Rihab Slama - Academia.edu (original) (raw)

Papers by Rihab Slama

Journal of Chemistry, 2013

The present study describes chemical composition as well as cytotoxic, antioxidant, and antimicro... more The present study describes chemical composition as well as cytotoxic, antioxidant, and antimicrobial activities of winter savorySatureja montanaL. essential oil (EO). The plant was collected from south France mountain, and its EO was extracted by hydrodistillation (HD) and analysed by gas chromatography/mass spectrometry (GC/MS). Thirty-two compounds were identified accounting for 99.85% of the total oil, where oxygenated monoterpenes constituted the main chemical class (59.11%). The oil was dominated by carvacrol (53.35%),γ-terpinene (13.54%), and the monoterpenic hydrocarbonsp-cymene (13.03%). Moreover,S. montanaL. EO exhibited high antibacterial activities with strong effectiveness against several pathogenic food isolatedSalmonellaspp. includingS. enteritidiswith a diameter of inhibition zones growth ranging from 21 to 51 mm and MIC and MBC values ranging from 0.39–1.56 mg/mL to 0.39–3.12 mg/mL, respectively. Furthermore, theS. montanaL. EO was investigated for its cytotoxic and...

Environmental toxicology and pharmacology, 2018

The production infrastructure in aquaculture invariably is a complex assortment of submerged comp... more The production infrastructure in aquaculture invariably is a complex assortment of submerged components with cages, nets, floats and ropes. Cages are generally made from polyamide or high density polyethylene (PEHD). All of these structures serve as surfaces for biofouling. However, cage nets and supporting infrastructure offer fouling organisms thousands of square meters of multifilament netting. That's why, before immersing them in seawater, they should be coated with an antifouling agent. It helps to prevent net occlusion and to increase its lifespan. Biofouling in marine aquaculture is a specific problem and has three main negative effects. It causes net occlusion and so restricts water and oxygen exchange. Besides, the low dissolved oxygen levels from poor water exchange increases the stress levels of fish, lowers immunity and increases vulnerability to disease. Also, the extra weight imposed by fouling causes cage deformation and structural fatigue. The maintenance and los...

Microbial Pathogenesis, 2016

In this study the minimal inhibitory concentration (MICs) of tetracycline (Tet), erythromycin (Er... more In this study the minimal inhibitory concentration (MICs) of tetracycline (Tet), erythromycin (Ery) and benzalkonium chloride (BC) in absence and in presence of a sub-MIC of juglone (Jug) were determined. In addition, the Ethidium bromide (EtBr) efflux assay was performed to assess the effect of Jug on EtBr cells accumulation. Our results showed a selective antimicrobial activity of Jug against the tested strains. A synergistic effect of Jug, drugs (Tet and Ery) and disinfectant (BC) was noticed with a reduction rate varied from 2 to 16-fold. In addition, the efflux of EtBr was inhibited depending on the Jug concentration. In the presence of Jug, a decrease in loss of EtBr from bacteria was observed. The concentration inducing 50 % of EtBr efflux inhibition after 15 min was about 182 μg mlfor S. aureus ATCC 25923, 236 μg mlfor S. aureus B193 and 195 μg ml for S. aureus B456. It appears from this study that Jug may be used as a natural source for resistance-modifying activity in same bacteria.

The Brazilian Journal of Infectious Diseases, 2016

Archives of Microbiology, 2016

Microbial Pathogenesis, 2016

In this study, three lactic acid bacteria (LAB), isolated from barley, traditional dried meat and... more In this study, three lactic acid bacteria (LAB), isolated from barley, traditional dried meat and fermented olive were characterized and tested for their anti-bacterial and anti-biofilm activities against oral bacteria. Our results revealed that the tested LAB were γ-hemolytic and were susceptible to four antibiotics. All the strains were resistant to low pH, bile salt, pepsin and pancreatin. Furthermore, FB2 displayed a high aut-oaggregative phenotype (99.54%) while FF2 exhibited the best co-aggregation rate. Concerning the microbial adhesion to solvent, FB2 was the most hydrophobic strain (data obtained with chloroform and n-hexadecane). In addition Pediococcus pentosaceus FB2 and Lactobacillus brevis FF2 displayed a significant inhibitory effect against Streptococcus salivarius B468 (MIC = 10%). Moreover the selected strains were able to inhibit biofilm formation of Bacillus cereus ATCC14579 (MBIC50 = 28.16%) and S. salivarius B468 (MBIC50 = 42.28%). The selected LAB could be considered as candidate probiotics for further application in functional food and mainly in the prevention of oral diseases.

Industrial Crops and Products, 2015

Microbial Pathogenesis, 2016

Plant extracts, and their essential oils (EOs) are rich in a wide variety of secondary metabolite... more Plant extracts, and their essential oils (EOs) are rich in a wide variety of secondary metabolites with antimicrobial properties. Our aim was to determine the bioactive compound in three mediterranean essential oils belonging to Lamiaceae family, Satureja montana L., Thymus vulgaris L. and Rosmarinus officinalis L., and to assess their antimicrobial, antibiofilm and anti-adhesive potentials against a foodborne pathogen Salmonella strain. The antibacterial activity of EOs and its biofilm inhibition potencies were investigated on 2 reference strains Salmonella typhimurium and 12 Salmonella spp. isolated from food. Biofilm inhibition were assessed using the 2, 3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) reduction assay. The analytical data indicated that various monoterpene hydrocarbons and phenolic monoterpenes constitute the major components of the oils, but their concentrations varied greatly among the oils examined. Our results showed that S. montana L. and T. vulgaris L. essential oils possess remarkable anti biofilm, anti-adhesive and bactericidal properties, compared to R. officinalis EO. There is an indication that Rosmary EO might inhibit biofilm formation at higher concentrations. Therefore, the witer savory and thyme EOs represent a source of natural compounds that exhibit potentials for use in food systems to prevent the growth of foodborne bacteria and extend the shelf life of the processed food.

Journal of Chemistry, 2013

ABSTRACT The present study describes chemical composition as well as cytotoxic, antioxidant, and ... more ABSTRACT The present study describes chemical composition as well as cytotoxic, antioxidant, and antimicrobial activities of winter savory Satureja montana L. essential oil (EO). The plant was collected from south France mountain, and its EO was extracted by hydrodistillation (HD) and analysed by gas chromatography/mass spectrometry (GC/MS). Thirty-two compounds were identified accounting for 99.85% of the total oil, where oxygenated monoterpenes constituted the main chemical class (59.11%). The oil was dominated by carvacrol (53.35%), -terpinene (13.54%), and the monoterpenic hydrocarbons p-cymene (13.03%). Moreover, S. montana L. EO exhibited high antibacterial activities with strong effectiveness against several pathogenic food isolated Salmonella spp. including S. enteritidis with a diameter of inhibition zones growth ranging from 21 to 51 mm and MIC and MBC values ranging from 0.39–1.56 mg/mL to 0.39–3.12 mg/mL, respectively. Furthermore, the S. montana L. EO was investigated for its cytotoxic and antioxidant activities. The results revealed a significant cytotoxic effect of S. montana L. EO against A549 cell line and an important antioxidant activity. These findings suggest that S. montana L. EO may be considered as an interesting source of components used as potent agents in food preservation and for therapeutic or nutraceutical industries.

Natural Science, 2013

The essential oil composition of Thymus vulgaris L. and Rosmarinus officinalis L. endemic to Fran... more The essential oil composition of Thymus vulgaris L. and Rosmarinus officinalis L. endemic to France were determined by GC and GC-MS. Oils were assessed for their cytotoxic, antioxidant and antimicrobial activity. 31 and 37 different compounds were identified representing 99.64% and 99.38% of the thyme and rosemary oils respectively, where oxygenated monoterpenes constituted the main chemical class. Thymol (41.33%) and 1.8-cineole (24.10%) were identified as the main constituents of T. vulgaris L. and R. officinalis L., respectively. Essential oils (EOs) of selected plant species were evaluated for their in vitro cytotoxicity against the human lung adenocarcinoma epithelial cell line (A549). Cytotoxicity was measured using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphynyltetra-zolium bromide] colorimetric assay. Dose-dependent studies revealed IC50 of 8.50 ± 0.01 μg/mL and 10.50 ± 0.01 μg/mL after 72 h on the A549 cells for R. officinalis L. and T. vulgaris L., respectively. Antioxidant activity was determined using a quantitative DPPH (1,1-diphenyl- 2-picryl hydrazyl) assay. Thymus and rosemary EOs exhibited effective radical scavenging capacity with 50% inhibitory concentration (IC50) of 437 ± 5.46 μg/mL and 189 ± 2.38 μg/mL respectively and therefore acts as a natural antioxidant agent. The antimicrobial activity of these species has also been studied against several foodborne pathogens and food isolated Salmonella spp. including S. enteritidis of significant importance. According to the results, T. vulgaris L. showed higher bactericidal effect than those from R. officinalis L. These results suggest that the essential oil from T. vulgaris L. and R. officinalis L. have potential to be used as a natural cytotoxic, antioxidant and antimicrobial agent in food processing.

Surface Innovations, 2014

Gold-and indium-tin-oxide (ITO)-coated glass plates grafted with polymer/Ag nanoparticle hybrid c... more Gold-and indium-tin-oxide (ITO)-coated glass plates grafted with polymer/Ag nanoparticle hybrid coatings were prepared and served as biocidal surfaces directed against two biofilm positive bacteria, namely L. monocytogenes ATCC 19115 and S.aureus ATCC25923. The polymer films were prepared by surface-initiated radical photopolymerization of methacrylic acid (MAA) and 2-hydroxyethyl methacrylate (HEMA) in the presence of gold or ITO surfaces grafted with photoinitiator groups from diazotized benzophenone or N,Ndimethylaminobenzenediazonium tetrafluoroborate (N 2 C 6 H 4 N(CH 3 ) 2 BF 4 ). The silver nanoparticles were generated in-situ on the polymer surfaces by reduction of silver nitrate. The degree of biofilm formation by L. monocytogenes ATCC 19115 and S.aureus ATCC25923 strains on these surfaces was evaluated. Viable attached cells were quantified using a colorimetric method based on the ability of viable attached cells to metabolically reduce 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) to a formazan dye. This study shows that diazonium salts permit to anchor robust hydrophilic coatings with immobilized silver nanoparticles of remarkable antifouling properties against pathogenic S. aureus and L. monocytogenes bacteria: antifouling due to both hydrophilic MAA and/or HEMA repeat units, and bactericidal due to the Ag NPs complexed by the COOH groups from MAA repeat units.

Journal of Herbs, Spices & Medicinal Plants, 2013

ABSTRACT Tunisian Juglans regia bark ethanol extract (JREE) was examined for antibacterial, antib... more ABSTRACT Tunisian Juglans regia bark ethanol extract (JREE) was examined for antibacterial, antibiofilm, and antioxidant activity. Its anti-proliferative effect was evaluated on normal (MRC-5) and cancer (HT29 and HEp-2) cell lines. The data revealed that JREE inhibited the growth of pathogenic bacteria (MICs value ranged from 32 to 128 μg.mL-1) and induced a strong antibiofilm effect (BIC50 was 23, 30, and 43 μg.mL-1 for Micrococcus luteus, Staphylococcus epidermidis, and Staphylococcus aureus, respectively). The JREE showed high scavenging property against 2,2-diphenyl-l-1-picrylhydrazil (DPPH) radical (IC50 = 3.5 μg.mL-1) and exhibited anti-proliferative effects with IC50 values ranging from 6.6 to 25.5 μg.mL-1.

Journal of Food Safety, 2013

ABSTRACT Three Lactobacilli were isolated from traditional Tunisian fermented food and then chara... more ABSTRACT Three Lactobacilli were isolated from traditional Tunisian fermented food and then characterized for its ability to inhibit Listeria monocytogenes growth. Antagonistic effect of Lactobacillus plantarum on four L. monocytogenes strains was tested in soft artisanal cheese. Anti-biofilm activity of Lactobacillus extracts was also tested. Our results demonstrate that the selected lactic acid bacteria (LAB) extract exhibited a good antibacterial effect against L. monocytogenes ATCC 19115 with low MICs values: 8.33 ± 2.1, 20 ± 1.2 and 23.33 ± 1, respectively. L. plantarum also exhibited a stronger inhibitory effect against L. monocytogenes when grown in cheese. Moreover, a potential anti-biofilm effect of the three LAB extracts with BIC50 values ranging from 5% to 15% for L. monocytogenes ATCC 19115 was demonstrated. Although LAB extracts were able to eradicate significantly a preformed L. monocytogenes biofilm (P < 0.05). Growth inhibition of preformed biofilm was more difficult to achieve. LAB could be used as a bioprotective culture in cheese ripening to prevent Listeria growth. A wide range of lactic acid bacteria (LAB) produce bacteriocins, which were essentially active against the food-borne pathogen Listeria monocytogenes. 2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction method was used to assess the anti-biofilm and anti-listerial activity of LAB extract. XTT reduction assay is dependent on the microbial respiratory activity. Since XTT is used for quantification of the microbial respiratory activity, it was used to quantify viable mature biofilm and to compare LAB activity against planktonic and biofilm cells.

Archives of Microbiology, 2013

The morphological changes and adhesive property of three Listeria monocytogenes strains submitted... more The morphological changes and adhesive property of three Listeria monocytogenes strains submitted to freezing stress (-20 °C) were studied. The atomic force micrographs showed a reduction in the cell size and an evolution to coccoid shape. The phenotypic slime production of L. monocytogenes and the expression of the adhesive gene were investigated before and after 10 months of incubation in salmon at -20°. Our results showed that after ten months, stressed stains become more adherent and able to produce slime. In addition, we noted that this pathogen presents same physiological changes to adapt to starvation conditions. The cellular fatty acids composition of adhered and floating cells of three L. monocytogenes strains was taken into consideration. The stressed strains presented different chain lengths and therefore an increase in the hydrophobicity level. Moreover, we noted that the adhesive property of L. monocytogenes strains affects the Benzalkonium chloride bacterial sensitivity which increased after biofilm formation.

Applied Biochemistry and Biotechnology, 2013

Listeria monocytogenes is the main bacteria incriminated in contaminating cold storage food and r... more Listeria monocytogenes is the main bacteria incriminated in contaminating cold storage food and ready-to-eat products. Survival of four L. monocytogenes food isolates was examined during freezing and cold storage. Slices of artisanal cheese were inoculated with Listeria strains and incubated at -20 °C. Their survival rate was recorded during the storage period. Then, transcript levels of four virulence genes (hlyA, iap, fri, and flaA) were evaluated using a semiquantitative reverse transcriptase PCR. Our results revealed that after 6 months of frozen storage, the number of L. monocytogenes cells had declined by 2.04 ± 0.1 log10 colony-forming units (CFU) g(-1), 2.52 ± 0.1 log10 CFU g(-1), and 2.58 ± 0.1 log10 CFU g(-1) for the strains S2, S3, and S4, respectively. Our data revealed that all the studied genes (hlyA, iap, fri, and flaA) were expressed after 6 months of incubation in artisanal cheese at -20 °C, and the transcript level has been affected by the factor freezing, whether for the reference strain ATCC 19115 or for other isolates. The iap gene expression was decreased for the four strains after 6 months of storage, and hlyA expression rate was consistently slightly lower. Transcript levels of fri and flaA genes were consistently higher in L. monocytogenes cells before cold exposure than in stressed cells and were significantly affected by the freezing process.

African Journal of Microbiology Research, 2012

The aim of this study is to give insight about the effect of long marine stress starvation condit... more The aim of this study is to give insight about the effect of long marine stress starvation conditions in the physiological responses of three potential halophilic probiotic Bacillus isolates isolated from Artemia culture. Bacteria were cultured in sterilized seawater and incubated at ambient temperature for one year. The obtained results showed that the isolates viability was maintained during the studied period. Compared to normal cells, starved cells increased their adhesive ability and cell surface hydrophobicity. Our data demonstrated that the tested isolates maintained their enzymatic profile in non-starvation conditions and under stress conditions they expressed enzymes like esterase lipase (C8), amylase, lipase, and caseinase. The present finding suggests that the tested strains have developed strategies that allow them to overcome stressful conditions in the absence of nutrients and makes them as a potential candidate probiotics.

Microbial Pathogenesis, 2014

The occurrence of several microbial species in the oral cavity of 4-12-year-old Tunisian children... more The occurrence of several microbial species in the oral cavity of 4-12-year-old Tunisian children was investigated. Samples were taken from 158 children (81 caries actives and 77 caries free). Genomic DNA was extracted and analyzed for the presence of 17 microbial species using a polymerase chain reaction assay. All samples were positive for at least one of the target microbial strains. Streptococcus mutans was the most prevalent species (76.5%) detected in genomic DNA collected from carious lesions. Other prevalent species were Candida spp (63%), Streptococcus salivarius (59%) and Streptococcus oralis (42%). The frequency of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus casei-group in caries lesions was 29.5%, 34.5% and 22% respectively. Pathogenic bacteria such as Staphylococcus aureus was found in 28.5% of carious lesion samples compared to 15.5% in the control. Frequency of Porphyromonas endodontali, Actinomyces radicidentis and Treponema denticola recovery did not differ significantly between origins of samples. PCR analysis of genomic DNA detect various oral bacteria that differ between caries actives and caries-free children. In addition, the association of same aciduric bacteria (S. mutans, S. salivarius, L. acidophilus) and caries formation was noticed.

Journal of Chemistry, 2013

The present study describes chemical composition as well as cytotoxic, antioxidant, and antimicro... more The present study describes chemical composition as well as cytotoxic, antioxidant, and antimicrobial activities of winter savorySatureja montanaL. essential oil (EO). The plant was collected from south France mountain, and its EO was extracted by hydrodistillation (HD) and analysed by gas chromatography/mass spectrometry (GC/MS). Thirty-two compounds were identified accounting for 99.85% of the total oil, where oxygenated monoterpenes constituted the main chemical class (59.11%). The oil was dominated by carvacrol (53.35%),γ-terpinene (13.54%), and the monoterpenic hydrocarbonsp-cymene (13.03%). Moreover,S. montanaL. EO exhibited high antibacterial activities with strong effectiveness against several pathogenic food isolatedSalmonellaspp. includingS. enteritidiswith a diameter of inhibition zones growth ranging from 21 to 51 mm and MIC and MBC values ranging from 0.39–1.56 mg/mL to 0.39–3.12 mg/mL, respectively. Furthermore, theS. montanaL. EO was investigated for its cytotoxic and...

Environmental toxicology and pharmacology, 2018

The production infrastructure in aquaculture invariably is a complex assortment of submerged comp... more The production infrastructure in aquaculture invariably is a complex assortment of submerged components with cages, nets, floats and ropes. Cages are generally made from polyamide or high density polyethylene (PEHD). All of these structures serve as surfaces for biofouling. However, cage nets and supporting infrastructure offer fouling organisms thousands of square meters of multifilament netting. That's why, before immersing them in seawater, they should be coated with an antifouling agent. It helps to prevent net occlusion and to increase its lifespan. Biofouling in marine aquaculture is a specific problem and has three main negative effects. It causes net occlusion and so restricts water and oxygen exchange. Besides, the low dissolved oxygen levels from poor water exchange increases the stress levels of fish, lowers immunity and increases vulnerability to disease. Also, the extra weight imposed by fouling causes cage deformation and structural fatigue. The maintenance and los...

Microbial Pathogenesis, 2016

In this study the minimal inhibitory concentration (MICs) of tetracycline (Tet), erythromycin (Er... more In this study the minimal inhibitory concentration (MICs) of tetracycline (Tet), erythromycin (Ery) and benzalkonium chloride (BC) in absence and in presence of a sub-MIC of juglone (Jug) were determined. In addition, the Ethidium bromide (EtBr) efflux assay was performed to assess the effect of Jug on EtBr cells accumulation. Our results showed a selective antimicrobial activity of Jug against the tested strains. A synergistic effect of Jug, drugs (Tet and Ery) and disinfectant (BC) was noticed with a reduction rate varied from 2 to 16-fold. In addition, the efflux of EtBr was inhibited depending on the Jug concentration. In the presence of Jug, a decrease in loss of EtBr from bacteria was observed. The concentration inducing 50 % of EtBr efflux inhibition after 15 min was about 182 μg mlfor S. aureus ATCC 25923, 236 μg mlfor S. aureus B193 and 195 μg ml for S. aureus B456. It appears from this study that Jug may be used as a natural source for resistance-modifying activity in same bacteria.

The Brazilian Journal of Infectious Diseases, 2016

Archives of Microbiology, 2016

Microbial Pathogenesis, 2016

In this study, three lactic acid bacteria (LAB), isolated from barley, traditional dried meat and... more In this study, three lactic acid bacteria (LAB), isolated from barley, traditional dried meat and fermented olive were characterized and tested for their anti-bacterial and anti-biofilm activities against oral bacteria. Our results revealed that the tested LAB were γ-hemolytic and were susceptible to four antibiotics. All the strains were resistant to low pH, bile salt, pepsin and pancreatin. Furthermore, FB2 displayed a high aut-oaggregative phenotype (99.54%) while FF2 exhibited the best co-aggregation rate. Concerning the microbial adhesion to solvent, FB2 was the most hydrophobic strain (data obtained with chloroform and n-hexadecane). In addition Pediococcus pentosaceus FB2 and Lactobacillus brevis FF2 displayed a significant inhibitory effect against Streptococcus salivarius B468 (MIC = 10%). Moreover the selected strains were able to inhibit biofilm formation of Bacillus cereus ATCC14579 (MBIC50 = 28.16%) and S. salivarius B468 (MBIC50 = 42.28%). The selected LAB could be considered as candidate probiotics for further application in functional food and mainly in the prevention of oral diseases.

Industrial Crops and Products, 2015

Microbial Pathogenesis, 2016

Plant extracts, and their essential oils (EOs) are rich in a wide variety of secondary metabolite... more Plant extracts, and their essential oils (EOs) are rich in a wide variety of secondary metabolites with antimicrobial properties. Our aim was to determine the bioactive compound in three mediterranean essential oils belonging to Lamiaceae family, Satureja montana L., Thymus vulgaris L. and Rosmarinus officinalis L., and to assess their antimicrobial, antibiofilm and anti-adhesive potentials against a foodborne pathogen Salmonella strain. The antibacterial activity of EOs and its biofilm inhibition potencies were investigated on 2 reference strains Salmonella typhimurium and 12 Salmonella spp. isolated from food. Biofilm inhibition were assessed using the 2, 3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) reduction assay. The analytical data indicated that various monoterpene hydrocarbons and phenolic monoterpenes constitute the major components of the oils, but their concentrations varied greatly among the oils examined. Our results showed that S. montana L. and T. vulgaris L. essential oils possess remarkable anti biofilm, anti-adhesive and bactericidal properties, compared to R. officinalis EO. There is an indication that Rosmary EO might inhibit biofilm formation at higher concentrations. Therefore, the witer savory and thyme EOs represent a source of natural compounds that exhibit potentials for use in food systems to prevent the growth of foodborne bacteria and extend the shelf life of the processed food.

Journal of Chemistry, 2013

ABSTRACT The present study describes chemical composition as well as cytotoxic, antioxidant, and ... more ABSTRACT The present study describes chemical composition as well as cytotoxic, antioxidant, and antimicrobial activities of winter savory Satureja montana L. essential oil (EO). The plant was collected from south France mountain, and its EO was extracted by hydrodistillation (HD) and analysed by gas chromatography/mass spectrometry (GC/MS). Thirty-two compounds were identified accounting for 99.85% of the total oil, where oxygenated monoterpenes constituted the main chemical class (59.11%). The oil was dominated by carvacrol (53.35%), -terpinene (13.54%), and the monoterpenic hydrocarbons p-cymene (13.03%). Moreover, S. montana L. EO exhibited high antibacterial activities with strong effectiveness against several pathogenic food isolated Salmonella spp. including S. enteritidis with a diameter of inhibition zones growth ranging from 21 to 51 mm and MIC and MBC values ranging from 0.39–1.56 mg/mL to 0.39–3.12 mg/mL, respectively. Furthermore, the S. montana L. EO was investigated for its cytotoxic and antioxidant activities. The results revealed a significant cytotoxic effect of S. montana L. EO against A549 cell line and an important antioxidant activity. These findings suggest that S. montana L. EO may be considered as an interesting source of components used as potent agents in food preservation and for therapeutic or nutraceutical industries.

Natural Science, 2013

The essential oil composition of Thymus vulgaris L. and Rosmarinus officinalis L. endemic to Fran... more The essential oil composition of Thymus vulgaris L. and Rosmarinus officinalis L. endemic to France were determined by GC and GC-MS. Oils were assessed for their cytotoxic, antioxidant and antimicrobial activity. 31 and 37 different compounds were identified representing 99.64% and 99.38% of the thyme and rosemary oils respectively, where oxygenated monoterpenes constituted the main chemical class. Thymol (41.33%) and 1.8-cineole (24.10%) were identified as the main constituents of T. vulgaris L. and R. officinalis L., respectively. Essential oils (EOs) of selected plant species were evaluated for their in vitro cytotoxicity against the human lung adenocarcinoma epithelial cell line (A549). Cytotoxicity was measured using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphynyltetra-zolium bromide] colorimetric assay. Dose-dependent studies revealed IC50 of 8.50 ± 0.01 μg/mL and 10.50 ± 0.01 μg/mL after 72 h on the A549 cells for R. officinalis L. and T. vulgaris L., respectively. Antioxidant activity was determined using a quantitative DPPH (1,1-diphenyl- 2-picryl hydrazyl) assay. Thymus and rosemary EOs exhibited effective radical scavenging capacity with 50% inhibitory concentration (IC50) of 437 ± 5.46 μg/mL and 189 ± 2.38 μg/mL respectively and therefore acts as a natural antioxidant agent. The antimicrobial activity of these species has also been studied against several foodborne pathogens and food isolated Salmonella spp. including S. enteritidis of significant importance. According to the results, T. vulgaris L. showed higher bactericidal effect than those from R. officinalis L. These results suggest that the essential oil from T. vulgaris L. and R. officinalis L. have potential to be used as a natural cytotoxic, antioxidant and antimicrobial agent in food processing.

Surface Innovations, 2014

Gold-and indium-tin-oxide (ITO)-coated glass plates grafted with polymer/Ag nanoparticle hybrid c... more Gold-and indium-tin-oxide (ITO)-coated glass plates grafted with polymer/Ag nanoparticle hybrid coatings were prepared and served as biocidal surfaces directed against two biofilm positive bacteria, namely L. monocytogenes ATCC 19115 and S.aureus ATCC25923. The polymer films were prepared by surface-initiated radical photopolymerization of methacrylic acid (MAA) and 2-hydroxyethyl methacrylate (HEMA) in the presence of gold or ITO surfaces grafted with photoinitiator groups from diazotized benzophenone or N,Ndimethylaminobenzenediazonium tetrafluoroborate (N 2 C 6 H 4 N(CH 3 ) 2 BF 4 ). The silver nanoparticles were generated in-situ on the polymer surfaces by reduction of silver nitrate. The degree of biofilm formation by L. monocytogenes ATCC 19115 and S.aureus ATCC25923 strains on these surfaces was evaluated. Viable attached cells were quantified using a colorimetric method based on the ability of viable attached cells to metabolically reduce 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) to a formazan dye. This study shows that diazonium salts permit to anchor robust hydrophilic coatings with immobilized silver nanoparticles of remarkable antifouling properties against pathogenic S. aureus and L. monocytogenes bacteria: antifouling due to both hydrophilic MAA and/or HEMA repeat units, and bactericidal due to the Ag NPs complexed by the COOH groups from MAA repeat units.

Journal of Herbs, Spices & Medicinal Plants, 2013

ABSTRACT Tunisian Juglans regia bark ethanol extract (JREE) was examined for antibacterial, antib... more ABSTRACT Tunisian Juglans regia bark ethanol extract (JREE) was examined for antibacterial, antibiofilm, and antioxidant activity. Its anti-proliferative effect was evaluated on normal (MRC-5) and cancer (HT29 and HEp-2) cell lines. The data revealed that JREE inhibited the growth of pathogenic bacteria (MICs value ranged from 32 to 128 μg.mL-1) and induced a strong antibiofilm effect (BIC50 was 23, 30, and 43 μg.mL-1 for Micrococcus luteus, Staphylococcus epidermidis, and Staphylococcus aureus, respectively). The JREE showed high scavenging property against 2,2-diphenyl-l-1-picrylhydrazil (DPPH) radical (IC50 = 3.5 μg.mL-1) and exhibited anti-proliferative effects with IC50 values ranging from 6.6 to 25.5 μg.mL-1.

Journal of Food Safety, 2013

ABSTRACT Three Lactobacilli were isolated from traditional Tunisian fermented food and then chara... more ABSTRACT Three Lactobacilli were isolated from traditional Tunisian fermented food and then characterized for its ability to inhibit Listeria monocytogenes growth. Antagonistic effect of Lactobacillus plantarum on four L. monocytogenes strains was tested in soft artisanal cheese. Anti-biofilm activity of Lactobacillus extracts was also tested. Our results demonstrate that the selected lactic acid bacteria (LAB) extract exhibited a good antibacterial effect against L. monocytogenes ATCC 19115 with low MICs values: 8.33 ± 2.1, 20 ± 1.2 and 23.33 ± 1, respectively. L. plantarum also exhibited a stronger inhibitory effect against L. monocytogenes when grown in cheese. Moreover, a potential anti-biofilm effect of the three LAB extracts with BIC50 values ranging from 5% to 15% for L. monocytogenes ATCC 19115 was demonstrated. Although LAB extracts were able to eradicate significantly a preformed L. monocytogenes biofilm (P < 0.05). Growth inhibition of preformed biofilm was more difficult to achieve. LAB could be used as a bioprotective culture in cheese ripening to prevent Listeria growth. A wide range of lactic acid bacteria (LAB) produce bacteriocins, which were essentially active against the food-borne pathogen Listeria monocytogenes. 2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide (XTT) reduction method was used to assess the anti-biofilm and anti-listerial activity of LAB extract. XTT reduction assay is dependent on the microbial respiratory activity. Since XTT is used for quantification of the microbial respiratory activity, it was used to quantify viable mature biofilm and to compare LAB activity against planktonic and biofilm cells.

Archives of Microbiology, 2013

The morphological changes and adhesive property of three Listeria monocytogenes strains submitted... more The morphological changes and adhesive property of three Listeria monocytogenes strains submitted to freezing stress (-20 °C) were studied. The atomic force micrographs showed a reduction in the cell size and an evolution to coccoid shape. The phenotypic slime production of L. monocytogenes and the expression of the adhesive gene were investigated before and after 10 months of incubation in salmon at -20°. Our results showed that after ten months, stressed stains become more adherent and able to produce slime. In addition, we noted that this pathogen presents same physiological changes to adapt to starvation conditions. The cellular fatty acids composition of adhered and floating cells of three L. monocytogenes strains was taken into consideration. The stressed strains presented different chain lengths and therefore an increase in the hydrophobicity level. Moreover, we noted that the adhesive property of L. monocytogenes strains affects the Benzalkonium chloride bacterial sensitivity which increased after biofilm formation.

Applied Biochemistry and Biotechnology, 2013

Listeria monocytogenes is the main bacteria incriminated in contaminating cold storage food and r... more Listeria monocytogenes is the main bacteria incriminated in contaminating cold storage food and ready-to-eat products. Survival of four L. monocytogenes food isolates was examined during freezing and cold storage. Slices of artisanal cheese were inoculated with Listeria strains and incubated at -20 °C. Their survival rate was recorded during the storage period. Then, transcript levels of four virulence genes (hlyA, iap, fri, and flaA) were evaluated using a semiquantitative reverse transcriptase PCR. Our results revealed that after 6 months of frozen storage, the number of L. monocytogenes cells had declined by 2.04 ± 0.1 log10 colony-forming units (CFU) g(-1), 2.52 ± 0.1 log10 CFU g(-1), and 2.58 ± 0.1 log10 CFU g(-1) for the strains S2, S3, and S4, respectively. Our data revealed that all the studied genes (hlyA, iap, fri, and flaA) were expressed after 6 months of incubation in artisanal cheese at -20 °C, and the transcript level has been affected by the factor freezing, whether for the reference strain ATCC 19115 or for other isolates. The iap gene expression was decreased for the four strains after 6 months of storage, and hlyA expression rate was consistently slightly lower. Transcript levels of fri and flaA genes were consistently higher in L. monocytogenes cells before cold exposure than in stressed cells and were significantly affected by the freezing process.

African Journal of Microbiology Research, 2012

The aim of this study is to give insight about the effect of long marine stress starvation condit... more The aim of this study is to give insight about the effect of long marine stress starvation conditions in the physiological responses of three potential halophilic probiotic Bacillus isolates isolated from Artemia culture. Bacteria were cultured in sterilized seawater and incubated at ambient temperature for one year. The obtained results showed that the isolates viability was maintained during the studied period. Compared to normal cells, starved cells increased their adhesive ability and cell surface hydrophobicity. Our data demonstrated that the tested isolates maintained their enzymatic profile in non-starvation conditions and under stress conditions they expressed enzymes like esterase lipase (C8), amylase, lipase, and caseinase. The present finding suggests that the tested strains have developed strategies that allow them to overcome stressful conditions in the absence of nutrients and makes them as a potential candidate probiotics.

Microbial Pathogenesis, 2014

The occurrence of several microbial species in the oral cavity of 4-12-year-old Tunisian children... more The occurrence of several microbial species in the oral cavity of 4-12-year-old Tunisian children was investigated. Samples were taken from 158 children (81 caries actives and 77 caries free). Genomic DNA was extracted and analyzed for the presence of 17 microbial species using a polymerase chain reaction assay. All samples were positive for at least one of the target microbial strains. Streptococcus mutans was the most prevalent species (76.5%) detected in genomic DNA collected from carious lesions. Other prevalent species were Candida spp (63%), Streptococcus salivarius (59%) and Streptococcus oralis (42%). The frequency of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus casei-group in caries lesions was 29.5%, 34.5% and 22% respectively. Pathogenic bacteria such as Staphylococcus aureus was found in 28.5% of carious lesion samples compared to 15.5% in the control. Frequency of Porphyromonas endodontali, Actinomyces radicidentis and Treponema denticola recovery did not differ significantly between origins of samples. PCR analysis of genomic DNA detect various oral bacteria that differ between caries actives and caries-free children. In addition, the association of same aciduric bacteria (S. mutans, S. salivarius, L. acidophilus) and caries formation was noticed.