Effect of interventions to improve safety culture on healthcare workers in hospital settings: a systematic review of the international literature.

BACKGROUND: In an era of safety systems, hospital interventions to build a culture of safety deliver organisational learning methodologies for staff. Their benefits to hospital staff are unknown. We examined the literature for evidence of staff outcomes. Research questions were: (1) how is safety culture defined in studies with interventions that aim to enhance it?; (2) what effects do interventions to improve safety culture have on hospital staff?; (3) what intervention features explain these effects? and (4) what staff outcomes and experiences are identified? METHODS AND ANALYSIS: We conducted a mixed-methods systematic review of published literature using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The search was conducted in MEDLINE, EMBASE, CINAHL, Health Business Elite and Scopus. We adopted a convergent approach to synthesis and integration. Identified intervention and staff outcomes were categorised thematically and combined with available data on measures and effects. RESULTS: We identified 42 articles for inclusion. Safety culture outcomes were most prominent under the themes of leadership and teamwork. Specific benefits for staff included increased stress recognition and job satisfaction, reduced emotional exhaustion, burnout and turnover, and improvements to working conditions. Effects were documented for interventions with longer time scales, strong institutional support and comprehensive theory-informed designs situated within specific units. DISCUSSION: This review contributes to international evidence on how interventions to improve safety culture may benefit hospital staff and how they can be designed and implemented. A focus on staff outcomes includes staff perceptions and behaviours as part of a safety culture and staff experiences resulting from a safety culture. The results generated by a small number of articles varied in quality and effect, and the review focused only on hospital staff. There is merit in using the concept of safety culture as a lens to understand staff experience in a complex healthcare system.

Evaluation of the American College of Surgeons risk calculator in hepatectomy for metastatic colorectal cancer in a Southeast Asian population.

PURPOSE: This study evaluated the accuracy of the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) calculator in predicting outcomes after hepatectomy for colorectal cancer (CRC) liver metastasis in a Southeast Asian population. METHODS: Predicted and actual outcomes were compared for 166 patients undergoing hepatectomy for CRC liver metastasis identified between 2017 and 2022, using receiver operating characteristic curves with area under the curve (AUC) and Brier score. RESULTS: The ACS-NSQIP calculator accurately predicted most postoperative complications (AUC > 0.70), except for surgical site infection (AUC = 0.678, Brier score = 0.045). It also exhibited satisfactory performance for readmission (AUC = 0.818, Brier score = 0.011), reoperation (AUC = 0.945, Brier score = 0.002), and length of stay (LOS, AUC = 0.909). The predicted LOS was close to the actual LOS (5.9 vs. 5.0 days, P = 0.985). CONCLUSION: The ACS-NSQIP calculator demonstrated generally accurate predictions for 30-day postoperative outcomes after hepatectomy for CRC liver metastasis in our patient population.

Iodoarene-directed photoredox ß-C(sp3)-H arylation of 1-(o-iodoaryl)alkan-1-ones with cyanoarenes via halogen atom transfer and hydrogen atom transfer.

Site selective functionalization of inert remote C(sp3)-H bonds to increase molecular complexity offers vital potential for chemical synthesis and new drug development, thus it has been attracting ongoing research interest. In particular, typical ß-C(sp3)-H arylation methods using chelation-assisted metal catalysis or metal-catalyzed oxidative/photochemical in situ generated allyl C(sp3)-H bond processes have been well developed. However, radical-mediated direct ß-C(sp3)-H arylation of carbonyls remains elusive. Herein, we describe an iodoarene-directed photoredox ß-C(sp3)-H arylation of 1-(o-iodoaryl)alkan-1-ones with cyanoarenes via halogen atom transfer (XAT) and hydrogen atom transfer (HAT). The method involves diethylaminoethyl radical-mediated generation of an aryl radical intermediate via XAT, then directed 1,5-HAT to form the remote alkyl radical intermediate and radical-radical coupling with cyanoarenes, and is applicable to a broad scope of unactivated remote C(sp3)-H bonds like ß-C(sp3)-H bonds of o-iodoaryl-substituted alkanones and α-C(sp3)-H bonds of o-iodoarylamides. Experimental findings are supported by computational studies (DFT calculations), revealing that this method operates via a radical-relay stepwise mechanism involving multiple SET, XAT, 1,5-HAT and radical-radical coupling processes.

Evaluation of the impact of prospective payment systems on cholecystectomy: A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to evaluate the impact of prospective payment systems (PPSs) on cholecystectomy. A comprehensive literature review was conducted, examining studies published until December 2023. The review process focused on identifying research across major databases that reported critical outcomes such as length of stay (LOS), mortality, complications, admissions, readmissions, and costs following PPS for cholecystectomy. The studies were specifically selected for their relevance to the impact of PPS or the transition from fee-for-service (FFS) to PPS. The study analyzed six papers, with three eligible for meta-analysis, to assess the impact of the shift from FFS to PPS in laparoscopic and open cholecystectomy procedures. Our findings indicated no significant changes in LOS and mortality rates following the transition from FFS to PPS. Complication rates varied and were influenced by the diagnosis-related group categorization and surgeon cost profiles under episode-based payment. There was a slight increase in admissions and readmissions, and mixed effects on hospital costs and financial margins, suggesting varied responses to PPS for cholecystectomy procedures. The impact of PPS on cholecystectomy is nuanced and varies across different aspects of healthcare delivery. Our findings indicate a need for adaptable, patient-centered PPS models that balance economic efficiency with high-quality patient care. The study emphasizes the importance of considering specific surgical procedures and patient demographics in healthcare payment reforms.

Enhanced hyaline cartilage formation and continuous osteochondral regeneration via 3D-Printed heterogeneous hydrogel with multi-crosslinking inks.

The unique gradient structure and complex composition of osteochondral tissue pose significant challenges in defect regeneration. Restoration of tissue heterogeneity while maintaining hyaline cartilage components has been a difficulty of an osteochondral tissue graft. A novel class of multi-crosslinked polysaccharide-based three-dimensional (3D) printing inks, including decellularized natural cartilage (dNC) and nano-hydroxyapatite, was designed to create a gradient scaffold with a robust interface-binding force. Herein, we report combining a dual-nozzle cross-printing technology and a gradient crosslinking method to create the scaffolds, demonstrating stable mechanical properties and heterogeneous bilayer structures. Biofunctional assessments revealed the remarkable regenerative effects of the scaffold, manifesting three orders of magnitude of mRNA upregulation during chondrogenesis and the formation of pure hyaline cartilage. Transcriptomics of the regeneration site in vivo and scaffold cell interaction tests in vitro showed that printed porous multilayer scaffolds could form the correct tissue structure for cell migration. More importantly, polysaccharides with dNC provided a hydrophilic microenvironment. The microenvironment is crucial in osteochondral regeneration because it could guide the regenerated cartilage to ensure the hyaline phenotype.

Effects of Ultrasonic Treatment on Physical Stability of Lily Juice: Rheological Behavior, Particle Size, and Microstructure.

The aim of this study was to investigate the rheological properties, particle size distribution, color change, and stability of lily juice under different ultrasonic treatment conditions (152 W, 304 W, 456 W, 608 W, and 760 W). The results showed that the lily juice exhibited non-Newtonian shear thinning behavior, and the viscosity decreased with the increase in ultrasonic power. Under ultrasonic treatment conditions, there was no significant change in the pH value and zeta potential value of the samples. The content of cloudy value and total soluble solids (TSS) increased gradually. However, both the sedimentation components and centrifugal sedimentation rate showed a downward trend and an asymptotic behavior. In addition, high-power ultrasound changed the color index (L* value decreased, a* value increased), tissue structure, and particle distribution of the sample, and small particles increased significantly. To sum up, ultrasonic treatment has great potential in improving the physical properties and suspension stability of lily juice.

Right Femoral Fragility Fracture in an Adolescent with Vitamin D Deficiency from COVID-19 Pandemic-Related Confinement.

Background: The COVID-19 pandemic has caused major impacts in various aspects of our life. In Malaysia, a Movement Control Order was imposed in March 2020. For almost two years, school going children and adolescents were not able to attend school physically, and their physical activity was confined within their room or house on most days. Case Description. We describe a case of a 14-year-old boy who was previously active in sports and sustained a low trauma fracture at the right neck of the femur following a prolonged period of extreme sedentary life along with poor dietary intake during the COVID-19 pandemic period. He underwent open reduction and screw fixation for the right neck femur fracture. He was thin with a low BMI (15.62 kg/m2) and a significant loss of muscle bulk in all limbs. Laboratory tests showed vitamin D deficiency (15.3 nmol/L) and the dual energy X-ray absorptiometry (DXA) showed a low Z-score for the total spine (-2.2) and total hip (-3.9). He was treated with activated vitamin D and vitamin D3 replacement. Sports physician was involved for individualized postoperative rehabilitation. Successive clinic visits showed remarkable improvements in physical fitness, sports participation, and normalization of vitamin D levels. Conclusion: A high degree of suspicion is needed to rule out secondary causes in adolescents who present with unusual fragility fractures.

Organo-Ptii Complexes for Potent Photodynamic Inactivation of Multi-Drug Resistant Bacteria and the Influence of Configuration.

PtII based organometallic photosensitizers (PSs) have emerged as novel potent photodynamic inactivation (PDI) reagents through their enhanced intersystem crossing (ISC) processes. Currently, few PtII PSs have been investigated as antibacterial materials, with relatively poor performances reported and with structure-activity relationships not well described. Herein, a pair of configurational isomers are reported of Bis-BODIPY (4,4-difluoro-boradizaindacene) embedded PtII PSs. The cis-isomer (cis-BBP) displayed enhanced 1O2 generation and better bacterial membrane anchoring capability as compared to the trans-isomer (trans-BBP). The effective PDI concentrations (efficiency > 99.9%) for cis-BBP in Acinetobacter baumannii (multi-drug resistant (MDR)) and Staphylococcus aureus are 400 nM (12 J cm-2) and 100 nM (18 J cm-2), respectively; corresponding concentrations and light doses for trans-BBP in the two bacteria are 2.50 µM (30 J cm-2) and 1.50 µM (18 J cm-2), respectively. The 50% and 90% minimum inhibitory concentration (MIC50 and MIC90) ratio of trans-BBP to cis-BBP is 22.22 and 24.02 in A. baumannii (MDR); 21.29 and 22.36 in methicillin resistant S. aureus (MRSA), respectively. Furthermore, cis-BBP displays superior in vivo antibacterial performance, with acceptable dark and photoinduced cytotoxicity. These results demonstrate cis-BBP is a robust light-assisted antibacterial reagent at sub-micromolecular concentrations. More importantly, configuration of PtII PSs should be an important issue to be considered in further PDI reagents design.

Nickel-Catalyzed Reductive Cross-Coupling of Propargylic Acetates with Chloro(vinyl)silanes: Access to Silylallenes.

Because of their various reactivities, propargyl acetates are refined chemical intermediates that are extensively applied in pharmaceutical synthesis. Currently, reactions between propargyl acetates and chlorosilanes may be the most effective method for synthesizing silylallenes. Nevertheless, owing to the adaptability and selectivity of substrates, transition metal catalysis is difficult to achieve. Herein, nickel-catalyzed reductive cross-coupling reactions between propargyl acetates and substituted vinyl chlorosilanes for the synthesis of tetrasubstituted silylallenes are described. Therein, metallic zinc is a crucial reductant that effectively enables two electrophilic reagents to selectively construct C(sp2)-Si bonds. Additionally, a Ni-catalyzed reductive mechanism involving a radical process is proposed on the basis of deuteration-labeled experiments.

Glyphosate exposure affected longevity-related pathways and reduced survival in asian honey bees (Apis cerana).

Glyphosate (N-(phosphonomethyl)glycine, GLY) ranks among the most extensively used and effective herbicides globally. However, excessive GLY utilization poses a substantial threat to the survival of honey bees (Apis cerana). Here we monitored the survival status of A. cerana treated with GLY, and conducted transcriptome sequencing of the bee gut and head to further explore potential GLY influences at the molecular level. We observed that the mortality rate of bees increased as GLY concentration escalated. Pivotal pathways emerged in response to the GLY treatment, with a substantial number of differentially expressed genes enriched in the longevity regulating pathway - multiple species. This strongly suggested that GLY may influence the physiological behavior of bees by impacting this particular pathway. Moreover, our analysis revealed a notable reduction in the enzymatic activities of CYP450 and AChE in both the bee head and intestines of when exposed to GLY. Conversely, the enzymatic activity of superoxide dismutase (SOD) in the head remained unaffected, whereas in the intestines, it exhibited a significant increase. Additionally, prophenol oxidase (PPO) and glutathione-S-transferases (GSTs) displayed contrasting trends in enzymatic activity in both organs. This study offers valuable insights into how GLY impacted the survival of A. cerana.

The Clinical and Cost-Effectiveness of an Individualized Nutritional CAre (INCA) Bundle versus Standard Care for Adults with Pressure Injuries Receiving Home Nursing Services: A Protocol for a Cluster Randomized and Pragmatic Clinical Trial with an Economic Evaluation.

BACKGROUND: Pressure injuries (PIs) represent a significant healthcare challenge in Singapore among the aging population. These injuries contribute to increased morbidity, mortality, and healthcare expenditure. Existing research predominantly explores single-component interventions in hospital environments, often yielding limited success. The INCA Trial aims to address this research gap by conducting a comprehensive, cluster randomized controlled trial that integrates education, individualized nutritional support, and community nursing care. This study is designed to evaluate clinical and cost-effectiveness outcomes, focusing on PI wound area reduction and incremental costs associated with the intervention. METHODS: The INCA Trial employs a two-group, non-blinded, cluster randomized, and pragmatic clinical trial design, recruiting 380 adult individuals (age ≥ 21 years) living in the community with stage II, III, IV, and unstageable PI(s) who are receiving home nursing service in Singapore. Cluster randomization is stratified by postal codes to minimize treatment contamination. The intervention arm will receive an individualized nutrition and nursing care bundle (dietary education with nutritional supplementation), while the control arm will receive standard care. The 90-day intervention will be followed by outcome assessments extending over one year. Primary outcomes include changes in PI wound area and the proportion of participants achieving a ≥40% area reduction. Secondary outcomes include health-related quality of life (HRQOL), nutritional status, and hospitalization rates. Data analysis will be conducted on an intention-to-treat (ITT) basis, supplemented by interim analyses for efficacy and futility and pre-specified sensitivity and subgroup analyses. The primary outcome for the cost-effectiveness analysis will be based on the change to total costs compared to the change to health benefits, as measured by quality-adjusted life years (QALYs). DISCUSSION: The INCA Trial serves as a pioneering effort in its approach to PI management in community settings. This study uniquely emphasizes both clinical and economic outcomes and melds education, intensive dietetic support, and community nursing care for a holistic approach to enhancing PI management.

Construction of a Decellularized Multicomponent Extracellular Matrix Interpenetrating Network Scaffold by Gelatin Microporous Hydrogel 3D Cell Culture System.

Interface tissue repair requires the construction of biomaterials with integrated structures of multiple protein types. Hydrogels that modulate internal porous structures provide a 3D microenvironment for encapsulated cells, making them promise for interface tissue repair. Currently, reduction of intrinsic immunogenicity and increase of bioactive extracellular matrix (ECM) secretion are issues to be considered in these materials. In this study, gelatin methacrylate (GelMA) hydrogel is used to encapsulate chondrocytes and construct a phase transition 3D cell culture system (PTCC) by utilizing the thermosensitivity of gelatin microspheres to create micropores within the hydrogel. The types of bioactive extracellular matrix protein formation by chondrocytes encapsulated in hydrogels are investigated in vitro. After 28 days of culture, GelMA PTCC forms an extracellular matrix predominantly composed of collagen type II, collagen type I, and fibronectin. After decellularization, the protein types and mechanical properties are well preserved, fabricating a decellularized tissue-engineered extracellular matrix and GelMA hydrogel interpenetrating network hydrogel (dECM-GelMA IPN) consisting of GelMA hydrogel as the first-level network and the ECM secreted by chondrocytes as the second-level network. This material has the potential to mediate the repair and regeneration of tendon-bone interface tissues with multiple protein types.

Visible-Light-Induced Photoredox 1,2-Dialkylation of Styrenes with α-Carbonyl Alkyl Bromides and Pyridin-1-ium Salts.

A visible-light-driven photoredox dialkylation of styrenes with α-carbonyl alkyl bromides and pyridin-1-ium salts for the synthesis of polysubstituted 1,4-dihydropyridines is reported. This reaction enables the formation of two new C(sp3)-C(sp3) bonds in a single reaction step and provides a strategy that employs pyridin-1-ium salts as the functionalized alkylating reagents via dearomatization to directly trap the resulting alkyl radicals from radical addition of alkenes and then terminate the alkene dialkylation.

Bile Acid Overload Induced by Bile Duct and Portal Vein Ligation Improves Survival after Staged Hepatectomy in Rats.

OBJECTIVE: Compared to portal vein ligation (PVL), simultaneous bile duct and portal vein ligation (BPL) can significantly enhance hypertrophy of the intact liver. This study aimed to investigate whether BPL could improve survival after extended hepatectomy independently of an increased remnant liver. METHODS: We adopted rat models of 90% BPL or 90% PVL. To investigate the role of bile acids (BAs) the BA pools in the PVL and BPL groups were altered by the diet. Staged resection preserving 10% of the estimated liver weight was performed 3 days after BPL; PVL; or sham operation. Histology, canalicular network (CN) continuity; and hepatocyte polarity were evaluated. RESULTS: At 3 days after BPL; PVL; or sham operation when the volumetric difference of the intended liver remained insignificant, the survival rates after extended hepatectomy were 86.7%, 47%, and 23.3%, respectively (P<0.01). BPL induced faster restoration of canalicular integrity along with an intensive but transient BA overload. Staged hepatectomy after BPL shortened the duration of the bile CN disturbance and limited BA retention. Decreasing the BA pools in the rats that underwent BPL could compromise these effects, whereas increasing the BA pools of rats that underwent PVL could induce similar effects. The changes in CN restoration were associated with activation of LKB1. CONCLUSION: In addition to increasing the future remnant liver, BPL shortened the duration of the spatial disturbance of the CN and could significantly improve the tolerance of the hypertrophied liver to staged resection. BPL may be a safe and efficient future option for patients with an insufficient remnant liver.

Palladium-Catalyzed ß-C(sp3)-H Arylation of Silyl Prop-1-en-1-ol Ethers with Aryl Halides: Entry to α,ß-Unsaturated Ketones.

A palladium(0)-catalyzed ß-C(sp3)-H arylation of silyl prop-1-en-1-ol ethers with aryl halides for the synthesis of α,ß-unsaturated ketones is presented. In contrast to the reported ß-C(sp3)-H arylation of ketones, the chemoselectivity of this current method relies on the Pd(0) catalytic systems and reaction temperatures: While using the Pd(dba)2/DavePhos/KF system at 80 °C resulted in ß-C(sp3)-H monoarylation to produce ß-monoarylated α,ß-unsaturated ketones, harnessing the Pd(OAc)2/t-Bu XPhos/K2HPO4 system at 110 °C induced ß-C(sp3)-H diarylation to afford ß,ß-diarylated α,ß-unsaturated ketones. The method provides a versatile route that uses readily available ketone-derivatized α-nonsubstituted silyl prop-1-en-1-ol ethers as the alkene sources and is characterized by a good functional group compatibility, a broad substrate scope, and an excellent selectivity.

Cobalt-Promoted Electroreductive Cross-Coupling of Prop-2-yn-1-yl Acetates with Chloro(vinyl)silanes.

An electroreductive cross-coupling of prop-2-yn-1-yl acetates with chloro(vinyl)silanes for producing tetrasubstituted silylallenes is developed. The method enables the formation of a new C─Si bond through the cathodic reduction formation of the silyl radical, radical addition across the C≡C bond, the alkenyl anion intermediate formation, and deacetoxylation and represents a mild, practical route to the synthesis of silylallenes. Mechanistic studies reveal that CoCl2 acts as the mediator to promote the formation of the alkenyl anion intermediate via electron transfer.

Gut microbiota-driven regulation of queen bee ovarian metabolism.

With the global prevalence of Varroa mites, more and more beekeepers resort to confining the queen bee in a queen cage to control mite infestation or to breed superior and robust queen bees. However, the impact of such practices on the queen bee remains largely unknown. Therefore, we subjected the queen bees to a 21-day egg-laying restriction treatment (from the egg stage to the emergence of adult worker bees) and analyzed the queen bees' ovarian metabolites and gut microbiota after 21 days, aiming to assess the queen bees' quality and assist beekeepers in better hive management. Our findings revealed a significant reduction in the relative expression levels of Vg and Hex110 genes in the ovaries of egg laying-restricted queen bees compared to unrestricted egg-laying queens. The diversity of gut microbiota in the queen bee exhibited a notable decrease, accompanied by corresponding changes in the core bacteria of the microbial community, the relative abundance of Lactobacillus and Bifidobacterium increased from 22.34% to 53.14% (P = 0.01) and from 0.053% to 0.580% (P = 0.04), respectively. The relative abundance of Bombella decreased from 25.85% to 1.720% (P = 0.002). Following egg-laying restriction, the activity of the queen bee's ovaries decreased, while the metabolism of glycerophospholipids remained or stored more lipid molecules, awaiting environmental changes for the queen bee to resume egg laying promptly. Furthermore, we observed that Bombella in the queen bee's gut may regulate the queen's ovarian metabolism through tryptophan metabolism. These findings provide novel insights into the interplay among queen egg laying, gut microbiota, and ovarian metabolism. IMPORTANCE With Varroa mite infestation, beekeepers often confine the queen bee in cages for control or breeding. However, the impact on the queen bee is largely unknown. We evaluated queen bee quality by restricting egg laying and analyzing ovarian metabolites and gut microbiota. In this study, we provided a comprehensive explanation of the expression of ovarian genes, the diversity of gut microbiota, and changes in ovarian metabolism in the queen bee. Through integrated analysis of the queen bee's gut microbiota and ovarian metabolism, we discovered that the gut microbiota can regulate the queen bee's ovarian metabolism. These findings provide valuable insights into the interplay among egg laying, gut microbiota, and the reproductive health of the queen bee. Understanding these relationships can contribute to the development of better strategies for Varroa mite control and queen bee breeding.

Computational exploration of the global microbiome for antibiotic discovery.

Novel antibiotics are urgently needed to combat the antibiotic-resistance crisis. We present a machine learning-based approach to predict prokaryotic antimicrobial peptides (AMPs) by leveraging a vast dataset of 63,410 metagenomes and 87,920 microbial genomes. This led to the creation of AMPSphere, a comprehensive catalog comprising 863,498 non-redundant peptides, the majority of which were previously unknown. We observed that AMP production varies by habitat, with animal-associated samples displaying the highest proportion of AMPs compared to other habitats. Furthermore, within different human-associated microbiota, strain-level differences were evident. To validate our predictions, we synthesized and experimentally tested 50 AMPs, demonstrating their efficacy against clinically relevant drug-resistant pathogens both in vitro and in vivo. These AMPs exhibited antibacterial activity by targeting the bacterial membrane. Additionally, AMPSphere provides valuable insights into the evolutionary origins of peptides. In conclusion, our approach identified AMP sequences within prokaryotic microbiomes, opening up new avenues for the discovery of antibiotics.

If you measure it, it matters!: a survey of factors influencing implementation of physical activity promotion in cardiac and pulmonary rehabilitation in Australia.

OBJECTIVE: To identify factors related to the frequency of physical activity (PA) promotion by health professionals working in cardiac and/or pulmonary rehabilitation. METHODS: A cross-sectional online survey of health professionals working in cardiac and/or pulmonary rehabilitation in Australia was conducted between July and November 2022. RESULTS: A total of 71 health professionals from four disciplines (physiotherapy, nursing, exercise physiology, occupational therapy) completed the survey. The majority agreed that PA promotion was part of their role. Despite this, only half of the participants encouraged ≥ 10 patients per month to be more physically active. In logistic regression modelling, health professionals that measured patients' PA levels (odds ratio 8.04, 95% confidence level 1.45-44.19) and prioritised PA promotion regardless of other patient problems (odds ratio 3.3, 95% confidence level 0.74-14.82) were much more likely to frequently promote PA to patients. CONCLUSION: Measurement of patients' PA levels within cardiac and pulmonary rehabilitation and making PA promotion a priority may impact the implementation of PA promotion within these programs. PRACTICAL IMPLICATIONS: Physical activity measurement as a key performance indicator in cardiac and pulmonary rehabilitation is indicated. This may be an important strategy to increase physical activity promotion by cardiac and pulmonary rehabilitation health professionals.

A hydrophilic polyimidazolium antibiotic targeting the membranes of Gram-negative bacteria.

OBJECTIVES: The rise of MDR Gram-negative bacteria (GNB), especially those resistant to last-resort drugs such as carbapenems and colistin, is a global health risk and calls for increased efforts to discover new antimicrobial compounds. We previously reported that polyimidazolium (PIM) compounds exhibited significant antimicrobial activity and minimal mammalian cytotoxicity. However, their mechanism of action is relatively unknown. We examined the efficacy and mechanism of action of a hydrophilic PIM (PIM5) against colistin- and meropenem-resistant clinical isolates. METHODS: MIC and time-kill testing was performed for drug-resistant Escherichia coli and Klebsiella pneumoniae clinical isolates. N-phenyl-1-naphthylamine and propidium iodide dyes were employed to determine membrane permeabilization. Spontaneous resistant mutants and single deletion mutants were generated to understand potential resistance mechanisms to the drug. RESULTS: PIM5 had the same effectiveness against colistin- and meropenem-resistant strains as susceptible strains of GNB. PIM5 exhibited a rapid bactericidal effect independent of bacterial growth phase and was especially effective in water. The polymer disrupts both the outer and cytoplasmic membranes. PIM5 binds and intercalates into bacterial genomic DNA upon entry of cells. GNB do not develop high resistance to PIM5. However, the susceptibility and uptake of the polymer is moderately affected by mutations in the two-component histidine kinase sensor BaeS. PIM5 has negligible cytotoxicity on human cells at bacterial-killing concentrations, comparable to the commercial antibiotics polymyxin B and colistin. CONCLUSIONS: PIM5 is a potent broad-spectrum antibiotic targeting GNB resistant to last-resort antibiotics.