Spectrum Of Antimicrobial Activity Research Articles

How antimicrobial peptide indolicidin and its derivatives interact with phospholipid membranes: Molecular dynamics simulation

Infections by drug-resistant bacteria pose a growing threat to human health, so developing new antimicrobial drugs is becoming an increasingly urgent requirement. Antimicrobial peptides are an important part of the innate immune system of many organisms, which have a broad spectrum of antimicrobial activity and little likelihood to trigger resistance, so they are considered good candidates for developing new antimicrobial drugs. In this paper, the interaction of indolicidin (IR13) and its derived peptides CP10A, CP-11 and cycloCP-11 with Gram-negative bacterial model membranes is investigated using coarse-grained molecular dynamics approach. The aim is to analyse the behaviour of these antimicrobial peptides when interacting with Gram-negative bacterial membranes. The widely studied phospholipid bilayer consisting of POPC and POPG is used as a Gram-negative bacterial membrane model in the simulations. The results show that the derived peptides CP-11 and cycloCP-11 are more active against Gram-negative bacteria than IR13 and CP10A. The dynamic behaviour of the four antimicrobial peptides on the membrane is different, and the peptide-membrane interactions induce changes in the thickness and surface area of the phospholipid bilayer, diminish membrane mobility, and so on. The present study provides important insights into the mechanism of interaction between antimicrobial peptides and phospholipid membranes by analysing them at the molecular level, and is therefore informative for designing new derivative peptides.

Oleuropein can Protect the Brain Against Deleterious Effects of Bile Duct Ligation in Male Mice

Oleuropein (OP) is a phenolic compound in olives. OP possesses potent antioxidant activity and an extensive spectrum of other pharmacological properties, including antiviral, anti-inflammatory, and antimicrobial activities. This study investigated the effects of OP on neural injuries caused by bile duct ligation (BDL) in male mice. The mice were randomly allocated to three groups: sham, BDL, and BDL + OP. Neurobehavioral tests histological and biochemical evaluations were accomplished to assess cerebral damage. The results demonstrated that the induction of BDL led to behavioral impairments and a rise in hepatic enzymes, and OP could protect the brain against BDL-induced injuries. OP significantly increased antioxidant enzymes. These results suggested that OP has valuable effects in the mice BDL model, probably due to its anti-inflammatory and antioxidant properties.

Combined effect of brazilin-rich extract and lawsone methyl ether against infection-causing bacteria

Bacterial contamination and infection widely affect the food, pharmaceutical and biomedical industries. Additionally, these bacteria developed resistance to synthetic antibiotics causing public health danger, globally. Natural plant extracts (NPE) are suitable alternatives to synthetic antibiotics to tackle antimicrobial resistance problems. Furthermore, a blend or combination of different NPEs exerts a wide spectrum of antimicrobial activity. Therefore, the combined effect of brazilin-rich extract (BRE) and lawsome methyl ether (LME) against infection-causing common bacteria were evaluated. BRE had a lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against most of the Gram-negative bacteria (Salmonella typhi, Salmonella typhimurium and Pseudomonas aeruginosa) while LME was active against most of the Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis). The combination of BRE and LME at 2:1 and 1:1 concentration significantly reduced the MIC value of each compound as compared to either BRE or LME concentration alone (P < 0.05). Further time-kill kinetics revealed a 3.0–3.5 log reduction in Gram-positive bacteria and a 2.5–3.0 log reduction in Gram-negative bacteria during 120 min of incubation, respectively. Therefore, a combination of BRE and LME was recommended as natural antibacterial to synthetic antibiotics for food and pharmaceutical applications.

Preliminary Phytochemical Evaluation and Antimicrobial studies of the methanol stem bark extract of Detarium microcarpum

Detarium microcarpum is an African native plant that grows in the wild in several African countries, notably in savannah areas. The plant has a wide therapeutic application and is often referred to as the miracle plant by the traditional herbalist. Folk medicine relies heavily on its leaves and fruits. Hence, this research was aimed at qualitatively and quantitatively estimating the phytoconstituents inherent in the plant as well as to evaluate its antimicrobial potentials. Qualitative analysis of the methanol crude extracts was carried out to identify the presence of the classes of secondary metabolites: The results of the phytochemical screening revealed the presence of alkaloids, saponins, tannins, flavonoids, steroids and Glycosides. Similarly, the quantitative estimation of these phytoconstituents revealed the following percentage of the metabolite; alkaloids (112.35 mg/100g Atropine sulfate eqv), saponins (96.84 mg/100g Gravimetric), Tannins (159.65 mg/100g Tannic acid eqv), Flavanoids (125.47 mg/100g Quarcetine eqv) Glycosides (397.53 mg/100g), Steroids (34.52 mg/100g Cholestrol), Total phenolics (228.24 mg/100 Gallic acid eqv). The paper disc diffusion method was used to determine the antimicrobial activity of the Crude methanol extract of Datarium microcarpum using standard procedures (Bauer et al 1996). The results of antimicrobial efficacies revealed that the crude methanol extract of stem bark Detarium microcarpum was effective in inhibiting the growth of the following microorganisms; Protius, Bacillus subtilis staphylococaccus aureus, Enterobacta, Eschericia coli Shigelia dysenteriae, Salmonella typhi, Pseudomonas aeruginosa, Aspergillus nigger, Aspergillus flavus, Candida albican and Rhezome. The methanol crude extract showed a broad spectrum of antimicrobial activity with minimum inhibitory concentration (MIC) from 1.0×104 to 4.0×104 . Keywords: Phytochemical, antimicrobial studies, stem bark, and Detarium microcarpum

Cell-Free Supernatant from a Strain of Bacillus siamensis Isolated from the Skin Showed a Broad Spectrum of Antimicrobial Activity.

In recent years, the search for new compounds with antibacterial activity has drastically increased due to the spread of antibiotic-resistant microorganisms. In this study, we analyzed Cell-Free Supernatant (CFS) from Bacillus siamensis, assessing its potential antimicrobial activity against some of the main pathogenic microorganisms of human interest. To achieve this goal, we exploited the natural antagonism of skin-colonizing bacteria and their ability to produce compounds with antimicrobial activity. Biochemical and molecular methods were used to identify 247 strains isolated from the skin. Among these, we found that CFS from a strain of Bacillus siamensis (that we named CPAY1) showed significant antimicrobial activity against Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, and Candida spp. In this study, we gathered information on CFS's antimicrobial activity and on its sensitivity to chemical-physical parameters. Time-kill studies were performed; anti-biofilm activity, antibiotic resistance, and plasmid presence were also investigated. The antimicrobial compounds included in the CFS showed resistance to the proteolytic enzymes and were heat stable. The production of antimicrobial compounds started after 4 h of culture (20 AU/mL). CPAY1 CFS showed antimicrobial activity after 7 h of bacteria co-culture. The anti-biofilm activity of the CPAY1 CFS against all the tested strains was also remarkable. B. siamensis CPAY1 did not reveal the presence of a plasmid and showed susceptibility to all the antibiotics tested.

Microbial lipopeptides: their pharmaceutical and biotechnological potential, applications, and way forward.

As lead molecules, cyclic lipopeptides with antibacterial, antifungal, and antiviral properties have garnered a lot of attention in recent years. Because of their potential, cyclic lipopeptides have earned recognition as a significant class of antimicrobial compounds with applications in pharmacology and biotechnology. These lipopeptides, often with biosurfactant properties, are amphiphilic, consisting of a hydrophilic moiety, like a carboxyl group, peptide backbone, or carbohydrates, and a hydrophobic moiety, mostly a fatty acid. Besides, several lipopeptides also have cationic groups that play an important role in biological activities. Antimicrobial lipopeptides can be considered as possible substitutes for antibiotics that are conventional to address the current drug-resistant issues as pharmaceutical industries modify the parent antibiotic molecules to render them more effective against antibiotic-resistant bacteria and fungi, leading to the development of more resistant microbial strains. Bacillus species produce lipopeptides, which are secondary metabolites that are amphiphilic and are typically synthesized by non-ribosomal peptide synthetases (NRPSs). They have been identified as potential biocontrol agents as they exhibit a broad spectrum of antimicrobial activity. A further benefit of lipopeptides is that they can be produced and purified biotechnologically or biochemically in a sustainable manner using readily available, affordable, renewable sources without harming the environment. In this review, we discuss the biochemical and functional characterization of antifungal lipopeptides, as well as their various modes of action, method of production and purification (in brief), and potential applications as novel antibiotic agents.

Understanding the Dynamics of Human Defensin Antimicrobial Peptides: Pathogen Resistance and Commensal Induction.

Antimicrobial peptides (AMPs), also known as host defense peptides, are petite molecules with inherent microbicidal properties that are synthesized by the host's innate immune response. These peptides serve as an initial barrier against pathogenic microorganisms, effectively eliminating them. Human defensin (HD) AMPs represent a prominent group of peptides involved in the innate immune response of humans. These peptides are primarily produced by neutrophils and epithelial cells, serving as a crucial defense mechanism against invading pathogens. The extensive research conducted has focused on the broad spectrum of antimicrobial activities and multifaceted immunomodulatory functions exhibited by human defensin AMPs. During the process of co-evolution between hosts and bacterial pathogens, bacteria have developed the ability to recognize and develop an adaptive response to AMPs to counterattack their bactericidal activity by different antibiotic-resistant mechanisms. However, numerous non-pathogenic commensal bacteria elicit the upregulation of defensins as a means to surmount the resistance mechanisms implemented by pathogens. The precise mechanism underlying the induction of HD by commensal organisms remains to be fully understood. This review summarizes the most recent research on the expression of human defensin by pathogens and discusses the various defense mechanisms used by pathogens to counter host AMP production. We also mention recent developments in the commensal induction of defensin AMPs. A better knowledge of the pathogens' defensin AMP resistance mechanisms and commensals' induction of AMP expression may shed light on the creation of fresh antibacterial tactics to get rid of bacterial infection.

Review of the book “Practical issues of rational antibacterial therapy”

In 2023, the book “Practical Issues of Rational Antibacterial Therapy” under general ed. Yarovoy SK, Khokhlov AL, was published. This monograph is devoted to practical issues of empirical therapy for the most common nonspecific infectious and inflammatory diseases. The monograph presents the main provisions of antimicrobial therapy from the perspective of clinical pharmacology. The general patterns of prescription and distribution of antibacterial agents, the concepts of basic and reserve drugs, selection of hospital strains, natural and acquired resistance are explained. Antibacterial drugs are compared in pairs with each other based on an analysis of their spectra of antimicrobial activity. Combination (multicomponent) antibacterial therapy is being considered. Undesirable regimens of antimicrobial therapy are described, options with insufficient effectiveness and an unsatisfactory safety profile are analyzed.

Unveiling the potential of Daldinia eschscholtzii MFLUCC 19-0629 through bioactivity and bioinformatics studies for enhanced sustainable agriculture production

Endophytic fungi constitute a rich source of secondary metabolites that can be manipulated to produce desirable novel analogs for combating current agricultural challenges for crop production, especially controlling plant disease. The endophytic fungus Daldinia eschscholtzii MFLUCC 19-0629, was newly isolated from tropical ancient plants, Oncosperma sp., and displays a broad-spectrum of antifungal and antibacterial activities against several plant pathogens including Ralstonia solanacearum, Fusarium oxysporum, Colletotrichum gloeosporioides, Colletotrichum acutatum, Stagonosporopsis cucurbitacearum, Corynespora cassiicola and Stemphylium spp. A high-quality genome sequence was obtained using Oxford nanopore technology, the accuracy and length of reads resulting in no need for Illumina or other sequencing techniques, for D. eschscholtzii MFLUCC 19-0629, resulting in a genome size of 37.56 Mb assembled over 11 contigs of significant size, likely to be at the chromosomal level. Bioinformatics analysis revealed that this strain is biosynthetically talented encoding 67 predicted biosynthetic gene clusters (BGCs). Only eight of the 67 BGCs matched or demonstrated high similarity to previously characterized BGCs linked to the production of known secondary metabolites. The high number of predicted unknown BGCs makes this strain a promising source of novel natural products. The discovery that D. eschscholtzii MFLUCC 19-0629 has a broad spectrum of antimicrobial activity against seven major plant pathogenic microorganisms relevant to crop production and its complete genome sequence carries immense importance in the advancement of novel microbial biocontrol agents (MBCAs). This also unveils the prospect of uncovering new compounds that could be utilized for sustainable agriculture and pharmaceutical purposes.

Mapping pathogenic bacteria resistance against common antibiotics and their potential susceptibility to methylated white kidney bean protein.

As antibiotics cannot inhibit multidrug-resistant bacteria (MDR), continuous research is mandatory to find other antibacterials from natural resources. Native legume proteins and their modified forms exhibited broad spectra of high antimicrobial activities. Sixteen bacterial isolates were mapped for antibiotic resistance, showing resistance in the range of (58-92%) and (42-92%) in the case of the Gram-negative and Gram-positive bacteria, respectively. White native Phaseolus vulgaris protein (NPP) was isolated from the seeds and methylated (MPP). The MIC range of MPP against 7 MDR bacteria was 10-25 times lower than NPP and could (1 MIC) considerably inhibit their 24h liquid growth. MPP showed higher antibacterial effectiveness than Gentamycin, the most effective antibiotic against Gram-positive bacteria and the second most effective against Gram-negative bacteria. However, MPP recorded MICs against the seven studied MDR bacteria in the 1-20µg/mL range, the same for Gentamycin. The combination of Gentamycin and MPP produced synergistic effects against the seven bacteria studied, as confirmed by the Transmission Electron Microscopic images. The antimicrobial activity of MPP against the seven MDR bacteria remained stable after two years of cold storage at 8-10°C as contrasted to Gentamycin, which lost 20-72% of its antimicrobial effectiveness.

Antibacterial Evaluation of Gallic Acid and its Derivatives against a Panel of Multi-drug Resistant Bacteria.

Infectious diseases are the second leading cause of deaths worldwide. Pathogenic bacteria have been developing tremendous resistance against antibiotics which has placed an additional burden on healthcare systems. Gallic acid belongs to a naturally occurring phenolic class of compounds and is known to possess a wide spectrum of antimicrobial activities. In this study, we synthesized thirteen derivatives of gallic acid and evaluated their antibacterial potential against seven multi-drug resistant bacteria, as well as cytotoxic effects against human embryonic kidney cell line in vitro. Methods: 13 compounds were successfully synthesized with moderate to good yield and evaluated. Synthesized derivatives were characterized by using nuclear magnetic resonance spectroscopy, mass spectrometry, and Fourier transformation infrared spectroscopy. Antibacterial activity was determined using microdilution while cytotoxicyt was assessed using MTT assay. The results of antibacterial assay showed that seven out of thirteen compounds exhibited antibacterial effects with compound 6 and 13 being most potent against Staphylococcus aureus (MIC 56 μg/mL) and Salmonella enterica (MIC 475 μg/mL) respectively. On the other hand, most of these compounds showed lower cytotoxicity against human embryonic kidney cells (HEK 293), with IC50 values ranging from over 700 μg/mL. Notably, compound 13 was found to be non-toxic at concentrations as high as 5000 μg/mL. These findings suggest that the present synthetic derivatives of gallic acid hold potential for further studies in the development of potent antibacterial agents.

Triphenylphosphonium Analogs of Short Peptide Related to Bactenecin 7 and Oncocin 112 as Antimicrobial Agents.

Antimicrobial peptides (AMPs) have recently attracted attention as promising antibacterial agents capable of acting against resistant bacterial strains. In this work, an approach was applied, consisting of the conjugation of a peptide related to the sequences of bactenecin 7 (Bac7) and oncocin (Onc112) with the alkyl(triphenyl)phosphonium (alkyl-TPP) fragment in order to improve the properties of the AMP and introduce new ones, expand the spectrum of antimicrobial activity, and reduce the inhibitory effect on the eukaryotic translation process. Triphenylphosphonium (TPP) derivatives of a decapeptide RRIRPRPPYL were synthesized. It was comprehensively studied how the modification of the AMP affected the properties of the new compounds. It was shown that while the reduction in the Bac7 length to 10 a.a. residues dramatically decreased the affinity to bacterial ribosomes, the modification of the peptide with alkyl-TPP moieties led to an increase in the affinity. New analogs with structures that combined a decapeptide related to Bac7 and Onc112-Bac(1-10, R/Y)-and TPP attached to the C-terminal amino acid residue via alkylamide linkers, inhibited translation in vitro and were found to be more selective inhibitors of bacterial translation compared with eukaryotic translation than Onc112 and Bac7. The TPP analogs of the decapeptide related to Bac7 and Onc112 suppressed the growth of both Gram-negative bacteria, similar to Onc112 and Bac7, and Gram-positive ones, similar to alkyl-TPP derivatives, and also acted against some resistant laboratory strains. Bac(1-10, R/Y)-C2-TPP, containing a short alkylamide linker between the decapeptide and TPP, was transferred into the E. coli cells via the SbmA transporter protein. TPP derivatives of the decapeptide Bac(1-10, R/Y) containing either a decylamide or ethylamide linker caused B. subtilis membrane depolarization, similar to alkyl-TPP. The Bac(1-10, R/Y)-C2-TPP analog was proven to be non-toxic for mammalian cells using the MTT test.

Mentha pulegium ekstraktı güçlü in vitro antimikrobiyal ve sitotoksik etki göstermiştir

Mentha pulegium is a medicinally important and well-known plant and used for various purposes such as medicinal, nutritional and spice. We are analyzed to observe the antimicrobial, antioxidant and cytotoxic properties of M. pulegium extracts in this study. The antimicrobial activity of M. pulegium was tested using the agar well method. MIC, MBC and antimicrobial activity were tested on Staphylococcus aureus (ATCC 25923), Klebsiella pneumoniae (ATCC 700603), Escherichia coli (ATCC 25322), Bacillus megaterium (DSM32) and Candida albicans (FMC17) microorganisms. Clindamycin (2 µg) and Amoxicillin (30 µg) were used as positive control and Dimethylsulfoxide (DMSO) as negative control. Cytotoxic activity of extracts at different concentrations obtained from solvents such as acetone, chloroform and methanol using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test method; µg/ml cytotoxic activity and cell death patterns after exposure to different concentrations of the extracts on human breast cancer (MDA-MB-231), human pancreatic cancer (PANC1), human ovarian cancer (OVCAR3) and human lung cancer (A549) cell lines determined accordingly. As a result, it was determined that M. pulegium extract has a strong antimicrobial activity spectrum and cytotoxic effect.

Recent Advances on Antimicrobial Peptides from Milk: Molecular Properties, Mechanisms, and Applications.

Traditional antibiotics are facing a tremendous challenge due to increased antimicrobial resistance; hence, there is an urgent need to find novel antibiotic alternatives. Milk protein-derived antimicrobial peptides (AMPs) are currently attracting substantial attention considering that they showcase an extensive spectrum of antimicrobial activities, with slower development of antimicrobial resistance and safety of raw materials. This review summarizes the molecular properties, and activity mechanisms and highlights the applications and limitations of AMPs derived from milk proteins comprehensively. Also the analytical technologies, especially bioinformatics methodologies, applied in the process of screening, identification, and mechanism illustration of AMPs were underlined. This review will give some ideas for further research and broadening of the applications of milk protein-derived AMPs in the food field.

Phenolic compounds and antimicrobial activity of leaves of the genus Sorbus species and natural hybrids

The identification of new sources of biologically active substances is an actual direction of research in recent years, in particular, the demand for antimicrobial compounds and natural preservatives of plant origin is growing. Plants of the genus Sorbus L. are known in folk medicine, but for the rational use of plant material, there is a lack of systematic study of the features of the secondary metabolites’ accumulation and the spectrum of biological activity of plants during vegetation in different environmental conditions. In the present work, the seasonal dynamics of the total content of polyphenols, flavonoids and free phenolic acids in the leaves of rowan plants natural to the flora of Ukraine and introduced in the steppe region were investigated. The highest accumulation of phenolic compounds was found in the leaves of S. domestica, S. latifolia, S. hybrida, S. torminalis and S. aucuparia in the first half of June, and in S. aria and S. intermedia in May, which will serve as a criterion for selecting the best plant material to obtain biologically active compounds. The seasonal dynamics of the content of flavonoids and phenolic acids in the leaves of plants had significant species differences, which require more in-depth studies of the phytocompounds component composition. Antimicrobial activity of leaf ethanol extracts of rowan plant was found to be high against gram-negative bacterial strain Klebsiella pneumoniae B920 (especially the activity of S. aria, S. intermedia and S. aucuparia extracts) and Pseudomonas aeruginosa B907 (especially the activity S. torminalis and S. domestica), clinical gram-positive strains of Staphylococcus epidermidis (the highest activity of S. aria, S. domestica and S. intermedia extracts), as well as against clinical strains of fluconazole-resistant fungus Candida albicans (especially the activity of extracts of S. latifolia S. torminalis and S. intermedia). A conclusion was made about the prospects of using leaf extracts of the genus Sorbus plants as an economical and affordable natural source of biologically active polyphenols with a wide spectrum of antimicrobial activity. Further research may be aimed at elucidating the component composition of rowan leaf extracts and establishing the relationship between individual phytocompounds and the antimicrobial effects of plant extracts.

Efficacy of biofilm disrupters against Candida auris and other Candida species in monomicrobial and polymicrobial biofilms

AbstractCandida species are now considered global threats by the CDC and WHO. Candida auris specifically is on the critical pathogen threat list along with Candida albicans. In addition, it is not uncommon to find Candida spp. in a mixed culture with bacterial organisms, especially Staphylococcus aureus producing polymicrobial infections. To eradicate these organisms from the environment and from patient surfaces, surface agents such as chlorhexidine (CHD) and Puracyn are used. Biofilm disrupters (BDs) are novel agents with a broad spectrum of antimicrobial activity and have been used in the management of chronic wounds and to sterilise environmental surfaces for the past several years. The goal of this study was to evaluate BDs (BlastX, Torrent, NSSD) and CHD against Candida spp. and S. aureus using zone of inhibition assays, biofilm and time‐kill assays. All BDs and CHD inhibited C. auris growth effectively in a concentration‐dependent manner. Additionally, CHD and the BDs showed excellent antimicrobial activity within polymicrobial biofilms. A comparative analysis of the BDs and CHD against C. auris and C. albicans using biofilm kill‐curves showed at least 99.999% killing. All three BDs and CHD have excellent activity against different Candida species, including C. auris. However, one isolate of C. auris in a polymicrobial biofilm assay showed resistance/tolerance to CHD, but not to the BDs. The fungicidal activity of these novel agents will be valuable in eradicating surface colonisation of Candida spp, especially C. auris from colonised environmental surfaces and from wounds in colonised patients.

A review on antibacterial potential of poly‐ionic liquid‐based biomaterials

AbstractIn recent years, bacterial infection has become one of the significant clinical challenges. The overuse or misuse of antibiotics increases the number of antibiotic‐resistant bacterial pathogens and causes enormous medical burdens with high morbidity and mortality. Several strategies have been adopted to tackle this; poly‐ionic liquids (PILs), a class of ionic liquids (ILs) systems demonstrating a broad spectrum of antimicrobial activities, have been widely used in biomedical applications. During polymerization, the charge density of the cations, molecular weight, and hydrophobic behavior can be regulated to accomplish more potent antibacterial efficacy with low cytotoxicity. However, inadequate literature is available highlighting the application of PIL‐based materials in biomedical applications. Keeping this in mind, the recent advances in PIL‐based biomaterials formed by conjugating PIL with natural and synthetic polymers as effective antimicrobial agents have been the focus area of this review.

Chemoprofiling and antimicrobial activity of medicinal herbs used in the treatment of inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a term utilized to illustrate two different chronic disorders of the gastro-intestinal tract i.e., Crohn's disease and ulcerative colitis. The symptoms of IBD are mainly characterized by inflammation, including abdominal pain, chronic diarrhoea, weight loss, shortening of the colon and rectal bleeding. The objective of this study was to evaluate the antimicrobial activity and Gas Chromatography-Mass Spectrometry (GC-MS) analysis of herbs used in the treatment of IBD in Saudi Arabia. Ethanolic extracts of five different herbs from Saudi Arabia namely Pimpinella anisum (Anise), Foeniculum vulgare (Fennel), Matricaria chamomilla (Chamomile), Linum usitatissimum (Linseed), and Punicagranatum (Pomegranate) were prepared by Soxhlet extraction. The systemic chemical composition of the extracts was identified by GC-MS with their relative concentrations. The ethanolic extract of P. anisum, F. vulgare, M. chamomilla, L. usitatissimum, and P.granatum showed the presence of 35, 42, 34, 37, and 47 chemical components in these extracts, respectively. The five extracts and an equal mixture of them were examined for their antimicrobial activity by broth dilution method against different organisms. These included Gram-positive (Staphylococcus aureus), Gram-negative (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Pseudomonas aeruginosa) bacteria and one yeast (Candida albicans). P. anisum, F. vulgare, M. chamomilla, L. usitatissimum, P.granatum and the mixture of all five extracts had good activity against E. coli (MIC=3.125, 0.050, 6.25, 0.050 and 0.100 mg/ml, respectively). P.granatum also had a MIC of 3.125 mg/ml against S. aureus. In conclusion. the plants' extracts and an equal mixture of them showed a narrow spectrum of antimicrobial activity against S. aureus, K. pneumoniae, P. mirabilis, P. aeruginosa and C. albicans.

Endophytic bacteria Klebsiella spp. and Bacillus spp. from Alternanthera philoxeroides in Madiwala Lake exhibit additive plant growth-promoting and biocontrol activities

BackgroundThe worldwide increase in human population and environmental damage has put immense pressure on the overall global crop production making it inadequate to feed the entire population. Therefore, the need for sustainable and environment-friendly practices to enhance agricultural productivity is a pressing priority. Endophytic bacteria with plant growth-promoting ability and biocontrol activity can strongly enhance plant growth under changing environmental biotic and abiotic conditions. Herein, we isolated halotolerant endophytic bacteria from an aquatic plant, Alternanthera philoxeroides, from the polluted waters of Madiwala Lake in Bangalore and studied their plant growth promotion (PGP) and biocontrol ability for use as bioinoculant. ResultsThe isolated bacterial endophytes were screened for salt tolerance ranging from 5 to 15% NaCl concentration. Klebsiella pneumoniae showed halotolerant up to 10% NaCl and Bacillus amyloliquefaciens and Bacillus subtilis showed up to 15%. All three strains demonstrated good PGP abilities such as aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, phosphate solubilization, ammonia production, and nitrogen fixation. In addition, K. pneumoniae also exhibited high indoleacetic acid (IAA) production (195.66 ± 2.51 µg/ml) and potassium solubilization (2.13 ± 0.07 ppm). B. amyloliquefaciens and B. subtilis showed good extracellular enzyme production against cellulase, lipase, protease, and amylase. Both the isolates showed a broad spectrum of antimicrobial activity against the tested organisms. The optimization of IAA production by K. pneumoniae was done by the response surface methodology (RSM) tool. Characterization of IAA produced by the isolate was done by gas chromatography-mass spectrometry (GCMS) analysis. The enhanced plant growth-promoting ability of K. pneumoniae was also demonstrated using various growth parameters in a pot trial experiment using the seeds of Vigna unguiculata. ConclusionThe isolated bacterial endophytes reported in this study can be utilized as PGP promotion and biocontrol agents in agricultural applications, to enhance crop yield under salinity stress. The isolate K. pneumoniae may be used as a biofertilizer in sustainable agriculture and more work can be done to optimize the best formulations for its application as a microbial inoculant for crops.

Evaluation of the impact of tragacanth/xanthan gum interpolymer complexation with chitosan on pharmaceutical performance of gels with secnidazole as potential periodontal treatment

Periodontitis consists a group of dental disorders that affect about 70 % of the world population. The therapy mainly relies on mechanical removing bacterial biofilm, nevertheless, local or systemic antibacterial agents play a key role in treating the acute conditions. Secnidazole is a newer derivative of commonly used metronidazole with high safety profile and broad spectrum of antimicrobial activity. The aim of the study was to evaluate the applicability of polyelectrolyte complex-based hydrogels composed of anionic tragacanth with addition of xanthan gum and cationic chitosan as carriers for buccal/intra pocket delivery of secnidazole. Prepared hydrogels with 5 % and 10 % (w/w) drug content were evaluated pharmaceutically towards inter alia physicomechanical, rheological and thermal properties, drug release kinetics, swelling behavior or antimicrobial activity. Cytotoxicity against human primary umbilical vein endothelial cells was also assessed with two independent method. Stable compositions with secnidazole were obtained, however, various miscibility of the drug with the polymers was noted. By adding chitosan, antibacterial activity and swelling performance of the gels were improved, nevertheless, drop of the mucoadhesiveness was also recorded. Hydrogels with 5 % secnidazole were selected as effective antimicrobial compositions with the highest cytocompatibility. They might be considered as promising for oromucosal application with special attention given to SEC as an alternative locally administered antimicrobial agent.