Relevance of biofilm formation and virulence of different species of coagulase-negative staphylococci to public health.

The ability of biofilm formation seems to play an essential role in the virulence of coagulase-negative staphylococci (CNS). The present work aimed to: (a) evaluate the biofilm-forming ability of different strains of CNS field isolates; (b) evaluate their virulence potential through the assessment of the Madin-Darby canine kidney (MDCK) cytotoxicity assay; (c) determine the frequency of biofilm-associated genes among these CNS isolates. Biofilm markers associated with biofilm formation and MDCK cells cytotoxicity were compared to find possible associations with pathogenicity. CNS isolates (n = 94) belonging to 11 different species were tested for slime production using the tube test (TA) and the Congo red agar plate test (CRA), while the presence of icaA and icaD genes were evaluated by d-PCR. Two points were addressed for the first time: (1) the specific relationship between slime phenotype and icaD gene expression; (2) the specific relationship between slime phenotype, icaAD genes, and MDCK cytotoxicity. The proportion of biofilm-positive/icaD-positive versus biofilm-positive/icaD-negative strains was 9:0 and 9:0 (81.8%) by the TA and CRA, which clearly indicates that icaD was a more reliable gene to be accounted for in the biofilm formation. MDCK recorded a higher proportion than that recorded by the CRA and TA results (MDCK-positive/icaD-positive versus MDCK-positive/icaD-negative 10:0, 90.9%). Evaluation of the ica operon, CRA plate test, TA, and MDCK can contribute to the high clinical impact in the management of antibiotic therapy, in infections associated with devices in veterinary medicine, the dairy industry, and food processing.

Chemical composition and antioxidant and anti-Listeria activities of essential oils obtained from some Egyptian plants.

The aim of this work was to (i) determine the chemical composition of the essential oils of six spices widely cultivated in Egypt (Origanum syriacum, Majorana hortensis, Rosmarinus officinalis, Cymbopogon citratus, Thymus vulgaris, and Artemisia annua); (ii) determine the antioxidant activity of the Egyptian essential oils by means of five different antioxidant tests; and (iii) determine the effectiveness of these essential oils on the inhibition of Listeria innocua CECT 910. There is a great variability in the chemical composition of essential oils obtained from the six Egyptian aromatic plants. Overall, thyme (highest percentage of inhibition of DPPH radical: 89.40%) and oregano (highest percentage of inhibition of TBARS: 85.79) essential oils presented the best antioxidant profiles, whereas marjoram, lemongrass, and artemisia were highly effective in metal chelating but had a pro-oxidative behavior by Rancimat induction test. Lemongrass essential oil showed the highest antibacterial activity against L. innocua with an inhibition zone of 49.00 mm, followed in effectiveness by thyme, marjoram, and oregano.