Effect of Citrus aurantium L. Essential Oil on Streptococcus mutans Growth, Biofilm Formation and Virulent Genes Expression.

In an oral cavity, dental caries, periodontal disease, and endodontic lesions are caused by well-known bacterial and fungal pathogens. Essential oils (EOs) have demonstrated antimicrobial activity suggesting their use for oral hygiene. The goal of this study was to evaluate the interaction of bitter orange flower (Citrus aurantium L.) essential oil with cariogenic bacteria Streptococcus mutans and human gingival epithelial cells. After extraction, the chemical composition of the essential oil was analyzed by gas chromatography, and its antimicrobial activity was evaluated against the growth and the expression of virulent genes in S. mutans. Finally, the effects of this essential oil on human gingival epithelial cell adhesion and growth were assessed using cell adhesion and proliferation assays. We showed that the major constituents of the tested essential oil were limonene, linalool, and ß-ocimene. The essential oil reduced the growth of S. mutans, and decreased expression of comC, comD, comE, gtfB, gtfC, and gbpB genes. It should, however, be noted that essential oil at high concentration was toxic to gingival epithelial cells. Overall, this study suggests that C. aurantium L. essential oil could be used to prevent/control oral infections.

The Effects of Mentha × piperita Essential Oil on C. albicans Growth, Transition, Biofilm Formation, and the Expression of Secreted Aspartyl Proteinases Genes.

The rise in resistance and changes in the spectrum of Candida infections have generated enormous interest in developing new antifungal drugs using natural molecules such as plant essential oils (EOs). Antimicrobial activity against foodborne pathogenic and spoilage microorganisms has been reported for EOs. The goal of this study was to assess the effect of Mentha × piperita essential oil (EO) on C. albicans growth, transition (change from blastospore to hyphae forms), and biofilm formation as well as on the expression of certain virulent genes. We show that whole EO and its vapor attenuated the yeast's growth, compared to that in the control. The effect of the EO was comparable to that of amphotericin-B (AmB). The EO and its vapor significantly decreased the morphological changes of C. albicans, reduced biofilm formation, and disrupted mature C. albicans biofilms. The effect produced by whole EO on biofilm formation/disruption was notably comparable to that observed with AmB. Exposure of C. albicans to EO and its vapor downregulated the expression of various genes, such as secreted aspartyl proteinases (SAP 1, 2, 3, 9, 10) and hyphal wall protein 1 (HWP1). Altogether, these results provide new insight into the efficacy of Mentha × piperita EO against C. albicans and suggest the potential of Mentha × piperita EO for use as an antifungal therapy in multiple applications.

Isolation, purification, structural elucidation and antimicrobial activities of kocumarin, a novel antibiotic isolated from actinobacterium Kocuria marina CMG S2 associated with the brown seaweed Pelvetia canaliculata.

AIMS: Screening of seaweed-associated bacteria capable of producing antimicrobials. METHODS AND RESULTS: Fifteen microbial strains, associated to the brown seaweed Pelvetia canaliculata (Linnaeus) attached to the rocks of Sonmiani Beach (Karachi, Pakistan), were screened. Crude extract filtrates of CMG S2 strain grew on Zobell marine agar (ZMA) had the most remarkable antimicrobial activity. Based on its phenotypic aspects (e.g. Gram-positive, microccoid form), biochemical characteristics (e.g. halotolerance) and genetic analyses, CMG S2 is identified as a putatively new Kocuria marina type strain belonging to the actinobacteria's class and micrococcaceae family. Thereby, the nucleotide sequence analysis of its full-length 16S ribosomal ribonucleic acid (rRNA) gene (GenBank accession number EU073966.1) displayed highest identity (i.e. 99%) and score (2630) with K. marina KMM 3905. Phylogenic trees analysis using the neighbor-joining method showed closest evolutionary distance of CMG S2 with KMM 3905 strain and K. carniphila (DC2201) specie. Interestingly, a unique ultraviolet (UV)-bioactive compound was purified from CMG S2 crude extracts by flash silica gel column and thin-layer chromatography (TLC) techniques. Its chemical structure was unraveled as 4-[(Z)-2 phenyl ethenyl] benzoic acid (PEBA, later named kocumarin) by nuclear magnetic resonance (NMR) spectroscopy techniques. Importantly, kocumarin demonstrated prominent and rapid growth inhibition against all tested fungi and pathogenic bacteria including methicillin-resistant Staphylococcus aureus (MRSA), with a minimal fungal inhibitory concentration (MFC) of 15-25µg/mL and a minimal (bacterial) inhibitory concentration (MIC) of 10-15µg/mL. SIGNIFICANCE AND IMPACT OF THE STUDY: Kocumarin represents a new promising natural antibiotic for in vivo and environmental applications.

A study of pH effects on the bacterial surface physicochemical properties of Acinetobacter baumannii.

The first step in the biofilm formation is the bacterial attachment to solid surfaces, which is dependent on the bacteria cell surface physico-chemical properties. The purpose of this work was to analyze the effect of pH on the physicochemical cell surface properties of Acinetobacter baumannii by two different methods. The cell surface properties were evaluated using the microbial adhesion to solvents method (MATS) and contact angle measurements (CAM). MATS technique allowed us to enlighten that A. baumannii was hydrophilic at the different values of pH. It was found that at a desired pH of 6.5, the strain presents a maximum and stable value of electron-donor characteristic, while the electron acceptor character increased as the pH increased. Regardless of the methods employed, the obtained results using MATS and CAM confirmed the influence of the pH on the surface physicochemical properties of A. baumannii. The cell surface electron-donor and electron-acceptor character at pH 6.5 was found to be quite similar using both methods.

Characterization of bacterial biofilms formed on urinary catheters.

BACKGROUND: The formation of bacterial biofilms on urinary catheters is a leading cause of urinary tract infections in intensive care units. Cytobacteriological examination of urine from patients is often misleading, due to the formation of these biofilms. Therefore, characterizing these biofilms and identifying the bacterial species residing on the surface of catheters are of major importance. METHODS: We studied the formation of biofilms on the inner surface of urinary catheters using microbiological culture techniques, with the direct contact of catheter pieces with blood agar. The bacterial species on the surface were characterized by scanning electron microscopy, and the kinetic profile of biofilm formation on a silicone substrate for an imipenem-resistant Acinetobacter baumannii bacterium was evaluated with a crystal violet staining assay. RESULTS: The bacterial species that constituted these biofilms were identified as a variety of gram-negative bacilli, with a predominance of strains belonging to Pseudomonas aeruginosa. The other isolated strains belonged to A baumannii and Klebsiella ornithinolytica. Kinetic profiling of biofilm formation identified the transient behavior of A baumannii between its biofilm and planktonic state. This strain was highly resistant to all of the antibiotics tested except colistin. Scanning electron microscopy images showed that the identified isolated species formed a dense and interconnected network of cellular multilayers formed from either a single cell or from different species that were surrounded and enveloped by a protective matrix. CONCLUSIONS: Microbiological analysis of the intraluminal surface of the catheter is required for true identification of the causative agents of catheter-associated urinary tract infections. This approach, combined with a routine cytobacteriological examination of urine, allows for the complete characterization of biofilm-associated species, and also may help prevent biofilm formation in such devices and help guide optimum antibiotic treatment.

N,N'-SUBStituted 1,2,5 thiadiazolidine 1,1-dioxides: synthesis, selected chemical and spectral proprieties and antimicrobial evaluation.

The sulfamide functional group is increasingly relevant in both medicinal and bioorganic chemistry. We report here practical access to a series of N2,N5-substituted five-membered cyclosulfamides. The five-membered heterocyclic motif was prepared starting from proteogenic amino acids and chlorosulfonyl isocyanate via the Mitsunobu reaction. Selected chemical and spectral proprieties and the antimicrobial evaluation of these compounds are detailed.