Updated antimicrobial dosing recommendations for obese patients

The prevalence of obesity has increased considerably in the last few decades. Pathophysiological changes in obese patients lead to pharmacokinetic (PK) and pharmacodynamic (PD) alterations that can condition the correct exposure to antimicrobials if standard dosages are used. Inadequate dosing in obese patients can lead to toxicity or therapeutic failure. In recent years, additional antimicrobial PK/PD data, extended infusion strategies, and studies in critically ill patients have made it possible to obtain data to provide a better dosage in obese patients. Despite this, it is usually difficult to find information on drug dosing in this population, which is sometimes contradictory. This is a comprehensive review of the dosing of different types of antimicrobials (antibiotics, antifungals, antivirals, and antituberculosis drugs) in obese patients, where the literature on PK and possible dosing strategies in obese adults was critically assessed.

Chronic cortisol stimulation enhances hypothalamus-specific enrichment of metabolites in the rainbow trout brain

The hypothalamus is a key integrating center that is involved in the initiation of the corticosteroid stress response, and in regulating nutrient homeostasis. Although cortisol, the principal glucocorticoid in humans and teleosts, plays a central role in feeding regulation, the mechanisms are far from clear. We tested the hypothesis that the metabolic changes to cortisol exposure signal an energy excess in the hypothalamus, leading to feeding suppression during stress in fish. Rainbow trout (Oncorhynchus mykiss) were administered a slow-release cortisol implant for 3 days, and the metabolite profiles in the plasma, hypothalamus, and the rest of the brain were assessed. Also, U-13C-glucose was injected into the hypothalamus by intracerebroventricular (ICV) route, and the metabolic fate of this energy substrate was followed in the brain regions by metabolomics. Chronic cortisol treatment reduced feed intake, and this corresponded with a downregulation of the orexigenic gene agrp, and an upregulation of the anorexigenic gene cart in the hypothalamus. The U-13C-glucose-mediated metabolite profiling indicated an enhancement of glycolytic flux and tricarboxylic acid intermediates in the rest of the brain compared with the hypothalamus. There was no effect of cortisol treatment on the phosphorylation status of AMPK or mechanistic target of rapamycin in the brain, whereas several endogenous metabolites, including leucine, citrate, and lactate were enriched in the hypothalamus, suggesting a tissue-specific metabolic shift in response to cortisol stimulation. Altogether, our results suggest that the hypothalamus-specific enrichment of leucine and the metabolic fate of this amino acid, including the generation of lipid intermediates, contribute to cortisol-mediated feeding suppression in fish.NEW & NOTEWORTHY Elevated cortisol levels during stress suppress feed intake in animals. We tested whether the feed suppression is associated with cortisol-mediated alteration in hypothalamus metabolism. The brain metabolome revealed a hypothalamus-specific metabolite profile suggesting nutrient excess. Specifically, we noted the enrichment of leucine and citrate in the hypothalamus, and the upregulation of pathways involved in leucine metabolism and fatty acid synthesis. This cortisol-mediated energy substrate repartitioning may modulate the feeding/satiety centers leading to the feeding suppression.

B cell receptors and free antibodies have different antigen-binding kinetics

Since the pioneering works of Berg and Purcell, discriminating between diffusion followed by binding has played a central role in understanding cell signaling. B cell receptors (BCR) and antibodies (Ab) challenge that simplified view as binding to the antigen follows after a chain of diffusion and rotations, including whole molecule rotation and independent tilts and twists of their Fab arms due to their Y-shaped structure and flexibility. In this paper, we combine analytical calculations with Brownian simulations to derive the first-passage times due to these three rotations positioning the Fab paratopes at a proper distance and orientation required for antigen binding. Our results indicate that when measuring Ab-Ag effective kinetic binding rates, using experimental methods in which the analyte is in solution only gives values proportional to the intrinsic binding rates, [Formula: see text], and [Formula: see text], for values of [Formula: see text] up to [Formula: see text]. Beyond that, a plateau of the effective 3D on rate between [Formula: see text] and [Formula: see text] is attained. Additionally, for BCR-Ag interactions, the effective 2D on and off binding rates can only be inferred from the corresponding effective 3D on and off rates for values of effective 3D on rates lower than [Formula: see text]. This is highly relevant when trying to relate BCR-antigen-binding strength and B cell response, especially during germinal center reactions. Therefore, there is a pressing need to reexamine our current understanding of the BCR-antigen kinetic rates in germinal centers using the latest experimental assays for BCR-Ag interactions.

Antimicrobial Activity of Cefiderocol against the Carbapenemase-Producing Enterobacter cloacae Complex and Characterization of Reduced Susceptibility Associated with Metallo-β-Lactamase VIM-1

Emergence of cefiderocol resistance among carbapenemase-producing Enterobacterales, particularly those in the Enterobacter cloacae complex (ECC), is becoming of alarming concern; however, the mechanistic basis of this phenomenon remains poorly understood. We describe the acquisition of VIM-1-mediated reduced cefiderocol susceptibility (MICs 0.5 to 4 mg/L) in a collection of 54 carbapenemase-producing isolates belonging to the ECC. MICs were determined by reference methodologies. Antimicrobial resistance genomic analysis was performed through hybrid WGS. The impact of VIM-1 production on cefiderocol resistance in the ECC background was examined at microbiological, molecular, biochemical, and atomic levels. Antimicrobial susceptibility testing yielded 83.3% susceptible isolates and MIC50/90 values of 1/4 mg/L. Decreased susceptibility to cefiderocol was mainly associated with isolates producing VIM-1, with cefiderocol MICs 2- to 4-fold higher than for isolates carrying other types of carbapenemases. E. cloacae and Escherichia coli VIM-1 transformants displayed significantly enhanced cefiderocol MICs. Biochemical assays with purified VIM-1 protein revealed low but detectable cefiderocol hydrolysis. Simulation studies revealed how cefiderocol is anchored to the VIM-1 active site. Additional molecular assays and WGS data analysis highlighted the implication of SHV-12 coproduction and suggested the inactivation of the FcuA-like siderophore receptor as further contributors to the higher cefiderocol MICs. Our findings warn of the potential of the VIM-1 carbapenemase to at least partly limit the activity of cefiderocol in the ECC. This effect is probably enhanced due to combination with additional mechanisms, such as ESBL production and siderophore inactivation, and indicates the need for active surveillance to extend the life span of this promising cephalosporin.