Agar Plate Methods for Assessing the Antibacterial Activity of Thyme and Oregano Essential Oils against S. epidermidis and E. coli

The resistance to antimicrobials (AMR), especially antibiotics, represents a serious problem and, at the same time, a challenge. In the last decade, a growing interest in the use of essential oils (EOs) as antimicrobial substances was observed. Commercial thyme and oregano EOs are reported to be the main responsible of the oil antimicrobial efficacy against both Gram-positive and Gramnegative pathogenic bacteria. The aim of the present work was to study the efficacy of EOs against Staphylococcus epidermidis and Escherichia coli in long-time treatments. In a preliminary microdilution test, a MIC value was obtained for thyme EO against S. epidermidis and E. coli. After that, disk diffusion and disk volatilization tests were set up to study the influence of main cultural parameters on EO activity in liquid or vapor phase. Both bacteria were inhibited by thyme and oregano EOs when applied pure (100% v/v) or diluted (75% and 50% v/v): a higher inhibition was observed in a disk diffusion test in which the antimicrobial effect was due to both liquid and vapor phase components. Finally, a comparison with literature data was carried out even if it was not so easy because standard methods are usually modified and adapted to specific case study. For this reason, the results have to be interpreted in relation to the analytical method applied

Sperm Factor Initiates Capacitance and Conductance Changes in Mouse Eggs That Are More Similar to Fertilization Than IP3- or Ca2+-induced Changes

AbstractWe used patch clamp electrophysiology and concurrent imaging with the Ca2+-sensitive dye, fura-2, to study the temporal relationship between membrane capacitance and conductance and intracellular free Ca2+ concentration ([Ca2+]i) during mouse egg fertilization. We found an ∼2 pF step increase in egg membrane capacitance and a minor increase in conductance with no change in [Ca2+]i at sperm fusion. This was followed ∼1 min later by a rise in [Ca2+]i that led to larger changes in capacitance and conductance. The most common pattern for these later capacitance changes was an initial capacitance decrease, followed by a larger increase and eventual return to the approximate starting value. There was some variation in this pattern, and sub-μM peak [Ca2+]i favored capacitance decrease, while higher [Ca2+]i favored capacitance increase. The magnitude of accompanying conductance increases was variable and did not correlate well with peak [Ca2+]i. The intracellular introduction of porcine sperm factor reproduced the postfusion capacitance and conductance changes with a similar [Ca2+]i dependence. Raising [Ca2+]i by the intracellular introduction of IP3 initiated fertilization-like capacitance changes, but the conductance changes were slower to activate. Capacitance decrease could be induced when [Ca2+]i was increased modestly by activation of an endogenous Ca2+ current, with little effect on resting conductance. These results suggest that net turnover of the mouse egg surface membrane is sensitive to [Ca2+]i and that sperm and the active component of sperm factor may be doing more than initiating the IP3-mediated release of intracellular Ca2+