Emira Noumi

Chemical composition and biological activities of Tunisian Cuminum cyminum L. essential oil: A high effectiveness against Vibrio spp. strains

Essential oil extracted by hydrodistillation from Tunisian variety of Cuminumcyminum was characterized by means of GC and GC-MS. Twenty-one components were identified and C. cyminum contained cuminlaldehyde (39.48%), gamma-terpinene (15.21%), O-cymene (11.82%), beta-pinene (11.13%), 2-caren-10-al (7.93%), trans-carveol (4.49%) and myrtenal (3.5%) as a major components. Moreover, C. cyminum oil exhibited higher antibacterial and antifungal activities with a high effectiveness against Vibrio spp. strains with a diameter of inhibition zones growth ranging from 11 to 23 mm and MIC and MBC values ranging from (0.078-0.31 mg/ml) to (0.31-1.25mg/ml), respectively. On the other hand, the cumin oil was investigated for its antioxidant activities using four different tests then compared with BHT. Results showed that cumin oil exhibit a higher activity in each antioxidant system with a special attention for beta-carotene bleaching test (IC(50): 20 microg/ml) and reducing power (EC(50): 11 microg/ml). In the light of these findings, we suggested that C. cyminum essential oil may be considered as an interesting source of antibacterial, antifungal and antioxidants components used as potent agents in food preservation and for therapeutic or nutraceutical industries.

Mentha spicata Essential Oil: Chemical Composition, Antioxidant and Antibacterial Activities against Planktonic and Biofilm Cultures of Vibrio spp. Strains.

Chemical composition, antioxidant and anti-Vibrio spp. activities of the essential oil isolated from the aerial parts of Mentha spicata L. (spearmint) are investigated in the present study. The effect of the essential oil on Vibrio spp. biofilm inhibition and eradication was tested using the XTT assay. A total of 63 chemical constituents were identified in spearmint oil using GC/MS, constituting 99.9% of the total identified compounds. The main components were carvone (40.8% ± 1.23%) and limonene (20.8% ± 1.12%). The antimicrobial activity against 30 Vibrio spp. strains (16 species) was evaluated by disc diffusion and microdilution assays. All microorganisms were strongly affected, indicating an appreciable antimicrobial potential of the oil. Moreover, the investigated oil exhibited high antioxidant potency, as assessed by four different tests in comparison with BHT. The ability of the oil, belonging to the carvone chemotype, to inhibit or reduce Vibrio spp. biofilm warrants further investigation to explore the use of natural products in antibiofilm adhesion and reinforce the possibility of its use in the pharmaceutical or food industry as a natural antibiotic and seafood preservative against Vibrio contamination.

Phenotypic and genetic diversity of Vibrio alginolyticus strains recovered from juveniles and older Sparus aurata reared in a Tunisian marine farm

This study characterises 43Vibrio alginolyticus strains associated with diseased juveniles and older fish ofSparus aurata reared in a marine hatchery installed along the seacoasts of Monastir (Centre of Tunisia).Vibrio alginolyticus strains were isolated using the TCBS modified agar plates and the biochemical activities were tested using the API 20 E strips. The exoenzymes production and antibiotics susceptibility were also investigated. The ERIC-PCR was used to evaluate the genetic diversity of these strains.Vibrio alginolyticus was isolated from seawater (n=16), juveniles with white nodular skin lesions (n=9) and from all the internal organs of the older fish presenting a large and deep lesions in the muscle and with a necrotic eyes (n=18). Most of the studiedV. alginolyticus strains were β-haemolytic, hydrolyze the DNA and produce many exoenzymes such as lecithinase, caseinase, amylase and lipase. All tested strains were resistant to at least three antimicrobial agents. The ERIC-PCR profiles among the isolated bacteria were generally heterogeneous, showing a high polymorphism and suggesting independent circulation with some evidence of cross-transmission.

High potential of adhesion to abiotic and biotic materials in fish aquaculture facility by Vibrio alginolyticus strains.

Aims:  The ability of Vibrio alginolyticus strains isolated from Sparus aurata and Dicentrarchus labrax nursery to adhere to epithelial cell lines (Hep‐2 and Caco‐2), fish mucus and their ability to form a biofilm on different surfaces (glass, polystyrene, polyethylene and polyvinyl‐chloride) was investigated in this study.

Phenotypic characterization and enterobacterial repetitive intergenic consensus polymerase chain reaction (eric-pcr) of Aeromonas spp. and Vibrio spp. strains isolated from Sparus aurata fish farm (Khenis, Tunisia)

This study characterises the Aeromonas and Vibrio strains isolated from seawater and sediments out of Sparus aurata marine farm. The bacterial strains were isolated on Thiosulfate-Citrate-Bile-Sucrose (TCBS) agar plates and described using different bacteriological tests and using standardised micromethods “API 20 NE strips”. The exoenzymes production and antibiotics susceptibility were also investigated. The enterobacterial repetitive intergenic consensus (ERIC)-PCR was used to evaluate the genetic diversity of the isolated strains. Two dominant genera of bacteria were found (Aeromonas and Vibrio). Aeromonas hydrophila strains were the dominant bacteria (56.5% of total isolates) followed by V. alginolyticus strains (26.1%). Most of the studied strains were -haemolytic, hydrolyze the DNA and produce many exoenzymes such as lecithinase, caseinase, amylase and lipase. All tested strains were resistant to at least three antimicrobial agents. The antibiotic resistance index was 0.683 for V. alginolyticus and 0.711 for A. hydrophila strains. The ERIC-PCR profiles among the isolated bacteria were generally heterogeneous, showing a high polymorphism between Aeromonas strains.

Assessment of the antibiofilm and antiquorum sensing activities of Eucalyptus globulus essential oil and its main component 1,8-cineole against methicillin-resistant Staphylococcus aureus strains

Antibacterial resistance is an increasingly serious threat to global public health. The search for new anti-infection agents from natural resources, with different mode of actions and competitive effects became a necessity. In this study, twenty height methicillin-resistant Staphylococcus aureus (MRSA) strains were investigated for their biofilm formation ability. Subsequently, the antibiofilm effects of Eucalyptus globulus essential oil and its main component 1,8-cineole, against MRSA, as well as their antiquorum sensing potential, were evaluated. Our results displayed the potent efficacy of both E. globulus essential oil and 1,8-cineole against the development of biofilms formed by the methicillin-resistant strains. Additionally, E. globulus essential oil showed more potent of anti-QS activity, even at a low concentration, when compared to 1,8-cineole. All these property of tested agents may pave the way to prevent the development of biofilm formation by MRSA and subsequently the spreading of nosocomial infection.

Chromobacterium violaceum and Pseudomonas aeruginosa PAO1: Models for Evaluating Anti-Quorum Sensing Activity of Melaleuca alternifolia Essential Oil and Its Main Component Terpinen-4-ol

The problem of antibiotic resistance among pathogens encourages searching for novel active molecules. The aim of the research was to assay the anti-quorum sensing (anti-QS) and antibiofilm potential of Melaleuca alternifolia essential oil and its main constituent, terpinen-4-ol, to prevent the infections due to methicillin-resistant Staphylococcus aureus strains as an alternate to antibiotics. The tea tree oil (TTO) was evaluated for its potential in inhibiting QS-dependent phenomena such as violacein production in Chromobacterium violaceum, swarming motility of Pseudomonas aeruginosa PAO1, and biofilm formation in MRSA strains on glass. The results showed that terpinen-4-ol was able to inhibit MRSA strain biofilm formation on the glass strips by 73.70%. TTO inhibited the violacein production at a mean inhibitory concentration (MIC) value of 0.048 mg/mL by 69.3%. At 100 µg/mL TTO and terpinen-4-ol exhibited inhibition in swarming motility of PAO1 by 33.33% and 25%, respectively. TTO revealed anti-QS and anti-biofilm activities at very low concentrations, but it could be further investigated for new molecules useful for the treatment of MRSA infections.

Phenotypic characterization and adhesive properties of vaginal Candida spp. strains provided by the CHU Farhat Hached (Sousse, Tunisia).

BACKGROUND Vulvovaginal candidiasis is a common infection among women worldwide, being Candida albicans the most commonly isolated species. Therefore, controlling this opportunistic yeast is one of the key factors for reducing nosocomial infection. AIMS We investigated several virulence properties of 28 vaginal strains of Candida isolated from Tunisian women suffering from vulvovaginitis. We also analyzed the virulence properties of a clinical Candida krusei strain and five Candida reference strains. METHODS Candida strains were subjected to microscopic analysis and culture in Candida ID2 chromogenic medium. The adhesive properties of these strains were estimated by the microtiter plate - the safranin-staining - and the Congo red agar (CRA) methods, for determining yeast ability to form biofilms on biomaterials used in urinary catheter manufacturing. Their potency to produce hydrolytic enzymes was also studied. RESULTS Our results showed that nine out of the total studied strains produced phospholipase. In addition, very high protease activity was detected in 23 Candida strains. All Candida strains were beta-hemolytic and adhered to polystyrene microtiter plates in varying degrees. Two vaginal C. albicans strains were strongly adhesive to polystyrene and glass slides. Also, our results showed that vaginal Candida strains were more adhesive to the three tested materials than the reference strains. CONCLUSIONS This study shows the presence of a range of virulence and adhesion factors in clinical isolates of vaginal Candida. Consequently, control and treatment of vaginal candidiasis as a means to prevent biofilm formation on urinary catheters is of crucial importance.

Effect of glucose supplementation on Candida albicans virulence in immunosuppressed Swiss albino mice (Mus musculus )

Laboratoire d’Analyse, Traitement et Valorisation des Polluants de l’Environnement et des Produits, Departement de Microbiologie, Faculte de Pharmacie, Rue Avicenne, Monastir 5000, Tunisie. Laboratoire d’Histologie-Embryologie, Faculte de Medecine Dentaire, Monastir 5000, Tunisie. Groupe de Recherche en Ecologie Buccale, Faculte de Medecine Dentaire, Universite Laval Quebec (Quebec), G1V 0A6, Canada.