Anticancer properties and mechanism insights of α-hederin

α-Hederin is a natural bioactive molecule very abundant in aromatic and medicinal plants (AMP). It was identified, characterized, and isolated using different extraction and characterization technologies, such as HPLC, LC-MS and NMR. Biological tests have revealed that this natural molecule possesses different biological properties, particularly anticancer activity. Indeed, this activity has been investigated against several cancers (e.g., esophageal, hepatic, breast, colon, colorectal, lung, ovarian, and gastric). The underlying mechanisms are varied and include induction of apoptosis and cell cycle arrest, reduction of ATP generation, as well as inhibition of autophagy, cell proliferation, invasion, and metastasis. In fact, these anticancer mechanisms are considered the most targeted for new chemotherapeutic agents' development. In the light of all these data, α-hederin could be a very interesting candidate as an anticancer drug for chemotherapy, as well as it could be used in combination with other molecules already validated or possibly investigated as an agent sensitizing tumor cells to chemotherapeutic treatments.

Mathematical modeling of Escherichia coli O157:H7 growth in carrot juice influenced by Thymbra capitata essential oil, heat treatment, and storage temperature

The aim of this study was to develop a mathematical model describing the survival of Escherichia coli O157:H7 in carrot juice treated with Thymbra capitata essential oil combined with mild heat treatment and stored at different temperatures. The viable count method was used to investigate the effect of the treatment on bacterial survival, and the response surface methodology was used to develop a statistical model fitting the data. The results showed that the variance of bacterial growth is explained by storage temperature (37 %) and heat treatment (35 %), these are followed by Thymbra capitata essential oil (18 %) and their interaction (9 %). Positive multiplicative interaction was obtained for any pair of the studied treatments and cooperative effect synergy was observed over a large domain of these factors. A mathematical model was successfully developed to describe Escherichia coli O157:H7 response to the selected factors, within the study limits, and to estimate the risk of juice contamination and shelf-life. Based on our results, the use of Thymbra capitata essential oil combined with heat treatment may control Escherichia coli O157:H7 growth in carrot juice stored at low temperature.

Probiotic Properties and Physicochemical Potential of Lactic Acid Bacteria Isolated from Moroccan Table Olives

Background: Lactic Acid Bacteria are a group of Gram-positive bacteria which are  widely used in the food industry as organic ferments called starter cultures. In this study, Enterococcus faecium, Leuconostoc mesenteroides, Lactococcus lactis, Weissella paramesenteroides, and Lactiplantibacillus plantarumisolated from Moroccan table olives were tested for their acquisition of probiotic and technological properties. Methods: The 5 strains were previously isolated from table olives in 2017. Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometer (MALDI-TOF MS) and intergenic space sequencing were used for molecular identification. Following that, probiotic and physicochemical properties were evaluated, including growth at  different pH levels (2, 3, and 10), temperatures (7, 45, and 50 °C), and sodium chloride (NaCl) concentrations (6.5 and 18% m/v). Antibacterial activity was tested out against Gram-positive and Gram-negatives bacteria. Results: The 5 strains (E. faecium 168, L. lactis 9, L. plantarum 11, L. mesenteroides 62, and W. paramesenteroides36) showed an ability to grow at low temperatures (7 °C). L. lactis 9 and L. plantarum 11 showed higher acid (pH 2) and salt (18% NaCl) tolerances. In addition, L. lactis 9 and L. plantarum 11 exhibited the highest level of free radical scavenging activity after 48 h of incubation, respectively). L. plantarum 11 and E. faecium 168 showed the highest antibacterial capacity. However, E. faecium 168 and W. paramesenteroides 36 demonstrated better and more rapid acid production capabilities. Conclusion: L. plantarum 11, E. faecium 168, and W. paramesenteroides 36 were  considered the best candidates as probiotic cultures for further in vivo studies and  functional food product development.

COMPARISON, VALIDATION, AND OPTIMIZATION OF INTERNAL GENOMIC DNA EXTRACTION PROTOCOL FOR CAMPYLOBACTER SPECIES

Campylobacter remains the leading cause responsible of human gastroenteritis worldwide. The current study aimed to compare the internal DNA extraction protocol with two commercially available kits, using C. jejuni (ATCC® 29428TM) and C. coli (ATCC®43478TM) and to validate and optimize the internal protocol through artificial contamination and confirmation of Campylobacter spp. from broiler chickens, turkeys, and beef meats samples. The extraction processes were carried out following the internal protocols steps and the manufacturer's instructions of PureLinkTM Genomic DNA Mini Kit and Wizard® Genomic DNA Purification Kit, respectively. The agarose gel electrophoresis system was used to control the DNA quality. After that, forty Campylobacter spp. isolates were confirmed, and finally, an artificial contamination of the aforementioned reference strains at three different concentrations was performed with sterilized minced meats. This is the first work comparing the PureLinkTM Genomic DNA Mini Kit and Wizard® Genomic DNA Purification Kit with internal genomic DNA extraction protocol for Campylobacter spp. The results indicated that the internal protocol provided similar efficiency to the two kits. All confirmed isolates were successfully amplified, in which28 isolates were C. coli and 12 were C. jejuni, as revealed by biochemical tests. A positive amplification was also observed in the three contaminated food matrices, after enrichment, at all examined doses. Except some reactions that were negative at 1 CFU/mL of C. jejuni and C. coli. This was explained by the detection limits of both internal protocol and qPCR. Based on our findings, three crucial steps in determining the extraction of DNA quality of this protocol were amended. Hence, the study highlighted the importance of validating simpler, cheaper and faster DNA extraction protocol, for each laboratory, as part of future risk assessment, control and monitoring programs of Campylobacter frequency required in molecular studies.

A REVIEW OF CURRENT KNOWLEDGE AND GAPS ABOUT CAMPYLOBACTER METHODS: FROM CULTURE TO CHARACTERIZATION

Campylobacteriosis is a zoonotic disease caused by Campylobacter, mostly associated with consumption of contaminated foodstuffs and water. Campylobacter jejuni and Campylobacter coli recognized as the leader of foodborne diarrheal illness in humans. The frequency of these microorganisms in poultry is fairly high than Salmonella and more challenging to measure, which represent an expensive burden charge on public health due to their difficulties to master them, especially with the fast increase rates of multidrug-resistant of thermophilic Campylobacter strains. It is well recognized that Campylobacter spp. is a fastidious cell, difficult to isolate in laboratories owing to their requirements and sensibility. That’s why; these factors must be taken into consideration during recovery protocols. A variety of phenotyping tests have been reported and widely used for confirmation and identification of Campylobacter species. Nonetheless, Whole Genome Sequencing (WGS) and Culture-Independent Diagnostic Tests (CIDTs) are new eras of hopeful technologies, mainly involved in the detection and characterization of threaten public health pathogens. This review aimed to describe the culture methods, phenotypic and genotypic schemes used to isolate, identify, and characterize Campylobacter isolates, through discussing the current knowledge and gaps related to the application of these techniques over others performed for typing this microaerophilic genus.

Effects of Lactiplantibacillus plantarum 11 and Chloride Sodium on Biochemical and Microbiological Quality of Table Olives during Fermentation

Background: Table olives are nutritionally a complete food and considered as one of the oldest fermented products. This study aimed to evaluate the effect of Lactiplantibacillus plantarum 11 as a starter culture on the fermentation of table olives at two incubation temperatures 22 and 30 °C and different salt concentrations (0, 4, 8, and 12% m/v) of sodium chloride (NaCl). Methods: The fermentation of table olives was carried out according to the Spanish style. L. plantarum 11 was inoculated as a starter culture (106 Colony Forming Unit (CFU)/ml), and Listeria monocytogenes CECT 4032 was used as an indicator strain. Under the same experimental conditions, the fermentation of olives without the inoculation of starter culture was used as a control. Then, biochemical and microbiological quality of each experimental batch was tested. Results: Unlike the incubation temperature of 22 °C, the pH values ​​obtained in salted batches and incubated at 30 °C were all below the marketing limits for table olives. At the end of the process, the maximum load of yeasts and molds (>5 log CFU/ml) was recorded in the batches incubated at 22 °C. At 22 °C, Listeria was absent in inoculated fermenters at a concentration greater than or equal to 8% (w/v) of NaCl. However, at 30 °C, Listeria was not detected in treatment groups and in the control group with 12% NaCl.  Conclusion: L. plantarum 11 could be potentially considered as a probiotic starter culture during the fermentation of black table olives.

Prevalence, typing and antimicrobial resistance of Salmonella isolates from commercial shellfish in the North coast of Morocco

Salmonellosis is one of the most common foodborne illnesses in the world. The irrational use of antibiotics in medicine and in animal nutrition has greatly favored the emergence and spread of resistant strains of non-typhoid Salmonella. This study aims the determination of the prevalence of Salmonella in bivalve mollusks in Northern Morocco, as well as the molecular typing and antibiotic susceptibility testing of the strains isolated from positive samples. In total, 150 samples from shellfish composed of mussels (Mytilus galloprovincialis), clams (Callista chione and Ruditapes descussatus) and oysters (Magallana gigas). Isolated Salmonella were characterized by Molecular techniques PCR, MLST and MLVA, phylogenetically grouped by MLSA, and susceptibilities were determined for 30 antimicrobial drugs using microdilution method by the BD Phoenix Automated Microbiology System. Prevalence of Salmonella enterica subsp. enterica was 12.67%, grouped in four serovars identified as Chester, Hadar, Typhimurium and Kentucky. Five different MLST STs (sequence types) were detected, ST1954 being the most common, which was mostly found in Chester isolates. Forty-two percent of the isolates showed resistance to more than one antibiotic, especially trimethoprim, sulfa drugs, quinolones and β-lactam. There was a marked change in the serovars and antimicrobial resistance profiles of the Salmonella isolates in this study compared to those in previous studies.

Prevalence and antimicrobial profiling of Campylobacter spp. isolated from meats, animal, and human feces in Northern of Morocco

The present work was carried out to understand the occurrence and antimicrobial susceptibility of Campylobacter spp., in various samples in Northern of Morocco. For this purpose, a random sampling was undertaken from butcher shops, traditional markets, and slaughterhouse. First, the research of Campylobacter was performed according to the Moroccan standard NM ISO: 10272-1 (2008). Second, the isolates were identified by biochemical tests and real time PCR. After the biochemical and molecular identification of suspected colonies, a disk diffusion method was executed to determine the sensitivity of Campylobacter spp. against 18 antibiotics. The results showed a moderate prevalence of Campylobacter species (130/466) recovered mainly on the Campylobacter blood base agar, where C. coli (108/130) were more prevalent comparable to C. jejuni (22/130) in poultry and cattle meat, raw milk, cloacal and surface swabs, and stool of patient suffering from diarrhea. The findings supported also the sensitivity of multiplex qPCR to detect Campylobacter strains compared to Moroccan standard NM ISO: 10272-1 (2008). Among our isolates, C. jejuni were the most susceptible strain toward colistin, florfenicol, gentamicin, streptomycin, and erythromycin. Nonetheless, the presence of multidrug Campylobacter resistant strains was highly observed in C. jejuni isolated, particularly, from broiler chickens toward the antibiotic classes of cephalosporin, penicillin, monobactam, quinolone, fluoroquinolone, sulfamide, as well as tetracycline. This may be due to common use of these drugs in veterinary medicine and farms as growth factor, which limits the usefulness of these molecules. Hence, the study highlights the importance of resistance profile monitoring of these pathogens in Northern of Morocco, in order to develop appropriate control measures and to reduce the emergence of multidrug-resistant strains.

The Contribution of Carotenoids, Phenolic Compounds, and Flavonoids to the Antioxidative Properties of Marine Microalgae Isolated from Mediterranean Morocco

This study aimed to investigate the potential of four sea water microalgae, isolated and cultivated at M′diq Bay in Morocco, as a new source of natural antioxidants. These microalgae belong to different classes, including Phaedactylium tricornitum (Bacillariophyceae), Nannochloropsis gaditana (Eustigmatophyceae), Nannochloris sp (Trebouxiophyceae), and Tetraselmis suecica (Chlorodendrophycea). The antioxidant properties were screened by the use of in vitro assays, namely 2,2-difenil-1-picrylhydrazyl, Ferric reducing antioxidant power, and Ferrous ions chelating activity, and compoundidentification was carried out in methanol and acetone extracts of both dried and fresh microalgae biomass by HPLC–PDA–MS analysis. Among the investigated microalgae, Phaedactylium tricornutum was the richest one regarding its carotenoid (especially all-E-fucoxanthin) and phenolic (especially protocatechuic acid) contents, as well as antioxidant activity (65.5%), followed by Nannochloris sp, Tetraselmis suicica, and Nannochloropsis gaditana, with antioxidant activity of 56.8%, 54.9%, and 51.1%, respectively.

Anti-dermatophytes Activity of Origanum compactum Essential Oil at Three Developmental Stages

The main aim of this study is to determine the chemical compounds of Origanum compactum essential oils (OCEO) at three phenological stages (vegetative, flowering, and post-flowering) and to evaluate their antifungal activity against three dermatophytes fungal strains: Trichophyton violaceum, Trichophyton tonsurans, and Trichophyton mentagrophytes using direct contact method. The main compounds of OCEO are carvacrol, thymol, p-cymene, and γ-terpinene. Oregano EOs showed important antifungal activities with some variability between EOs and fungal testing. At a concentration of 0.75% (v/v), the best inhibition values showed with OCEO at vegetative stage against Trichophyton mentagrophytes (95.17%), Trichophyton tonsurans (92.47%), and Trichophyton violaceum (91.41%). The OCEO at vegetative stage also showed the best IC50 (concentration of an inhibitor where the response is reduced by half) values of 52.86, 0.56, and 0.57% (v/v) against Trichophyton mentagrophytes, Trichophyton tonsurans, and Trichophyton violaceum, respectively. The findings reveal that OCEO is a good source of anti-dermatophytes agents.

Marinobacter maroccanus sp. nov., a moderately halophilic bacterium isolated from a saline soil

During the taxonomic investigation of exopolymer-producing halophilic bacteria, a rod-shaped, motile, Gram-stain-negative, halophilic bacterium, designated strain N4^T, was isolated from a saline soil located in northern Morocco. Optimal growth of the isolate was at 30-37 ºC and at pH 7.0-8.0, in the presence of 5-7 % (w/v) NaCl. Useful characteristics for the phenotypic differentiation of strain N4^T from other Marinobacter species included α-chymotrypsin and α-glucosidase activities and the carbohydrate assimilation profile. The major fatty acids detected in strain N4^T were C16:0 and C18:1ω9c and the predominant respiratory quinone was ubiquinone-9. Sequence analysis of the 16S rRNA gene indicated that strain N4^T belonged to the genus Marinobacter and was closely related to the type strains of Marinobacter adhaerens (99.04 % similarity), Marinobacter salsuginis (98.97 %) and Marinobacter flavimaris (98.36 %). Phylogenetic analysis of the rpoD gene sequence also showed that the nearest neighbours of strain N4^T were M. salsuginis (91.49 % similarity), M. adhaerens and M. flavimaris (90.63 %). Strain N4^T showed 87.98 % average nucleotide identity with M. flavimaris and M. salsuginis, and 87.47 % with M. adhaerens. Regarding in-silico genome-to-genome distance, strain N4^T showed DNA-DNA hybridization values of 33.30 % with M. adhaerens, 34.60 % with M. flavimaris and 34.70 % with M. salsuginis. The DNA G+C content of strain N4^T was 57.3 mol%. Based on the results of phenotypic characterization, phylogenetic analysis and genome comparison, strain N4^T represents a novel species of the genus Marinobacter, for which the name Marinobacter maroccanus sp. nov. is proposed. The type strain is N4^T (=CECT 9525^T=LMG 30466^T).

Les huiles essentielles comme agents anticancéreux : actualité sur le mode d’action

Le cancer est une maladie complexe qui présente un réel problème de santé publique à travers le monde et cause statiquement sept millions de décès chaque année. Au cours des dernières décennies, la thérapie anticancéreuse a connu un réel bouleversement et un foisonnement de découvertes fondamentales. Plusieurs études accumulatives ont révélé l’activité antitumorale des substances naturelles isolées à partir de plantes. Les huiles essentielles (HE) et leurs constituants ont montré des activités anticancéreuses puissantes in vitro et in vivo. Cependant, les mécanismes d’action sont encore peu étudiés et moins connus. Par ailleurs, leur application dans l’industrie pharmaceutique nécessite une spécificité– sélectivité pharmacodynamique absolue. Dans le présent travail, nous présentons une synthèse des travaux réalisés sur les mécanismes d’actions anticancéreuses des HE et leurs composés bioactifs.

Evaluation of Antimicrobial Activity of Four Organic Acids Used in Chicks Feed to Control Salmonella typhimurium: Suggestion of Amendment in the Search Standard

Today, the general public has become increasingly aware of salmonellosis problems. Organic acids are known by their antimicrobial potential and commonly used for improving the quality of poultry feed. In this context, the present work evaluated the inhibitory effect of four organic acids, namely, acetic acid, citric acid, lactic acid, and tartaric acid, at different levels of contamination by Salmonella typhimurium. The neutralization of these organic acids in vitro and in the presence of one-day-old chick's organs was also investigated during the search for Salmonella serovars in birds as described in the Moroccan standard "NM 08.0.550." The effect of four organic acids on Salmonella typhimurium was tested in vitro and in the presence of chick's organs at different concentrations set of strain and organic acids tested. The MIC results demonstrated that tartaric acid, citric acid, and acetic acid inhibited Salmonella typhimurium at concentrations of 0.312%, 0.625%, and 0.512% for the three levels of strain: 10, 100, and 103 CFU/ml, respectively, while lactic acid and depending on the amount of the strain introduced acts differently: 0.078% for 10 CFU/ml and 0.156% for 100 and 103 CFU/ml. The concentration of 0.04M of Na2HPO4 solution has proved, in vitro, in caecums and organs of chicks (in presence of organic acids) that strain introduced, even at low concentrations, can be recovered. The use of additives has beneficial effects in Salmonella control program. However, the present results recommend the amendment of Salmonella research standard, taking into account the probable presence of organic acids in digestive content of one-day-old chicks.

Chemical composition of Mentha pulegium and Rosmarinus officinalis essential oils and their antileishmanial, antibacterial and antioxidant activities

The aim of the study was the determination of the chemical composition of Mentha pulegium L. and Rosmarinus officinalis L. essential oils and the evaluation of their antileishmanial, antibacterial and antioxidant activities. Essential oils (EOs) were isolated using steam distillation and the chemical composition was determined using GC-MS analysis. The antibacterial activity was tested against ten pathogenic strains using the diffusion method, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) by microtitration assay. The antioxidant activity was estimated by DPPH free radical scavenging ability and ferric-reducing power. The antileishmanial activity was tested against Leishmania major, Leishmania tropica and Leishmania infantum using MTT (3-(4.5-dimethylthiazol-2yl)-2.5-diphenyltetrazolium bromide) assay. The yield of essential oils (v/w %) M. puleguim and R. officinalis based on dry weight were 5.4 and 2.7% respectively. GC/MS analysis of R. officinalis essential oil (ROEO) revealed the presence of 29 components, mainly represented by oxygenated monoterpenes (63.743%) and hydrocarbons monoterpenes (21.231%). Mentha pulegium essential oil (MPEO) revealed 21 components, mainly represented by oxygenated monoterpenes (83.865%). The major components of ROEO were α-pinene (14.076), 1,8-Cineole (23.673) and camphor (18.743), while menthone (21.164) and pulegone (40.98) were the main major components of MPEO. M. pulegium and R. officinalis EOs showed a significant antioxidant activity compared with ascorbic acid and Trolox to the IC₅₀ values of 58.27 ± 2.72 and 85.74 ± 7.57 μg/mL respectively revealed by reducing power assay. As for the antibacterial effect, the highest zone diameters were shown by the MPEO against Bacillus subtilis (30 ± 1.43 mm) and Proteus mirabilis (28 ± 1.32 mm). These values are significantly important compared with those of the commercialized antibiotic (Erythromycin and Chlorophenicol). The lowest MIC and MBC values were obtained with MPEO against S. aureus MBLA (MIC = MBC = 0.25% (v/v)). While, ROEO has exhibited a bactericidal effect against Listeria monocytogenes (MIC = MBC = 0.5% (v/v)), Bacillus subtilis (MIC = MBC = 1% (v/v)) and Escherichia coli (MIC = MBC = 1% (v/v)). For the antileishmanial effect, ROEO is the most active against L. major (IC₅₀ = 1.2 ± 0.36 μg/mL. While, the MPEO has the most leishmanicidal effect against L. major (IC₅₀ = 1.3 ± 0.45 μg/mL). These findings show that the EOs of M. pulegium and R. officinalis are good sources of bioactive molecules that could have potential applications in the food and pharmaceutical industries.

Antimicrobial characterization and safety aspects of the bacteriocinogenic Enterococcus hirae F420 isolated from Moroccan raw goat milk

The F420 strain, isolated from raw goat milk and identified as Enterococcus hirae, was selected because of its strong activity against gram-positive bacteria, including Listeria monocytogenes. Interestingly, the F420 strain lacks the virulence genes and decarboxylase activity of histidine, lysine, and ornithine, and it is susceptible to 11 of 14 tested antibiotics, including vancomycin. The antimicrobial compounds produced by E. hirae F420 strain showed high resistance to heat treatment and to acidic and basic pHs. The MALDI-TOF mass spectrometry analysis coupled with the sequence of peptide and structural gene analysis of one of the purified enterocins showed 100% identity with enterocin P (EntP), previously described in E. faecium strains. The structural gene for EntP is located on a plasmid of 65 kb. Other enterocins with molecular mass higher than 7 kDa were also detected. This is the first report of the production of EntP by E. hirae species naturally occurring in foods. The biotechnological characteristics of the F420 strain and its enterocins indicate their potential for application in the control of L. monocytogenes and other undesirable bacteria in food systems.

Halomonas rifensis sp. nov., an exopolysaccharide-producing, halophilic bacterium isolated from a solar saltern

A polyphasic taxonomic study was conducted on strain HK31T, a moderately halophilic bacterium isolated from a solar saltern in Chefchaouen, Morocco. The strain was a Gram-reaction-negative, oxidase-positive rod, which was motile by means of peritrichous flagella. The strain required NaCl for growth and grew in salt concentrations (mixture of sea salts) of 0.5–20 % (w/v) (optimum 5–7.5 %, w/v), at 25–45 °C (optimum 32 °C) and at pH 5–10 (optimum pH 6–9). Strain HK31T did not produce acids from sugars and its metabolism was respiratory, using oxygen as terminal electron acceptor. The strain was positive for the accumulation of poly-β-hydroxyalkanoate granules and formed mucoid colonies due to the excretion of an exopolysaccharide. The DNA G+C content was 61.5 mol%. 16S rRNA gene sequence analysis indicated that it belonged to the genus Halomonas in the class Gammaproteobacteria. The most phylogenetically related species was Halomonas anticariensis, with which strain HK31T showed a 16S rRNA gene sequence similarity of 96.48 %. Its major fatty acids were C18 : 1ω7c, C16 : 0, C19 : 0 cyclo ω8c , C16 : 1ω7c/iso-C15 : 0 2-OH and C12 : 0 3-OH and the predominant respiratory lipoquinone was ubiquinone with nine isoprene units (Q-9). Based on the evidence provided in this study, strain HK31T ( = CECT 7698T  = LMG 25695T) represents a novel species of the genus Halomonas, for which the name Halomonas rifensis is proposed.

Functional and ultrastructural changes in Pseudomonas aeruginosa and Staphylococcus aureus cells induced by Cinnamomum verum essential oil

AIMS

To study cellular damage induced by Cinnamomum verum essential oil in Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213.

METHODS AND RESULTS

The effect of cinnamon bark essential oil on these two strains was evaluated by plate counts, potassium leakage, flow cytometry and transmission electron microscopy (TEM). Exposure to this oil induced alterations in the bacterial membrane of Ps. aeruginosa, which led to the collapse of membrane potential, as demonstrated by bis-oxonol staining, and loss of membrane-selective permeability, as indicated by efflux of K(+) and propidium iodide accumulation. Thus, respiratory activity was inhibited, leading to cell death. In Staph. aureus, cells treated with the oil entered a viable but noncultivable (VNC) state. The oil initially caused a considerable decrease in the metabolic activity and in the replication capacity of these bacterial cells. The loss of membrane integrity appeared later, as indicated by bis-oxonol and Propidium iodide (PI) staining. Data provided by TEM showed various structural effects in response to cinnamon essential oil. In Ps. aeruginosa cells, coagulated cytoplasmic material was observed, and intracellular material was seen in the surrounding environment, while oil-treated Staph. aureus showed fibres extending from the cell surface.

CONCLUSIONS

Cinnamon essential oil damages the cellular membrane of Ps. aeruginosa, which leads to cell death. There is evidence of VNC Staph. aureus after exposure to the oil.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cinnamon essential oil shows effective antimicrobial activity and health benefits and is therefore considered a potential food additive. To use this oil as a natural food preservative, especially in combination with other preservation methods, a thorough understanding of the mechanism through which this oil exerts its antibacterial action is required.

Total Phenolic Content and Antioxidant Activity of Myrtle (Myrtus communis) Extracts

The total phenolic content and antioxidant activity of methanolic, ethanolic and aqueous extracts of myrtle ( Myrtus communis) leaves and berries were measured to find new potential sources of natural antioxidants. Total phenolic content was assessed by the Folin-Ciocalteau assay, while the antioxidant activity was evaluated by three methods: diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity assay, the reducing antioxidant power assay and β-carotene linoleic acid assay. The total phenol content of myrtle extracts ranged between 9.0 and 35.6 mg GAE per g extract. For each solvent, leaf extracts contained significantly higher amount of total phenolic compounds than berry extracts. All of the extracts presented antioxidant capacity assessed by the three methods, but at different levels depending on the concentration, the extraction solvent and the part of the plant used. Generally, leaf extracts showed higher antioxidant activities than berry extracts, while the overall antioxidant strength was in the order methanol > water > ethanol in leaf extracts and methanol > ethanol >water in berry extracts. The phenolic content exhibited a positive correlation with the antioxidant activity: DPPH assay showed the highest correlation (r = 0.949), followed by the reducing power assay (r = 0.914) and the lowest for the β-carotene linoleic acid assay (r = 0.722).

Total phenolic content and antioxidant activity of myrtle (Myrtus communis) extracts

The total phenolic content and antioxidant activity of methanolic, ethanolic and aqueous extracts of myrtle (Myrtus communis) leaves and berries were measured to find new potential sources of natural antioxidants. Total phenolic content was assessed by the Folin-Ciocalteau assay, while the antioxidant activity was evaluated by three methods: diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity assay, the reducing antioxidant power assay and beta-carotene linoleic acid assay. The total phenol content of myrtle extracts ranged between 9.0 and 35.6 mg GAE per g extract. For each solvent, leaf extracts contained significantly higher amount of total phenolic compounds than berry extracts. All of the extracts presented antioxidant capacity assessed by the three methods, but at different levels depending on the concentration, the extraction solvent and the part of the plant used. Generally, leaf extracts showed higher antioxidant activities than berry extracts, while the overall antioxidant strength was in the order methanol > water > ethanol in leaf extracts and methanol > ethanol > water in berry extracts. The phenolic content exhibited a positive correlation with the antioxidant activity: DPPH assay showed the highest correlation (r = 0.949), followed by the reducing power assay (r = 0.914) and the lowest for the beta-carotene linoleic acid assay (r = 0.722).

Investigation of functional and morphological changes in Pseudomonas aeruginosa and Staphylococcus aureus cells induced by Origanum compactum essential oil

AIMS

Evaluation of the cellular effects of Origanum compactum essential oil on Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213.

METHODS AND RESULTS

The damage induced by O. compactum essential oil on these two strains has been studied using different techniques: plate count, potassium leakage, flow cytometry (FC) and transmission electron microscopy (TEM). The results showed that oil treatment led to reduction of cells viability and dissipated potassium ion gradients. Flow cytometric analysis showed that oil treatment promoted the accumulation of bis-oxonol and the membrane-impermeable nucleic acid stain propidium iodide (PI), indicating the loss of membrane potential and permeability. The ability to reduce 5-cyano-2,3-ditolyl tetrazolium chloride was inhibited. Unlike in Ps. aeruginosa, membrane potential and membrane permeability in Staph. aureus cells were affected by oil concentration and contact time. Finally, TEM showed various structural effects. Mesosome-like structures were seen in oil-treated Staph. aureus cells whereas in Ps. aeruginosa, coagulated cytoplasmic material and liberation of membrane vesicles were observed, and intracellular material was seen in the surrounding environment. Both FC and TEM revealed that the effects in Ps. aeruginosa were greater than in Staph. aureus.

CONCLUSIONS

Oregano essential oil induces membrane damage showed by the leakage of potassium and uptake of PI and bis-oxonol. Ultrastructural alterations and the loss of cell viability were observed.

SIGNIFICANCE AND IMPACT OF THE STUDY

Understanding the mode of antibacterial effect of the oil studied is of a great interest in it further application as natural preservative in food or pharmaceutical industries.

Investigation of the mutagenic and antimutagenic effects of Origanum compactum essential oil and some of its constituents

In the present study, the chemical composition of Origanum compactum essential oil was determined by gas chromatography and mass spectrometry, and its mutagenic and antimutagenic activities were investigated by the somatic mutation and recombination test (SMART) in Drosophila melanogaster. No significant increase in the number of somatic mutations was observed with the essential oil tested using both the standard (ST) and high bio-activation (HB) cross. In order to investigate the antimutagenic effect of the essential oil, we have tested the effect on the indirect-acting mutagen urethane (URE), as well as the direct-acting mutagen methyl methanesulfonate (MMS). O. compactum essential oil showed a strong inhibitory effect against URE-induced mutagenicity, especially with the HB cross. However, only a weak inhibitory effect on the mutagenicity induced by MMS was observed. These results suggest that the detected antimutagenicity could be mediated by an inhibitory effect on metabolic activation. The essential oil was fractionated to identify the components responsible of the suppressing effect detected. Seven fractions were obtained: two of them showed the most potent inhibitory effect against URE-induced mutagenicity and were further fractionated. The sub-fractions obtained from the second chromatographic fractionation were tested for their antimutagenic activity, together with carvacrol and thymol. The highest antimutagenic effect obtained with the sub-fractions was similar to the effect of the crude essential oil, as well as to the effect of carvacrol alone. These results suggest the absence of a synergic antimutagenic effect between the components of O. compactum essential oil and indicate that carvacrol was the most active oil component.

Control of Listeria monocytogenes in goat's milk and goat's jben by the bacteriocinogenic Enterococcus faecium F58 strain

The bacteriocinogenic Enterococcus faecium F58 strain, a natural goat's jben cheese isolate, lacks decarboxylase activity involved in most biogenic amine formation. It was also sensitive to 13 antibiotics assayed and free of virulence and vancomycin resistance genes. The F58 strain reached the stationary phase after 12 h of growth in sterile goat's milk, and the production of enterocin F-58 (Ent L50) was first detected after 48 h (400 AU/ml), thereafter remaining stable up to 5 days. The effectiveness of the F58 strain in controlling Listeria monocytogenes serovar 4b in reduced fat and whole goat's milk, and in goat's jben has been examined. Coculture experiments of F58-L. monocytogenes in both types of milk demonstrated that listeriae were not eliminated, although reductions by 1 to 4 log units were found. Nevertheless, when the F58 strain was previously inoculated in whole milk and left to grow for 12 h before contamination, the pathogen was completely eliminated after 130 h of coculture. Production of jben cheese contaminated with L. monocytogenes prior to packaging, using preparations of F58-producer strain, caused a significant decrease in the number of viable listeriae, which were undetectable after 1 week of cheese storage at 22 degrees C. Altogether, results from this study suggest that E. faecium F58 strain may be used as an adjunct culture in cheese to control contamination and growth of L. monocytogenes by in situ enterocin production, thus providing an additional hurdle to enhance control of this pathogen.

Enterococcus faeciumF58, a bacteriocinogenic strain naturally occurring in Jben, a soft, farmhouse goat's cheese made in Morocco

AIMS

Characterization of Ent F-58 produced by Enterococcus faecium strain F58 isolated from Jben, a soft, farmhouse goat's cheese manufactured without starter cultures.

METHODS AND RESULTS

E. faecium strain F58 was isolated because of its broad inhibitory spectrum, including activity against food-borne pathogenic and spoilage bacteria. The antimicrobial substance was produced during the growth phase, with maximum production after 16-20 h of incubation at 30 degrees C, and was stable over a wide pH range (4-8) and at high temperatures (5 min at 100 degrees C). The enterocin was purified to homogeneity using cation exchange and hydrophobic interaction on C-18 and reverse-phase high-performance liquid chromatography. The activity was eluted as two individual active fractions (F-58A and F-58B) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis showed masses of 5210.5 and 5234.3 Da respectively. Both peptides were partially sequenced by Edman degradation, and amino-acid sequencing revealed high similarity with enterocin L50 (I). PCR-amplified fragments containing the structural genes for F-58 A and B were located in a 22-kb plasmid harboured by this strain. We verified that it also holds the structural gene for P-like enterocin.

CONCLUSION

E. faecium strain F58 from Jben cheese, a producer of enterocin L50, exerts an inhibitory effect against strains of genera such as Listeria, Staphylococcus, Clostridium, Brochothrix and Bacillus. Enterocin was characterized according to its functional and biological properties, purification to homogeneity and an analysis of its amino acid and genetic sequences.

SIGNIFICANCE AND IMPACT OF THE STUDY

E. faecium strain F58 is a newly discovered producer of enterocin L50, the biotechnological characteristics of which indicate its potential for application as a protective agent against pathogens and spoilage bacteria in foods.