Recent studies on advance spectroscopic techniques for the identification of microorganisms: A review

The continuous development of resistance to antibiotic drugs by microorganisms causes high mortality and morbidity. Pathogens with distinct features and biochemical abilities make them destructive to human health. Therefore, early identification of the pathogen is of substantial importance for quick ailments and healthcare outcomes. Several phenotype methods are used for the identification and resistance determination but most of the conventional procedures are time-consuming, costly, and give qualitative results. Recently, great focus has been made on the utilization of advanced techniques for microbial identification. This review is focused on the research studies performed in the last five years for the identification of microorganisms particularly, bacteria using advanced spectroscopic techniques including mass spectrometry (MS), infrared (IR) spectroscopy, Raman spectroscopy (RS), and nuclear magnetic resonance (NMR) spectroscopy. Among all the techniques, MS techniques, particularly MALDI-TOF/MS have been widely utilized for microbial identification. A total of 44 bacteria i.e., 6 Staphylococcus spp., 3 Enterococcus spp., 6 Bacillus spp., 4 Streptococcus spp., 6 Salmonella spp., and one from each genus including Escherichia, Acinetobacter, Pseudomonas, Proteus, Clostridioides, Candida, Brucella, Burkholderia, Francisella, Yersinia, Moraxella, Vibrio, Shigella, Serratia, Citrobacter, and Haemophilus (spp.) were discussed in the review for their identification using the above-mentioned techniques. Among all the identified microorganisms, 21% of studies have been conducted for the identification of E. coli, 14% for S. aureus followed by 37% for other microorganisms.     

Novel 3-Acetyl-2,5-disubstituted-1,3,4-oxadiazolines: Synthesis and Biological Activity

The aim of our study was the two-stage synthesis of 1,3,4-oxadiazole derivatives. The first step was the synthesis of hydrazide–hydrazones from 3-methyl-4-nitrobenzhydrazide and the corresponding substituted aromatic aldehydes. Then, the synthesized hydrazide–hydrazones were cyclized with acetic anhydride to obtain new 3-acetyl-2,3-disubstituted-1,3,4-oxadiazolines. All of obtained compounds were tested in in vitro assays to establish their potential antimicrobial activity and cytotoxicity. Our results indicated that few of the newly synthesized compounds had some antimicrobial activity, mainly compounds 20 and 37 towards all used reference bacterial strains (except Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa) and fungi. These substances showed a strong or powerful bactericidal effect, especially against Staphylococcus spp. belonging to Gram-positive bacteria. Compound 37 was active against Staphylococcus epidermidis at minimal inhibitory concentration (MIC) = 0.48 µg/mL and was characterized by low cytotoxicity. This compound possessed quinolin-4-yl substituent in the second position of 1,3,4-oxadiazole ring and 3-methyl-4-nitrophenyl in position 5. High effectiveness and safety of these derivatives make them promising candidates as antimicrobial agents. Whereas the compound 20 with the 5-iodofurane substituent in position 2 of the 1,3,4-oxadiazole ring showed the greatest activity against S. epidermidis at MIC = 1.95 µg/mL.     

Potential antimicrobial compounds in flower extract of Plumeria alba

This study was carried out to investigate the antimicrobial activity of methanolic flower extract of Plumeria alba and identification of the possible antimicrobial compounds through GC–MS analysis. Antimicrobial efficacy of the methanolic extract of 5 ppm to 1000 ppm concentrations was assessed against five fungal (Trichoderma viride, T. reesei, T. harzianum, T. hamatum and T. koningii) and five bacterial species (Escherichia coli, Salmonella sp., Pseudomonas sp., Bacillus sp. and Staphylococcus sp.). In general, all the concentrations of the extract significantly reduced growth of all the fungal and bacterial species. However, there was a significant variation in susceptibility of different fungal and bacterial species to the applied concentrations of the extract. The extract was the most effective against T. reesii followed by T. viride, T. harzianum, T. hamatum and T. koningii causing 11–97%, 36–90%, 24–86%, 7–77% and 9–76% reduction in their growth. Similarly, there was 23–93%, 12–92%, 36–90%, 19–90% and 8–84% reduction in growth of Bacillus sp., Staphylococcus sp., E. coli, Pseudomonas sp., and Salmonella sp., respectively, due to different concentrations of methanolic extract. GC–MS analysis of the extract showed the presence of 21 constituents. The most abundant compound was benzofuran, 2,3-dihydro- (27.95%). Other important compounds included cyclononanone (14.59%), 9-octadecyne (14.29%), 9,12,15-octadecatrienoic acid, methyl ester, (Z,Z,Z)- (10.28%), benzyl alcohol (5.57%), 1-decanol, 2-hexyl- (5.44%), 2,6-octadien-1-ol, 3,7-dimethyl-, acetate, (Z)- (3.76%), 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- (2.48%) and heptadecane (2.43%). It is concluded that methanolic extract of P. alba flowers has the potential to control both fungal as well as bacterial growth.     

Synthesis of Silver Nanoparticles from Extracts of Wild Ginger (Zingiber zerumbet) with Antibacterial Activity against Selective Multidrug Resistant Oral Bacteria

Antibiotic resistance rate is rising worldwide. Silver nanoparticles (AgNPs) are potent for fighting antimicrobial resistance (AMR), independently or synergistically. The purpose of this study was to prepare AgNPs using wild ginger extracts and to evaluate the antibacterial efficacy of these AgNPs against multidrug-resistant (MDR) Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis. AgNPs were synthesized using wild ginger extracts at room temperature through different parameters for optimization, i.e., pH and variable molar concentration. Synthesis of AgNPs was confirmed by UV/visible spectroscopy and further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDXA), and Fourier-transform infrared spectroscopy (FTIR). Disc and agar well diffusion techniques were utilized to determine the in vitro antibacterial activity of plant extracts and AgNPs. The surface plasmon resonance peaks in absorption spectra for silver suspension showed the absorption maxima in the range of 400–420 nm. Functional biomolecules such as N–H, C–H, O–H, C–O, and C–O–C were present in Zingiber zerumbet (Z. zerumbet) (aqueous and organic extracts) responsible for the AgNP formation characterized by FTIR. The crystalline structure of ZZAE-AgCl-NPs and ZZEE-AgCl-NPs was displayed in the XRD analysis. SEM analysis revealed the surface morphology. The EDXA analysis also confirmed the element of silver. It was revealed that AgNPs were seemingly spherical in morphology. The biosynthesized AgNPs exhibited complete antibacterial activity against the tested MDR bacterial strains. This study indicates that AgNPs of wild ginger extracts exhibit potent antibacterial activity against MDR bacterial strains.     

Functional properties of nisin–carbohydrate conjugates formed by radiation induced Maillard reaction

Nisin–carbohydrate conjugates were prepared by irradiating nisin either with glucose or dextran. Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino and reducing sugar groups indicating occurrence of the Maillard reaction catalyzed by irradiation. Nisin–carbohydrate conjugates showed a broad spectrum antibacterial activity against Gram negative bacteria (Escherichia coli, Pseudomonas fluorescence) as well as Gram positive bacteria (Staphylococcus aureus, Bacillus cereus). Results of antioxidant assays, including that of DPPH radical-scavenging activity and reducing power, showed that the nisin–dextran conjugates possessed better antioxidant potential than nisin–glucose conjugate. These results suggested that it was possible to enhance the functional properties of nisin by preparing radiation induced conjugates suitable for application in food industry.     

A novel synergistic formulation between a cationic surfactant from lysine and hyaluronic acid as an antimicrobial coating for advanced cellulose materials

In this investigation, a novel coating for viscose fabric surface modification was developed using a synergistic formulation between a natural antimicrobial cationic surfactant from lysine (MKM) and a biopolymer hyaluronic acid (HA). The interaction between MKM and HA in aqueous solutions, as well as the interactions between their synergistic formulation (HA-MKM) and viscose fabric (CV) were studied using pH-potentiometric titrations’, turbidity measurements, the Kjeldahl method for the determination of nitrogen amounts, attenuated total reflectance fourier transform infrared spectroscopy, and scanning electron microscopy. The hydrophilic and antimicrobial properties of the functionalised CV were examined in order to evaluate its usages for medical applications. The results of the interaction studies showed that MKM and HA interact with each other by forming a precipitate when the binding sites of HA are saturated. The precipitate has a slightly positive charge at neutral pH due to excess binding of the MKM to HA. The excess positive charge was also detected on CV coated with HA-MKM. This was proven to be very beneficial for the antimicrobial properties of the functionalised CV. The antimicrobial tests showed exceptional antimicrobial activity of the functionalised CV against Escherichia Coli, Staphylococcus Aureus, Streptococcus Agalactiae, Candida Albicans, and Candida Glabrata, making the CV fabric highly interesting for potential use in medicine.     

New metabolites with antibacterial activity from the marine angiosperm Cymodocea nodosa

Four new metabolites (1-4) have been isolated from the organic extract of the seagrass Cymodocea nodosa, collected at the coastal area of Porto Germeno, in Attica Greece. Compounds 1 and 2 belong to the structural class of diarylheptanoids, which have been found only once before in marine organisms [Kontiza, I.; Vagias, C.; Jakupovic, J.; Moreau, D.; Roussakis, C.; Roussis, V. Tetrahedron Lett.2005, 46, 2845-2847]. Compound 3 is a new meroterpenoid, while compound 4, to the best of our knowledge, is the first briarane diterpene isolated from seaweeds, and only the second analog of this class with a tricyclic skeleton. Furthermore metabolite 4 is the first brominated briarane diterpene. The structures and the relative stereochemistry of the new natural products were established by spectral data analyses. The new metabolites were submitted for evaluation of their antibacterial activity against multidrug-resistant (MDR) pathogens including methicillin-resistant (MRSA) strains of Staphylococcus aureus, as well as the rapidly growing mycobacteria, Mycobacterium phlei, Mycobacterium smegmatis, and Mycobacterium fortuitum.     

Phytogenic-mediated silver nanoparticles using Persicaria hydropiper extracts and its catalytic activity against multidrug resistant bacteria

Multidrug resistance (MDR) is one of the major global threats of this century. So new innovative approaches are needed for the development of existing antibiotics to limit antibacterial resistance. The current study was aimed to utilize extracts of root, stem, and leaves of Persicaria hydropiper for the synthesis of silver nanoparticles (AgNPs) using standard procedure. Synthesis of AgNPs was evident from the change in color of the solution to dark brownish and then it was further revealed by UV–Vis and Fourier Transformed Infrared Spectroscopy (FTIR). UV–Vis spectroscopy has revealed absorbance peak at 370 nm while, FTIR spectrum displayed that aromatics amines were used as reducing agent in the fabrication of AgNPs. In addition, Scanning Electron Microscopy (SEM micrograph) displaying tetrahedron, spherical and oval shapes of synthesized AgNPs whereas, average size of synthesized AgNPs was found in the range of 32–77 nm. Beside this, it was also observed that the potency of antibiotics against MDR bacteria increased after coating with synthesized AgNPs i.e., the potency of Ceftazidime and Ciprofloxacin increased up to 450% and 500% against Bacillus respectively while, the potency of Gentamicin, Vancomycin and Linezolid increased up to 150%, 200% and 58% against Bacillus, Staphylococcus, and Proteus species respectively. Furthermore, it was concluded that utilizing AgNPs in combination with commercially available antibiotics would provide an alternate therapy for the treatment of infectious diseases caused by MDR bacteria.     

Rosa spp. Extracts as a Factor That Limits the Growth of Staphylococcus spp. Bacteria,a Food Contaminant

Due to their richness of bioactive substances, rose hips are a valuable raw material for obtaining extracts with potential antimicrobial activity. The aim of the study was to determine the antagonistic potential of whole pseudo-fruit and flesh extracts of three Rosa sp. varieties against Staphylococcus spp. bacteria isolated as food contaminants. The biological material in this study consisted of seven strains of bacteria from the genus Staphylococcus. Two strains—Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis DSMZ 3270—were used as reference strains. The other five strains were food-derived isolates—S. epidermidis A5, S. xylosus M5, S. haemolyticus M6, S. capitis KR6, and S. warneri KR2A. The material was the pseudo-fruits of Rosa canina, Rosa pomifera Karpatia, and Rosa rugosa. The polyphenols were extracted from the fleshy part and the whole pseudo-fruit for all rose varieties. The tested preparations differed significantly in their polyphenol composition. The sum of polyphenols ranged from 28 862 to 35 358 mg/100 g of lyophilisate. The main groups of polyphenols found in the preparations were flavanols and ellagitannins. All of the tested extracts inhibited the growth of staphylococci at a concentration of 500 mg/mL. Rosa rugosa fruit extract showed the strongest antimicrobial properties among the studied extracts. For all the strains, the growth inhibition had a diameter of 20.3–29.0 mm. Moreover, six out of the seven tested strains showed the highest inhibition with the use of this extract. The MIC of rose extracts was in the range of 3.125–500 mg/mL and was strictly dependent on the bacterial species, the species of the rose, and the part of the fruit from which the extract was obtained. Correlations were assessed between the main groups of polyphenols in the extracts and their inhibition of bacterial growth. In the case of pseudo-fruit extracts, the inhibitory effect on bacterial growth positively correlated with the content of ellagitannins, and this effect was observed for almost all the tested strains. The results presented herein follow the current trend of minimising the use of chemical preservatives in food; from this point of view, rose extracts are very promising.     

Integration of microfiltration and anion-exchange nanoparticles-based magnetic separation with MALDI mass spectrometry for bacterial analysis

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is powerful in characterizing and identifying bacterial isolates. However, sufficient quantities of bacterial cells are required for generating MALDI mass spectra and a procedure to isolate and enrich target bacteria from sample matrix prior to MALDI-MS analysis is often necessary. In this paper, anion-exchange superparamagnetic nanoparticles (NPs), i.e., fluidMAG-DEAE and fluidMAG-Q, were employed to capture Aeromonas, Salmonella, Pseudomonas, Enterococcus, Bacillus, Staphylococcus and Escherichia coli from aqueous solutions and fresh water. The magnetically isolated bacteria were then characterized by whole cell MALDI-MS. The capture efficiency was found to be dependent on bacterial species, medium pH, the functional group and concentration of the NPs. The experimental results demonstrated that fluidMAG-DEAE and fluidMAG-Q were broad spectrum probes for bacteria. Furthermore, both dead and live bacteria could be captured by the NPs, and the live bacteria captured remained viable. Membrane filtration prior to the magnetic isolation could increase enrichment factor and eliminate potential matrix interference. A detection limit of 1 × 10³ cfu/ml was achieved for the bacteria spiked in tap water and reservoir water, and the analytical time was around 2 h.     

Polylactic acid-based polyurethane/polyamide 6,12 and graphene nanocomposite: Structure and physical property study for packaging application

This effort reports on novel polylactic acid-derived polyurethane (PU) and polyamide 6,12 (PA6,12)-based blends and graphene-reinforced nanocomposite. PU/PA6,12 (50:50) blend was opted as matrix based on molecular weight and shear stress performance. PU/PA6,12 with 5?wt% graphene (PU/PA6,12/graphene 3) showed improved T₀ and T_max of 515 and 541°C relative to neat blend. PU/PA6,12/graphene 3 also revealed significantly high tensile (53?MPa) and flexural strength (1,711?MPa). For Eschericia coli, Staphylococcus, and Pseudomonas bacterial strains, nanocomposite with higher graphene loading produced significant inhibitory effects. Novel nanocomposites displayed fine antimicrobial and barrier properties against O₂ and H₂O to be used as a packaging material.     

Synthesis of N-functionalized oleamide derivatives

Oleamide is an interesting compound, which shows various pharmacological activities including the inhibitory effect of gap junction formation. Recently, the studies of the gap junction have been some of the hot topics in biology and its inhibitors have become more useful tools [Cravatt, B. F.; Garcia, O. P.; Siuzdak, G.; Gilula, N. B.; Henriksen, S. J.; Boger, D. L.; Lerner, R. A. Science1995, 268, 1506-1509; Cravatt, B. F.; Lerner, R. A.; Boger, D. L. J. Am. Chem. Soc.1996, 118, 580-590; Guan, X; Cravatt, B. F.; Ehring, G. R.; Hall, J. E.; Boger, D. L.; Lerner, R. A.; Gilula, N. B. J. Cell Biol.1997, 139, 1785-1792; Boger, D. L.; Patterson, J. E.; Guan, X.; Cravatt, B. F.; Lerner, R. A.; Gilula, N. B. Proc. Natl. Acad. Sci. U.S.A.1998, 95, 4810-4815; Ito, A.; Morita, N.; Miura, D.; Koma, Y.; Kataoka, T. R.; Yamasaki, H.; Kitamura, Y.; Kita, Y.; Nojima, H. Carcinogenesis2004, 25, 2015-2022]. However, many reports suggest that the functionalizations of oleamide to retain its biological activity were difficult [Boger, D. L.; Patterson, J. E.; Guan, X.; Cravatt, B. F.; Lerner, R. A.; Gilula, N. B. Proc. Natl. Acad. Sci. U.S.A.1998, 95, 4810-4815; Ito, A.; Morita, N.; Miura, D.; Koma, Y.; Kataoka, T. R.; Yamasaki, H.; Kitamura, Y.; Kita, Y.; Nojima, H. Carcinogenesis2004, 25, 2015-2022]. The synthesis of the functionalized oleamide derivatives, whose biological activity is not blocked, has become attractive in both the biological and chemical fields.Herein, by linking the fluorophore to the oleamide by alkyl chains, we synthesized the fluorescently tagged oleamide whose biological feature is similar to that of oleamide. Moreover, we also synthesized other bioactive derivatives tagged by other groups such as the sugars and biotin via alkyl chain linkers.     

Mass spectrometry profiling of single bacterial cells reveals metabolic regulation during antibiotics induced bacterial filamentation

Bacterial antimicrobial resistance (AMR) is a severe threat to global health and development. Under the stimulation of antibiotics, bacterial cells can undergo filamentation and generate daughter cells with stronger AMR. The current research on bacterial AMR mechanism is mainly conducted with a population of cells. However, bacterial cells exhibit heteroresistance, making the study at population level not reliable. Herein, we developed single bacterial cell metabolic profiling by mass spectrometry (MS) to study bacterial AMR at single-cell level. By utilizing a microprobe controlled by a microoperation platform, single filamentous extended spectrum beta-lactamase (ESBL) producing Escherichia coli (ESBL-E. coli) cells generated by ceftriaxone sodium stimulation can be extracted and spray-ionized for MS analysis. Heterogeneous among ESBL-E. coli cells under the same antibiotic stimulus condition was observed from mass spectra as well as cell morphology. The metabolic profiles by MS of different individual cells can be clustered into subgroups well in accordance with bacterial cell length. Metabolic pathways including arginine and proline metabolism, as well as cysteine and methionine metabolism were disclosed to play an important role in the bacterial SOS-associated filamentation against antibiotics. The microprobe electrospray ionization-MS-based single bacterial cell analysis method is promising in the study of various bacterial AMR mechanism and can reveal the heterogeneity of bacterial AMR from-cell-to-cell.     

An efficient one-pot synthesis of pyrazolyl-[1,2,4]triazolo[3,4-b][1,3,4] thiadiazin-6-yl)-2H-pyran-2-one derivatives via multicomponent approach and their potential antimicrobial and nematicidal activities

A series of simple or/and aryl, heteryl hydrazono pyrazolyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-6-yl)-2H-pyran-2-one derivatives have been efficiently synthesized in excellent yields via one-pot, multi-component approach. The importance of this methodology is that in a one-pot operation four new bonds (3C–N and 1C–S) are generated. The structure of compound 5a was confirmed by single-crystal X-ray diffraction. The newly synthesized compounds were evaluated for their in vitro antimicrobial activity against gram-positive bacteria (Staphylococcusaureus and Bacillussubtilis), gram-negative bacteria (Escherichiacoli andKlebsiellapneumoniae), antifungal activity against Candida albicans, and nematicidal activity against Meloidogyneincognita. Among all the compounds 6f showed excellent antimicrobial and nematicidal activity against tested bacteria, fungi, and nematodes.     

Synergistic and antagonistic effects of Citrus bergamia distilled extract and its major components on drug resistant clinical isolates

Abstract

In this study we determine the in vitro antimicrobial activities of Citrus bergamia distilled extract and compounds isolated from such extract against clinical MDR strains. The activity of these substances were tested using a broth microdilution assay, their MBC and their FBC to evaluate the nature of the interactions in tested components. Among Gram negative bacteria Enterobacter spp, Klebsiella spp and Pseudomonas spp exhibited the higher MBC values range (2.5–5% v/v). Among Gram positive and Yeast isolates, Corynebacterium spp, Enterococcus faecalis and Staphylococcus spp, as well as Candida lipolytica and lusitanae showed a range of 2.5 to >5% of MBC. To overcome such resistance toward the distilled extract, were used combination of isolated compounds from the same extract. Klebsiella pneumoniae 16/15 and Pseudomonas aeruginosa 7/15 were sensitive to synergistic effect of some tested combinations. Broad spectrum of antimicrobial activity was demonstrated for C. bergamia components and their combinations.     

Efficacy of Souroubea-Platanus Dietary Supplement Containing Triterpenes in Beagle Dogs Using a Thunderstorm Noise-Induced Model of Fear and Anxiety

A novel botanical dietary supplement, formulated as a chewable tablet containing a defined mixture of Souroubea spp. vine and Platanus spp. Bark, was tested as a canine anxiolytic for thunderstorm noise-induced stress (noise aversion). The tablet contained five highly stable triterpenes and delivered 10 mg of the active ingredient betulinic acid (BA) for an intended 1 mg/kg dose in a 10 kg dog. BA in tablets was stable for 30 months in storage at 23 °C. Efficacy of the tablets in reducing anxiety in dogs was assessed in a blinded, placebo-controlled study by recording changes in blood cortisol levels and measures of behavioral activity in response to recorded intermittent thunder. Sixty beagles were assigned into groups receiving: placebo, 0.5×, 1×, 2×, and 4× dose, or the positive control (diazepam), for five days. Reduction in anxiety measures was partially dose-dependent and the 1× dose was effective in reducing inactivity time (p = 0.0111) or increased activity time (p = 0.0299) compared with placebo, indicating a decrease in anxiety response. Cortisol measures also showed a dose-dependent reduction in cortisol in dogs treated with the test tablet.     

Identification of Bacteria Associated with Post-Operative Wounds of Patients with the Use of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Approach

The bacterial infection of post-operative wounds is a common health problem. Therefore, it is important to investigate fast and accurate methods of identifying bacteria in clinical samples. The aim of the study was to analyse the use of the MALDI-TOF MS technique to identify microorganism wounds that are difficult to heal. The most common bacteria are Escherichia coli, Staphylococcus spp., and Enterococcus spp. We also demonstrate the effect of culture conditions, such as the used growth medium (solid: Brain Heart Infusion Agar, Mueller Hilton Agar, Glucose Bromocresol Purple Agar, and Vancomycin Resistance Enterococci Agar Base and liquid: Tryptic Soy Broth and BACTEC Lytic/10 Anaerobic/F), the incubation time (4, 6, and 24h), and the method of the preparation of bacterial protein extracts (the standard method based on the Bruker guideline, the Sepsityper method) to identify factors and the quality of the obtained mass spectra. By comparing the protein profiles of bacteria from patients not treated with antibiotics to those treated with antibiotics based on the presence/absence of specific signals and using the UniProt platform, it was possible to predict the probable mechanism of the action of the antibiotic used and the mechanism of drug resistance.     

Salmon (Salmo salar) Cooking: Achieving Optimal Quality on Select Nutritional and Microbiological Safety Characteristics for Ready-to-Eat and Stored Products

This study was performed in order to assess technological characteristics, proximate composition, fatty acids profile, and microbiological safety of sous-vide processed salmon in comparison with steaming and roasting. The cooking loss was lower in the sous-vide method (6.3–9.1%) than in conventional methods (11.6–16.2%). The preparation of salmon using sous-vide was more time- and energy-consuming than steaming. The dry matter content of the salmon fillets was higher in conventionally processed samples than sous-vide due to the evaporation of water, and it was connected with total protein (r = 0.85) and lipid content (r = 0.73). Analysis of the fatty acids profile only revealed significant differences in six fatty acids. All of the heat treatment methods ensured microbiological safety with regard to coagulase-positive Staphylococcus, E. coli, Listeria monocytogenes, and Salmonella spp. However, in sous-vide (57 °C, 20 min) and steamed samples after storage Enterobacteriaceae bacteria (<10⁴) was detected. Summing up, high parameters of sous-vide salmon cooking, when considering both technological parameters, nutritional value, and microbiological status should be recommended.     

In Vitro Antimicrobial Activity of Lavender,Mint, and Rosemary Essential Oils and the Effect of Their Vapours on Growth of Penicillium spp. in a Bread Model System

The chemical composition, antioxidant activity, and antimicrobial properties of three commercially available essential oils: rosemary (REO), lavender (LEO), and mint (MEO), were determined in the current study. Our data revealed that the major components of REO, MEO, and LEO were 1,8-cineole (40.4%), menthol (40.1%), and linalool acetate (35.0%), respectively. The highest DPPH radical-scavenging activity was identified in MEO (36.85 ± 0.49%) among the investigated EOs. Regarding antimicrobial activities, we found that LEO had the strongest inhibitory efficiencies against the growth of Pseudomonas aeruginosa and Candida (C.) tropicalis, MEO against Salmonella (S.) enterica, and REO against Staphylococcus (S.) aureus. The strongest antifungal activity was displayed by mint EO, which totally inhibited the growth of Penicillium (P.) expansum and P. crustosum in all concentrations; the growth of P. citrinum was completely suppressed only by the lowest MEO concentration. The lowest minimal inhibitory concentrations (MICs) against S. enterica, S. aureus, and C. krusei were assessed for MEO. In situ analysis on the bread model showed that 125 µL/L of REO exhibited the lowest mycelial growth inhibition (MGI) of P. citrinum, and 500 µL/L of MEO caused the highest MGI of P. crustosum. Our results allow us to make conclusion that the analysed EOs have promising potential for use as innovative agents in the storage of bakery products in order to extend their shelf-life.     

Broad spectrum antibacterial zinc oxide-reduced graphene oxide nanocomposite for water depollution

Antimicrobial-resistance (AMR) is a global health challenge arising from the evolution of bacteria, viruses, fungi, and parasites, such that pathogenic microorganisms no longer respond to classical therapies. AMR and the rise of so-called ‘superbugs’ requires innovative nanomaterials and biostatic strategies. Here we report a broad spectrum, antimicrobial nanomaterial integrating light-responsive ZnO nanoparticles (NP) and reduced graphene oxide (rGO) into a heterojunction semiconductor nanocomposite for water depollution. Simultaneous chemical reduction of Zn sulphate and GO sheets yields a low concentration (0.5 mol%) of 10 nm ZnO nanoparticles decorating fragmented rGO nanosheets, with a total surface area of 12 m²/g and optical band gap of 1.6 eV. Antimicrobial performance of the ZnO-rGO nanocomposite was evaluated against methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli 0157:H7 and Salmonella typhimurium bacteria, which are prevalent in contaminated aquatic systems; antimicrobial efficacy against these organisms was 96%, 97%, and 73%, respectively, for a loading of 2 mg/mL, evidencing a strong synergy compared with pure ZnO or rGO components. ZnO-rGO was also an effective photocatalyst for the aqueous degradation of Malachite Green dye, suggesting that its mode of antibacterial action reflects the production of reactive oxygen species under ambient illumination.