The objective of this study was to identify and quantify the chemical constituents, as well as the antimicrobial, antibiofilm and synergistic activity with florfenicol of essential oils of Aloysia ...triphylla (EOAT) and Lippia alba (EOLA) against Aeromonas spp. The antimicrobial activity of EOAT and EOLA was verified by the minimum bactericidal concentration (MBC) and the action against biofilm forming and consolidated biofilm. The synergistic activity of EOAT and EOLA with florfenicol was performed by the checkerboard technique. The main components of EOAT were α-citral (39.91%), E-carveol (25.36%) and limonene (21.52%), while that of EOLA was linalool (81.64%). Aeromonas spp. isolates showed sensitivity to both essential oils with MBC between 195.3 and 3125.0 μL/mL. Two isolates were classified as non-producing, three as moderate and 16 as weak biofilm producers. The EOAT and EOLA interfered in the biofilm formation, from moderate to weak producers, but did not cause any interference in the consolidated biofilm. The EOAT and EOLA combined with florfenicol showed synergistic effect and reduced MBC. The EOAT and EOLA have potential for application as antimicrobial agents, as they interfere in the initial formation of biofilm and when combined with florfenicol, present a synergic effect with a reduction in the minimum dose of the antibiotic.
•Synergistic activity of essential oils with florfenicol was performed by checkerboard technique.•Determination of chemical compounds of essential oils was carried out by GC-MS.•The essential oils interfered in the biofilm formation, but did not in the consolidated biofilm.•The essential oils had a synergistic effect with florfenicol, reducing the dose used.•The efficacy of traditional antibiotics can still be improved.
A library of 24 pyridinium-, imidazolium-, and cholinium-based ionic liquids (ILs) with varying alkyl chain from C2 to C16 was toxicologically profiled using naturally luminescent marine bacteria ...Vibrio fischeri. The toxicity (30-min EC50) of studied ILs to Vibrio fischeri ranged from 7.82 µM (4.2 mg/L) (PyC12Phe) to 3096 µM (1227 mg/L) (ImidC2Phe), i.e. from “toxic” (EC50 1–10 mg/L) to “not harmful” (EC50 > 100 mg/L). Inhibition of the bacterial luminescence upon 30-min exposure to ILs correlated well with bacterial viability (exposure for 4 h). The toxicity of studied ILs was largely driven by the length of the alkyl chain (hydrophobicity) and not the type of cationic part of the IL: starting from C10 all the ILs irrespective of the cationic part proved “toxic”. The toxicity of the studied ILs was increasing in parallel to their hydrophobicity up to log Kow = 1 (C8–C10) and then levelling up, being consistent with the previously obtained analogous data sets. The “cut-off” effect reported in this study for longer chain length members of the ILs series leads to the “limit” toxicity level for this type of ILs to be ca. 8 mM. Two open-access online tools (www.molinspiration.com and www.vcclab.org) have been applied for the calculation of the Kow values for the 24 ILs reported in this study and 21 ILs reported in the literature. This lead to plotting two nonlinear monotonic correlations between the values of experimental log (1/EC50) and calculated log Kow. The limitation of the online tools and an effect of the ILs structure on the “cut-off” effect have been discussed. The challenge of developing low microbial toxicity surface active ILs remains a significant task to overcome. Our results shed light on the new approaches for designing environmentally benign ILs and functional surfactants. As the hydrophobicity of the ILs significantly correlated with the toxicity, the Vibrio fischeri assay could be considered a powerful tool in providing toxicity data for building and evaluating the QSAR toxicity models for ILs.
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•24 L-phenylalanine derived ILs were screened for toxicity using bacteria V. fischeri.•The toxicity of 24 ILs to V. fischeri ranged from toxic to not harmful.•Adverse effects of ILs depended on the length of the alkyl chain.•Bacterial light output inhibition was more sensitive endpoint than viability.•V. fischeri test allows toxicity screening of big panels of ILs for QSAR analysis.
This study aimed to investigate the antimicrobial effect and membrane damage mechanism of blueberry extract against Vibrio parahaemolyticus. The minimal inhibitory concentration (MIC) and minimal ...bactericidal concentration (MBC) of blueberry extract against three strains of V. parahaemolyticus were determined. The antimicrobial activity of blueberry extract on V. parahaemolyticus inoculated in salmon was evaluated. The effect of blueberry extract on V. parahaemolyticus cell membrane was visualized by scanning electron microscopy and transmission electron microscopy. We examined the antimicrobial mechanism of blueberry extract in the regulation of the seven membrane genes expression. The MIC for V. parahaemolyticus ATCC 17802, ATCC 33847 and F 13 was 25, 25 and 12.5 mg/mL, respectively, whereas the MBC was 50, 50 and 25 mg/mL, respectively. The blueberry extract has antimicrobial effect on V. parahaemolyticus in salmon samples. The V. parahaemolyticus exposed to 1 × MIC showed distorted membrane morphology and leakage of cellular contents. The cytoplasmic constituents were aggregated, causing a wide range of hollow areas in the cells. The expression of seven membrane genes in V. parahaemolyticus treated with blueberry extract was investigated by quantitative real-time PCR. Compared to that in the control, the gene expression of fadL and nusA was upregulated by 1.1-, 2.1-, 4.1-fold and 7.4-, 4.3-, 3.6-fold in V. parahaemolyticus ATCC 17802, ATCC 33847 and F 13, respectively. The gene expression of ef-Tu was downregulated by 1.1-, 2.7-, 3.3-fold in the three strains of V. parahaemolyticus. Findings from this study revealed that blueberry extract had strong antibacterial effect and inhibited gene transcription to disrupt cell membrane structure and energy transport. Further studies investigating potential antimicrobial applications of blueberry extract are necessary to provide a basis for the development and utilization of blueberries as an antimicrobial agent.
•Blueberry extract showed antimicrobial effect against V. parahaemolyticus strains.•Blueberry extract disrupted bacterial cell membrane integrity.•Blueberry extract interrupted normal growth of bacterial cells.•Blueberry extract altered the expression of seven membrane genes.
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•Differently coated 10 and 50 nm nanoAg were synthesised and tested in DI water.•10 nm nanoAg were more soluble and more antibacterial than 50 nm nanoAg.•Gram (−) E. coli was more ...susceptible to nanoAg and Ag-ions than Gram (+) S. aureus.•Surface coating effect on antibacterial potency was observed only for 50 nm nanoAg.•The toxicity of nanoAg was interplay of NP size, solubility and surface coating.
Silver nanoparticles (nanoAg) are effective antimicrobials and promising alternatives to traditional antibiotics. This study aimed at evaluating potency of different nanoAg against healthcare infections associated bacteria: Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. A library of differently coated nanoAg of two different sizes (10 and 50 nm) were prepared using coating agents poly-L-Lysine (PLL), cetyltrimethyl-ammonium bromide (CTAB), citrate (CIT), polyvinyl-pyrrolidone (PVP), polysorbate 80 (Tween 80), and dioctyl-sodium sulfosuccinate (AOT). Stability evaluation by means of agglomeration and dissolution behaviour was performed for all nanoAg under conditions relevant for this study.
Antibacterial properties of nanoAg were addressed by determining their minimal bactericidal concentrations (MBC) in deionised (DI) water to minimise the influence of silver speciation on its bioavailability. In parallel, AgNO3 was analysed as an ionic control.
Studied nanoAg were efficient antimicrobials being remarkably more potent towards E. coli than to S. aureus (4 h MBC values for different nanoAg ranged from 0.08 to 5.0 mg Ag/L and 1.0–10 mg Ag/L, respectively). The toxicity of all nanoAg to S. aureus (but not to E. coli) increased with exposure time (4 h vs 24 h). 10 nm sized nanoAg released more Ag-ions and were more toxic than 50 nm nanoAg. Coating-dependent toxicity was more prominent for 50 nm nanoAg coated with Tween 80 or CTAB rendering the least toxic nanoAg. Obtained results showed that the antimicrobial effects of nanoAg were driven by shed Ag-ions, depended on target bacteria, exposure time and were the interplay of NP size, solubility and surface coating.
Miramistin is a widely used antiseptic, disinfectant and preservative, and one of the most popular antimicrobial agents on pharmaceutical market of the Russian Federation ...(http://www.dsm.ru/en/news/385/). However, there is a lack of reported systematic data on antibacterial efficacy of this agent obtained in accordance with the international standards.
This paper represents a systematic study of antibacterial properties of miramistin. Another objective of this work is to evaluate and compare the exploratory performance of in vitro and in vivo protocols of antiseptics’ efficacy testing using miramistin as the reference antiseptic.
Antibacterial activity of 0.1% and 0.2% aqueous solutions of miramistin against two museum strains of S. aureus (ATCC 209p) and E. coli (CDC F-50) was studied. Three standard in vitro laboratory tests (microdilution test, suspension test, and metal surface test), and one in vivo test (on rat's skin) were used. The study was conducted in accordance with the international regulatory documents.
Miramistin showed high bactericidal activity against the studied bacterial pathogens in the standard in vitro tests. Thus, in the microdilution test it showed expressed activity against S. aureus (MIC 8 μg/ml, MBC 16 μg/ml) and E. coli (MIC 32 μg/ml, MBC 128 μg/ml). In the suspension test, miramistin decreased the amount of colony forming units by at least 6 log10 units for S. aureus, and by at least 4.5 log10 units for E. coli. Transition to the metal surface test led to significant decrease of antibacterial activity by 1–3 log10 units as compared to the suspension test. Further dramatic reduction of antiseptic activity (by 3–4 log10 units) was observed in in vivo rat skin test. Addition of a protein contaminant (bovine serum albumin) led to a general decrease in the effectiveness of miramistin against the test pathogens (typically, by 1–2 log10 units). An interesting effect of exposure time-dependent reversal of miramistin's specificity to the studied Gram-positive S. aureus and the Gram-negative E. coli organisms was observed in the metal surface test.
The results of this work provide systematic data on antibacterial efficacy of miramistin. They also underscore the need in relevant in vivo models for evaluation of antiseptics' efficacy. While the existing in vitro methods can be successfully applied at the discovery stages, it is necessary to use more realistic in vivo models at more advanced development stages. The observed selectivity reversal effect should be taken into account when carrying out the antiseptics’ efficacy testing and surface disinfection procedures.
•The data indicate bactericidal activity of miramistin against S.aureus (ATCC209p™) and E.coli (CDC F-50™) in vitro.•Miramistin demonstrated decreasing microbicidal activity in vitro on metal surface, in comparison with suspension test.•Antiseptic activity of miramistin was studied on S. aureus (ATCC209p™) and E coli (CDC F-50™) in vivo on rat skin surface.
A fast and efficient synthesis of some 1,4-disubstituted thiosemicarbazide derivatives is described. The reaction of 3-chlorobenzoic acid hydrazide with various aryl isothiocyanates gave ...thiosemicarbazide derivatives (1–11) in good yield. The cyclization of compounds (1–11) in the presence of 2% NaOH resulted in the formation of compounds (12–22) containing the 1,2,4-triazole ring. A series of new Mannich bases (23–33) related to the structure of 1,2,4-triazole has been also synthesized. All of these compounds were tested for their in vitro antibacterial activity against the reference strains of aerobic bacteria - 6 Gram-positive and 3 Gram-negative ones; 12 Staphylococcus aureus clinical isolates were also examined. An attempt was made to clarify the influence of the nature/position of substituents on antibacterial activity of compounds described.
Synthesis and antimicrobial evaluation of some 1,4-disubstituted thiosemicarbazides, s-triazoles and Mannich bases were described. Compounds 4, 6, 15 appeared to be four-fold more effective against Bacillus cereus ATCC 10876 than ampicillin. Display omitted
► Fast and efficient method for the preparation of thiosemicarbazides is described. ► Antimicrobial activity depends on the nature/position of substituents. ► Some derivatives appeared to be more effective than ampicillin
Context: Helminthostachys zeylanica (L.) Hook. has been used as a traditional medicine plant to treat diabetic mellitus and various infectious in China, Malaysia, and Indonesia. Aims: To determine ...the antibacterial activity of H. zeylanica root extracts against various pathogenic bacteria. Methods: The extraction was carried out by maceration of fresh roots using methanol, then partitioned to obtain extracts of n-hexane, dichloromethane, ethyl acetate, and water. The extracts were tested for antibacterial activity using the agar diffusion method, minimal inhibition concentration (MIC), and minimal bactericidal concentration (MBC). Results: Dichloromethane and ethyl acetate extracts showed inhibitory activity against Bacillus subtilis ATCC 1965, Staphylococcus aureus ATCC 6538, B. cereus ATCC 10876, Vibrio parahaemolyticus ATCC 17802, V. alginolyticus ATCC 17749, Listeria monocytogenes ATCC 7644, and Salmonella typhimurium ATCC 142028. The MIC value of dichloromethane extract against these bacteria was 125-500 µg/mL, while the ethyl acetate extract was 500 µg/mL. Furthermore, the MBC for dichloromethane against bacteria B. subtilis and V. parahaemolyticus were 250 µg/mL. Conclusions: The study demonstrated the in vitro antibacterial potential of the species extracts against pathogenic bacteria. The dichloromethane and ethyl acetate extracts showed the most significant inhibitory activity, suggesting that this plant could be a potential source for developing new antimicrobial agents. Further research is needed to identify the active compounds responsible for the observed effects.
The threat of antibiotic-resistance calls for novel antibacterial agents. This study was aimed at screening medicinal plants for their antibacterial properties, phytochemical content and safety. ...Leaves of Allophylus abyssinicus (Hochst.) Radlk., Dicliptera laxata C.B.Clarke, Ligustrum vulgare L., Solanecio gigas (Vatke) c. Jeffrey and Gymnanthemum myrianthum (Hook.f.) H.Rob.; leaf and stem-bark of Olinia rochetiana A. Juss. and the seed of Cucurbita pepo L. were used. Chloroform and ethanol were used to extract G. myrianthum, D. laxata and O. rochetiana; ethyl acetate and methanol for the rest, and water for all. The extracts were tested against clinical/standard strains of Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Staphylococcus aureus by the agar-diffusion method. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined. Acute toxicity to mice was checked and preliminary phytochemical screening was done. Thirteen extracts, out of 24, were active (inhibition zone >7 mm) at differing levels (9.67±0.33-25.66±0.57 mm) against at least one bacterial strain. The MICs and MBCs were 1.95-15.6 mg/mL and 7.8-125 mg/mL respectively. The aqueous extract of S. gigas, methanol extracts of L. vulgare and A. abyssinicus, and ethanol extract of O. rochetiana leaf were the most active (MIC 1.95mg/ml) against S. aureus. Ethyl acetate extracts of A. abyssinicus, L. vulgare and S. gigas; aqueous of C. pepo, O. rochetiana and G. myrianthum; and all D. laxata had no antibacterial activity. P. aeruginosa was the least susceptible to any extract, although the methanol and aqueous extracts of S. gigas performed better against it. Preliminary phytochemical screening of selected extracts for phenols, flavonoids, tannins, steroids, terpenoids, steroidal glycosides, alkaloids, saponins, resins and glycosides showed positivity at least for four of these phytochemicals with glycoside and terpenoids in nearly all extracts and resin in none. The plants were not toxic to mice at 2000 mg/kg. Further consideration of S. gigas, L. vulgare, A. abyssinicus and O. rochetiana is recommended in light of their promising potential and safety.
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