gas was predominantly formed in the lake. In contrast, the 17 O anomaly in nitrate (NO3-) in Lake Vida brine indicates that approximately half or more of the NO3- present is derived from atmospheric deposition. Lake Vida brine was incubated in the presence of 15 N-enriched substrates for 40days. We did not detect microbial nitrification, dissimilatory reduction of NO3- to ammonium (NH4+), anaerobic ammonium oxidation, or denitrification of N2 O under the conditions tested. In the presence of 15 N-enriched nitrite (NO2-), both N2 and N2 O exhibited substantial 15 N enrichments; however, isotopic enrichment declined with time, which is unexpected. Additions of 15 N-NO2- alone and in the presence of HgCl2 and ZnCl2 to aged brine at -13°C resulted in linear increases in the δ15 N of N2 O with time. As HgCl2 and ZnCl2 are effective biocides, we interpret N2 O production in the aged brine to be the result of chemodenitrification. With this understanding, we interpret our results from the field incubations as the result of chemodenitrification stimulated by the addition of 15 N-enriched NO2- and ZnCl2 and determined rates of N2 O and N2 production of 4.11-41.18 and 0.55-1.75nmolL-1 day-1 , respectively. If these rates are representative of natural production, the current concentration of N2 O in Lake Vida could have been reached between 6 and 465years. Thus, chemodenitrification alone is sufficient to explain the high levels of N2 O present in Lake Vida.

Spray- and spin-assisted layer-by-layer assembly of copper nanoparticles on thin-film composite reverse osmosis membrane for biofouling mitigation

Copper nanoparticles (CuNPs) have long been considered as highly effective biocides; however, the lack of suitable methods for loading CuNPs onto polymeric membranes is recognized as being one of the primary reasons for the limited research concerning their application in membrane industries. A highly efficient spray- and spin-assisted layer-by-layer (SSLbL) method was developed to functionalize the TFC polyamide RO membranes with controllable loading of CuNPs for biofouling control. The SSLbL method was able to produce a uniform bilayer of polyethyleneimine-coated CuNPs and poly(acrylic) acid in less than 1 min, which is far more efficient than the traditional dipping approach (25–60 min). The successful loading of CuNPs onto the membrane surface was confirmed by XPS analysis. Increasing the number of bilayers from 2 to 10 led to an increased quantity of CuNPs on the membrane surface, from 1.75 to 23.7 μg cm−2. Multi-layer coating exhibited minor impact on the membrane water permeation flux (13.3% reduction) while retaining the original salt rejection ability. Both static bacterial inactivation and cross-flow filtration tests demonstrated that CuNPs could significantly improve anti-biofouling property of a polyamide membrane and effectively inhibit the permeate flux reduction caused by bacterial deposition on the membrane surface. Once depleted, CuNPs can also be potentially regenerated on the membrane surface via the same SSLbL method.

Effects of simulated microgravity on the microbial physiology of Ralstonia pickettii isolates from the International Space Station

Bacterial growth in the potable water system aboard the International Space Station is currently controlled using iodine. While iodine has been shown to be an effective biocide, it can accumulate in the thyroid of some individuals, impart a bad taste to drinking water, and is incompatible with the biocidal silver system used in the Russian segment. In comparison, silver is effective as an antimicrobial at very low concentrations, poses health risks only at very high intake levels, and is readily excreted from the body. In addition to controlling bacteria‐related risks to crew and spacecraft health, biocide is also necessary to prevent interplanetary transport of microorganisms. In this study, we investigated the effects of various stress assays on the bacterial isolate Ralstonia pickettii in a simulated microgravity environment. Isolates were subjected to acid, thermal, and silver biocide stress assays at three different concentrations. A rotating wall vessel culture apparatus was used to provide a low‐shear culture environment, simulating certain aspects of spaceflight. This environment is known as low‐shear modeled microgravity (LSMMG). Isolates used in this study were originally identified by 16S ribosomal gene sequencing of return water samples from long‐duration expeditions 29 and 35 to the International Space Station. Isolates were grown in sterile water to simulate the potable water environment aboard the ISS. The thermal stress and silver biocide assays showed significant effectiveness in bacterial control, while the acid stress assay showed minimal effectiveness. All three concentrations of silver biocide produced a zero percent survival rate in both control and LSMMG environments. An increased growth rate in isolates grown in the LSMMG environment was shown. No differences between the control and LSMMG environments were evident in the response of R.pickettii to stress assays. A ten percent difference in survival rate was seen in the acid stress assay results, with LSMMG culture having a lower survival rate. These results suggest silver as a promising candidate to replace iodine as we move towards long duration spaceflight.

Microbial Contaminants in the Commercial Aviation Fuel Obtained from Benin City Airport, Nigeria

The primary function of aviation fuel is to provide propulsive energy to the aircraft. Microorganisms may contribute to aging instability in the fuel, induce corrosion of the storage tanks and pipeworks, form mats which can block filters and pipelines and increase wear in fuel pumps eventually leading to engine failure, therefore, in this study, the microbial contaminants in the commercial aviation fuel obtained from Benin City Airport, Nigeria were isolated, characterized, identified and their hydrocarbon-utilizing potentials determined using standard methods. The microbial contaminants were Micrococcus luteus, Serratia marcescens, Pseudomonas aeruginosa, Bacillus subtilis, Citrobacter freundii, Klebsiella aerogenes, Acinetobacter calcoaceticus, Fusarium oxysporum, Penicillium italicum, Rhizopus stolonifer, Aspergillus fumigatus and Candida tropicalis. Serratia marcescens had the highest percentage distribution (16%) in the fuel. Serratia marcescens, Pseudomonas aeruginosa, Acinetobacter calcoaceticus, Rhizopus stolonifer and Aspergillus fumigatus were the best utilizers of the fuel among the organisms isolated. There was a drop in the initial pH of the mineral salts oil medium inoculated with the isolates indicating hydrocarbon utilization. The result of this work showed that the fuel examined was contaminated with bacteria and fungi, therefore the incorporation of effective biocides, frequent inspection and drainage of water from fuel tanks and pipeworks are recommended.

Conjugated Polyelectrolytes with Imidazolium Solubilizing Groups. Properties and Application to Photodynamic Inactivation of Bacteria.

This article reports an investigation of the photophysical properties and the light- and dark-biocidal activity of two poly(phenyleneethynylene) (PPE)-based conjugated polyelectrolytes (CPEs) bearing cationic imidazolium solubilizing groups. The two polymers feature the same PPE-type backbone, but they differ in the frequency of imidazoliums on the chains: PIM-4 features two imidazolium units on every phenylene repeat, whereas PIM-2 contains two imidazolium units on every other phenylene unit. Both polymers are very soluble in water and polar organic solvents, but their propensity to aggregate in water differs with the density of the imidazolium units. The polymers are highly fluorescent, and they exhibit the amplified quenching effect when exposed to a low concentration of anionic electron-acceptor anthraquinone disulfonate. The CPEs are also quenched by a relatively low concentration of pyrophosphate by an aggregation-induced quenching mechanism. The biocidal activity of the cationic imidazolium CPEs was studied against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria in the dark and under blue-light illumination. Both polymers are effective biocides, exhibiting greater than 3 log kill with 30-60 min of light exposure at concentrations of ≤10 μg mL(-1).

Larvicidal Activity ofNerium oleanderagainst Larvae West Nile Vector MosquitoCulex pipiens(Diptera: Culicidae)

Background. Outbreaks of the West Nile virus infection were reported in Morocco in 1996, 2003, and 2010. Culex pipiens was strongly suspected as the vector responsible for transmission. In the North center of Morocco, this species has developed resistance to synthetic insecticides. There is an urgent need to find alternatives to the insecticides as natural biocides. Objective. In this work, the insecticidal activity of the extract of the local plant Nerium oleander, which has never been tested before in the North center of Morocco, was studied on larval stages 3 and 4 of Culex pipiens. Methods. Biological tests were realized according to a methodology inspired from standard World Health Organization protocol. The mortality values were determined after 24 h of exposure and LC50 and LC90 values were calculated. Results. The extract had toxic effects on the larvae of culicid mosquitoes. The ethanolic extract of Nerium oleander applied against the larvae of Culex pipiens has given the lethal concentrations LC50 and LC90 in the order of 57.57 mg/mL and 166.35 mg/mL, respectively. Conclusion. This investigation indicates that N. oleander could serve as a potential larvicidal, effective natural biocide against mosquito larvae, particularly Culex pipiens.

N-chlorosuccinimide as a novel agent for biofouling control in the polyamide reverse osmosis membrane process

One of the biggest challenges in reverse osmosis membrane process is formation of biofilms on membrane surface (biofouling) which significantly lowers membrane performance and shortens life cycle of the membrane. In an effort to find a more effective biocide to control biofouling, we investigated the potential of N-chlorosuccinimide (NCS) as a biofouling control agent in polyamide membrane. The results of this study show that there are no significant changes in the surface characteristics of polyamide membrane (measured by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR)) when it is exposed to a high concentration of NCS (5000mg/L as Cl2). Also, there were no significant changes in membrane performance based on permeate flux and salt rejection after exposure to the same concentration of NCS. Most importantly, inactivation of Pseudomonas aeruginosa PAO1 GFP biofilm cells by 10mg/L of NCS was 2.2 log after 30min, which is far greater than that of chlorine. Overall, the results of this study suggest that NCS is a promising novel agent for biofouling control in polyamide membrane processes due to its effective inactivation of biofilm cells on membrane and minimum effect on membrane structure and performance.

Bacillus subtilis chitinase identified by matrix-assisted laser desorption/ionization time-of flight/time of flight mass spectrometry has insecticidal activity against Spodoptera litura Fab.

An extracellular chitinase was identified and purified (CS1 and CS2) from Bacillus subtilis. The 16S rRNA sequencing was submitted in GenBank (accession numbers KC336487 and KC412256). The purified crude enzymes were identified through matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The peptide sequences were matched with chitinase sequences. The peak m/z with 1297. 592 and 3094.570 mascot search resulted sequence was blasted with NCBI protein sequences and confirmed that it is a chitinase enzyme. The effects of chitinase on gut enzymes lactate dehydrogenase, acid phosphatase, alkaline phosphatase and adenosine triphosphatase of the tobacco cutworm Spodoptera litura larvae were investigated. At all concentrations tested, chitinase decreased the activities of these gut enzymes relative to the control. When chitinase treated leaves were fed to larvae in bioassays, gut tissue and gut enzymes were affected. The histological study clearly shows the chitinase treated larval gut, peritrophic membrane and epithelial cells were affected significantly. Chitinase isolated from B. subtilis has effectively reduced the gut enzyme activity and growth of S. litura. The chitin based bioformulation may serve as an effective biocide against the polyphagous pest like S. litura.

Ecotoxicity of triphenyltin on the marine copepod Tigriopus japonicus at various biological organisations: from molecular to population-level effects.

Triphenyltin compounds (TPTs), as effective biocides for different industrial and agricultural purposes, have been detected in coastal marine environments worldwide, in particular in Asian countries. However, little is known about their toxicity to marine organisms. This study comprehensively investigated the molecular, individual and population responses of the marine copepod, Tigriopus japonicus upon waterborne exposure to TPT chloride (TPTCl). Our results indicated that TPTCl was highly toxic to adult T. japonicus, with a 96-h LC50 concentration at 6.3 μg/L. As shown in a chronic full life-cycle test, T. japonicus exposed to 1.0 μg/L TPTCl exhibited a delay in development and a significant reduction of population growth, in terms of the intrinsic rate of increase (r m ). Based on the negative relationship between the r m and exposure concentration, a critical effect concentration was estimated at 1.6 μg/L TPTCl; at or above which population extinction could occur. At 0.1 μg/L TPTCl or above, the sex ratio of the second generation of the copepod was significantly altered and changed to a male-biased population. At molecular level, the inhibition of the transcriptional expression of glutathione S-transferase related genes might lead to dysfunction of detoxification, and the inhibition of retinoid X receptor mRNA expression implied an interruption of the growth and moulting process in T. japonicus. As the only gene that observed up-regulated in this study, the expression of heat shock protein 70 (hsp70) increased in a concentration-dependent manner, indicating its function in protecting the copepod from TPT-mediated oxidative stress. The study advances our understanding on the ecotoxicity of TPT, and provides some initial data on its toxic mechanisms in small crustaceans like copepods.

Effects of different concentrations of biocides on biofilm microorganisms in oil pipelines in Irri, Delta State, Nigeria

Biofilm can be defined as microbial communities containing large different numbers of microorganisms, which produce a wide range of biopolymers. This leads to adhesion to surfaces within hours of immersion. The attachment results in pit corrosion of oil pipelines. The study to assess the effect of different concentrations of biocides (0, 1,2,3,4 and 5 per cent) on bacterial diversity associated with corrosive biofilms in steel pipelines in Irri, Delta State was conducted in University of Calabar, Nigeria. Microbial communities associated with biofilms promote corrosion of oil and gas pipelines, which is a major problem confronting these industries. The community structure of bacteria in the biofilm formed in oil pipelines is a basic knowledge to understand the complexity and mechanisms of metal corrosion. To assess bacterial diversity, biofilm samples were obtained from mild steel coupons corroded after 127 days of exposure to normal operation and flow of petroleum. Microbial community analysis in biofilms of oil pipeline was determined by traditional cultivation technique. Most of the bacterial species detected in biofilms of oil pipelines included the following Halomonas subglaciescola, Pseudomonas aeruginosa, Klebsiella oxytoca, Bacillus subtilis, Serratia marcescens, Bacillus cereus, Acidithiobacillus ferrooxidans and Staphylococcus epidermidis. The sensitivity test results showed that Ozone (oxidizing biocide) exhibited the best biocidal characteristics and at the concentration of 1 percent, eliminated most of the bacterial species except the Gram positive and spore formers. The next effective biocide was sodium hypochlorite (oxidizing biocide) and then followed by formaldehyde as the least effective biocide. For effective control of biofilm bacteria, Ozone (oxidising biocide) and formaldehyde (non-oxidising biocide and persistent) should be used simultaneously as these biocides are effective against biofilms, bacteria and other microbes and are also environmental friendly biocides. The elimination or inhibition of these organisms in oil pipelines will keep our agricultural lands free of contamination from oil spills cause by corrosion.

Cationic oligo- p-phenylene ethynylenes form complexes with surfactants for long-term light-activated biocidal applications

Cationic oligo-p-phenylene ethynylenes are highly effective light-activated biocides that deal broad-spectrum damage to a variety of pathogens, including bacteria. A potential problem arising in the long-term usage of these compounds is photochemical breakdown, which nullifies their biocidal activity. Recent work has shown that these molecules complex with oppositely-charged surfactants, and that the resulting complexes are protected from photodegradation. In this manuscript, we determine the biocidal activity of an oligomer and a complex formed between it and sodium dodecyl sulfate. The complexes are able to withstand prolonged periods of irradiation, continuing to effectively kill both Gram-negative and Gram-positive bacteria, while the oligomer by itself loses its biocidal effectiveness quickly in the presence of light. In addition, damage and stress responses induced by these biocides in both E. coli and S. aureus are discussed. This work shows that complexation with surfactants is a viable method for long-term light-activated biocidal applications.

Multilocus sequence typing and antimicrobial resistance in Enterococcus faecium isolates from fresh produce

The purpose of the present study was to determine the relatedness of Enterococcus faecium isolates from fresh produce to E. faecium strains from other sources by using multi-locus sequence typing (MLST) and to determine the antimicrobial resistance of the isolates. MLST analysis of 22 E. faecium isolates from fresh produce revealed 7 different sequence types (ST 22, ST 26, ST 43, ST 46, ST 55, ST 94 and ST 296). Most isolates belonged to ST 296 (40.9 %), followed by ST 94 (27.3 %). All isolates were sensitive to vancomycin and to imipenem, and only one was resistant to ampicillin (MIC 32 mg/l). However, all were resistant to cefotaxime and ceftazidine. E. faecium isolates from fresh produce were inhibited by quaternary compounds (benzalkonium chloride, cetrimide, hexadecylpyridinium chloride, didecyldimethylammonium bromide), biguanides (chlorhexidine), polyguanides [poly-(hexamethylene guanidinium) hydrochloride], bisphenols (triclosan, hexachlorophene) and biocidal solutions of P3 oxonia and P3 topax 66. Didecyldimethylammonium bromide and triclosan were the least effective biocides in growth inhibition, while hexadecylpyridinium chloride was the most effective. Results from MLST typing and antibiotic resistance suggest that the studied E. faecium isolates from fresh produce are not related to the clinically-relevant clonal complex CC17.

Disinfection of Ballast Water with Iron Activated Persulfate

The treatment of ballast water carried onboard ships is critical to reduce the spread of nonindigenous aquatic organisms that potentially include noxious and harmful taxa. We tested the efficacy of persulfate (peroxydisulfate, S2O8(2-), PS) activated with zerovalent iron (Fe(0)) as a chemical biocide against two taxa of marine phytoplankton grown in bench-scale, batch cultures: the diatom, Pseudonitzshia delicatissima and the green alga, Dunaliella tertiolecta . After testing a range of PS concentrations (0-4 mM activated PS) and exposure times (1-7 days), we determined that a dosage of 4 mM of activated PS was required to inactivate cells from both species, as indicated by reduced or halted growth and a reduction in photosynthetic performance. Longer exposure times were required to fully inactivate D. tertiolecta (7 days) compared to P. delicatissima (5 days). Under these conditions, no recovery was observed upon placing cells from the exposed cultures into fresh media lacking biocide. The results demonstrate that activated PS is an effective chemical biocide against species of marine phytoplankton. The lack of harmful byproducts produced during application makes PS an attractive alternative to other biocides currently in use for ballast water treatments and merits further testing at a larger scale.

Green synthesis of silver nanoparticles using Sida acuta (Malvaceae) leaf extract against Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti (Diptera: Culicidae)

Mosquitoes act as a vector for most of the life-threatening diseases like malaria, yellow fever, dengue fever, chikungunya fever, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management, emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain, and adverse effects on environmental quality and nontarget organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are nontoxic, easily available at affordable prices, biodegradable, and show broad-spectrum target-specific activities against different species of vector mosquitoes. In the present study, the larvicidal activity of silver nanoparticles (AgNPs) synthesized using Sida acuta plant leaf extract against late third instar larvae of Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti was determined. Range of concentrations of synthesized AgNPs (10, 20, 30, 40, and 50μg/mL) and aqueous leaf extract (50, 100, 150, 200, and 250μg/mL) were tested against the larvae of C. quinquefasciatus, A. stephensi and A. aegypti. The synthesized AgNPs from S. acuta leaf were highly toxic than crude leaf aqueous extract in three important vector mosquito species. The results were recorded from UV-Vis spectrum, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Larvae were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24h. Considerable mortality was evident after the treatment of S. acuta for all three important vector mosquitoes. The LC50 and LC90 values of S. acuta aqueous leaf extract appeared to be most effective against A. stephensi (LC50, 109.94μg/mL and LC90, 202.42μg/mL) followed by A. aegypti LC50 (119.32μg/mL and LC90, 213.84μg/mL) and C. quinquefasciatus (LC50, 130.30μg/mL and LC90, 228.20μg/mL). Synthesized AgNPs against the vector mosquitoes of A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC50 and LC90 values: A. stephensi had LC50 and LC90 values of 21.92, and 41.07μg/mL; A. aegypti had LC50 and LC90 values of 23.96, and 44.05μg/mL; C. quinquefasciatus had LC50 and LC90 values of 26.13 and 47.52μg/mL. These results suggest that the use of S. acuta synthesized silver nanoparticles can be a rapid, environmentally safer biopesticide which can form a novel approach to develop effective biocides for controlling the target vector mosquitoes. This is the first report on the mosquito larvicidal activity of the plant aqueous extract and synthesized nanoparticles.