Aztreonam

The Blood-Brain Barrier and Pharmacokinetic/Pharmacodynamic Optimization of Antibiotics for the Treatment of Central Nervous System Infections in Adults

Bacterial central nervous system (CNS) infections are serious and carry significant morbidity and mortality. They encompass many syndromes, the most common being meningitis, which may occur spontaneously or as a consequence of neurosurgical procedures. Many classes of antimicrobials are in clinical use for therapy of CNS infections, some with established roles and indications, others with experimental reporting based on case studies or small series. This review delves into the specifics of the commonly utilized antibacterial agents, updating their therapeutic use in CNS infections from the pharmacokinetic and pharmacodynamic perspectives, with a focus on the optimization of dosing and route of administration that have been described to achieve good clinical outcomes. We also provide a concise synopsis regarding the most focused, clinically relevant information as pertains to each class and subclass of antimicrobial therapeutics. CNS infection morbidity and mortality remain high, and aggressive management is critical in ensuring favorable patient outcomes while averting toxicity and upholding patient safety.

Insight into the Interaction Mechanism of HSA with Aztreonam: A Multispectroscopic and Computational Approach

Aztreonam is a Gram-negative bacteria-targeting synthetic monobactam antibiotic. Human serum albumin (HSA) plays an important role in the transference of pharmaceuticals, hormones, and fatty acids, along with other compounds, determining their biodistribution and physiological fate. Using several biophysical and in silico approaches, we studied the interaction of aztreonam with HSA under physiological environments in this study. Results confirm the formation of HSA-aztreonam complex where aztreonam showed moderate affinity towards HSA. A static mode of quenching was confirmed from the steady state fluorescence data. FRET findings also showed that there was a significant feasibility of energy transfer between HSA and aztreonam. Site marker displacement experimental conclusion suggested the binding site of aztreonam was the sub-domain IB of HSA. Circular dichroic spectroscopic analysis suggested that aztreonam interaction decreases the α-helical content of HSA. Changes in microenvironment were studied through synchronous fluorescence data. According to molecular docking results, the HSA-aztreonam complex is mostly maintained by non-covalent forces, with a binding energy of 7.7 kcal mol^-1. The presence of a hydrogen bond, van der Waal interaction, and pi-anion interaction in the binding process, as well as conformational changes in HSA after binding with aztreonam, are all confirmed by molecular dynamic simulation.

The Chemical Relationship Among Beta-Lactam Antibiotics and Potential Impacts on Reactivity and Decomposition

Beta-lactam antibiotics remain one of the most commonly prescribed drug classes, but they are limited by their propensity to cause hypersensitivity reactions (e.g., from allergy to anaphylaxis) as well as by the emergence of bacteria with a myriad of resistance mechanisms such as β-lactamases. While development efforts continue to focus on overcoming resistance, there are ongoing concerns regarding cross-contamination of β-lactams during manufacturing and compounding of these drugs. Additionally, there is a need to reduce levels of drugs such as β-lactam antibiotics in waste-water to mitigate the risk of environmental exposure. To help address future development of effective remediation chemistries and processes, it is desired to better understand the structural relationship among the most common β-lactams. This study includes the creation of a class-wide structural ordering of the entire β-lactam series, including both United States Food and Drug Association (US-FDA)-approved drugs and experimental therapies. The result is a structural relational map: the “Lactamome,” which positions each substance according to architecture and chemical end-group. We utilized a novel method to compare the structural relationships of β-lactam antibiotics among the radial cladogram and describe the positioning with respect to efficacy, resistance to hydrolysis, reported hypersensitivity, and Woodward height. The resulting classification scheme may help with the development of broad-spectrum treatments that reduce the risk of occupational exposure and negative environmental impacts, assist practitioners with avoiding adverse patient reactions, and help direct future drug research.

An inhibitor of the human UDP-GlcNAc 4-epimerase identified from a uridine-based library: a strategy to inhibit O-linked glycosylation

The biological study of O-linked glycosylation is particularly problematic, as chemical tools to control this modification are lacking. An inhibitor of the UDP-GlcNAc 4-epimerase that synthesizes UDP-GalNAc, the donor initiating O-linked glycosylation, would be a powerful reagent for reversibly inhibiting O-linked glycosylation. We synthesized a 1338 member library of uridine analogs directed to the epimerase by virtue of substrate mimicry. Screening of the library identified an inhibitor with a K(i) value of 11 microM. Tests against related enzymes confirmed the compound's specificity for the UDP-GlcNAc 4-epimerase. Inhibitors of a key step of O-linked glycan biosynthesis can be discovered from a directed library screen. Progeny thereof may be powerful tools for controlling O-linked glycosylation in cells.

Combinatorial target-guided ligand assembly: identification of potent subtype-selective c-Src inhibitors

A method for the rapid and efficient identification of ligands to biological targets is reported. The combinatorial method does not require structural or mechanistic information and is accomplished in four straightforward steps. (i) A set of potential binding elements is prepared wherein each molecule incorporates a common chemical linkage group. (ii) The set of potential binding elements is screened to identify all binding elements that interact even weakly with the biological target. (iii) A combinatorial library of linked binding elements is prepared whereby the binding elements are connected by the common chemical linkage groups through a set of flexible linkers. (iv) The combinatorial library is screened to identify the tightest-binding ligands. The utility of the method was demonstrated by the identification of a potent and subtype-selective small molecule inhibitor of the non-receptor tyrosine kinase c-Src (IC(50) = 64 nM). Because the method relies on connecting two distinct binding elements, the relative contributions of the two binding elements to the potency and selectivity of the inhibitor were readily determined. This information provides valuable insight into the molecular basis of inhibition.

Antibiotic use in the emergency department. III. The quinolones, new beta lactams, beta lactam combination agents, and miscellaneous antibiotics

This article reviews several new, relatively broad-spectrum antibiotics that have utility in the emergency department (ED). The quinolones have excellent activity against gram-negative organisms, including gonococcus, and are characterized by very high bioavailability after oral administration. The new beta-lactams aztreonam and imipenem have broad spectra but limited usefulness to the emergency physician, and should be reserved for judicious use in severe infections, particularly those involving Pseudomonas. Clavulanate, sulbactam, and tazobactam are themselves antimicrobials that have been combined with beta-lactams such as ampicillin and ticarcillin to produce agents with significant potential utility in the ED; these are typically not first-line agents, however, and their use should be governed by both clinical and cost concerns. Finally, three older antibiotics--vancomycin, metronidazole, and clindamycin--are reviewed with respect to updated indications for their use in the ED.

Aztreonam

Aztreonam is a monocyclic beta-lactam antibiotic that is active exclusively against the aerobic gram-negative bacilli. It is not ototoxic or nephrotoxic and so is used as an alternative to aminoglycosides in a variety of clinical situations. In polymicrobial infections or when used for empiric therapy, aztreonam must be combined with other antimicrobial agents active against gram-positive and anaerobic species. Aztreonam is often effective against resistant strains of gram-negative organisms, which are often involved in nosocomial infections. Overuse of aztreonam should be avoided to prevent the emergence of resistant P. aeruginosa strains. Except in the treatment of P. aeruginosa infections, aztreonam should not be added to beta-lactam regimens for additional gram-negative coverage.