Preparation,characterization, and antibacterial activity of chitosan/silicone rubber filled zeolite,silver, and copper nanocomposites against Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus

The ongoing emergence of antibiotic-resistant bacteria has become one of the biggest threats to global health and development today. Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) are important antibiotic-resistant bacteria due to their increasing resistance to a broad array of antimicrobial agents. Herein, we developed a novel antibacterial nanocomposite based on chitosan and liquid silicone rubber filled zeolite-A, Ag, and Cu nanoparticles with remarkable antibacterial activity against P. aeruginosa and MRSA. The antibacterial activity of the nanocomposite was studied by disc diffusion and broth culture methods. Besides, the mechanical properties, wetting behavior, and chemical structure of the present nanocomposite were also investigated. The results exhibited that the inhibition zone diameter of the nanocomposite for P. aeruginosa and MRSA were 40 and 27 mm, respectively. It also took approximately 1 h to inhibit the growth of the tested bacteria. The nanocomposite sample with a thickness of around 1 mm showed an elastic elongation of nearly 49% and a contact angle of roughly 120°. Thus, the present nanocomposite was found to be useful in killing and inhibiting the growth of P. aeruginosa and MRSA, and it could also be qualified as a superior elastic and hydrophobic material.     

Radiation-Induced Acrylamide/4-Vinyl Pyridine Biocidal Hydrogels: Synthesis,Characterization, and Antimicrobial Activities

Acrylamide/4-vinyl pyridine hydrogels were synthesized by radiation polymerization technique using a γ-irradiator. The prepared radiation-synthesized acrylamide/4-vinyl pyridine hydrogels were then treated using a modifying agent with aromatic functional group. The modifying agent used in the modification of acrylamide/4-vinyl pyridine hydrogels was the N-aromatic alkyl quaternizing agent of chloromethyl benzene. The functional group on the modified acrylamide/4-vinyl pyridine hydrogels was confirmed with Fourier transform infrared (FTIR) spectrometry. Thermal analysis, surface morphology investigation, and swelling of the modified and unmodified hydrogels were completed. The antibacterial and antifungal activities of the modified and unmodified hydrogels were also tested against gram-positive Staphylococcus aureus (ATCC 25923); two gram-negative Escherichia coli (ATCC 25922), and Pseudomonas aeruginosa (ATCC 27853) human pathogenic bacteria and a fungal strain—Candida albicans (ATCC 10231) for their MBC values. It was found that acrylamide/4-vinyl pyridine hydrogels do not possess biocidal properties, whereas the modified form of acrylamide/4-vinyl pyridine?chloromethyl benzene showed highly bactericidal characteristics.     

Antibacterial and biodegradable properties of polyhydroxyalkanoates grafted with chitosan and chitooligosaccharides via ozone treatment

Acrylic acid was grafted to ozone‐treated poly(3‐hydroxybutyric acid) (PHB) and poly(3‐hydroxybutyric acid‐co‐3‐hydroxyvaleric acid) (PHBV) membranes. The resulting membranes were further grafted with chitosan (CS) or chitooligosaccharide (COS) via esterification. These CS‐ or COS‐grafted membranes showed antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, methicilin‐resistant Staphylococcus aureus (MRSA), and S. aureus. The antibacterial activity to E. coli was the highest, whereas the antibacterial activity to MRSA was the lowest among these four bacteria tested. Acrylic acid grafting can increase the biodegradability with Alcaligens faecalis, whereas CS and COS grafting can reduce the biodegradability. In addition, CS‐grafted PHBV membrane showed higher antibacterial activity and lower biodegradability than COS‐grafted PHBV membrane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2797–2803, 2003     

Surface grafting of polyester fiber with chitosan and the antibacterial activity of pathogenic bacteria

Three polyesters—poly(ethylene terephthalate), poly(2‐methyl‐1,3‐propylene terephthalate‐co‐ethylene terephthalate), and poly(1,4‐cyclohexylene terephthalate‐co‐ethylene terephthalate)—were preirradiated with ⁶⁰Co‐γ‐rays. Then, acrylic acid and N‐vinylformamide were grafted to these irradiated fibers. Fibers grafted with N‐vinylformamide were further hydrolyzed with acid so that the amide groups would convert into amino groups, and they were treated with glutaraldehyde so that aldehyde groups would be introduced. Chitosan or chitooligosaccharide was then grafted to these fibers via either esterification or imine formation. Four pathogenic bacteria—methicillin‐resistant Staphylococcus aureus‐1 (MRSA), Staphylococcus aureus‐2, Escherichid coli, and Pseudomonas aeruginosa—were tested to determine the antibacterial activities of chitosan‐grafted and chitooligosaccharide‐grafted fibers. The results showed that grafting chitosan via imine formation could achieve a higher surface density for amino groups and give higher antibacterial activity to those four bacteria tested. The antibacterial activity for E. coli was the highest and that for MRSA was the lowest among the four bacteria tested. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2977–2983, 2002     

Biodegradability, antimicrobial activity and properties of PVA/PVP hydrogels prepared by γ-irradiation

Polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) hydrogel has been prepared by using γ-irradiation technique. In the present study the conclusion on miscibility of PVA/PVP blends, confirmed qualitatively and quantitatively by using Fourier transform infrared spectroscopy and differential scanning calorimetry, respectively. PVA and PVP are found to form a thermodynamically miscible pair. The physical properties such as gel fraction and water absorption performance of the prepared hydrogels were measured, it was found that the gel fraction increases with increasing irradiation dose while the swelling of PVA/PVP blended hydrogels nearly tends to increase with increasing PVP content and reduced with enhanced irradiation doses. The hydrogel pore structure of various PVA/PVP compositions were tested with SEM. Ability of PVA/PVP hydrogels to absorb and release antimicrobial compounds was tested using amoxicillin as an antibacterial and ketoconazole as an antifungal. Antimicrobial activity of PVA/PVP hydrogels was examined using four bacteria, and four fungi. No antibacterial or antifungal activities of non-loaded PVA/PVP of various compositions were detected while the loading ones found to have antimicrobial activity. Results showed resistance of Pseudomonas aeruginosa and Candida albicans to PVA/PVP, while Bacillus subtilis was very sensitive. Biodegradation of PVA/PVP hydrogels was investigated by burial method in two types of local soils (clay and sandy soils). The highest degradation rate was found to be achieved using clay soil. Also, effect of irradiation dose on its biodegradability was tested. The results showed that the radiation prepared PVA/PVP hydrogels can be use as biomaterials.     

Synthesis and water absorbency of polyampholytic hydrogels with antibacterial activity

Amphoteric terpolymers of acrylic acid (AA), acrylamide (AM), and N,N′‐dimethyl‐N‐ethylmeth‐acryloxylethylammoniumbromide (DMAEA‐EB) with varied compositions P[AA‐AM‐(DMAEA‐EB)] were synthesized by inverse suspension polymerization. The components of P[AA‐AM‐(DMAEA‐EB)] were verified by FTIR spectroscopy. The water absorption ability and antibacterial activity of the copolymer against Escherichia coli(E. coli) and Staphylococcus hyicus(S. hyicus) suspended in sterilized physiological saline were investigated. The introduction of  N⁺R₄ may increase the water absorbency of P[AA‐AM‐(DMAEA‐EB)] in some degree because of the excellent hydrophilicity of  N⁺R₄. The AA‐AM‐(DMAEA‐EB) hydrogels exhibited high antibacterial activity against bacteria tested. The process of adsorption between live bacteria cells and resins was at least partially reversible. A peak of antibacterial efficiency existed with increasing contact time. The resin killed 96.6% E. coli organisms and 90.3% S. hyicus organisms, respectively, within 30 min of contact at dosage of 0.1g. The concentration of DMAEA‐EB has a special effect on the antibacterial activity of the polyampholytic hydrogels, which is different from polycation. It was observed that the antibacterial activity of the resin with 2 mol % of DMAEA‐EB is superior to the copolymers tested with other compositions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(2‐hydroxyethyl methacrylate)/boric acid composite hydrogel as soft contact lens material: Thermal,optical, rheological,and enhanced antibacterial properties

The present work proposes to fabricate a composite hydrogel material that well characterized, transparent, biocompatible, and self‐antibacterial as potential soft contact lens material. For this purpose, poly(2‐hydroxyethyl methacrylate) (PHEMA)/boric acid (BA) composite hydrogels were successfully prepared by chemical crosslinking with BA through in situ polymerization using different BA ratios between 1 and 10% w/w. Afterward, the compositions, thermal stability, transparence, oxygen permeability, water uptake capacity, swelling ratio as well as morphological and rheological properties, in vitro degradability, in vitro cytotoxicity, and antibacterial properties of the all prepared materials were analyzed using a series of different techniques. The thermal stability, hydrophilicity, water uptake, oxygen permeability gradually increased depending ratio of BA, which is desirable for biomaterial. While the transparence and refractive index decreased, the composite hydrogels, except for BA content of 10 wt %, maintained enough transparency to be used for contact lens. In addition, PHEMA/BA composite hydrogels exhibited good cytocompatibility (PHEMA‐1%BA and PHEMA‐3%BA) and excellent antibacterial activity against Gram‐positive (Staphylococcus aureus and Enterococcus faecium) and Gram‐negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. Overall, the results demonstrated that the obtained PHEMA/BA composite hydrogels could be considered as self‐antibacterial contact lens and a potential composite biomaterial for other applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46575.     

γ-Ray assisted synthesis of silver nanoparticles in chitosan solution and the antibacterial properties

In the present study, chitosan had been utilized as a “green” stabilizing agent for the synthesis of spherical silver nanoparticles in the range of 5–30 nm depending on the percentage of chitosan used (0.1, 0.5, 1.0 and 2.0 wt%) under γ-irradiation. X-ray diffractometer identified the nanoparticles as pure silver having face-centered cubic phase. Ultraviolet–visible spectra exhibited the influence of γ-irradiation total absorbed dose and chitosan concentration on the yield of silver nanoparticles. The antibacterial properties of the silver nanoparticles were tested against Methicillin-resistant Staphylococcus aureus (MRSA) (gram-positive) and Aeromonas hydrophila (gram-negative) bacteria. This work provides a simple and “green” method for the synthesis of highly stable silver nanoparticles in aqueous solution with good antibacterial property.     

Evaluation of Antibacterial Activity and Characterization of Synthesized Biodegradable Copolymers

Green copolymer Poly(MA-CA) was developed by the thermal condensation polymerization of monomers such as DL-Malic acid (MA) and Citric acid (CA). The copolymer of Poly(MA-CA) was synthesized by varying the ratio of MA and CA monomers with 1:0, 1:3, 1:1, 3:1 and 0:1, and their antibacterial properties were studied with respect to their activity on Gram-positive and Gram-negative bacteria by the bacterial count method. Furthermore, the biocidal activity of the plain monomers was also investigated and compared to those of the copolymers. Synthesized copolymers show good antibacterial effects towards both Gram-positive and Gram-negative bacteria. The antimicrobial properties of the copolymers and the monomers were studied by varying the ratio of polymers, effect of polymer concentration and effect of pH. Results indicated that the antibacterial activity of the copolymers increased with MA content and polymer dose. At low content of MA (wt.%), the copolymers poly(MA-CA)(1:3) possessed a higher effect on Gram-positive bacteria Bacillus cereus and Micrococcus luteus than Gram-negative bacteria Salmonella and Shigella. The other copolymers with the ratio of 1:1 and 3:1 including MA homopolymer possesses 100% inhibition of both Gram-positive and Gram-negative bacteria under the conditions studied. The developed polymers were extensively characterized by Fourier transform infrared spectroscopy analysis, thermal gravimetric analysis, X-ray diffraction analysis and scanning electron microscope-energy dispersive spectroscopy to understand their physicochemical properties.     

Development of Green Dual Polymers for Antibacterial Applications

In this article, we report on the antibacterial properties of a novel antimicrobial poly(citric acid-co-curcumin) polymer system that was prepared by a catalyst–free polyesterification process. The dual polymer of poly(citric acid-co-curcumin) was synthesized by varying the weight ratio of citric acid and curcumin monomers. Details of the synthesis, spectral (Fourier transform infrared, ultraviolet), thermal stability (Thermogravimetric analyses), and the morphological (Scanning electron microscopy/energy dispersive spectroscopy) characterization of dual polymers are presented in this scientific article. The UV–visible spectrometry was used to confirm the copolymerization of curcumin dispersion in the dual polymer systems. The presence of functional groups of copolymers was confirmed by Fourier transform infrared spectroscopy. The thermogravimetric analysis results indicated that poly(citric acid-co-curcumin) have a thermal stability up to 225°C. The ratios used were 1:0.25, 1:0.5, 1:0.75, and 1:1 and their antibacterial properties were studied with respect to their activity on gram-positive and gram-negative bacteria. This dual polymer was inoculated onto a Petri dish and its ability to inhibit the growth of Escherichia coli, Staphylococcus, Bacillus subtilis, Candida albicans (fungus), and Micrococcus luteus was evaluated using the bacterial disc method. Results indicated inhibition properties to increase with increasing curcumin content and the dual polymer with highest curcumin content showed excellent antimicrobial activities against both gram-negative and gram-positive microorganisms. Hence, it was clear that the developed dual polymers may be effectively used for antibacterial applications such as wound dressing.     

Gamma irradiation synthesis and characterization of AgNP/gelatin/PVA hydrogels for antibacterial wound dressings

An antibacterial hydrogel wound dressing was successfully synthesized by the gamma irradiation method. A gelatin solution was mixed with a poly(vinyl alcohol) (PVA) solution of similar concentrations at different weight ratios of 100 : 0, 80 : 20, and 60 : 40 w/w, and irradiated at 30, 40, or 50 kGy. The testing of physical properties showed that the addition of PVA could improve both durability and mechanical integrity. The 60 : 40 hydrogels irradiated at 30 kGy were optimal, and chosen to add silver nitrate at 0.25, 0.50, 0.75, or 1.00 wt % (based on the solid content) to improve the antibacterial properties. After gamma irradiation, silver nanoparticles (AgNPs) were formed. The AgNP/gelatin/PVA hydrogels were characterized for physical properties, cytotoxicity, and antibacterial activity. The AgNP/gelatin/PVA hydrogels could be used as antibacterial wound dressings because they exhibited appropriate physical properties, noncytotoxicity, and could inhibit the growth of tested bacteria. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41138.     

Antibacterial Activity of Hexadecynoic Acid Isomers toward Clinical Isolates of Multidrug-Resistant Staphylococcus aureus

In the present study, the structural characteristics that impart antibacterial activity to C₁₆ alkynoic fatty acids (aFA) were further investigated. The syntheses of hexadecynoic acids (HDA) containing triple bonds at C-3, C-6, C-8, C-9, C-10, and C-12 were carried out in four steps and with an overall yield of 34–78%. In addition, HDA analogs containing a sulfur atom at either C-4 or C-5 were also prepared in 69–77% overall yields, respectively. Results from this study revealed that the triple bond at C-2 is pivotal for the antibacterial activity displayed by 2-HDA, while the farther the position of the triple bond from the carbonyl group, the lower its bactericidal activity against gram-positive bacteria, including clinical isolates of methicillin-resistant Staphylococcus aureus (CIMRSA) strains. The potential of 2-HDA as an antibacterial agent was also assessed in five CIMRSA strains that were resistant to Ciprofloxacin (Cipro) demonstrating that 2-HDA was the most effective treatment in inhibiting their growth when compared with either Cipro alone or equimolar combinations of Cipro and 2-HDA. Moreover, it was proved that the inhibition of S. aureus DNA gyrase can be linked to the antibacterial activity displayed by 2-HDA. Finally, it was determined that the ability of HDA analogs to form micelles can be linked to their decreased activity against gram-positive bacteria, since critical micellar concentrations (CMC) between 50 and 300 μg/mL were obtained.     

Glass microparticle- versus microsphere-filled experimental dental adhesives

This study aimed to formulate antibacterial dental adhesives. Phosphate-substituted methacrylate adhesives were modified with 0–20 wt % copper-doped glass microparticles. Two shapes of microparticles were used: regular shaped (microspheres) and irregular shaped (microparticles). The morphology/composition, roughness, monomer conversion (DC%), thermogravimetric analysis, and antibacterial action against S. mutans and P. aeruginosa and ion release were investigated. The results showed that microspheres produced adhesives with a relatively smoother surface than microparticles did. The DC% of adhesives increased with increasing glass filler content. Filled adhesives showed polymer decomposition at ~315 °C and glass melting at 600–1000 °C. The weight loss percent of adhesives decreased with increasing weight percent of fillers. Glass microparticles at 0–20 wt % significantly increased the antibacterial action of adhesives against both bacteria. Glass microspheres at 0–5 wt % significantly increased the antibacterial action of adhesives against both bacteria. Only 20 wt % microparticle-filled adhesive showed an inhibition zone similar to tobramycin (positive control). Microparticle-filled adhesives (with >5 wt % filler) significantly reduced S. mutans more than their microsphere counterparts. Microsphere-filled adhesives (with ≤5 wt % filler) significantly reduced P. aeruginosa more than their microparticle counterparts. Microsphere-filled adhesives showed higher Cu release than their microparticle counterparts. Accordingly, phosphate-substituted methacrylate filled with glass could be used as an antibacterial adhesive. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47832.     

Discovery of Benzimidazole–Quinolone Hybrids as New Cleaving Agents toward Drug‐Resistant Pseudomonas aeruginosa DNA

A series of benzimidazole–quinolone hybrids as new potential antimicrobial agents were designed and synthesized. Bioactive assays indicated that some of the prepared compounds exhibited potent antibacterial and antifungal activities. Notably, 2‐fluorobenzyl derivative 5 b (ethyl 7‐chloro‐6‐fluoro‐1‐[[1‐[(2‐fluorophenyl)methyl]benzimidazol‐2‐yl]methyl]‐4‐oxo‐quinoline‐3‐carboxylate) showed remarkable antimicrobial activity against resistant Pseudomonas aeruginosa and Candida tropicalis isolated from infected patients. Active molecule 5 b could not only rapidly kill the tested strains, but also exhibit low toxicity toward Hep‐2 cells. It was more difficult to trigger the development of bacterial resistance of P. aeruginosa against 5 b than that against norfloxacin. Molecular docking demonstrated that 5 b could effectively bind with topoisomerase IV–DNA complexes, and quantum chemical studies theoretically elucidated the good antimicrobial activity of compound 5 b . Preliminary experimental reaction mechanism exploration suggested that derivative 5 b could not intercalate into DNA isolated from drug‐resistant P. aeruginosa, but was able to cleave DNA effectively, which might further block DNA replication to exert powerful bioactivities. In addition, compound 5 b is a promising antibacterial agent with membrane disruption abilities.     

Multicomponent Petasis‐borono Mannich Preparation of Alkylaminophenols and Antimicrobial Activity Studies

In this work we report the antibacterial activity of alkylaminophenols. A series of such compounds was prepared by a multicomponent Petasis‐borono Mannich reaction starting from salicylaldehyde and its derivatives. The obtained compounds were tested against a large panel of microorganisms, Gram‐positive and Gram‐negative bacteria, and a yeast. Among the several tertiary amine derivatives tested, indoline‐derived aminophenols containing a nitro group at the para‐phenol position showed considerable activity against bacteria tested with minimal inhibitory concentrations as low as 1.36 μm against Staphyloccocus aureus and Mycobacterium smegmatis. Cytotoxicity of the new para‐nitrophenol derivatives was observed only at concentrations much higher than those required for antibacterial activity.     

Evaluation of the Antimicrobial Potential and Toxicity of a Newly Synthesised 4-(4-(Benzylamino)butoxy)-9H-carbazole

One of the greatest threats to human and animal health is posed by infections caused by drug-resistant bacterial strains. Therefore, newly synthesised substances are tested for their antimicrobial activity. Carbazole derivatives seem to be promising antibacterial agents. This study aimed at investigating the toxicity and activity of newly synthesised, functionalised carbazole derivative 2 (4-(4-(benzylamino)butoxy)-9H-carbazole) against various microorganisms. Its antimicrobial potential against Gram-positive and Gram-negative bacteria, yeast, and filamentous fungi was examined according to CLSI (Clinical and Laboratory Standards Institute) standards. The tested compound was found to efficiently inhibit the growth of Gram-positive strains. The addition of carbazole derivative 2 at the concentration of 30 µg/mL caused inhibition of bacterial growth by over 95%. Moreover, about 50 and 45% limitation of Pseudomonas aeruginosa and Aspergillus flavus growth was observed in the samples incubated with the addition of 20 and 60 µg/mL of the compound, respectively. Its addition to the microbial cultures caused an increase in the permeability of the cellular membrane. Slight haemolysis of red blood cells was observed after 24-h treatment with carbazole derivative 2. On the other hand, human fibroblasts were found to be more sensitive to its effects. The activity of the tested compound indicates a possibility of its further modification in order to obtain effective drugs, especially against drug-resistant staphylococci.     

The studies of cytotoxicity and antibacterial activity of composites with ZnO-doped bioglass

The paper presents results of the studies on porous composites obtained using lyophilization method based on the solutions of the following polymers: chitosan, sodium alginate and polylactide, as well as ZnO-doped CaO–SiO₂–P₂O₅ bioglass. The researchers took the advantage of zinc ions demonstrating the bactericidal, immune-stimulating, and tissue-regenerating functions in the organism. The cytotoxicity of the composites was tested on L929 cells by means of the direct and the indirect contact method. The antibacterial properties were determined against the gram-negative bacteria Pseudomonas aeruginosa and the gram-positive bacteria Staphylococcus aureus at 24, 48 hours, and 7 days. The study demonstrated that changes due to cytotoxicity effect of the composites depend on the type of polymer and on the duration of contact with cells. The composite with polylactide was found to be the least toxic for L929 cells. ZnO added to the chemical composition of bioglass ensured bactericidal effects. The antibacterial properties of the composites depended on the ZnO content, bioglass grain size, polymer type, and composite microstructure. The composites presented in this paper are innovative as biomaterials for filling bone cavities because they can be a matrix for cells and have an antibacterial effect while supporting the regeneration of damaged tissue.     

Comparative Study of the Micellar and Antimicrobial Activity of Gemini-Conventional Surfactants in Pure and Mixed Micelles

We have carried out mixed micellization of pentanediyl-α,ω-bis(dimethyl cetylammonium bromide) (G5) with conventional cationic cetylpyridinium chloride (CPC) and nonionic polyoxyethylene (20) cetyl ether (C16E20) in aqueous media and explored their antimicrobial activity in single and binary systems against Escherichia coli (E.coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The compounds tested showed excellent antibacterial activity: 0.76–3.38 g/l minimum inhibitory concentration (MIC) and were more active against gram +ve bacteria. For surfactant mixtures G5-C16E20 > G5-CPC, the ionic-nonionic binary surfactant showed greater antibacterial activity. The experimental results of this study may be profitably used to understand and predict the antibacterial activity of gemini-conventional surfactant systems and provide valuable information for selection of surfactant for microbiocidal action.     

Antibacterial properties of polyaniline derivatives

This work presents a detailed study on the effect of various functional groups both at the ortho position of the aromatic ring and in the amino group of PANI on the antibacterial properties of polymers against gram-positive (Bacillus subtilis) and gram-negative (Pseudomonas aureofaciens) microorganisms. It was found that incorporation of methyl, methoxy, or pentyl groups into the ortho-position of PANI did not increase the antibacterial activity but in most cases causes a significant decrease in the antibacterial properties of functionally substituted polyanilines. At the same time, PANI derivatives modified by incorporation of pentyl groups into the amino group were found to be more efficient antibacterial compounds against both gram-positive and gram-negative microorganisms than the original polymer. It was also found that N-substituted PANI derivatives manifest not only bactericidal but also bacteriostatic properties toward the test microorganisms. Varying the nature and position of the substituent allowed us to conclude that the synthesis of various N-substituted PANI derivatives with a high degree of doping is the most promising approach to PANI modification for application in bacterial growth inhibition.     

Screening and Molecular Identification of Bacteria from the Midgut of Amphimallon solstitiale Larvae Exhibiting Antagonistic Activity against Bacterial Symbionts of Entomopathogenic Nematodes

Entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) are a group of organisms capable of infecting larvae of insects living in soil, including representatives of the family Scarabaeidae. Their insecticidal activity is related to the presence of symbiotic bacteria Xenorhabdus spp. or Photorhabdus spp. in the alimentary tract, which are released into the insect body, leading to its death caused by bacterial toxins and septicemia. Although the antibacterial activities of symbionts of entomopathogenic nematodes have been well described, there is insufficient knowledge of the interactions between these bacteria and microorganisms that naturally inhabit the alimentary tract of insects infested by nematodes. In this study, 900 bacterial strains isolated from midgut samples of Amphimallon solstitiale larvae were tested for their antagonistic activity against the selected five Xenorhabdus and Photorhabdus species. Cross-streak tests showed significant antibacterial activity of 20 isolates. These bacteria were identified as Bacillus [Brevibacterium] frigoritolerans, Bacillus toyonensis, Bacillus wiedmannii, Chryseobacterium lathyri, Chryseobacterium sp., Citrobacter murliniae, Enterococcus malodoratus, Paenibacillus sp., Serratia marcescens and Serratia sp. Since some representatives of the intestinal microbiota of A. solstitiale are able to inhibit the growth of Xenorhabdus and Photorhrhabdus bacteria in vitro, it can be assumed that this type of bacterial interaction may occur at certain stages of insect infection by Steinernema or Heterorhabditis nematodes.