A New Approach for the Discovery of Antibiotics by Targeting Non-Multiplying Bacteria: A Novel Topical Antibiotic for Staphylococcal Infections

In a clinical infection, multiplying and non-multiplying bacteria co-exist. Antibiotics kill multiplying bacteria, but they are very inefficient at killing non-multipliers which leads to slow or partial death of the total target population of microbes in an infected tissue. This prolongs the duration of therapy, increases the emergence of resistance and so contributes to the short life span of antibiotics after they reach the market. Targeting non-multiplying bacteria from the onset of an antibiotic development program is a new concept. This paper describes the proof of principle for this concept, which has resulted in the development of the first antibiotic using this approach. The antibiotic, called HT61, is a small quinolone-derived compound with a molecular mass of about 400 Daltons, and is active against non-multiplying bacteria, including methicillin sensitive and resistant, as well as Panton-Valentine leukocidin-carrying Staphylococcus aureus. It also kills mupirocin resistant MRSA. The mechanism of action of the drug is depolarisation of the cell membrane and destruction of the cell wall. The speed of kill is within two hours. In comparison to the conventional antibiotics, HT61 kills non-multiplying cells more effectively, 6 logs versus less than one log for major marketed antibiotics. HT61 kills methicillin sensitive and resistant S. aureus in the murine skin bacterial colonization and infection models. No resistant phenotype was produced during 50 serial cultures over a one year period. The antibiotic caused no adverse affects after application to the skin of minipigs. Targeting non-multiplying bacteria using this method should be able to yield many new classes of antibiotic. These antibiotics may be able to reduce the rate of emergence of resistance, shorten the duration of therapy, and reduce relapse rates

Interaction between Protein Subunits of the Type IV Secretion System of Bartonella henselae

In this study we used the yeast two-hybrid system to identify interactions between protein subunits of the virB type IV secretion system of Bartonella henselae. We report interactions between inner membrane and periplasmic proteins, the pilus polypeptide, and the core complex and a novel interaction between VirB3 and VirB5

Stressing the obvious? Cell stress and cell stress proteins in cardiovascular disease

It is only some forty years since the discovery of the heat shock or cell stress response and just over twenty years since the heat shock/cell stress response was linked to protein misfolding. The plethora of intracellular proteins which promote correct protein folding in the cell, variously termed molecular chaperones, heat shock proteins, or cell stress proteins, have only been identified in the last fifteen years. During this period it has also been discovered that: (i) molecular chaperones are potent immunogens with immunomodulatory activity and (ii) they can be secreted by cells and exhibit intercellular signaling actions. These various functions of molecular chaperones are increasingly being linked to the pathology of the cardiovascular system. Molecular chaperones within cells can exhibit cardioprotection if their levels are artificially elevated, suggesting that these proteins may have therapeutic activity. In contrast, there is evidence that atherogenesis may be linked to immunity to one specific molecular chaperone, Hsp60. This may offer the possibility of treating atherosclerosis by vaccination. However, there is also growing evidence that secreted molecular chaperones have pro- or anti-inflammatory actions that are relevant to cardiovascular pathology. This review brings these various strands of research together to provide an overview of the role of molecular chaperones in cardiovascular disease

The MSC₅₀ and MIC of HT61 against clinically isolated MRSA, VISA and VRSA.

<p>The MSC₅₀ and MIC of HT61 against clinically isolated MRSA, VISA and VRSA.</p

Effects of HT61 and marketed antibiotics against stationary phase non-multiplying MSSA and MRSA.

<p>HT61 and the antibiotics were added to the non-multiplying cultures at different concentrations. CFU counts were carried out after 24 hours of incubation. A. Effects of HT61, amoxicillin/clavulanic acid, azithromyicin, levofloxacin, linezolid, daptomycin and mupirocin against MSSA. B. Effects of HT61, vancomycin, daptomycin and mupirocin against MRSA. These results were confirmed in two independent experiments.</p

Thin sectioned electron micrographs of <i>S. aurues</i> analyzed by transmission electron microscopy.

<p>The cells were fixed 10 minutes after HT61 treatment. A. normal <i>S. aureus</i> cells. B. HT61 at 10 µg/ml. C. HT61 at 20 µg/ml. D. HT61 at 40 µg/ml. The scale bar is 0.2 µm.</p