Decrease In Antibacterial Activity Research Articles

Influence of different heat treatment regimes on the change of chemical composition and antibacterial activity of bee honey

The studies of the chemical composition and antibacterial activity of heather honey (Calluna vulgaris) subjected to heat treatment at 35–40°C for 12 hours were carried out. The temperature range (38–40°C), at which decrease in the H2O2 concentration, decrease in D-glucose-1-oxidase activity and increase in the 5-hydroxymethylfurfural content, was identified. The degree of chemical changes was directly proportional to the temperature and time of thermal exposure. The correlation between changes in the chemical composition and antibacterial activity of honey against test microorganisms Escherichia coli (strain 1257), Staphylococcus aureus (strain 209-P) and Bacillus cereus (strain 96) was established. The obtained results showed that heating honey to 37 °C even for 12 hours didn’t cause undesirable changes in its chemical composition and decrease in antibacterial activity. Thus, this temperature regime can be considered more gentle and recommended for use in the heat treatment of this food product.

Evaluation of the physical properties and antibacterial effects on Candida albicans of denture base resin containing silver sulfadiazine

Objectives: The purpose of this study was to evaluate the physical properties and antibacterial activity of denture base resin with added silver sulfadiazine. Methods: Specimens were made from self-curing denture base resin and silver sulfadiazine as an inorganic antibacterial agent. For physical evaluation of the specimens, surface roughness, surface hardness, and contact angle were measured. Bacterial growth was assessed by optical densityat 600 nm (OD600) and colony forming units (CFU) measurements to confirm antibacterial activity. Results: There was no significant difference in surface roughness, surface hardness, and contact angle in the experimental group containing silver sulfadiazine compared to the control group. In contrast, the experimental group showed a significant decrease in antibacterial activity compared to the control group in terms of OD value. Analysis of CFU confirmed a significant decrease in colonies in the experimental group compared to the control group. Conclusions: Denture base resin containing silver sulfadiazine, an inorganic antibacterial agent, exhibited enhanced antibacterial activity without physical changes. In conclusion, the use of denture base resin containing inorganic antibacterial agents may be expected in the future.

Towards Antibacterial Agents: Synthesis and Biological Activity of Multivalent Amide Derivatives of Thiacalix[4]arene with Hydroxyl and Amine Groups.

Antimicrobial resistance to modern antibiotics stimulates the search for new ways to synthesize and modify antimicrobial drugs. The development of synthetic approaches that can easily change different fragments of the molecule is a promising solution to this problem. In this work, a synthetic approach was developed to obtain multivalent thiacalix[4]arene derivatives containing different number of amine and hydroxyl groups. A series of macrocyclic compounds in cone, partial cone, and 1,3-alternate stereoisomeric forms containing -NHCH2CH2R (R = NH2, N(CH3)2, and OH) and -N(CH2CH2OH)2 terminal fragments, and their model non-macrocyclic analogues were obtained. The antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains and cytotoxicity of the obtained compounds were studied. Structure-activity relationships were established: (1) the macrocyclic compounds had high antibacterial activity, while the monomeric compounds had low activity; (2) the compounds in cone and partial cone conformations had better antibacterial activity compared to the compounds in 1,3-alternate stereoisomeric form; (3) the macrocyclic compounds containing -NHCH2CH2N(CH3)2 terminal fragments had the highest antibacterial activity; (4) introduction of additional terminal hydroxyl groups led to a significant decrease in antibacterial activity; (5) the compounds in partial cone conformation had significant bactericidal activity against all studied cell strains; the best selectivity was observed for the compounds in cone conformation. The mechanism of antibacterial activity of lead compounds with terminal fragments -NHCH2CH2N(CH3)2 was proved using model negatively charged POPG vesicles, i.e., the addition of these compounds led to an increase in the size and zeta potential of the vesicles. The obtained results open up the possibility of using the synthesized macrocyclic compounds as promising antibacterial agents.

Structural and biological characterization of shortened derivatives of the cathelicidin PMAP-36

Cathelicidins, a family of host defence peptides in vertebrates, play an important role in the innate immune response, exhibiting antimicrobial activity against many bacteria, as well as viruses and fungi. This work describes the design and synthesis of shortened analogues of porcine cathelicidin PMAP-36, which contain structural changes to improve the pharmacokinetic properties. In particular, 20-mers based on PMAP-36 (residues 12-31) and 13-mers (residues 12-24) with modification of amino acid residues at critical positions and introduction of lipid moieties of different lengths were studied to identify the physical parameters, including hydrophobicity, charge, and helical structure, required to optimise their antibacterial activity. Extensive conformational analysis, performed by CD and NMR, revealed that the substitution of Pro25-Pro26 with Ala25-Lys26 increased the α-helix content of the 20-mer peptides, resulting in broad-spectrum antibacterial activity against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus epidermidis strains. Interestingly, shortening to just 13 residues resulted in only a slight decrease in antibacterial activity. Furthermore, two sequences, a 13-mer and a 20-mer, did not show cytotoxicity against HaCat cells up to 64 µM, indicating that both derivatives are not only effective but also selective antimicrobial peptides. In the short peptide, the introduction of the helicogenic α-aminoisobutyric acid forced the helix toward a prevailing 310 structure, allowing the antimicrobial activity to be maintained. Preliminary tests of resistance to Ser protease chymotrypsin indicated that this modification resulted in a peptide with an increased in vivo lifespan. Thus, some of the PMAP-36 derivatives studied in this work show a good balance between chain length, antibacterial activity, and selectivity, so they represent a good starting point for the development of even more effective and proteolysis-resistant active peptides.

New Demethylated Derivatives of Carolacton and Structure–Activity Relationship (SAR) Studies on Their Biofilm Inhibitory Properties

AbstractThe total synthesis of a series of new carolacton derivatives that mainly lack selected methyl substituents along the polyketide backbone is reported. Their inhibitory activity towards bacterial biofilms revealed that selective removal of the methyl group at C10 does not have a major effect on biological activity, whereas additional removal of the methyl group at C14 in carolacton results in a large decrease in antibacterial activity. A key new feature of this work is the replacement of the Nozaki–Hiyama–Kishi (NHK) vinylation with a titanium-mediated protocol for the fusion of the two main fragments.

Enhanced hydrolytic removal of tylosin in wastewater using polymer-based solid acid catalysts converted from polystyrene

Antibiotic production wastewater usually contains high concentrations of antibiotic residues, which can cause instability and deterioration of biological wastewater treatment units and also domestication and proliferation of antibiotic-resistance bacteria. An effective pretreatment on antibiotics production wastewater is expected to selectively reduce the concentration of antibiotics and decrease the toxicity, rather than mitigate organic and other contaminants before further treatments. In this work, two polymer-based solid acids, PS-S and CPS-S bearing high concentrations of -SOH3 groups (up to 4.57 mmol/g), were prepared and successfully used for hydrolytic mitigation of 100 mg/L tylosin within 20 min. The co-existence of high concentrations of COD and humic substances did not affect the mitigation of tylosin obviously, while more than 500 mg/L of nitrogenous compounds suppressed the hydrolytic efficiency. Recycle and reuse experiments showed that the solid acids performed well in five cycles after regeneration. Three transformation products (P1, P2 and P3) were identified using UPLC-QTOF-MS/MS. Sugar moieties including mycarse, mycaminose, and mycinose detached and released simultaneously or in order from the 16-member lactone ring through desugarization, which led to a dramatic decrease in antibacterial activity as revealed by cytotoxicity evaluations using S. aureus. Ecotoxicity estimation indicated the acute toxicities of the hydrolyzed products to model species (e.g., fish, daphnid and green algae) were classified as “not harmful”. This work suggested an effective and selective method to pretreat tylosin-contained production wastewater by using polymer-based solid acids. These results will shed light on effective elimination of antibiotics pollution from pharmaceutical industries through strengthening the pretreatments.

Effect of the ratio of R =[Na2O]/[B2O3] on the structure, Ag species, and antibacterial activity of Ag-doped borosilicate glass

Ag-doped borosilicate glass exhibits antibacterial activity because Ag+ ions that can inactivate bacterial proteins can be released from the glass matrix. However, Ag+ ions can be reduced to Ag0 in the glass, which is generally controlled by various preparation approaches and depends on the chemical composition of the glass system. This possibly results in a decrease in antibacterial activity. Therefore, this work mainly investigates the composition effect, especially the effect of the ratio (R) of [Na2O]/[B2O3], on the structure, Ag species, and antibacterial activity of Ag-doped three-component Na2O-B2O3-SiO2 glass systems. The experimental results indicated that the increased addition of Na2O could facilitate the reduction of Ag+ to Ag0 and decrease the extent of Ag+ ion release achieved. Nonetheless, the antibacterial activity against E. coli declines as R increases when R < 0.62 but increases when R > 0.62. This is attributed not only to Ag+ ion release but also to Na+ ion release that could cause the change of aqueous pH value, as the composition influences the durability of the glass systems.

Sustained Antibacterial Effect of Levofloxacin Drug in a Polymer Matrix by Hybridization With A Layered Double Hydroxide

AbstractThe immobilization of antimicrobial drugs can be used to expand the application of antibacterial properties to consumer products. The purpose of this study was to stabilize an antimicrobial agent, levofloxacin (LVX), for sustained antibacterial activity by immobilizing the drug molecules in a layered double hydroxide (LDH) and embedded in a polyurethane substrate. As-prepared MgAl-LDH was calcined at 400°C and reconstructed with LVX for intercalation. The X-ray diffraction patterns and cross-sectional transmission electron microscopy images showed lattice expansion along the crystallographic c axis upon LVX intercalation, suggesting successful loading of the drug. Fourier-transform infrared spectra revealed that the structure of LVX was well preserved between LDH layers. Elemental analysis indicated that the loading capacity of LVX in the hybrid was 41.7%. Bacterial-colony forming inhibitory assay on Bacillus subtilis exhibited ~100% antibacterial activity of both LVX alone and LVX-LDH hybrid (LL). To determine sustainability of antibacterial activity by the hybrid, either LVX alone or LL hybrid was loaded in the polyurethane (PU) substrate for which antibacterial activity was evaluated before and after immersion in a phosphate-buffered saline for 3 days. The LVX-composited PU showed a dramatic decrease in antibacterial activity, down to 0% after buffer treatment; LL-composited PU still contained antibacterial activity (~34% of colony suppression) after phosphate-buffered saline immersion.

Electrochemical Regulation of Antibacterial Activity Using Ferrocene-Containing Antibiotics

Electrochemical Regulation of Antibacterial Activity Using Ferrocene-Containing Antibiotics

The effect of combining nanosilver and new injection form of rexod on the periodontal tissues state on experimental periodontitis in rats

A representative and randomized study of the effect of a combination of nanosilver and a new injection form of Rexod® on the periodontal tissues state of animals (rats) in an experimental model of inflammatory pathology of periodontal tissues (experimental periodontitis) was carried out. It was shown that the improvement of the dental status of periodontal tissues against the background of the course application of a combination of nanosilver (topically) and a new injection form of Rexod® was accompanied by a decrease in the amount of gingival fluid of the sulcular gingival sulcus, an improvement in the clinical condition of the marginal periodontal mucosa (hyperemia was leveled, swelling decreased, the bleeding indexPBI Muhllemann-Cowell decreased, test Schiller-Pisarev results normalised). The decrease in the number of gum fluids is due to the decrease in antibacterial activity of pathogenic microflora and their products of their life-based hemodynamics of the peripheral microvascular network (exchange capabulars) of the periodontal, a decrease in perfusion pressure in them, reduced (narrowing) of their lumen, reduce their permeability and restoration of oxidation-reduction processes.

Identification of antibacterial peptides generated from enzymatic hydrolysis of cottonseed proteins

In this study, we explored the fractionation and identification of antibacterial peptides from cottonseed protein hydrolysates obtained using Alcalase. The cottonseed protein hydrolysates were preliminarily separated using Sephadex C-25, and fraction P5 exhibited antibacterial activity against four tested strains, including Gram-positive and Gram-negative bacteria, at concentrations ranging from 1 to 4 mg/mL. The potential antibacterial peptides in fraction P5 were then isolated by reverse-phase high-performance liquid chromatography based on a specific reaction of Arg with benzaldehyde. Nine novel peptides encoded in cottonseed proteins were identified by mass spectrometry, and three peptides (KDFPGRR, LGLRSGIILCNV, and DENFRKF) with antibacterial activities of 77.7%, 69.3%, and 45.0% at 1.0 mg/mL, respectively, were chemically synthesized. Fluorescence labeling and staining assays confirmed that antibacterial peptides could combine and interact with the surface of the cell membrane. In addition, sensitivity analysis of the environmental conditions revealed that antibacterial peptides were not influenced by temperature and pH, but they were sensitive to Ca2+, with a decrease in antibacterial activity decreased of 40% occurring as the concentration of Ca2+ increased from 0.05% to 5%.Our results indicated that cottonseed protein could be used as a potential source of antibacterial peptides that could be applied to food systems and the feed industry.

Age-dependent variation in the terminal investment threshold in male crickets.

The terminal investment hypothesis proposes that decreased expectation of future reproduction (e.g., arising from a threat to survival) should precipitate increased investment in current reproduction. The level at which a cue of decreased survival is sufficient to trigger terminal investment (i.e., the terminal investment threshold) may vary according to other factors that influence expectation for future reproduction. We test whether the terminal investment threshold varies with age in male crickets, using heat-killed bacteria to simulate an immune-inducing infection. We measured calling effort (a behavior essential for mating) and hemolymph antimicrobial activity in young and old males across a gradient of increasing infection cue intensity. There was a significant interaction between the infection cue and age in their effect on calling effort, confirming the existence of a dynamic terminal investment threshold: young males reduced effort at all infection levels, whereas old males increased effort at the highest levels relative to naïve individuals. A lack of a corresponding decrease in antibacterial activity suggests that altered reproductive effort is not traded against investment in this component of immunity. Collectively, these results support the existence of a dynamic terminal investment threshold, perhaps accounting for some of the conflicting evidence in support of terminal investment.

Peripheral Blood Plasma Clot as a Local Antimicrobial Drug Delivery Matrix.

Platelet-free blood plasma clots were loaded either with antibiotics (vancomycin, gentamicin, or linezolid) at concentrations of 5-300 μg/mL or with silver ions (silver acetate) at concentrations of 3.3-129 μg/mL. The release of antibiotics or silver from the clot matrix was analyzed after repeated immersion of the plasma clots using reversed-phase high-performance liquid chromatography (RP-HPLC) or atomic absorption spectroscopy (AAS). The antimicrobial activity was tested against Staphylococcus aureus; tissue cell compatibility was analyzed using human mesenchymal stem cells (hMSC). Fibrin fiber thickness of the clots was analyzed by scanning electron microscopy. While addition of linezolid and vancomycin did not significantly change the fibrin fiber thickness, gentamicin and silver ions led to an increase in fiber thickness. All antibiotics showed a concentration-dependent burst-like release from the plasma clots within 1 h followed by a general decay in elution. The release of vancomycin and gentamicin, or silver lasted up to 7 days (depending on initial concentrations), but lasted only up to 4 h for linezolid. A correlation (p < 0.0001) was noted between the concentration of released antibiotics analyzed by HPLC and antimicrobial activity (agar diffusion test). A decrease in antibacterial activity of gentamicin- and vancomycin-containing clots occurred within 4 or 5 days. In contrast, the corresponding antibacterial activity of plasma clots containing linezolid was limited to 3 h. Antibacterial activity of plasma clots containing silver at the highest concentrations decreased after day 3, but clots with lower concentrations induced incomplete bacterial lysis or displayed no antibacterial activity. The antibiotic-containing clots did not induce cytotoxic effects on the embedded hMSC in contrast to all clots containing silver. Our results indicate that an autologous plasma clot can be used to deliver antibiotics such as vancomycin and gentamicin in combination with hMSC and the antibacterial effects persist for days without inducing cytotoxic effects on the embedded stem cells.

PARTIAL PURIFICATION AND CHARACTERIZATION OF BACTERIOCIN-LIKE PEPTIDE PRODUCED BY STAPHYLOCOCCUS XYLOSUS

The extensive use of antibiotics leads to an increasing number of antibiotic-resistant pathogenic microorganisms. The development of new antimicrobials is needed for clinical, veterinary, and food applications. Bacteriocins are small peptides with antimicrobial activity ribosomally synthesized by bacteria and could be applied as an alternative to classical antibiotics. In this study, the bacteriocin-like (BLIS) peptide, produced by Staphylococcus xylosus was partially purified and main characteristics (pH, thermal stability, resistance to some protease enzymes and molecular weight) were evaluated. Ammonium sulfate precipitation, acetone extraction and ion-exchange chromatography methods were applied for purification of bacteriocin. The activity of bacteriocin was detected using a well diffusion assay method and the amount of protein concentration was estimated by Lowry method. Molecular weight (~ 6 kDa) of purified bacteriocin was determined by sodium dodecyl sulphate polyacrilamide gel electrophoresis (SDS PAGE) method. The highest purification yield (80 %) was obtained using ion-exange chromatography and SP-sepharose as sorbent. The purified bacteriocin remained stable at pH values between 2.0 and 12.0 for 4 h. No decrease in antibacterial activity was estimated after 30 min at 121º C temperature. The purified bacteriocin was resistant to papain, pepsin and trypsin action. The BLIS inhibits a growth of Listeria monocytogenes (93 ± 3.0 %), Bacillus subtilis (85 ± 4.0 %), Pediococcus pentosaceus (79 ± 4.0 %), Staphylococcus aureus (51 ± 5.0 %) and Propionibacterium acnes (70 ± 5 %) up to 24 hours. Such bacteriocin preparation could be applied as antimicrobial agent in medical and food industry.

Mechanism of action and in vitro activity of short hybrid antimicrobial peptide PV3 against Pseudomonas aeruginosa

Antimicrobial peptides are attractive candidates for developing novel therapeutic agents, since they are lethal to a broad spectrum of pathogens and have a unique low tendency for resistance development. In this study, mechanism of action and in vitro anti-pseudomonal activity of previously designed short hybrid antimicrobial peptide PV3 were investigated. Compared to ceftazidime, PV3 had not only higher antibacterial activity but also faster bactericidal activity. PV3 reduced biofilm biomass and viability of biofilm embedded bacteria in a concentration-dependent manner. Although the antimicrobial activity of PV3 was reduced in Mueller-Hinton broth (MHB) containing human serum, it was still active enough to eradication of bacteria at low concentrations. Compared with standard condition (MHB only), there was no significant decrease in antibacterial activity of PV3 against P. aeruginosa strains under 150 mM NaCl (p = 0.615) and 1 mM MgCl2 (p = 0.3466). Fluorescence microscopy and field emission scanning electron microscopy further indicated that PV3 killed bacteria by disrupting the cell membrane. Since PV3 has potent anti-pseudomonal activity and has little cytotoxicity in vitro, it seems plausible that the peptide should be further investigated with animal studies to support future pharmacological formulations and potential topical applications.

Biosynthesis and antibacterial activity of gold nanoparticles coated with reductase enzymes

Potential of luminescent bacteria in production of metal nanoparticles (NPs) has not been well evaluated up until now. These bacteria contain lux operon which is included of reductase enzymes, by increasing bacterial cell density, the expression of aldehyde synthetic enzymes elevate and enhance the yields of NPs synthesis. Therefore, extracellular synthesis of gold NPs (AuNPs) using natural occurring luminescent bacteria, VLA, VLB, VLC and genetically engineered luminescent bacteria, Pseudomonas putida KT2440 and Pseudomonas fluorescence OS8 have been successfully conducted. NPs were characterised and their antibacterial activity evaluated using microtitre plates at different concentrations against some hospital pathogenic bacteria. Biosynthetic AuNPs produced had maximum absorption at the ranges of 500–550 nanometre wavelengths. Transmission electron microscopy images showed particle sizes between 10 and 50 nanometres and confirmed the success of purification process. The NPs were spherical and the FTIR analysis showed the existence of biomolecules on surface of purified NPs that could be most probably related to reductase enzymes that are stabilised on NPs surfaces. Further investigation on antibacterial properties of these novel NPs which coated by reductase enzymes showed that any increase or decrease in antibacterial activity is dependent on NPs concentration.

Influence of fixing treatment on the color fastness and bioactivities of silk fabric dyed with curcumin

The curcumin dyed silk has poor color fastness to wash, rub, and light. Two cationic polyamine fixing agents, one cationic etherifying agent and one cross-linker were applied to the fixing treatment of the curcumin dyed silk fabric. The color parameters, color fastness, and antioxidant and antibacterial bioactivities of the treated silk fabrics were determined. All the fixing treatments increased the rub and light fastness. In comparison to the non-reactive fixing agents, the cross-linker and etherifying agent exhibited stronger ability for improving the rub fastness and the wash fastness for staining, but they had greater influence on the color parameters due to their alkaline application conditions. Fixing treatment caused a great decrease in antioxidant activity, and a minor decrease in antibacterial activity. Among the four fixing agents, the cross-linker exerted the greatest impact on antioxidant and antibacterial activities due to its high ability of reaction with the phenolic hydroxyl groups of curcumin.

Antibacterial Activity of Copper Nanoparticles and Copper Nanocomposites against Escherichia Coli Bacteria

Nanotechnology is an emerging technology which has wide applications in many fields. The major objective of the study is to synthesise copper nanoparticles and its composites and to determine their antibacterial activity. A filter based on the developed material was fabricated. Copper nanoparticles were synthesised by chemical reduction method and were encapsulated in a biopolymer, alginate and fabricated anti bacterial water filter using copper nanoparticle-coated polyurethane foams. The synthesised copper nanoparticle, copper nanoparticle encapsulated in alginate beads and copper nanoparticle coated PU foam were characterized by several techniques including SEM and EDS analysis. Finally antimicrobial efficiency was determined against E.coli. Well diffusion method was used for testing the antibacterial effect of synthesised nanoparticls. The time and dose dependant study of copper alginate beads showed that the effectiveness of particle increase with increasing particle dose and contact time. The results obtained from the effect of bacterial load indicated that there was a decrease in antibacterial activity as the bacterial concentration increased. Flow test was conducted for the antibacterial filter by passing contaminated water through the filter and no bacteria were detected. The antimicrobial activity of metal nanoparticles is due to the large surface area which ensures a broad range of reactions with bio-organics present on the cell surface. Our research suggests that copper-coated polyurethane foams can be used as excellent antibacterial water filter.

Nutritional value, bioactive compounds, antimicrobial activity and bioaccessibility studies with wild edible mushrooms

Wild mushrooms are important sources of nutrients and bioactive compounds, namely phenolic acids. After their ingestion, bioactive molecules have to be released from the matrix to be absorbed by the organism. In the present work, two wild edible mushrooms (Volvopluteus gloiocephalus and Clitocybe subconnexa) were studied for their nutritional value, detailed chemical composition and antimicrobial activity. Bioaccessibility studies were also performed using the in vitro digestion of the crude powder, phenolic extracts and individual phenolic acids identified in the samples. The studied species proved to be rich sources of nutrients, minerals and bioactive molecules such as phenolic acids. The in vitro digestion conducted to a decrease in antibacterial activity, but not in antifungal and demelanizing properties. Nevertheless, in most of the cases, the analyzed samples presented higher antibacterial and antifungal activities than the standards. The bioactive molecules (phenolic acids) were found in higher concentrations in the phenolic extracts before in vitro digestion, which is agreement with the highest antibacterial activity revealed by these extracts. It should be highlighted that the phenolic acids were still bioavailable after digestion.

A few atoms make the difference: Synthetic, CD, NMR and computational studies on antiviral and antibacterial activities of glycopeptide antibiotic aglycon derivatives

Despite the close structural similarity between the heptapeptide cores of the glycopeptide antibiotics teicoplanin and ristocetin, synthetically modified derivatives of their aglycons show significantly different antibacterial and antiviral properties. The teicoplanin aglycon derivatives with one exception proved to be potent antibacterials but they did not exhibit anti-influenza virus activity. In contrast, the aglycoristocetin derivatives generally showed high anti-influenza virus activity and possessed moderate antibacterial activity. A systematic structure-activity relationship study has been carried out on ristocetin and teicoplanin aglycon derivatives, to explore which structural differences are responsible for these markedly different biological activities. According to electronic circular dichroism and in silico conformational studies, it was found that the differences in anti-influenza virus activity are mainly determined by the conformation of the heptapeptide core of the antibiotics controlled by the presence or absence of chloro substituents. Knowledge of the bioactive conformation will help to design new analogs with improved anti-influenza virus activity. For the teicoplanin derivatives, it was shown that derivatization to improve the antiviral efficacy was accompanied by a significant decrease in antibacterial activity.