Hyaluronidases of Gram-Positive Bacteria

Bacterial hyaluronidases, enzymes capable of breaking down hyaluronate, are produced by a number of pathogenic Gram-positive bacteria that initiate infections at the skin or mucosal surfaces. Since reports of the hyaluronidases first appeared, there have been numerous suggestions as to the role of the enzyme in the disease process. Unlike some of the other more well studied virulence factors, much of the information on the role of hyaluronidase is speculative, with little or no data to substantiate proposed roles. Over the last 5 years, a number of these enzymes from Gram-positive organisms have been cloned, and the nucleotide sequence determined. Phylogenetic analysis, using the deduced amino acid sequences of the Gram-positive hyaluronidases, suggests a relatedness among some of the enzymes. Molecular advances may lend to a more thorough understanding of the role of hyaluronidases in bacterial physiology and pathogenesis. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved

Physiological proteomics of gram-positive bacteria

Comunicaciones a congreso

Gram Positive Bacteria in Clinical Medicine

The goals of this presentation are to: define the molecular structure of Gram-positive organisms; highlight differences between Gram-positives and Gram-negatives; discuss the most important clinically-relevant Gram-positive bacteria; review treatments for Gram-positives; and illustrate clinical scenarios involving Gram-positive infection

Activity of meropenem, against Gram-positive bacteria

A new carbapenem antibiotic, meropenem, was shown to be active against a large number of Gram-positive bacteria. The drug inhibited penicillinase-positive and -negative, methicillin-susceptible staphylococci equally well. Among the comparative antimicrobials examined, only N-fonnimidoyl-thienamycin (imipenem) was two to four times more active than meropenem. Compared with vancomycin or methicillin, meropenem was 10-20 times more active. Strains of 11 species of streptococci were highly susceptible to meropenem; the geometric mean MICs of the drug for these species ranged from 0.01 to 0.04mg/l. The agent, however, only had moderate activity against Enterococcus faecalis (mean MIC 5mg/l) and Ent. faecium (mean MIC 11.6 mg/l). Among Corynebacterium jeikeium, strains were encountered that showed susceptibility to meropenem but resistance to imipenem and other β-lactams. Strains of other corynebacteria, Rhodococcus equi, Erysopelothrix rhusio-pathiae, Listeria monocytogenes, and Bacillus spp. all were highly susceptible to meropenem (mean MICs 0.04-0.17 mg/l). Although methicillin-resistant staphylo-cocci were inhibited by concentrations of 1-2 mg/l of meropenem in agar dilution tests, such strains showed heteroresistance in population studies, as is typical for all β-lactam antibiotics. In addition, the biochemical correlate of methicillin-resistance, penicillin-binding protein 2′, showed low affinity for meropenem, similar to that for imipenem. Meropenem was as bactericidal as imipenem and comparative bactericidal antimicrobials in killing-curve experiments. Strains of Ent. faecium, C. jeikeium, and L. monocytogenes were killed at a slower rate than streptococci or staphylococc

Antimicrobial activity of Androstachys johnsonii Prain

Extracts of leaf, root, bark and soil leachates of Androstachys johnsonii screened for antibacterial activity had a significant inhibitory effect on most Gram-positive bacteria tested. Gram-negative bacteria were resistant to most extracts. Of the Gram-negative bacteria tested, 1% leaf extract significantly inhibited the growth of all bacteria tested and both 1% root and bark extract inhibited only one bacterial strain. At the concentration of 1 mg/ml, soil extracts showed less inhibitory activity against the bacteria tested. The growth of three out of five Gram-positive bacteria was inhibited by leaf extracts. At 0.1 mg/ml, four Gram-positive bacteria were inhibited. In both 0.01 and 0.1 mg/ml of leaf extracts, all Gram-negative bacteria were uninhibited. Root extract did not inhibit the growth of four Gram-positive bacteria at 0.01 mg/ml and two Gram-positive bacteria at 0.1 mg/ml, but had a noticeably higher level of activity against all Gram-positive bacteria, than bark and soil extracts. From the results obtained in this study, we conclude that the crude extracts of A. johnsonii exhibit significant antibacterial activity.Key words: Antimicrobial activity, Androstachys johnsonii, bacteria

Novel synthetic polymyxins kill Gram-positive bacteria

Background: Staphylococcus aureus, including 'superbug' MRSA, is a major cause of nosocomial infections. In the European Union, up to 171 200 new nosocomial MRSA infections are acquired annually, and in the USA S. aureus causes more deaths than HIV/AIDS and tuberculosis combined. MRSA is also the first group of pathogens that infect the pulmonary tract in young patients with cystic fibrosis. Objectives: We describe two newly developed and synthesized colistin (polymyxin E)-inspired molecules. Methods: A collection of several isolates of S. aureus [including MRSA and vancomycin-resistant S. aureus (VRSA)] was tested. To check the antimicrobial activity, we performed time-kill curves, growth curves, biofilm eradication, toxicity and isothermal titration calorimetry. Results: Both peptides showed high antimicrobial activities (MIC 4 mg/L) and low relative toxicities (selectivity index close to 23). Conclusions: Successful production of polymyxin-scaffold molecules active against S. aureus, both MRSA and VRSA, opens up new approaches to the treatment of these complicated infections

Novel Antimicrobials to Combat Gram Positive Bacteria

A novel class of antibacterial substances has been discovered in a collaborative project between the Chemistry and Biology Departments at Grand Valley State University (GVSU). These compounds do not rely on currently accepted antibiotic chemical structure but seemingly have a mechanism of action different from understood mechanistic pathways for treatment of infections and are readily synthesized, avoiding complex, stereoselective, multi-step synthesis. This new class of antibiotics is composed of chemical derivatives of the telomerase inhibitor BIBR1532 [US Patent 6362210]. Our compounds demonstrated significant antimicrobial activity against a group of Gram-Positive microorganisms. The antibiotic’s minimum inhibitory concentrations (MICs) against these bacteria are equivalent to existing antibiotics (2-78 ug/ml). In subsequent in-vitro tests these compounds showed activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin resistant enterococci (VRE), Bacillus anthracis (anthrax), and Clostridium difficile (Cdiff). The antibacterial activity against MRSA, VRE, and Cdiff strains of bacteria is promising as it demonstrates the ability of BIBR 1532 to inhibit microbial growth in organisms with resistance to common antibiotics. In 2008, GVSU patented this antibiotic family. Since then, we determined that the frequency of bacterial resistance to this class of antibiotics is extremely low. Over 70 compounds were tested for antibacterial activity. Sixty demonstrated antibacterial activity and of these 18 were more thoroughly tested against 25 bacterial and fungal strains. We discovered that a number of compounds had low minimum inhibitory concentrations (MICs) against Staphylococcus aureus (including MRSA strains), Bacillus anthracis (anthrax), Clostridium difficile, and Streptococcus pneumonia. These results were encouraging as they demonstrate multiple bacterial targets with low drug concentrations (2-8 ug/ml). Additionally, we tested six compounds in acute in vitro toxicity screening in a rat hepatoma (H4IIE) cell line at 24 hour exposure. All compounds demonstrated minimal toxicity to the cell line. These toxicity results demonstrate that potential negative side-effects to patients appear to be minimal. Further testing of our antibiotics revealed significant binding to human serum protein. This is potentially problematic in clinical use as there is less available compound in the blood. There are conflicting opinions as to the significance of binding to serum protein. For example, nine of the top 10 best-selling small molecule, single agent prescription drugs of 2006 had 90% or greater binding to serum protein and seven of the top ten had 95% or greater [Rydzewski, R.M., 2008]. A potential problem exists and we continue to work towards lowering this binding to increase potential available drug concentrations in the blood. *This scholar and faculty mentor have requested that only an abstract be published

Cyclic diguanylate signaling in Gram-positive bacteria

The nucleotide second messenger 3′-5′ cyclic diguanylate monophosphate (c-di-GMP) is a central regulator of the transition between motile and non-motile lifestyles in bacteria, favoring sessility. Most research investigating the functions of c-di-GMP has focused on Gram-negative species, especially pathogens. Recent work in Gram-positive species has revealed that c-di-GMP plays similar roles in Gram-positives, though the precise targets and mechanisms of regulation may differ. The majority of bacterial life exists in a surface-associated state, with motility allowing bacteria to disseminate and colonize new environments. c-di-GMP signaling regulates flagellum biosynthesis and production of adherence factors and appears to be a primary mechanism by which bacteria sense and respond to surfaces. Ultimately, c-di-GMP influences the ability of a bacterium to alter its transcriptional program, physiology and behavior upon surface contact. This review discusses how bacteria are able to sense a surface via flagella and type IV pili, and the role of c-di-GMP in regulating the response to surfaces, with emphasis on studies of Gram-positive bacteria

Response of Gram-positive bacteria to copper stress

The Gram-positive bacteria Enterococcus hirae, Lactococcus lactis, and Bacillus subtilis have received wide attention in the study of copper homeostasis. Consequently, copper extrusion by ATPases, gene regulation by copper, and intracellular copper chaperoning are understood in some detail. This has provided profound insight into basic principles of how organisms handle copper. It also emerged that many bacterial species may not require copper for life, making copper homeostatic systems pure defense mechanisms. Structural work on copper homeostatic proteins has given insight into copper coordination and bonding and has started to give molecular insight into copper handling in biological systems. Finally, recent biochemical work has shed new light on the mechanism of copper toxicity, which may not primarily be mediated by reactive oxygen radical

Expression systems for industrial Gram-positive bacteria with low guanine and cytosine content

Recent years have seen an increase in the development of gene expression systems for industrial Gram-positive bacteria with low guanine and cytosine content that belong to the genera Bacillus, Clostridium, Lactococcus, Lactobacillus, Staphylococcus and Streptococcus. In particular, considerable advances have been made in the construction of inducible gene expression systems based on the capacity of these bacteria to utilize specific sugars or to secrete autoinducing peptides that are involved in quorum sensing. These controlled expression systems allow for present and future exploitation of these bacteria as cell factories in medical, agricultural, and food biotechnology.