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Hemolysins are lytic exotoxins expressed in most strains of S. aureus , but hemolytic activity varies between strains. We have previously reported several novel anti-virulence compounds that disrupt the S. aureus transcriptome, including hemolysin gene expression. This report delves further into our two lead compounds, loratadine and a structurally related brominated carbazole, and their effects on hemolysin production in methicillin-resistant S. aureus (MRSA). To gain understanding into how these compounds affect hemolysis, we analyzed these exotoxins at the DNA, RNA, and protein level after in vitro treatment. While lysis of red blood cells varied between strains, DNA sequence variation did not account for it. We hypothesized that our compounds would modulate gene expression of multiple hemolysins in two hospital-acquired strains of MRSA, both with staphylococcal cassette chromosome mec (SCC mec ) type II. RNA-seq analysis of differential gene expression in untreated and compound-treated cultures revealed hundreds of differentially expressed genes, with a significant enrichment in genes involved in hemolysis. The brominated carbazole and loratadine both displayed the ability to reduce hemolysis in strain 43300 but displayed differential activity in strain USA100. These results corroborate gene expression studies as well as western blots of alpha hemolysin. Together, this work suggests that small molecules may alter exotoxin production in MRSA but that the directionality and/or magnitude of the difference are likely strain dependent.IMPORTANCEMethicillin-resistant S. aureus (MRSA) is a deadly human pathogen. In addition to evading antibiotics, these bacteria produce a wide range of toxins that negatively affect the host. Our work aims to identify and characterize novel compounds that can decrease the pathogenic effects of MRSA. Two lead compounds investigated in this study triggered changes in the production of multiple toxins. These changes were specific to the strain of MRSA investigated. Specifically, this work sheds light on novel compounds that decrease MRSA's ability to lyse host red blood cells. Importantly, it also highlights the importance of examining strain-specific differences in response to therapeutic interventions that could ultimately affect clinical outcomes.

Purpose: We aimed to identify the optimal reconstruction settings based on qualitative and quantitative image quality parameters on standard and ultra-high resolution (UHR) images using photon-counting CT (PCCT)., Method: We analysed 45 patients, 29 with standard and 16 with UHR acquisition, applying both smoother and sharper kernel settings. Coronary CT angiography images were performed on a dual-source PCCT system using standard (0.4/0.6 mm slice thickness, Bv40/Bv44 kernels, QIR levels 0-4) or UHR acquisition (0.2/0.4 mm slice thickness, Bv44/Bv56 kernels, QIR levels 0-4). Qualitative image quality was assessed using a 4-point Likert scale. Image noise (SD), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated in both the proximal and distal segments., Results: On standard resolution, larger slice thickness resulted in an average increase of 12.5 % in CNR, whereas sharper kernel led to an average 8.7 % decrease in CNR. Highest CNR was measured on 0.6 mm, Bv40, QIR4 images and lowest on 0.4 mm, Bv44, QIR0 images: 25.8 ± 4.1vs.8.3 ± 1.6 (p < 0.001). On UHR images, highest CNR was observed on 0.4 mm, Bv40, QIR4 and lowest on 0.2 mm, Bv56 and QIR0 images: 21.5 ± 3.9vs.3.6 ± 0.8 (p < 0.001). Highest qualitative image quality was found on images with Bv44 kernel and QIR level 3/4 with both slice thicknesses on standard reconstruction. Additionally, Bv56 with QIR4 on 0.2 mm slice thickness images showed highest subjective image quality. Preserved distal vessel visualization was detected using QIR 2-4, Bv56 and 0.2 mm slice thickness., Conclusions: Photon-counting CT demonstrated high qualitative and quantitative image quality for the assessment of coronaries and stents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved to become resistant to multiple classes of antibiotics. New antibiotics are costly to develop and deploy, and they have a limited effective lifespan. Antibiotic adjuvants are molecules that potentiate existing antibiotics through nontoxic mechanisms. We previously reported that loratadine, the active ingredient in Claritin, potentiates multiple cell-wall active antibiotics in vitro and disrupts biofilm formation through a hypothesized inhibition of the master regulatory kinase Stk1. Loratadine and oxacillin combined repressed the expression of key antibiotic resistance genes in the bla and mec operons. We hypothesized that additional genes involved in antibiotic resistance, biofilm formation, and other cellular pathways would be modulated when looking transcriptome-wide. To test this, we used RNA-seq to quantify transcript levels and found significant effects in gene expression, including genes controlling virulence, antibiotic resistance, metabolism, transcription (core RNA polymerase subunits and sigma factors), and translation (a plethora of genes encoding ribosomal proteins and elongation factor Tu). We further demonstrated the impacts of these transcriptional effects by investigating loratadine treatment on intracellular ATP levels, persister formation, and biofilm formation and morphology. Loratadine minimized biofilm formation in vitro and enhanced the survival of infected Caenorhabditis elegans . These pleiotropic effects and their demonstrated outcomes on MRSA virulence and survival phenotypes position loratadine as an attractive anti-infective against MRSA.

Background: Overuse of fluoroquinolone antibiotics is associated with outbreaks of methicillin-resistant Staphylococcus aureus and of Clostridium difficile-associated diarrhea and increasing resistance in gram-negative organisms. Over the past decade, resistance of Escherichia coli to ciprofloxacin has increased in the Regina Qu'Appelle Health Region. In August 2011, an exploratory audit of the Regina General Hospital (RGH) emergency department showed that 20% of new antibiotic orders were for fluoroquinolones, and 60% of these new fluoroquinolone orders were for ciprofloxacin. It was postulated that ciprofloxacin was predominantly prescribed for outpatients with urinary tract infection., Objective: To develop, implement, and evaluate a best-practice algorithm for the empiric treatment of uncomplicated urinary tract infection in the RGH emergency department, as part of an educational initiative for emergency physicians., Methods: A literature review was conducted and local antibiogram data were analyzed to establish a best-practice algorithm for treatment of uncomplicated urinary tract infection in outpatients seen in the emergency department. A chart review was conducted from January to March 2011 to establish a baseline of empiric antibiotic use. An educational strategy targeting emergency physicians described changes in antibiotic resistance patterns in the health region, principles of antimicrobial stewardship, drivers of resistance, and the results of a literature review of best practice for urinary tract infection in outpatients. A post-intervention audit was conducted from January to March 2012 to determine changes in practice., Results: Comparison of results from the post-intervention audit with baseline data showed that adherence to best practice increased significantly, from 41% (39/96) before the intervention to 66% (50/76) after the intervention (odds ratio [OR] 2.81, 95% confidence interval [CI] 1.51-5.25; p < 0.001). There was also a significant change in overall antibiotic selection (OR 0.25, 95% CI 0.11-0.58; p < 0.001). Further analysis suggested that this significant change was driven by a decrease in use of ciprofloxacin, from 32% (31/96) to 11% (8/76)., Conclusion: Creation of a best-practice algorithm and education focused on emergency physicians significantly increased adherence to best practice and optimized antibiotic prescribing for outpatients with uncomplicated urinary tract infection by limiting overuse of fluoroquinolones, primarily ciprofloxacin.

Fungi synthesize lysine via the alpha-aminoadipate pathway, which is not found in plants or animals. This pathway has been proposed as a target for antifungal agents, but until now no reports have appeared to test this proposal. Hampering studies on the susceptibility of filamentous fungi such as those of the clinically important genus Aspergillus is the fact that growth quantitation is notoriously difficult. We have used the recently-reported XTT-based method of biomass quantitation to measure the susceptibility of Aspergillus nidulans strain A28 to growth suppression by novel compounds designed to target early steps in the alpha-aminoadipate lysine biosynthesis pathway, specifically those steps involving (R)-homocitrate and (2R,3S)-homoisocitrate. Three compounds show moderate inhibition of fungal growth, which can be partially restored by the presence of lysine in the growth medium.