Target-based antimicrobial drug discovery.

The continued increase in antibiotic resistance among bacterial pathogens, coupled with a decrease in infectious disease research among pharmaceutical companies, has escalated the need for novel and effective antibacterial chemotherapies. While current agents have emerged almost exclusively from whole-cell screening of natural products and small molecules that cause microbial death, recent advances in target identification and assay development have resulted in a flood of target-driven drug discovery methods. Whether genome-based methodologies will yield new classes of agents that conventional methods have been unable to is yet to be seen.

Development of an HPLC assay for Staphylococcus aureus sortase: evidence for the formation of the kinetically competent acyl enzyme intermediate.

Many bacterial surface proteins containing an LPXTG motif are anchored to the cell wall peptidoglycan by catalysis with the thiol transpeptidase sortase. The transpeptidation and hydrolysis reactions of sortase have been proposed to proceed through a common acyl enzyme intermediate. The reactions of Staphylococcus aureus sortase with fluorogenic substrate Abz-LPETG-Dnp in the presence or absence of triglycine were characterized in this study to gain additional insight into the kinetic mechanism of sortase.

Effect of srtA and srtB gene expression on the virulence of Staphylococcus aureus in animal models of infection.

Objective: The role that the surface proteins anchored by the srtA and srtB gene products play in the ability of Staphylococcus aureus bacteria to establish infection was investigated in several animal models.

Methods: Wild-type and corresponding mutants with deletions of the srtA and/or srtB genes were used in murine acute lethal infection, septic arthritis, kidney infection and rat endocarditis models.

Results: The LD(50) of the wild-type and srtB- knockout were comparable and approximately two- to four-fold lower than the required inoculum of the srtA- and srtA-B- strains.

Kinetic mechanism of Staphylococcus aureus sortase SrtA.

Staphylococcus aureus sortase (SrtA) is a thiol transpeptidase. The enzyme catalyzes a cell wall sorting reaction in which a surface protein with a sorting signal containing a LPXTG motif is cleaved between the threonine and glycine residues. The resulting threonine carboxyl end of this protein is covalently attached to a pentaglycine cross-bridge of peptidoglycan.

Balofloxacin Choongwae.

Balofloxacin, an orally active fluoroquinolone antibiotic, has been developed by Choongwae Pharma in Korea, for the treatment of urinary tract infection (UTI). Chugai and Ciba were developing balofloxacin for respiratory tract infections (RTI) but discontinued development in 1995 due to changes in Chugai's R&D focus and a lack of efficacy of the drug. Following phase II trials, Choongwae bought the rights to develop balofloxacin in Korea from Chugai.

Virulence as a target for antimicrobial chemotherapy.

Bacterial resistance to present day antibiotics has become a dangerous threat to public health. Consequently, the pharmaceutical industry must provide new agents and novel classes to combat bacterial disease and to stay a step ahead of the rapid evolution of bacterial resistance mechanisms. The need for novel antibacterials has resulted in a search for previously unexplored targets for chemotherapy, utilising the new techniques of genomics to identify them.

Genomics in anti-infective drug discovery--getting to endgame.

Whole chromosome sequence of prokaryotes has provided the availability of multiple bacterial pathogen sequence data and it has become a widely used tool in the drug discovery process. However the sequence data in itself is merely a starting point for drug discovery of novel antibacterial targets and, eventually, drugs. In order to leverage this large amount of data it is necessary to match an understanding of the microbial physiology of pathogenic bacteria to disease processes and identifying the gene products for which intervention may reduce or eliminate the infectious state.

Anchoring of surface proteins to the cell wall of Staphylococcus aureus. Cysteine 184 and histidine 120 of sortase form a thiolate-imidazolium ion pair for catalysis.

Surface proteins of Staphylococcus aureus are anchored to the cell wall peptidoglycan by a mechanism requiring a C-terminal sorting signal with a LPXTG motif. Sortase cleaves polypeptides between the threonine and the glycine of the LPXTG motif. The carboxyl group of threonine is subsequently amide-linked to the amino group of peptidoglycan cross-bridges.