Rhamnolipids from Planococcus spp. and their mechanism of action against pathogenic bacteria

Two bacterial species with the ability to produce biosurfactants were isolated from a pesticide contaminated soil and identified as Planococcus rifietoensis IITR53 and Planococcus halotolerans IITR55. Formation of froth indicating the surfactant production was observed when grown in basal salt medium containing 2% glucose. The culture supernatant after 72 h showed reduction in surface tension from 72 N/m to 46 and 42 N/m for strain IITR53 and IITR55 with emulsification index of 51 and 54% respectively. The biosurfactant identified as rhamnolipid based on liquid chromatography-mass spectrometry analysis, was found to inhibit the growth of both gram- positive and negative pathogenic bacteria. Both the rhamnolipids at 40 mg/mL exhibited the release of extracellular DNA and protein content. Also at one third of the MIC, a significant generation of reactive oxygen species was recorded. These rhamnolipids effectively emulsified different vegetable oils suggesting their possible utilization as antimicrobial agent.

Comparative in vitro activities of meropenem in combination with colistin, levofloxacin, or chloramphenicol against Achromobacter xylosoxidans strains isolated from patients with cystic fibrosis

OBJECTIVES

Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis (CF). Relatively little is known about its clinical impact and optimal management. In the present study, the in vitro bactericidal activities of meropenem, either alone or in combination with colistin, levofloxacin, or chloramphenicol, were assessed using A. xylosoxidans strains isolated from CF patients. The synergistic interactions of these combinations were also investigated.

METHODS

Minimal inhibitory concentrations (MICs) were determined by microbroth dilution. Bactericidal and synergistic effects of the tested antibiotic combinations were assessed by using the time-kill curve technique.

RESULTS

Based on the time-kill curves, we found that meropenem-colistin combinations have bactericidal and synergistic activities for 24 h against A. xylosoxidans strains, both at 1 × MIC and 4 × MIC. Although synergistic interactions were seen with meropenem-levofloxacin combinations, no bactericidal interactions were observed. Additionally, the meropenem-chloramphenicol combinations were found to be neither bactericidal nor synergistic. No antagonism was observed with any combination tested.

CONCLUSIONS

This study's findings could have important implications for empirical or combination antimicrobial therapy with tested antibiotics.

Inhibition of pathogenic Vibrio harveyi using calamenene, derived from the Indian gorgonian Subergorgia reticulata, and its synthetic analog

We report the synthesis and antimicrobial properties of a partially reduced dihydronathphthoquinone analogue of 2-methoxy, 5-acetoxy calamenene, extracted from Subergorgia reticulata. The growth of a pathogenic Vibrio harveyi strain was effectively controlled by the calamenene derivative 1 (Cala1) and its synthetic analog 2 (Cala2). Complete mortality of V. harveyi was observed with 2.5 and 0.5 µg mL-1 concentrations of Cala1 and Cala2, respectively. The metabolic assays demonstrated that Cala1 is a bacteriostatic agent while Cala2 showed bactericidal properties. It was confirmed that translocation of Cala2 into the cytoplasm does not induce any change to the integrity of the bacterial cell wall. The Cala2 induced damage to the genetic material of 70% of cells while genetic material of 91% of cells treated with Cala1 remained intact. The Cala2 is, therefore, proposed as a potential bactericidal compound against the aquaculture pathogen V. harveyi. The fact that the Cala2 exhibited minimal cytotoxicity to Artemia nauplii indicates its potential use as an antimicrobial agent for aquaculture operations.

Biosynthesis, characterization, bactericidal and sporicidal activity of silver nanoparticles using the leaves extract of Litchi chinensis

Biosynthesis of silver nanoparticles (AgNPs) using plant extracts has become a promising alternative to the conventional chemical synthesis approach. In this study, cost-effective synthesis of AgNPs was attempted using leaves extract of Litchi chinensis. Bio-reduction reaction for the synthesis of NPs was checked by confirming the presence of AgNPs in solution by UV-vis spectrophotometry and with further characterization by fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Surface plasmon resonance (SPR) band showed absorption peak at 422 nm indicating the formation of AgNPs, and FTIR spectra confirmed the presence of biological molecules involved in AgNPs synthesis. TEM analysis revealed the spherical shape of AgNPs with particle size distribution in a range of 5-15 nm. Further, the biosynthesized AgNPs showed significant bactericidal and sporicidal activity against model spore former Bacillus subtilis. AgNPs at concentrations ranging from 25 to 100 µg/mL showed bactericidal activity with inhibition zone ranging from 4-19 mm and sporicidal activity at 100-200 µg/mL in a range of 4.46-61.6% with an exposure time of 2-8 h. These findings exhibit distinctive potential of biogenic AgNPs for their efficient use in developing novel bactericidal and sporicidal agent against spore forming bacilli.

Antimicrobial evaluation of thiadiazino and thiazolo quinoxaline hybrids as potential DNA gyrase inhibitors; design, synthesis, characterization and morphological studies

A series of thiadiazino[5,6-b]quinoxaline and thiazolo[4,5-b]quinoxaline derivatives was designed and synthetized from the reaction of 2,3-dichloro-6-(morpholinosulfonyl)quinoxaline (2) with thiosemicarbazide or thiocarbohydrazide and thiourea derivatives to give nineteen quinoxaline derivatives 3-16. All the synthesized compounds were evaluated for in vitro antimicrobial potential against various bacteria and fungi strains that showed considerable antimicrobial activity against tested microorganisms. The most potent compounds 2, 7, 9, 10, 12 and 13c were exhibited bactericidal activity, in addition to fungistatic activity by dead live assay. Moreover, these compounds showed a significant result against all multi-drug resistance (MDRB) used especially compound 13c that displayed the best results with MICs of MDRB (1.95, 3.9, 2.6, 3.9 µg/mL) for stains used in this study, compared with Norfloxacin (1.25, 0.78, 1.57, 3.13 µg/mL). Also, cytotoxicity on normal cell (Vero cells ATCC CCL-81) by MTT assay was performed with lower toxicity results. Additionally, morphological studies, immunostimulatory potency and DNA gyrase inhibition assay of most active compounds was done. A molecular docking study has also been carried out to support the effective binding of the most promising compounds at the active site of the target enzyme S. aureus DNA gyrase (2XCT).

Substituted sulfonamide bioisosteres of 8-hydroxyquinoline as zinc-dependent antibacterial compounds

A series of substituted sulfonamide bioisosteres of 8-hydroxyquinoline were evaluated for their antibacterial activity against the common mastitis causative pathogens Streptococcus uberis, Staphylococcus aureus and Escherichia coli, both in the presence and absence of supplementary zinc. Compounds 9a-e, 10a-c, 11a-e, 12 and 13 were demonstrated to have MICs of 0.0625 µg/mL against S. uberis in the presence of 50 µM ZnSO₄. Against S. aureus compounds 9g (MIC 4 µg/mL) and 11d (MIC 8 µg/mL) showed the greatest activity, whereas all compounds were found to be inactive against E. coli (MIC > 256 µg/mL); again in the presence of 50 µM ZnSO₄. All compounds were demonstrated to be significantly less active in the absence of supplementary zinc. Compound 9g was subsequently confirmed to be bactericidal, with an MBC (≥3log₁₀ cfu/mL reduction) of 0.125 µg/mL against S. uberis in the presence of 50 µM ZnSO₄. To validate the sanitising activity of compound 9g in the presence of supplementary zinc, a quantitative suspension disinfection (sanitizer) test was performed. In this preliminary test, sanitizing activity (>5log₁₀ reduction of CFU/mL in 5 min) was observed against S. uberis for compound 9g at concentrations as low as 1 mg/mL, validating the potential of this compound to function as a topical sanitizer against the major environmental mastitis-causing microorganism S. uberis.

Effect of the lantibiotic nisin on inhibitory and bactericidal activities of antibiotics used against vancomycin-resistant enterococci

OBJECTIVES

Antibiotic resistance is a serious issue facing clinicians all over the world. Vancomycin-resistant enterococci (VRE) are amongst the most common resistant pathogens that are isolated from patients suffering from infections in our locality. New antimicrobial agents such as the lantibiotic nisin have been previously examined against resistant bacteria as it has strong antibacterial action with no chance of resistance development. This study aimed to explore the effect of nisin in combination with the conventional antibiotics against VRE, with a view to using it as an auxiliary therapy with such antibiotics for combating resistant isolates.

METHODS

Twenty-three VRE had been examined for the combined effect of nisin with the routine sets of antibiotics using the microplate dilution technique for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) testing. Checkerboard microbroth assay was conducted for inspection of synergism between nisin and either ampicillin or chloramphenicol.

RESULTS

An obvious improvement of inhibitory and bactericidal activities of the tested antibiotics after addition of lantibiotic nisin was observed, with a remarkable reduction in the MIC values of vancomycin against all of the isolates. Nisin recorded a synergistic outcome when combined with either ampicillin or chloramphenicol using the checkerboard assay.

CONCLUSION

Nisin could be effectively considered as a supplementary agent to traditional antibiotics in the management of VRE-associated infections, as it had a synergistic outcome with commonly prescribed antibiotics such as ampicillin and chloramphenicol.

Effect of complement Factor H on antibody repertoire and protection elicited by meningococcal capsular group B vaccines containing Factor H binding protein

Bacteria produce surface ligands for host complement regulators including Factor H (FH), which allows the bacteria to evade immunity. Meningococcal Factor H binding protein (FHbp) is both a virulence factor and a vaccine antigen. Antibodies to FHbp can neutralize its function by inhibiting binding of FH to the bacteria and confer robust complement-mediated protection. However, in the presence of human or primate FH, antibodies to FHbp do not inhibit FH binding and the protective antibody responses are decreased. This immune suppression can be overcome by modification of the FHbp antigen to decrease FH binding, which modulates the antibody repertoire to inhibit FH binding and increase protection. When FHbp is present at sufficient density on the bacterial surface, two or more antibodies can synergize to activate the complement system. Thus, modification of FHbp antigens to decrease FH binding expands the anti-FHbp antibody repertoire and increases the potential for synergistic activity.

Multifarious Pharmacological Applications of Green Routed Eco-Friendly Iron Nanoparticles Synthesized by Streptomyces Sp. (SRT12)

A simple, eco-friendly, green routine co-precipitation method was experimented to synthesize iron nanoparticles (Fe-NPs) using the cell-free supernatant of actinobacteria. The biosynthesized nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffractometer (XRD), energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), atomic force microscopy (AFM), zeta potential analyser and Fourier transform infrared (FTIR) spectroscopy. The synthesized nanoparticles were crystalline, quasi-spherical in shape and their average size ranged from 65.0 to 86.7 nm. In our radical scavenging assays, the nanoparticles have revealed a strong antioxidant activity with respective standard ascorbic acid. The nanoparticles also exhibited a wide bactericidal action on pathogens namely Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Shigella flexneri and Escherichia coli. At 75 μg/ml concentration, the nanoparticles showed the highest inhibition against S. aureus (16.2 ± 0.45 mm), the lowest zone of inhibition was seen against K. pneumoniae (12.3 ± 0.50 mm) and moderate inhibition on other strains. Further, its cytotoxicity was seen as effective against DU145 and PC3 cells. The morphological changes caused in the prostate cell lines due to antiproliferative effect were observed through DAPI and AO/EB staining. This synthesis method specifies a new route for biosynthesis of Fe-NPs and the accomplished results illustrates that it can be used for a wide range of biomedical applications.

Bactericidal activity of hexylresorcinol lozenges against oropharyngeal organisms associated with acute sore throat

Objective

For the majority of people with acute sore throat, over-the-counter treatments represent the primary option for symptomatic relief. This study evaluated the in vitro bactericidal activity of lozenges containing the antiseptic hexylresorcinol against five bacteria associated with acute sore throat: Staphylococcus aureus, Streptococcus pyogenes, Moraxella catarrhalis, Haemophilus influenzae and Fusobacterium necrophorum.

Results

Hexylresorcinol 2.4 mg lozenges were dissolved into 5 mL of artificial saliva medium. Inoculum cultures were prepared in triplicate for each test organism to give an approximate population of 10⁸ colony-forming units (cfu)/mL. Bactericidal activity was measured by log reduction in cfu. Greater than 3log₁₀ reductions in cfu were observed at 1 min after dissolved hexylresorcinol lozenges were added to S. aureus (log₁₀ reduction cfu/mL ± standard deviation, 3.3 ± 0.2), M. catarrhalis (4.7 ± 0.4), H. influenzae (5.8 ± 0.4) and F. necrophorum (4.5 ± 0.2) and by 5 min for S. pyogenes (4.3 ± 0.4). Hexylresorcinol lozenges achieved a > 99.9% reduction in cfu against all tested organisms within 5 min, which is consistent with the duration for a lozenge to dissolve in the mouth. In conclusion, in vitro data indicate that hexylresorcinol lozenges offer rapid bactericidal activity against organisms implicated in acute sore throat.

Assessment of a novel nanostructured flocculant with elevated flocculation and antimicrobial activity

In this work, a novel process involving the preparation of nanochitosan-grafted flocculants (CPAM-g-NCS) to treat low turbid and salmonella suspensions simultaneously was introduced. Nanotechnology was employed to enhance the adsorption-adhesion and sterilization abilities of dual-functional flocculants. The monomers of chitosan, acrylamide, methacryloyl ethyl trimethyl ammonium chloride, and sodium tripolyphosphate were utilized for flocculants copolymerization. Then, using fourier-transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum, and thermogravimetric and differential scanning calorimetry analysis, the successful synthesis of CPAM-g-NCS was verified. Scanning electron microscopy and size analysis suggested that nanostructured flocculants with irregular morphology and nanocolloids of 60.44 nm were formed. CPAM-g-NCS was applied to treat a series of simulated low turbid and salmonella suspensions. The simulation results showed that the minimum residual turbidity of 1.97 NTU and optical density of 0.16 (initial 0.89) can be achieved at dosages of 2.5 and 8.75 mg L^-1, respectively, which were superior to conventional organics flocculants. Mechanistic studies suggested that the excellent adsorption property, and large numbers of quaternary ammonium and amino groups of nanoflocculants contributed to the superior flocculation and antibacterial performance of CPAM-g-NCS.

4-Chloromercuribenzoic acid enhances carbapenem sensitivity among pathogenic Gram negative bacteria by altering blaVIM, adeB and ompC expression

BACKGROUND

Rapid global dissemination of carbapenem resistant Gram negative bacteria (CRGNB) is supposed to be clinically most alarming. Since, p-chloromercuribenzoic acid (pCMB) is a well known metallo-beta-lactamase inhibitor; evaluation of its bactericidal and carbapenem resistance reversing potential would be important.

METHODS

In this study, bactericidal and meropenem resistance reversing potential of pCMB was investigated against CRGNB by MIC determination, checkerboard assay, time-kill assay and cellular viability assay. Effect of pCMB on cellular morphology was visualized by Scanning Electron Microscopy. Further, quantitative Real Time-PCR was performed to evaluate effects of pCMB on clinically relevant metallo-beta-lactamases, major efflux pumps and outer membrane proteins expression.

RESULTS

pCMB exhibited at least four fold reduced MIC value (2-256μg/ml) than that of meropenem against CRGNB. Moreover, pCMB exhibited synergism with meropenem against 86.06% of CRGNB. MIC of pCMB (16-32μg/ml) could kill upto 99.96% bacteria within 6-8h of dosing. pCMB exerted bactericidal activity by severely disrupting cell wall integrity. Reversal of carbapenemase property of CRGNB by pCMB might have developed through alteration of bla_VIM, acrB, mexB and ompk36 expression.

CONCLUSIONS

Hence, the current study identified pCMB as a potential bactericidal agent which enhanced meropenem sensitivity by altering bla_VIM, acrB, mexB and ompk36 expression.

Amphiphilic p-sulfonatocalix[6]arene based self-assembled nanostructures for enhanced clarithromycin activity against resistant Streptococcus Pneumoniae

Amphiphilic calixarenes are preferred to generate nano-cargos for drugs due to their stability, possibilities for modification and intrinsic host cavities. Here we are reporting the synthesis of amphiphilic calixarene and its evaluation as drug delivery system. Water soluble amphiphilic p-sulfonatocalix[6]arene was synthesized through sulfonation and lipophilic conjugation on its upper and lower rims respectively. The synthesized amphiphile self-assembled into nanostructures in the presence of Clarithromycin and FITC as model hydrophobic drugs followed by a wide range of characterization. Clarithromycin loaded self-assembled nanostructures was screened for its bactericidal potential in resistant S. pneumonia through various in-vitro assays. The amphiphilic calixarene self-assembled into polydispersed nanostructures with 136.45 ± 2.41 nm mean diameter and -49.93 ± 0.35 mV surface charges. The amphiphile was capable to load Clarithromycin (57.54 ± 1.88 %) and fluorescent dye and was highly stable. Clarithromycin loaded nanostructures revealed significant biofilm and bacterial growth inhibition and cell destruction properties. Results authenticate calixarene amphiphile as an efficient nano-carrier for improving Clarithromycin efficacy.

Antimicrobial potentials of medicinal plant's extract and their derived silver nanoparticles: A focus on honey bee pathogen

Infectious (or Communicable) diseases are not only the past but also the present problem in developing as well as developed countries. It is caused by various pathogenic microbes like fungi, bacteria, parasites and virus etc. The medicinal plants and nano-silver have been used against the pathogenic microbes. Herbal medicines are generally used for healthcare because they have low price and wealthy source of antimicrobial properties. Like medicinal plants, silver nanoparticles also have emergent applications in biomedical fields due to their immanent therapeutic performance. Here, we also explore the various plant parts such as bark, stem, leaf, fruit and seed against Gram negative and Gram-positive bacteria, using different solvents for extraction i.e. methanol, ethyl acetate, chloroform, acetone, n. hexane, butanol, petroleum ether and benzene. Since ancient to date most of the countries have been used herbal medicines, but in Asia, some medicinal plants are commonly used in rural and backward areas as a treatment for infectious diseases. In this review, we provide simple information about medicinal plants and Silver nanoparticles with their potentialities such as antiviral, bactericidal and fungicidal. Additionally, the present review to highlights the versatile applications of medicinal plants against honey bee pathogen such as fungi (Ascosphaera apis), mites (Varroa spp. and Tropilaelaps sp.), bacteria (Melissococcus plutonius Paenibacillus larvae), and microsporidia (Nosema apis and Nosema ceranae). In conclusion, promising nonchemical (plant extracts) are innocuous to adult bees. So, we strongly believed that this effort was made to evaluate the status of medicinal plants researches globally.

Disinfectant-like activity of lipopeptide biosurfactant produced by Bacillus tequilensis strain SDS21

Antiseptics and disinfectants are widely applied for eliminating microorganisms. However, microorganisms dwelling in the biofilm are less susceptible and in some cases resistant to biocide treatment. The present study describes isolation and characterization of lipopeptide biosurfactant exhibiting disinfectant-like activity. Biosurfactant was produced by an endo-rhizospheric bacterium Bacillus tequilensis strain SDS21. Biosurfactant reduced the surface tension of water from 72 to 30 mN/m with CMC of 40 mg/l. The Liquid Chromatography-Mass Spectrometry analysis of biosurfactant suggested it to be a mixture of C₁₄, C₁₅, C₁₆ and C₁₇ surfactin homologues. The lipopeptide biosurfactant exhibited bactericidal activity against planktonic cells and biofilm residing sessile cells. The biosurfactant treatment eradicated more than 99% of bacterial biofilm present on polystyrene, glass and stainless steel surface. The biosurfactant retained its bactericidal and biofilm eradicating activities even after exposure to extreme conditions like high temperate and extreme pH. Unlike some of the commonly used disinfectant, biosurfactant retained its bactericidal and biofilm removing activity even in the hard water containing Mg²⁺ and Ca²⁺ ions. Thus, suggesting that biosurfactant produced by strain SDS21 can be used as a disinfectant or in disinfectant-like formulations effective against both planktonic and biofilm residing bacteria.

Meningococcal Serogroup A, B, C, W, X, and Y Serum Bactericidal Antibody Assays

Serum bactericidal antibody (SBA) assays measure functional antibody titers against Neisseria meningitidis in sera. Induction of complement-dependent SBA after vaccination with meningococcal polysaccharide or conjugate or protein based vaccines is regarded as the surrogate of protection and thus acceptable evidence of the potential efficacy of these vaccines. This chapter discusses and details SBA assay protocols for measuring the complement-mediated lysis of serogroup A, B, C, W, X, and Y meningococci by human sera, for example, following vaccination or disease.

Multi-bioactive silver nanoparticles synthesized using mosquitocidal Bacilli and their characterization

Silver nanoparticles (AgNPs) were synthesized using cell-free filtrates of some mosquitocidal Bacilli. They showed the optical absorption peaks at 386-412 nm. They were polycrystalline spherical, hexagonal, cuboidal, rod and anisotropic shapes as detected by TEM. These nanoparticles were negatively charged with sizes ranging from 15 to 21 nm average diameter as detected by DLS. FTIR spectra showed that the main absorption bands of biomolecules capping AgNPs appeared at average wave numbers of 3435 cm^-1 [ν(N-H) of amide A overlapped by ν(O-H)], 1631 cm^-1 [(ν(C=O) of amide I], 1396 cm^-1 [ν(C-N) of amide I], 2929 cm^-1 (aliphatic C-H) and 1040 cm^-1 (C-C-O). FTIR spectra confirmed the presence of protein biomolecules in the bacterial filtrate-formed coat covering AgNPs through free amide groups resulting in their stabilization in the aqueous medium. Nitrate reductase activity was found in all tested bacterial filtrates and ranged from 1.66 to 2.51 µmol/ml/min. These findings point to the probable role of nitrate reductase in reducing silver ions to silver nanoparticles and their stabilization. Tested AgNPs were multi-bioactive nanometals and showed mosquitocidal, bactericidal, fungicidal and virucidal activities. In addition, they exhibited highly synergistic mosquitocidal effect to spore toxin complex of mosquitocidal Bacilli at a very low concentration. AgNPs exhibited activities that were not or slightly cytotoxic to MA 104 cell line at tested concentrations. Therefore, they can be applied in the medical field. Finally, this study offered a simple, highly efficient, eco-friendly, economic method for biosynthesis of multi-bioactive AgNPs by some mosquitocidal Bacilli.

Inhibitory effects of Azadirachta indica secondary metabolites formulated cosmetics on some infectious pathogens and oxidative stress radicals

BACKGROUND

Infectious diseases, particularly those due to multi-drug resistant bacterial strains are almost impossible to cure globally. In this study we investigated the inhibitory effects of Azadirachta indica A. Juss secondary metabolites (AISM) formulated soap and cream for management of infectious and oxidative stress-related diseases (OSD).

METHODS

The antibacterial, radical scavenging and cytotoxic effects of the neem cosmetics were examined by serial dilution, spectrophotometric and hemolytic techniques respectively, while the AISM in the essential oils (EOs) were elucidated by Gas chromatography-mass spectrometry (GC-MS) and retention index.

RESULTS

The neem cosmetics without AISM exhibited bacteriostatic effects against five reference bacterial strains (Staphylococcus aureus, Listeria ivanovii, Enterobacter cloacae, Mycobacterium smegmatis, and Streptococcus uberis) and two confirmed multi-drug resistant bacterial strains (Vibrio paraheamolyticues, Escherichia coli 180) at 0.80 mg/mL. Conversely, at less than 0.50 mg/mL the neem soap produced with AISM demonstrated bactericidal effects against most of these test pathogens linked to infectious diseases. The neem soap containing AISMs displayed noteworthy effects in scavenging radicals associated with OSD at < 1.76 mg/mL. The cosmetics were not toxic to human red blood cells below 0.70 mg/ mL. To our known, the AISM predominantly caryophyllene (30.02%), phytol (14.12%), elemene (13.40%) and linoleic acid (10.5%) exceptional inhibitory effects in neem cosmetics are reported here for the first time.

CONCLUSION

The study indicates that apart from traditional uses of A. indica, the EO contained potent bioactive AISM and feasible as an antimicrobial agent, an alternative to synthetic antioxidant, likewise considered novel in the pharmaceutical, cosmetics industries and as food preservatives.

Granulin peptide GRN-41 of Mozambique tilapia is a novel antimicrobial peptide against Vibrio species

In our previous study, the novel GRN-41 peptide generated from alternative splicing of the Mozambique tilapia PGRN1 gene was identified to be a potent peptide that protected against V. vulnificus in the transgenic zebrafish model by modulating innate immune-related genes. In this study, the anti-bacterial activities of synthetic Mozambique tilapia GRN-41 peptide (OmGRN-41) against various bacterial pathogens were investigated. The results showed that OmGRN-41 had bactericidal activity against Vibrio species, including V. vulnificus, V. alginolyticus, and V. harveyi, but exhibited bacteriostatic activity against V. parahaemolyticus. OmGRN-41 maintained bactericidal activity (64 μM) against V. vulnificus at pH 2 to pH 10 or after heat treatment for 1 h at high temperatures between 40 °C and 100 °C. TEM observations revealed that the outer membrane of V. vulnificus was disrupted by OmGRN-41, leading to morphological rupture and loss of cytoplasmic contents. Additionally, little hemolytic activity against tilapia and sheep erythrocytes was detected after treatment with 128 μM OmGRN-41. OmGRN-41 can effectively enhance the survival of Nile tilapia infected by V. vulnificus. Our results suggest that the OmGRN-41 is a novel antimicrobial peptide possessing bactericidal activity, especially against Vibrio species. These results indicate that OmGRN-41 can be applied in human Vibriosis treatment and has the potential to defend against Vibrio spp. infection in critical aquaculture organisms.

In vitro bactericidal effect of Ho:YAG laser and pneumatic lithotripsy on ureteral stones colonized with Escherichia coli and Enterococcus faecalis

The endoscopic treatment of urolithiasis has a high success rate and the complications decreased after the development of lithotripsy techniques. The aim of this study is to investigate the in vitro bactericidal effect of laser and pneumatic lithotripsy on urinary stones colonized with Escherichia coli and Enterococcus faecalis. A total of 40 natural calcium oxalate stones, which were obtained from the patients' urinary systems with rigid ureteroscopy were used in the study. Surfaces of the stones were colonized with E. coli and E. faecalis strains. The fragmentation of the stones was performed using holmium:yttrium-aluminum-garnet laser (Ho:YAG laser) and pneumatic lithotripters in vitro in Eppendorf tubes filled with liquid. After fragmentation, samples taken from Eppendorf tubes were inoculated on blood and EMB agar. The number of colonies was evaluated after 18-24-hour incubation period. The laser lithotripsy technique reduced the number of colonies by 100% and had bactericidal effect on E. coli and E. faecalis. Pneumatic lithotripsy technique had no bactericidal effect on these strains (0%). In the fifth minute of laser irradiation, the average temperature in the Eppendorf tube was 51-55 °C, and the average temperature in the tenth minute was 54-60 °C. The temperatures did not change in the fifth and tenth minutes with the pneumatic lithotripsy procedure. The present study revealed the bactericidal effect of Ho:YAG laser on E. coli and E. faecalis in vitro. Increased ambient temperature during Ho:YAG laser lithotripsy is thought to play a role in the bactericidal effect. But the question of whether an ideal lithotripter efficiently inactivates or destroys bacteria has still not been answered in urology practice. This preliminary study showed the bactericidal effect of Ho:YAG laser lithotripsy, but further studies are needed to investigate the bactericidal effect of Ho:YAG laser in vivo.

The advanced role of carbon quantum dots in nanomedical applications

Carbon quantum dots (CQDs) have emerged as a potential material in the diverse fields of biomedical applications due to their numerous advantageous properties including fluorescence, water solubility, biocompatibility, low toxicity, small size and ease of modification, inexpensive scale-up production, and versatile conjugation with other nanoparticles. Thus, CQDs became a preferable choice in various biomedical applications such as nanocarriers for drugs, therapeutic genes, photosensitizers, and antibacterial molecules. Further, their potentials have also been verified in multifunctional diagnostic platforms, cellular and bacterial bio-imaging, development of theranostics nanomedicine, etc. This review provides a concise insight into the progress and evolution in the field of CQD research with respect to methods/materials available in bio-imaging, theranostics, cancer/gene therapy, diagnostics, etc. Further, our discussion is extended to explore the role of CQDs in nanomedicine which is considered to be the future of biomedicine. This study will thus help biomedical researchers in tapping the potential of CQDs to overcome various existing technological challenges.

Transforming an inert nanopolymer into broad-spectrum bactericidal by superstructure tuning

Poloxamer block copolymers (also known as Pluronic®) are particularly useful for drug delivery and self-assembly techniques. These nanopolymers are generally considered to be biologically inert and they were used to generate only bacteria repellent surfaces but keeps bacteria alive and as a latent threat. However, the inherent capabilities of these nanopolymers to kill bacteria have been largely overlooked. Here, we report that Pluronic shaped as superstructures (self-organized array of micelles) in fact possess a broad-spectrum bactericidal activity (capability of killing bacteria) similar to that shown for some antibiotics. This further represents the first report that shows that appropriate control of superstructured mesophase architecture is a key parameter for bactericidal efficacy. Based on this finding, we have developed a highly bactericidal coating (>99.9% kill) against all tested Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Salmonella typhimurium LT2, Escherichia coli K12 and Pseudomonas aeruginosa PAO1) bacteria which moreover allows the adhesion and proliferation of mammalian cells. The inexpensiveness and ease of production make these versatile nanopolymer structures a powerful tool for the development of a new generation of highly effective antimicrobial coatings.

Biological properties of modified bioactive glass on dental pulp cells

Dental caries is a bacteria-caused condition classified among the most common chronic diseases worldwide. Treatment of dental caries implies the use of materials having regenerative and anti-bacterial properties, and controlling inflammation is critical for successful endodontic regeneration.

OBJECTIVES

The aim of this study was to fabricate and characterize a novel composite incorporating sol-gel derived silver-doped bioactive glass (BG) in a chitosan (CS) hydrogel at a 1:1 wt ratio(Ag-BG/CS).

METHODS

The effect of Ag-BG/CS on dental pulp cells (DPCs) proliferation was analyzed by CCK-8 assay, whereas the adhesion of DPCs was evaluated by confocal microscopy. The physical morphology of Ag-BG/CS was analyzed by scanning electron microscope. The anti-inflammatory effect of Ag-BG/CS was investigated by quantitative polymerase chain reaction (qPCR). Moreover, the effect of Ag-BG/CS on odontogenic differentiation of DPCs was studied by immunochemical staining, tissue-nonspecific alkaline phosphatase staining, qPCR, and western blot analyses. The antibacterial activity against dental caries key pathogenic bacteria was also evaluated.

RESULTS

The results of this study showed that Ag-BG/CS did not affect the proliferation of DPCs, it down-regulated the inflammatory-associated markers (IL-1β, IL-6, IL-8, TNF-α) of DPCs treated with Escherichia coli lipopolysaccharide (LPS) by inhibiting NF-κB pathway, and enhanced the in vitro odontogenic differentiation potential of DPCs. Furthermore, Ag-BG/CS strongly inhibited Streptococcus mutans and Lactobacillus casei growth.

CONCLUSIONS

This novel biomaterial possessed antibacterial and anti-inflammatory activity, also enhanced the odontogenic differentiation potential of LPS-induced inflammatory-reacted dental pulp cells. The material introduced in this study may thus represent a suitable dental pulp-capping material for future clinical applications.

Increased antibacterial activity of ZnO nanoparticles: Influence of size and surface modification

In the current study, the size and surface of ZnO nanoparticle (ZnO NP) suspensions and powders were finely controlled to evaluate their influence on the ZnO antibacterial activity against Staphylococcus aureus and Escherichia coli. The ZnO NP were prepared by the sol-gel method with different reaction times for NP size control and followed by the addition of (3-glycidyloxypropyl) trimethoxysilane (GPTMS) as a surface modifier. The ZnO NP were characterized by different techniques and the antibacterial activity was assessed through the minimum inhibitory concentration assay (MIC), minimum bactericidal concentration assay (MBC) and scanning electron microscopy (SEM). The ZnO NP exhibited significant antibacterial activity against Staphylococcus aureus. The NP size highly influenced the antibacterial activity, which increased with decreasing particle size. The small ZnO NP presented bactericidal activity whereas the largest showed bacteriostatic activity. The use of GPTMS, in general, led to increase of MIC and MBC. The formation of holes in the cell wall of Staphylococcus aureus was evidenced by SEM after contact between the bacteria and ZnO NP. The cytotoxicity assay showed that ZnO NP did not cause a loss of cell viability in the human keratinocyte cell line (HaCat) at the maximum concentration assessed. Thus, this study indicated that 5 nm ZnO NP modified by GPTMS has great potential for use as an inorganic antibacterial material.

A review and new insights to antimicrobial action of local anesthetics

Local anesthetics (LAs) are medications which can provide analgesia in distinct body regions through the blockade of voltage-gated sodium channels. Besides pain management, the supplemental role of LAs as antimicrobial agents has been documented in several studies. Different databases including PubMed, Scopus, and Web of Science with the name of different local anesthetics and related names for antimicrobial keywords were searched without time limitation. This review summarized different in vitro and in vivo studies regarding antimicrobial effects of different LAs with focuses on antimicrobial applications of most studied LAs, interaction with different agents which combined with LAs, and mechanisms of action and structural dependence of LAs antibacterial effects. Among different LAs, lidocaine is the most studied preparation. Reduction of the incidence of endophthalmitis after intravitreal injection, prophylaxis for surgical wound infections, prevention of the incidence of catheter-associated infections, oral biofilm reduction on the buccal mucosa, and prevention against bacteria that produced nosocomial infection are some examples of lidocaine antimicrobial application. Studies showed that different factors including structure, concentration, duration of exposure, type of microorganism tested, and temperature affect the degree of LA antimicrobial activity. In addition, various agents such as antibiotics, preservatives, opioids, epinephrine, and propofol can combine with LAs and affect their antimicrobial properties through synergistic or antagonistic action. Due to antibacterial activities, LAs could be applied in a clinic for prophylaxis of surgical site infection. In the application of LAs prior to diagnostic procedures caution should be needed; otherwise, when culturing the specimen, they could lead to false negative results.