Mechanistic study of novel antimicrobials for infection prevention and cure

The rise of antibiotic resistance development has increased the need for conventional compounds and unconventional antimicrobials to increase the artillery of medical practitioners in the combat against resistant pathogens. This study aimed in identifying novel synthetic compounds and to determine the mode of action of unconventional antimicrobials known as alpha-helical cationic antimicrobial peptides (AMPs). Initially, we improved the SporeTracker software, used for live-imaging of spore-forming bacteria, resulting in SporeTrackerX. We then established the value of live-imaging analysis and SporeTrackerX in screening of novel synthetic compounds, derived from combinatorial chemistry, using B. subtilis and B. cereus spores. Subsequently, we established the mode of action of AMPs derived from the human thombocidin, TC19 and TC84, and the bactericidal permeability increasing protein (BPI), BP2, using B. subtilis vegetative cells and spores. We found, in vivo, that alpha-helical cationic AMPs cause “membrane leaks” at the site of membrane insertion by altering the organization and fluidity of the membrane. Also for the first time, we show that alpha-helical cationic AMPs target the inner membrane of germinated spores and hint at a potential additional application for AMPs in preventing spore outgrowth after covering the dormant spore-coat

Antimicrobial Activity of Cationic Antimicrobial Peptides against Gram-Positives: Current Progress Made in Understanding the Mode of Action and the Response of Bacteria

Antimicrobial peptides (AMPs) have been proposed as a novel class of antimicrobials that could aid the fight against antibiotic resistant bacteria. The mode of action of AMPs as acting on the bacterial cytoplasmic membrane has often been presented as an enigma and there are doubts whether the membrane is the sole target of AMPs. Progress has been made in clarifying the possible targets of these peptides, which is reported in this review with as focus gram-positive vegetative cells and spores. Numerical estimates are discussed to evaluate the possibility that targets, other than the membrane, could play a role in susceptibility to AMPs. Concerns about possible resistance that bacteria might develop to AMPs are addressed. Proteomics, transcriptomics, and other molecular techniques are reviewed in the context of explaining the response of bacteria to the presence of AMPs and to predict what resistance strategies might be. Emergent mechanisms are cell envelope stress responses as well as enzymes able to degrade and/or specifically bind (and thus inactivate) AMPs. Further studies are needed to address the broadness of the AMP resistance and stress responses observed

Exposure to traffic related hazards among high-school going learners in South Africa: Findings from the 1st SA National Youth Risk Behaviour Survey, 2002

No Abstract.African Safety Promotion Vol. 6(1) 2008: pp. 22-2

Olivier Callot. Catalogue des monnaies du musée de Sharjah (Émirats arabes unis). Essai sur les monnayages arabes préislamiques de la péninsule d’Oman/ Essay on the Pre-Islamic Arabian Coinage of the Oman Peninsula

Duyrat Frédérique. Olivier Callot. Catalogue des monnaies du musée de Sharjah (Émirats arabes unis). Essai sur les monnayages arabes préislamiques de la péninsule d’Oman/ Essay on the Pre-Islamic Arabian Coinage of the Oman Peninsula. In: Syria. Tome 82, 2005. pp. 379-380

Bactericidal activity of amphipathic cationic antimicrobial peptides involves altering the membrane fluidity when interacting with the phospholipid bilayer

Background Amphipathic cationic antimicrobial peptides (AMPs) TC19 and TC84, derived from the major AMPs of human blood platelets, thrombocidins, and Bactericidal Peptide 2 (BP2), a synthetic designer peptide showed to perturb the membrane of Bacillus subtilis. We aimed to determine the means by which the three AMPs cause membrane perturbation in vivo using B. subtilis and to evaluate whether the membrane alterations are dependent on the phospholipid composition of the membrane. Methods Physiological analysis was employed using Alexa Fluor 488 labelled TC84, various fluorescence dyes, fluorescent microscopy techniques and structured illumination microscopy. Results TC19, TC84 and BP2 created extensive fluidity domains in the membrane that are permeable, thus facilitating the entering of the peptides and the leakage of the cytosol. The direct interaction of the peptides with the bilayer create the fluid domains. The changes caused in the packing of the phospholipids lead to the delocalization of membrane bound proteins, thus contributing to the cell's destruction. The changes made to the membrane appeared to be not dependent on the composition of the phospholipid bilayer. Conclusions The distortion caused to the fluidity of the membrane by the AMPs is sufficient to facilitate the entering of the peptides and leakage of the cytosol. General significance Here we show in vivo that cationic AMPs cause “membrane leaks” at the site of membrane insertion by altering the organization and fluidity of the membrane. Our findings thus contribute to the understanding of the membrane perturbation characteristic of cationic AMPs

Umthente Uhlaba Usamila: the 3rd South African National Youth Risk Behaviour Survey 2011

The objectives of the studies is to provide provincially and nationally representative data, inform intervention development, inform policy development and adaptation, to assess and project how risk behaviours change over time, and provide an early warning system for future epidemics related to risk behaviours.

Evaluating novel synthetic compounds active against Bacillus subtilis and Bacillus cereus spores using Live imaging with SporeTrackerX

An empirical approach was taken to screen a novel synthetic compound library designed to be active against Gram-positive bacteria. We obtained five compounds that were active against spores from the model organism Bacillus subtilis and the food-borne pathogen Bacillus cereus during our population based experiments. Using single cell live imaging we were able to observe effects of the compounds on spore germination and outgrowth. Difference in sensitivity to the compounds could be observed between B. subtilis and B. cereus using live imaging, with minor difference in the minimal inhibitory and bactericidal concentrations of the compounds against the spores. The compounds all delayed the bursting time of germinated spores and affected the generation time of vegetative cells at sub-inhibitory concentrations. At inhibitory concentrations spore outgrowth was prevented. One compound showed an unexpected potential for preventing spore germination at inhibitory concentrations, which merits further investigation. Our study shows the valuable role single cell live imaging can play in the final selection process of antimicrobial compounds