Minimum Bactericidal Concentration Tests Research Articles

In Vitro Antimicrobial Activity of Green Synthesized Silver Nanoparticles Against Selected Gram-negative Foodborne Pathogens.

Silver nanoparticles (AgNPs) used in this study were synthesized using pu-erh tea leaves extract with particle size of 4.06 nm. The antibacterial activity of green synthesized AgNPs against a diverse range of Gram-negative foodborne pathogens was determined using disk diffusion method, resazurin microtitre-plate assay (minimum inhibitory concentration, MIC), and minimum bactericidal concentration test (MBC). The MIC and MBC of AgNPs against Escherichia coli, Klebsiella pneumoniae, Salmonella Typhimurium, and Salmonella Enteritidis were 7.8, 3.9, 3.9, 3.9 and 7.8, 3.9, 7.8, 3.9 μg/mL, respectively. Time-kill curves were used to evaluate the concentration between MIC and bactericidal activity of AgNPs at concentrations ranging from 0×MIC to 8×MIC. The killing activity of AgNPs was fast acting against all the Gram-negative bacteria tested; the reduction in the number of CFU mL-1 was >3 Log10 units (99.9%) in 1–2 h. This study indicates that AgNPs exhibit a strong antimicrobial activity and thus might be developed as a new type of antimicrobial agents for the treatment of bacterial infection including multidrug resistant bacterial infection.

Comparative Study of Bioactivities and Chemical Constituents of Cymbopogon jwarancusa subsp. olivieri (Boiss.) Soenarko Harvested in Spring and Winter

Essential oils and solvent extracts of Cymbopogon jwarancusa subsp. olivieri (Boiss.) Soenarko plants harvested during two different seasons were investigated in terms of chemical composition and biological activities. Piperitone was the major constituent of essential oil extracted from plants harvested in spring and winter (49.1 and 54.1 %, respectively). The highest total phenolic and flavonoid contents were measured in ethanol extract obtained from spring plants (31.72±0.08 mg gallic acid equivalents/g and 40.93±1.12 mg quercetin equivalents/g, respectively), and in acetone extract from plants collected in winter (31.24±0.17 mg GAE/g and 38.32±0.74 mg QE/g, respectively). Amongst the various extracts and essential oils, the highest DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging capacity was recorded in ethanol extract (IC50 = 40.51±3.89 ppm) from plants collected in spring, in comparison with butylated hydroxytoluene (IC50 = 5.85±1.84 ppm) and ascorbic acid (IC50 = 1.28±0.06 ppm) as controls. Antibacterial and antifungal activities of all samples were tested by disc-diffusion, MIC (minimum inhibitory concentration), MBC (minimum bactericidal concentration) and MFC (minimum fungicidal concentration) tests. Diethyl ether extract from winter plants exhibited the highest inhibitory activity against Streptococcus pneumoniae (inhibition zone diameter, IZD = 19.28±1.51 mm), compared with gentamicin and penicillin (IZD = 19.87±0.37 and IZD = 13.61±1.84, respectively). Overall, the results showed that the essential oil of C. jwarancusa subsp. olivieri could be considered as a source of piperitone, whereas the diethyl ether extract of the plant could be developed as a promising antibacterial agent in food and pharmaceutical industries.

Antibacterial activity of lime (Citrus aurantifolia) essential oil and limonene against fish pathogenic bacteria isolated from cultured olive flounder (Paralichthys olivaceus)

Abstract The antibacterial activity of lime (Citrus aurantifolia) essential oil (LEO) and limonene was tested against seven Gram-negative and nine Gram-positive fish pathogenic bacteria isolated from cultured olive flounder, Paralichthys olivaceus (Temminck & Schlegel) in Korea. Limonene was >99% concentrated and LEO consisted of eleven chemical compounds including 56.22% of limonene. Disk diffusion assay, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests were done. LEO and limonene inhibited the growth of both Gram-negative and Gram-positive bacteria. LEO and limonene (MBC/MIC= 2-8) were both bactericidal and bacteriostatic for the strains tested. In every fish pathogenic bacteria, the inhibition zone diameter (IZD) increased in proportion to the oil concentration and the maximum effect was found at 100% (V/V) concentrations of LEO and limonene. The antibiogram pattern indicated that all the bacterial strains, excluding three strains of S. iniae (S186, S530, and S131), showed resistance to one or more antibiotics. The percentage of the relative inhibition zone diameter (RIZD %) exhibited high values at higher concentrations of all the agents. Since antibacterial activities of LEO and limonene were considerably effective against fish pathogenic bacteria, they could be used as alternatives to treat bacterial infections in aquaculture.

POTENSI ANTIBAKTERI EKSTRAK ETANOL JAMUR KANCING (Agaricus bisporus) SEBAGAI ANTIBAKTERI

A research had been done on antibacterial activity of extract and the aim was to determine the antibacterial activity and inhibitory potency. The research was started by screening test using Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus epidermidis, Shigella dysenteriae, Staphylococcus aureus, Streptococcus mutans and Vibrio cholerae. Results showed that the Agaricus bisporus ekstract inhibited Bacillus subtilis, Shigella dysenteriae, Staphylococcus aureus, and Vibrio cholera at concentrations 0,1% and 1%. The results obtained Minimum Inhibitory Concentration (MIC) Agaricus bisporus extract against at concentrations of 0,1%. In the Minimum Bactericidal Concentration (MBC) test Agaricus bisporus extract against at concentrations of 0,8%. Agaricus bisporus extract has antibacterial activity wich was indicated by the inhibitory zone diameter. The biggest inhibitory zone diameter of Agaricus bisporus contained in bacteria Bacillus subtilis on the concentration of 6.4% (13 mm)

Qac genes and biocide tolerance in clinical veterinary methicillin-resistant and methicillin-susceptible Staphylococcus aureus and Staphylococcus pseudintermedius

Qac genes are associated with increased tolerance to quaternary ammonium compounds and other cationic biocides such as chlorhexidine. This study aimed to determine whether qac genes and increased biocide tolerance were present in 125 clinical methicillin-resistant and susceptible veterinary staphylococci. A total of 125 methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant and -susceptible Staphylococcus pseudintermedius (MRSP and MSSP) from three archived Australian veterinary staphylococci collections underwent whole genome sequencing, multilocus sequence typing and qac gene screening. Two MRSA isolates (12%) harboured qacA/B genes; both isolates were ST8 from horses. QacJ, qacG and smr genes were identified in 28/90 (31%) MRSP and 1/18 (6%) MSSP isolates. ST71 MRSP was significantly more likely to harbour qac genes than other MRSP clones (p < 0.05). A random subset of 31 isolates underwent minimum bactericidal concentration (MBC) testing against F10SCTM (benzalkonium chloride and biguanide), and HexaconTM (chlorhexidine gluconate), with and without the addition of bovine serum albumin (BSA) as an in vitro substitute for organic matter contamination. Qac genes were not associated with increased phenotypic biocide tolerance but biocide efficacy was significantly affected by the presence of BSA. In the absence of BSA, all MBC values were well below the recommended usage concentration. When BSA was present, regardless of qac gene presence, 50% of MRSA and 43% of MRSP had an F10SCTM MBC above the recommended concentration for general disinfection. Qac genes did not confer increased in vitro biocide tolerance to veterinary staphylococci. Organic matter contamination must be minimized to ensure the efficacy of biocides against MRSA and MRSP.

Cost-effective downstream processing of recombinantly produced pexiganan peptide and its antimicrobial activity

Antimicrobial peptides (AMPs) have significant potential as alternatives to classical antibiotics. However, AMPs are currently prepared using processes which are often laborious, expensive and of low-yield, thus hindering their research and application. Large-scale methods for production of AMPs using a cost-effective approach is urgently required. In this study, we report a scalable, chromatography-free downstream processing method for producing an antimicrobial peptide, pexiganan, using recombinant Escherichia coli (E. coli). The four helix bundle structure of the unique carrier protein DAMP4 was used to facilitate a simple and cheap purification process based on a selective thermochemical precipitation. Highly pure fusion protein DAMP4var-pexiganan was obtained at high yield (around 24 mg per 800 mL cell culture with a final cultivation OD600 ~ 2). The purification yield of DAMP4var-pexiganan protein is increased twofold with a 72.9% of the protein recovery in this study as compared to the previous purification processes (Dwyer in Chem Eng Sci 105:12–21, 2014). The antimicrobial peptide pexiganan was released and activated from the fusion protein by a simple acid-cleavage. Isoelectric precipitation was then applied to separate the pexiganan peptide from the DAMP4var protein carrier. The final yield of pure bio-produced pexiganan was 1.6 mg from 800 mL of bacterial cell culture (final cultivation OD600 ~ 2). The minimum bactericidal concentration (MBC) test demonstrated that the bio-produced pexiganan has the same antimicrobial activity as chemically synthesized counterpart. This novel downstream process provides a new strategy for simple and probable economic production of antimicrobial peptides.

Evaluation of Antibacterial Properties of Oregano Essence on Pathogenic Bacteria Isolated from Hospital Infections

Introduction: The use of antimicrobial properties of medicinal plants can solve common problems in the use of antibiotics. The aim of this study was to evaluate the antibacterial properties of the Mentha longifolia essence on bacteria isolated from hospital infections. Materials & methods: In this experimental study the Mentha longifolia essence was extracted using Clevenger device and its antimicrobial activity agar disk diffusion method for determination of bacterial sensitivity and dilution method for determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was used separately. Findings: The results of bacterial sensitivity test in the case of the standard antibiotics of tetracycline, amikacine, and also disks impregnated with Mentha longifolia essence showed that the diameter of the zone of inhibition caused by the compound being tested on four strains of isolates was far larger and this difference about Escherichia coli and Klebsiella isolates was significant (p less-than 0.05). Also the results of MIC and MBC tests indicated that the inhibition of bacterial growth by Mentha longifolia essence had a direct relationship with the amount of available Mentha longifolia essence in the dilution and increasing of Mentha longifolia essence in each dilution reduced the number of cultured bacterial colonies and no bacterial growth was observed in the dilution equivalent to MBC of Mentha longifolia essence. Discussion & conclusions: The results suggest that Mentha longifolia essence can be used as a source of cheap and accessible replacing chemical drugs to treat some bacterial infections.

Investigation of the antimicrobial activity of Gagea Dubia

The main objective of this study is to evaluate the antimicrobial effect of ethanol solution extracts of G. dubia A. Terracc. on nineteen gram positive and negative bacteria (Bacillus subtilis, Enterococcus faecium, Enterococcus faecalis, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella infantis, Salmonella typhimurium, Salmonella kentucky, Salmonella enterica, Pseudomonas aeruginosa, Pseudomonas fluorescens) and one fungi (Candida albicans). Different parts (flowers, leaves, stems, and roots) of Gagea dubia samples, were extracted with 80% ethanol solution. These extracts were tested in vitro for their antimicrobial activity against 15 microorganism by disk diffusion (DD) and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests. Ethanol extracts showed antimicrobial activity against some bacteria. According to the results of disk diffusion test G. dubia have effect on four bacteria (B. subtilis, S. aureus, L. innocua and E. durans) and (C. albicans) and didn’t show effect on other microorganisms. The antibacterial effect observed in 10 µL extract of G.dubia against B. subtilis, S. aureus, L.innocua with 7,66; 13 and 9 mm zone diameter respectively and 50 µL extract of G. dubia against E.durans with 11 mm zone diameter. G. dubia extract show antimicrobial activity at three concentration (10;50 and 100 µL) against C. albicans between 915,66 mm zone diameter. MIC result for G. dubia determined as 5; 1,25; 10; 5 and 0,15 mg/100 µL against B. subtilis, S. aureus, L.innocua, E.durans and C. albicans respectively. According to MBC test all MIC value against maicroorganism determined as bacteriostatic

Toxicity effects of AgZnO nanoparticles and rifampicin on Mycobacterium tuberculosis into the macrophage.

The World Health Organization acknowledges tuberculosis as a global threat. Tuberculosis infection is one of the top 10 causes of death worldwide. Nanotechnology and microbiology researchers are looking for new and safe nano drugs for eliminating Mycobacterium tuberculosis, the causative agent of tuberculosis. In this study, AgZnO nano-crystals (AgZnONCs) is synthesized via the decomposition of the precursor of oxalate method. Characterization of AgZnONCs were evaluated. Next, various concentrations of AgZnONCs, as well AgZnONCs+Rifampicin, were prepared. The MTT assay was employed to study the viability of human macrophage cell lines (THP-1) exposed to AgZnONCs. The bactericidal effects of AgZnONCs and AgZnONCs+Rifampicin were studied by Minimum Bactericidal Concentration (MBC) test. Subsequently, THP-1 were infected by H37 Rv strain of M. tuberculosis (H37 RvMtb). Also, bactericidal effects of AgZnONCs and AgZnONCs+Rifampicin were compared with ex-vivo conditions. The MBC of AgZnONCs and AgZnONCs+Rifampicin were ratios of 1:4 and 1:32 respectively (p-value <0.05). Also, more than 50% and 80% of THP-1 were alive in ratios of 1:4 and 1:32 in the presence of AgZnONCs, respectively. All phagocytic H37 RvMtb were killed in the presence of AgZnONCs+Rifampicin (p-value <0.05), while AgZnONCs were not able to kill all the H37 RvMtb (p-value >0.05). This study showed that, AgZnONCs+Rifampicin has the most anti-tubercular behavior with respect to the macrophages.

Antimicrobial Effects of Peptides from Human Beta-Defensin-3 on Planktonic and Biofilm States of Streptococci

Human beta-defensin-3 (hBD3) acts as a first line of defense against both Gram-positive and Gram-negative bacteria infection. Streptococci are the significant cause for oral biofilm associated diseases. We synthesized three fragments (hBD3-1, hBD3-2, hBD3-3) from the hBD3 and evaluated the antibacterial efficacy on oral streptococci. All of the three fragments from hBD3 had good estimated solubility and hBD3-3 had a higher net positive charge than others. Structure analysis showed that the three fragments shared stable β-sheet structure, but tyrosine were not found in hBD3-2 and hBD3-3 by using Raman and circular dichroism spectroscopy. The inhibition ability of the peptides was examined on the bioactivity of Streptococcus oralis (S.oralis), Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) by minimal inhibitory concentration, minimum bactericidal concentration and anti-biofilm formation test. Three fragments had antimicrobial activity on planktonic state of streptococci, and S. oralis had much more sensitive to the three peptides. Results of antibiofilm experiment showed that streptococci biofilm formation was more sensitive to hBD3-3. Confocal laser scanning microscopy and scanning electron microscopy showed the decrease of biomass and bacterial morphology destruction, which indicated that the antimicrobial mechanism of hBD3-3 might involve an electrostatic charge-based impact on membrane permeability. In conclusion, hBD3-3 possessed the potential capacity for depressing the growth of bacteria, especially first colonizers during the development of oral biofilm. Powerful, endogenous antimicrobial peptide provides the potential to interfere with biofilm by disorganizing early biofilm formation and thereby inhibiting biofilm-associated diseases.

In Vitro Study For The Effect Of Cinnamon Oil On Multi-Drug Resistant Staphylococcus aureus And Proteus mirabilis Strains

The study was carried out to assess the effect of cinnamon oil on multi-drug resistant (MDR) strains of Staphylococcus aureus and Proteus mirabilis isolated from patient infected with otitis media. 50 specimens were collected at AL Hakeem Teaching Hospital in AL-Najaf governorate, 20 isolates were found to be Staphylococcus spp. and Proteus spp. on further studying for the species level only six of these isolates were found to be multi-drug resistant Staphylococcus aureus and Proteus mirabilis. The results of antibiotic sensitivity testing showed that most of these isolates were highly resistant (resistance percentage was 40-90%) for the used antibiotics. The antimicrobial effect of cinnamon oil on these isolates was tested via performing Disk Diffusion Method, Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) tests. The results showed a similarity in the antimicrobial actions between this oil and Ciprofloxacin antibiotic . The study concluded that Cinnamon Oil could be used as an effective antimicrobial even in case of difficult treated MDR Staphylococcus aureus and Proteus mirabilis.

Identification and biocide susceptibility of dominant bacteria after cleaning and disinfection of broiler houses

Hygiene in animal production is key for both farm management and food safety. Cleaning and disinfection (C&D) of broiler houses is essential to manage farm hygiene. Still high levels of total aerobic flora after C&D in broiler houses are reported. However, little is known about the microbial composition after cleaning (AC) and after disinfection (AD). In addition, the question why some bacterial species/isolates are still present AD whereas others are killed remains.The study was carried out in 4 broiler houses. Sampling was performed AC and AD. The disinfectant was based on hydrogen peroxide and peracetic acid. Enumerations were carried out for total aerobic flora, Enterococcus spp. and Enterobacteriaceae. The dominant bacteria present was assessed by (GTG)5 analysis and 16S rRNA gene sequence analysis. Moreover, minimum bactericidal concentration (MBC) tests were carried out on 18 selected isolates belonging to the Enterobacteriaceae family and 10 Enterococcus faecium isolates.A wide variety of bacteria were detected AC and AD. In total, 363 and 255 isolates were identified AC and AD, respectively, resulting in a total of 109 identified species. The most dominant bacteria belonged to Brevibacterium, Brachybacterium, and Staphylococcus AC and Bacillus, Brevibacterium, and Staphylococcus AD. At both sampling moments, Enterococcus faecium was dominant among the Enterococcus spp. isolates. On the selective medium for Enterobacteriaceae, the genera Enterobacter and Pantoea and Aeromonas (non Enterobacteriaceae) were dominant AC while Escherichia, Lelliottia, and Pantoea were dominant AD. In addition, species pathogenic to poultry and humans were identified not only AC but also AD. MBC results showed no trend in selection of less susceptible isolates for the used disinfectant AD compared to AC. Finally, the recommended concentration of the disinfectant (i.e., 0.5% commercial solution of hydrogen peroxide and peracetic acid) seemed too low to kill Enterobacteriaceae.

Antibacterial Activity of Ethyl Acetate the Extract of Noni Fruit (Morinda citrifolia L.) Against Bacterial Spoilage in Fish

Noni fruit (Morinda citrifolia L.) contains compounds that have potential as antibacterial agent. Antibacterial compounds produced noni fruit (M. citrifolia L.) can inhibit bacterial growth. This study was conducted to test the antibacterial activity of ethyl acetate extract of noni fruit (M. citrifolia L.) against spoilage bacterial in fish. Pseudomonas aeruginosa, Bacillus cereus, Escherichia coli, Klebsiella oxytoca, and Enterobacter aerogenes isolates and examine antibacterial phytochemical profile. Extraction of noni compounds was done by maceration, followed by partition with ethyl acetate to obtain the soluble and insoluble ethyl acetate fraction. Previews result show that the ethyl acetate extract had very strong activity. Extraction process continued by separation and isolation used preparative thin layer chromatography method, so that obtained five isolates and mark them as A, B, C, D and E. Antibacterial activity assay performed on isolates A, B, C, D, and E with 20 and 30% concentration. The test results showed that isolates A could not be inhibit the growth of bacteria, isolates B, C, D, and E has antibacterial activity with weak to strong inhibition. Isolate B had the greatest inhibition activity against the B. cereus, whereas isolates E had the greatest inhibition activity against P. aeroginosa. MIC (Minimum Inhibitor Concentration) and MBC (Minimum Bactericidal Concentration) test result showed that MIC and MBC values could not be determined. Analysis of compounds by TLC showed that isolate B suspected contains coumarin or flavonoids compounds that have antibacterial activity.

Microwave assisted extraction as an efficient approach for biosynthesis of zinc oxide nanoparticles: Synthesis, characterization, and biological properties

In the present study, microwave assisted extraction (MAE) was applied as an efficient, green and rapid approach to prepare the aqueous extract of Suaeda aegyptiaca (SA) plant. The obtained aqueous extracts at two different irradiation power (90 and 270W; 15min) in MAE process as well as maceration method (24h) were used in a green and eco-friendly approach for the synthesis of zinc oxide nanoparticles (ZnO NPs). The synthesized ZnO NPs have been characterized via different techniques including UV–Vis absorption; fluorescence and Fourier transform infrared (FT-IR) spectroscopices, scanning electron microscopy (SEM), and X-ray diffraction (XRD). According to the results, the average size of the prepared ZnO particles was estimated around 60nm. A broad absorption band around 382nm in UV–Vis absorption spectrum and a maximum emission at wavelength of 458nm in fluorescence spectrum clarified the successful biosynthesis of ZnO NPs. Moreover, the biological properties of the extracts and biosynthesized ZnO NPs were investigated by antimicrobial tests (i.e. Well-diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) tests), antifungal and antioxidant tests (total phenolic and flovonoid content, antioxidant activity against dipheny-picrylhydrazyl (DPPH), and ethylbenzothiazolin-6sulphonic acid (ABTS+)). Finally, DNA cleavage potential of the samples was studied, too.

Comparison Between Antibacterial Effect of Chlorhexidine 0.2% and Different Concentrations of Cyperus rotundus Extract: An In vitro Study.

Aims and Objectives:Modern methods of caries prevention concentrated on natural ingredients usage such as probiotics and polyphenols that are safer for young children with Streptococcus mutans inhibitory properties. The purpose of this study was to compare antibacterial effects of different concentration of Cyperus rotundus extract and chlorhexidine (CHX) 0.2% mouthwash on S. mutans and Lactobacillus acidophilus.Materials and Methods:In this in vitro study, the antibacterial effectiveness of the C. rotundus extract and CHX was compared with minimum inhibitory concentration (MIC) test in tube, minimum bactericidal concentration (MBC) test in solid medium, and disc diffusion for measurement of inhibition zone. Data were analyzed using one-way ANOVA, one sample t-test, and independent sample t-test statistical methods by SPSS. 24 software (SPSS Inc., Chicago, USA).Results:MIC and MBC values of the C. rotundus extract were obtained 225 and 450 mg/ml, respectively, for S. mutans and 108 and 225 mg/ml for L. acidophilus, which are more than CHX (0.5, 1 res.). The inhibition zone increased in a dose-dependent manner but lower than CHX.Conclusion:The C. rotundus extract had antibacterial effects (bactericide and bacteriostatic) on S. mutans and L. acidophillus. Although this effect was lower than CHX. With regard to adverse effect of CHX, this extract can be a potential antibacterial agent.

Antibacterial activity of essential oil from lavender (Lavandula angustifolia) against pet turtle-borne pathogenic bacteria

Pet turtles are well-known to harbor an array of bacterial pathogens which can cause zoonotic infections in humans as well as opportunistic infections in the turtles itself. Essential oils are the natural plant extracts which have been traditionally used for disease treatment. In the present study, the essential oil of lavender (EOL) was examined for its antibacterial activity against thirty-eight strains of turtle-borne pathogenic bacteria belonging to seven species; Aeromonas hydrophila, A. caviae, A. dhakensis, Citrobacter freundii, Proteus mirabilis, Salmonella enterica and Pseudomonas aeruginosa. Antibacterial activity of EOL was tested by means of disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. In addition, the antimicrobial susceptibility pattern of 11 commonly used antimicrobials was examined and the multiple antibiotic resistance (MAR) index was calculated. The results revealed that EOL was active against all tested turtle-borne pathogenic bacteria except P. aeruginosa. The range of MIC and MBC values of EOL against isolates except P. aeruginosa were recorded as 0.5–1% (V/V) and 0.5–2% (V/V), respectively. The MBC/MIC ratio was detected as <4, revealing that the tested EOL was bactericidal. Besides, most of the isolates were resistant to different antimicrobials in antimicrobial disk diffusion test. MAR index values of the tested strains were ranging from 0.27 to 0.91. The outcomes indicate that EOL has a potential to be used as an antibacterial agent against pathogenic bacteria isolated from pet turtles.

Antimicrobial property of lemongrass (Cymbopogon citratus) oil against pathogenic bacteria isolated from pet turtles

The usage of essential oils as antimicrobial agents is gaining attention. Besides, pet turtles were known to harbor a range of pathogenic bacteria while the turtle keeping is a growing trend worldwide.The current study examined the antimicrobial activity of lemon grass oil (LGO) against seven species of Gram negative bacteria namely; Aeromonas hydrophila, A. caviae, Citrobacter freundii, Salmonella enterica, Edwardsiella tarda, Pseudomonas aeruginosa, and Proteus mirabilis isolated from three popular species of pet turtles. Along with the results of disc diffusion, minimum inhibitory and minimum bactericidal concentration (MIC and MBC) tests, LGO was detected as effective against 6 species of bacteria excluding P. aeruginosa. MIC of LGO for the strains except P. aeruginosa ranged from 0.016 to 0.5% (V/V). The lowest MIC recorded in the E. tarda strain followed by A. hydrophilla, C. freundii, P. mirabilis, and S. enterica. Interestingly, all the bacterial species except E. tarda were showing high multiple antimicrobial resistance (MAR) index values ranging from 0.36 to 0.91 upon the 11 antibiotics tested although they were sensitive to LGO.

The anti-Staphylococcus aureus activity of the phenanthrene fraction from fibrous roots of Bletilla striata.

BackgroundBletillae Rhizoma, the tuber of Bletilla striata, has been used in Chinese traditional medicine to treat infectious diseases. Chemical studies indicated that phenanthrene was one of the most important components of the herb, with a broad spectrum of antibiotic activity against Gram-positive bacteria. The objective of this study was to further characterize the antibacterial activity of the phenanthrene fraction from the fibrous root of the pseudobulb of B. striata.MethodsThe phenanthrene fraction (EF60) from the ethanol extract of fibrous roots of Bletilla striata pseudobulbs was isolated using polyamide column chromatography. The antibacterial activity of the fraction was evaluated in vitro using a 96-well microtiter plate and microbroth dilution method. The cytotoxicity of EF60 against mammalian cells was tested by hemolysis and MTT assays.ResultsEF60 was obtained using alcohol extraction and polyamide column chromatography, with a yield of 14.9 g per 1 kg of the fibrous roots of B. striata. In vitro tests indicated that EF60 was active against all tested strains of Staphylococcus aureus, including clinical isolates and methicillin-resistant S. aureus (MRSA). The minimum inhibitory concentration (MIC) values of EF60 against these pathogens ranged from 8 to 64 μg/mL. Minimum bactericidal concentration tests demonstrated that EF60 was bactericidal against S. aureus 3304 and ATCC 29213 and was bacteriostatic against S. aureus 3211, ATCC 25923, and ATCC 43300. Consistently, the time-kill assay indicated that EF60 could completely kill S. aureus ATCC 29213 at 2× the MIC within 3 h but could kill less than two logarithmic units of ATCC 43300, even at 4× the MIC within 24 h. The postantibiotic effects (PAE) of EF60 (4× MIC) against strains 29213 and 43300 were 2.0 and 0.38 h, respectively. Further studies indicated that EF60 (160 μg/mL) showed no cytotoxicity against human erythrocytes, and was minimally toxic to Human Umbilical Vein Endothelial Cells with an IC50 of 75 μg/mL.ConclusionsOur studies indicated that EF60 is worthy of further investigation as a potential phytotherapeutic agent for treating infections caused by S. aureus and MRSA.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1488-z) contains supplementary material, which is available to authorized users.

Comparative in vitro activity of oritavancin and other agents against methicillin-susceptible and methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infections constitute a threat to the public health due to their prevalence and associated mortality and morbidity. Several agents have been recently approved to treat MRSA skin infections including lipoglycopeptides (dalbavancin, oritavancin, and telavancin), ceftaroline, and tedizolid. This study compared the MIC, minimum bactericidal concentration (MBC), and time-kill of these agents alongside daptomycin, linezolid, and vancomycin against MRSA (n=15); meropenem, cefazolin, and nafcillin were also included against methicillin-susceptible S. aureus (MSSA [n=12]). MIC and MBC testing was conducted in accordance with Clinical and Laboratory Standards Institute guidelines, and time-kills were evaluated at multiples of the MIC and the free-drug maximum plasma concentration (fCmax) at both standard and high inoculum densities for a subset of MRSA (n=2) and MSSA (n=2). MRSA and MSSA were highly susceptible to all agents, with the lipoglycopeptides having the most potent activity by MIC50/90. All agents excluding tedizolid and linezolid were bactericidal by MBC for MRSA and MSSA, though dalbavancin and telavancin exhibited strain-specific bactericidal activity for MRSA. All agents excluding tedizolid and linezolid were bactericidal by time-kill at their respective fCmax against MRSA and MSSA at standard inoculum density, though oritavancin exhibited the most rapid bactericidal activity. Oritavancin and daptomycin at their respective fCmax maintained similar kill curves at high inoculum density. In contrast, the killing observed with other agents was typically reduced or slowed at high inoculum density. These data demonstrate the rapid bactericidal activity of oritavancin and daptomycin against S. aureus relative to other MRSA agents regardless of bacterial burden.

Isolation and identification of anti-methicillin resistant Staphylococcus aureus compounds from Phyllanthus columnaris stem bark

Aim: Phyllanthus columnaris Mull.Arg. was found to possess anti-methicillin resistant Staphylococcus aureus (antiMRSA) activities. This study aimed at isolating, identifying and evaluating the active compounds from the stem bark of Phyllanthus columnaris Mull.Arg. against MRSA. Methodology and results: Stem bark extracts (methanol, acetone and aqueous) of Phyllanthus columnaris were subjected to anti-MRSA screening by disc diffusion method. MIC and MBC tests were carried out to compare the lowest concentration to inhibit and kill the sixteen MRSA tested among the three extracts. TLC bioautography were performed to detect the bioactive compounds. Isolation of the two active compounds was performed by means of preparative TLC. Morphological and ultra-structure alterations of the MRSA treated with bioactive compounds after 24 h were revealed by scanning and transmission electron microscopy. Both methanol and acetone extracts exhibited good anti-MRSA activity with the lowest minimum inhibitory concentration (MIC) value for both extracts were 0.78 mg/mL and the lowest minimum bactericidal concentration (MBC) were 1.56 mg/mL. Bioassay-guided chromatography by bioautography revealed two active anti-MRSA compounds from both tannin-free methanol and acetone extracts and characterized as stigmasterol and lupeol by nuclear magnetic resonance (NMR) spectral data. Scanning and transmission electron microscopy of MRSA treated with stigmasterol and lupeol showed cell wall disruption, release of cytoplasmic compounds and decreased in cellular volume. Conclusion, significance and impact of study: Results obtained herein, may suggest that the stem bark of Phyllanthus columnaris possess anti-MRSA and the two of the active compounds isolated were stigmasterol and lupeol. Their anti-MRSA effects up to the morphological and ultra-structure studies were not reported earlier.