Role for dithiolopyrrolones in disrupting bacterial metal homeostasis

Antibiotic resistance is a rising health threat worldwide, against which novel strategies are urgently needed. We have taken a systems approach to examine a potent and underexplored class of broad-spectrum antibiotics, the dithiolopyrrolones (DTPs). Our results indicate that DTPs disrupt cellular processes by high-affinity chelation of essential metal ions and inhibition of a subset of metalloenzymes. This mode of action is unique amongst antibiotics and may be further explored for treatment of multidrug-resistant infections. Our study also highlights chemical genomics as a powerful approach for the identification of antimicrobial mechanisms of action

Catabolic Ornithine Carbamoyltransferase Activity Facilitates Growth of Staphylococcus aureus in Defined Medium Lacking Glucose and Arginine

Previous studies have found that arginine biosynthesis in Staphylococcus aureus is repressed via carbon catabolite repression (CcpA), and proline is used as a precursor. Unexpectedly, however, robust growth of S. aureus is not observed in complete defined medium lacking both glucose and arginine (CDM-R). Mutants able to grow on agar-containing defined medium lacking arginine (CDM-R) were selected and found to contain mutations within ahrC, encoding the canonical arginine biosynthesis pathway repressor (AhrC), or single nucleotide polymorphisms (SNPs) upstream of the native arginine deiminase (ADI) operon arcA1B1D1C1. Reverse transcription-PCR (RT-PCR) studies found that mutations within ccpA or ahrC or SNPs identified upstream of arcA1B1D1C1 increased the transcription of both arcB1 and argGH, encoding ornithine carbamoyltransferase and argininosuccinate synthase/lyase, respectively, facilitating arginine biosynthesis. Furthermore, mutations within the AhrC homologue argR2 facilitated robust growth within CDM-R. Complementation with arcB1 or arcA1B1D1C1, but not argGH, rescued growth in CDM-R. Finally, supplementation of CDM-R with ornithine stimulated growth, as did mutations in genes (proC and rocA) that presumably increased the pyrroline-5-carboxylate and ornithine pools. Collectively, these data suggest that the transcriptional regulation of ornithine carbamoyltransferase and, in addition, the availability of intracellular ornithine pools regulate arginine biosynthesis in S. aureus in the absence of glucose. Surprisingly, ~50% of clinical S. aureus isolates were able to grow in CDM-R. These data suggest that S. aureus is selected to repress arginine biosynthesis in environments with or without glucose; however, mutants may be readily selected that facilitate arginine biosynthesis and growth in specific environments lacking arginine. IMPORTANCE Staphylococcus aureus can cause infection in virtually any niche of the human host, suggesting that it has significant metabolic versatility. Indeed, bioinformatic analysis suggests that it has the biosynthetic capability to synthesize all 20 amino acids. Paradoxically, however, it is conditionally auxotrophic for several amino acids, including arginine. Studies in our laboratory are designed to assess the biological function of amino acid auxotrophy in this significant pathogen. This study reveals that the metabolic block repressing arginine biosynthesis in media lacking glucose is the transcriptional repression of ornithine carbamoyltransferase encoded by arcB1 within the native arginine deiminase operon in addition to limited intracellular pools of ornithine. Surprisingly, approximately 50% of S. aureus clinical isolates can grow in media lacking arginine, suggesting that mutations are selected in S. aureus that allow growth in particular niches of the human host

Prevalence, Characteristics and Outcomes of Older Patients with Hereditary versus Wild-Type Transthyretin Amyloid Cardiomyopathy

BACKGROUND: Transthyretin amyloid cardiomyopathy (ATTR-CM) is often assumed to be associated with wild-type TTR genotype (ATTRwt) in elderly patients (aged >70), some of whom are not offered genetic testing. We sought to estimate the prevalence, clinical characteristics and prognostic implications of TTR variants among elderly patients diagnosed with ATTR-CM. METHODS: Data from consecutive patients over 70 years of age diagnosed with ATTR-CM at the UK National Amyloidosis Centre between January 2010 and August 2022 were retrospectively evaluated. All patients underwent clinical evaluation, biochemical tests, echocardiography and TTR genotyping. The study outcome was all-cause mortality. RESULTS: The study population consisted of 2029 patients with ATTR-CM (median age 79 years at diagnosis, 13.2% females, 80.4% Caucasian). Variant ATTR-CM (ATTRv-CM) was diagnosed in 20.7% (n=421) of the study population of whom 329 (76.3%) carried V122I, 49 (11.4%) T60A, 18 (4.2%) V30M and 35 (8.1%) other pathogenic TTR variants. During a median (range) follow up of 29 (12-48) months, ATTRv-CM was associated with increased all-cause mortality compared to ATTRwt-CM, with the poorest survival observed in V122I-associated ATTRv-CM (p<0.001). Univariable and multivariable logistic regression analyses in those with ATTR-CM showed younger age at diagnosis (odds ratio [OR] 0.85 per year, p<0.001), female sex (OR 2.73, p<0.001), Afro-Caribbean ethnicity (OR 65.5, p<0.001), atrial fibrillation (OR 0.65, p=0.015), ischemic heart disease (OR 0.54, p=0.007), peripheral polyneuropathy (OR 5.70, p<0.001) and orthostatic hypotension (OR 6.29, p<0.001) to be independently associated with ATTRv-CM. CONCLUSION: Up to 20.7% of elderly patients with ATTR-CM have a pathogenic TTR variant. These findings support routine sequencing of the TTR gene in all patients with ATTR-CM regardless of age. This article is protected by copyright. All rights reserved

Randomized controlled trial comparing three different modalities of lithotrites for intracorporeal lithotripsy in pcnl

Purpose: To compare the efficiency (stone fragmentation and removal time) and complications of three models of intracorporeal lithotripters in percutaneous nephrolithotomy (PCNL). Materials and Methods: Prospective, randomized controlled trial at nine centers in the North America from 2009 to 2016. Patients were randomized to one of three lithotripter devices: the Cyberwand, a dual probe ultrasonic device; the Swiss Lithoclast Select, a combination pneumatic and ultrasonic device; and the StoneBreaker, a portable pneumatic device powered by CO2 cartridges. Since the StoneBreaker lacks an ultrasonic component, it was used with the LUS‐II ultrasonic lithotripter to allow fair comparison with combination devices. Results: 270 patients were enrolled, 69 were excluded after randomization. 201 patients completed the study: 71 in the Cyberwand group, 66 in the Lithoclast Select, and 64 in the StoneBreaker group. The baseline patient characteristics of the three groups were similar. Mean stone surface area was smaller in the StoneBreaker group at 407.8mm2 vs 577.5mm2 (Lithoclast Select) and 627.9mm2 (Cyberwand). The stone clearance rate was slowest in the StoneBreaker group at 24.0 mm2/min vs 28.9 mm2/min and 32.3 mm2/min in the Lithoclast Select and Cyberwand groups respectively. After statistically adjusting for the smaller mean stone size in the StoneBreaker group, there was no difference in the stone clearance rate among the three groups (p=0.249). Secondary outcomes, including complications and stone free rates, were similar between the groups. Conclusions: The Cyberwand, Lithoclast Select, and the StoneBreaker lithotripters have similar adjusted stone clearance rates in PCNL for stones > 2cm. The safety and efficacy of these devices are comparable

Tracking Multiorgan Treatment Response in Systemic AL-Amyloidosis With Cardiac Magnetic Resonance Derived Extracellular Volume Mapping

Background: Systemic light chain amyloidosis is a multisystem disorder that commonly involves the heart, liver, and spleen. Cardiac magnetic resonance with extracellular volume (ECV) mapping provides a surrogate measure of the myocardial, liver, and spleen amyloid burden. Objectives: The purpose of this study was to assess multiorgan response to treatment using ECV mapping, and assess the association between multiorgan treatment response and prognosis. Methods: The authors identified 351 patients who underwent baseline serum amyloid-P-component (SAP) scintigraphy and cardiac magnetic resonance at diagnosis, of which 171 had follow-up imaging. Results: At diagnosis, ECV mapping demonstrated that 304 (87%) had cardiac involvement, 114 (33%) significant hepatic involvement, and 147 (42%) significant splenic involvement. Baseline myocardial and liver ECV independently predict mortality (myocardial HR: 1.03 [95% CI: 1.01-1.06]; P = 0.009; liver HR: 1.03; [95% CI: 1.01-1.05]; P = 0.001). Liver and spleen ECV correlated with amyloid load assessed by SAP scintigraphy (R = 0.751; P < 0.001; R = 0.765; P < 0.001, respectively). Serial measurements demonstrated ECV correctly identified changes in liver and spleen amyloid load derived from SAP scintigraphy in 85% and 82% of cases, respectively. At 6 months, more patients with a good hematologic response had liver (30%) and spleen (36%) ECV regression than myocardial regression (5%). By 12 months, more patients with a good response demonstrated myocardial regression (heart 32%, liver 30%, spleen 36%). Myocardial regression was associated with reduced median N-terminal pro-brain natriuretic peptide (P < 0.001), and liver regression with reduced median alkaline phosphatase (P = 0.001). Changes in myocardial and liver ECV, 6 months after initiating chemotherapy, independently predict mortality (myocardial HR: 1.11 [95% CI: 1.02-1.20]; P = 0.011; liver HR: 1.07 [95% CI: 1.01-1.13]; P = 0.014). Conclusions: Multiorgan ECV quantification accurately tracks treatment response and demonstrates different rates of organ regression, with the liver and spleen regressing more rapidly than the heart. Baseline myocardial and liver ECV and changes at 6 months independently predict mortality, even after adjusting for traditional predictors of prognosis

Impaired alanine transport or exposure to d-cycloserine increases the susceptibility of MRSA to β-lactam antibiotics

Prolonging the clinical effectiveness of β-lactams, which remain first-line antibiotics for many infections, is an important part of efforts to address antimicrobial resistance. We report here that inactivation of the predicted d-cycloserine (DCS) transporter gene cycA re-sensitized MRSA to β-lactam antibiotics. The cycA mutation also resulted in hyper-susceptibility to DCS, an alanine analogue antibiotic that inhibits alanine racemase and d-alanine ligase required for d-alanine incorporation into cell wall peptidoglycan (PG). Alanine transport was impaired in the cycA mutant and this correlated with increased susceptibility to oxacillin and DCS. The cycA mutation or exposure to DCS were both associated with the accumulation of muropeptides with tripeptide stems lacking the terminal d-ala-d-ala and reduced PG crosslinking, prompting us to investigate synergism between β-lactams and DCS. DCS re-sensitised MRSA to β-lactams in vitro and significantly enhanced MRSA eradication by oxacillin in a mouse bacteraemia model. These findings reveal alanine transport as a new therapeutic target to enhance the susceptibility of MRSA to β-lactam antibiotics.</jats:p

Misoprostol in addition to routine treatment of postpartum hemorrhage: A hospital-based randomized-controlled trial in Karachi, Pakistan

<p>Abstract</p> <p>Background</p> <p>Postpartum hemorrhage (PPH) remains a major killer of women worldwide. Standard uterotonic treatments used to control postpartum bleeding do not always work and are not always available. Misoprostol's potential as a treatment option for PPH is increasingly known, but its use remains ad hoc and available evidence does not support the safety or efficacy of one particular regimen. This study aimed to determine the adjunct benefit of misoprostol when combined with standard oxytocics for PPH treatment.</p> <p>Methods</p> <p>A randomized controlled trial was conducted in four Karachi hospitals from December 2005 – April 2007 to assess the benefit of a 600 mcg dose of misoprostol given sublingually in addition to standard oxytocics for postpartum hemorrhage treatment. Consenting women had their blood loss measured after normal vaginal delivery and were enrolled in the study after losing more than 500 ml of blood. Women were randomly assigned to receive either 600 mcg sublingual misoprostol or matching placebo in addition to standard PPH treatment with injectable oxytocics. Both women and providers were blinded to the treatment assignment. Blood loss was collected until active bleeding stopped and for a minimum of one hour after PPH diagnosis. Total blood loss, hemoglobin measures, and treatment outcomes were recorded for all participants.</p> <p>Results</p> <p>Due to a much lower rate of PPH than expected (1.2%), only sixty-one patients were diagnosed and treated for their PPH in this study, and we were therefore unable to measure statistical significance in any of the primary endpoints. The addition of 600 mcg sublingual misoprostol to standard PPH treatments does, however, suggest a trend in reduced postpartum blood loss, a smaller drop in postpartum hemoglobin, and need for fewer additional interventions. Women who bled less overall had a significantly smaller drop in hemoglobin and received fewer additional interventions. There were no hysterectomies or maternal deaths among study participants. The rate of transient shivering and fever was significantly higher among women receiving misoprostol</p> <p>Conclusion</p> <p>A 600 mcg dose of misoprostol given sublingually shows promise as an adjunct treatment for PPH and its use should continue to be explored for its life-saving potential in the care of women experiencing PPH.</p> <p>Trial Registration</p> <p>Clinical trials.gov, Registry No. NCT00116480</p