Multidrug-resistant Gram-negative Bacteria Research Articles

Regional insights on the prevalence and antimicrobial susceptibility pattern of carbapenem and colistin-resistant gram-negative bacteria: an observational cross-sectional study from Karachi, Pakistan

BackgroundColistin is used to treat multidrug-resistant gram-negative bacteria. Rising colistin resistance worldwide has created challenges in effective treatment and raised treatment costs. Our study aimed to understand the prevalence of colistin resistance in carbapenem-resistant gram-negative bacteria, associated pathogens and their antimicrobial susceptibility pattern at our institute, to help limit further development of resistance.MethodsAn observational, cross-sectional study was conducted at the Microbiology laboratory of Indus Hospital & Health Network, Karachi, Pakistan from January 1, 2022 to December 31, 2023. Variables extracted from the electronic patient care database included the type of patient samples, clinical diagnoses, frequency of carbapenem-resistant gram-negative bacteria and antimicrobial susceptibility profiles. Microsoft Excel software (Microsoft Excel 2013 {15.0.5553.1000} 32-bit) was used for analysis. Susceptibility results were interpreted in accordance with the M100 guidelines of the Clinical and Laboratory Standards Institute.ResultsA total of 1,785 carbapenem-resistant gram-negative bacteria were isolated during the study period. Thirty (1.7%) of these exhibited colistin minimum inhibitory concentrations of ≥ 4 µg/ml and were characterized as colistin-resistant. Most patients with colistin-resistant gram-negative bacterial infections were males (57%), aged 31–49 and ≥ 50 years (37% each), and in-patients (60%). Majority had urinary tract infection (34%), followed by bloodstream infection (30%), ventilator-associated pneumonia (23%), and skin and soft tissue infection (13%). Organisms included Klebsiella species (77%), Acinetobacter baumanii (20%) and Pseudomonas aeruginosa (3%). Tigecycline was the most susceptible antibiotic among isolates (96%) while, fosfomycin (53%), minocycline (50%), doxycycline (45%) and tetracycline (42%) exhibited moderate susceptibility.ConclusionOur study highlights a concerning prevalence of colistin resistance (1.7%) among carbapenem-resistant gram-negative bacteria, particularly Klebsiella species, predominantly affecting male in-patients aged 31–49 and ≥ 50 years. This significant therapeutic challenge is underscored by the limited efficacy of available antibiotics, with only tigecycline showing high susceptibility (96%) and others like fosfomycin (53%) and minocycline (50%) offering moderate alternatives.

Roles of the rpoEc-chrR-chrA operon in superoxide tolerance and β-lactam susceptibility of Stenotrophomonas maltophilia

IntroductionThe rpoE-chrR pair is a regulatory system used by photosynthetic microorganisms to overcome singlet oxygen stress. rpoE and chrR encode the sigma factor σE and anti-sigma factor ChrR, respectively. Stenotrophomonas maltophilia, an opportunistic pathogen, is a multidrug-resistant gram-negative bacterium. Although it is not a photosynthetic microorganism, a rpoE-chrR homolog (smlt2377-smlt2378) was found in the S. maltophilia genome. In this study, we aimed to assess the significance of σEc-ChrR pair in oxidative stress alleviation and antibiotic susceptibility of S. maltophilia KJ.MethodsReverse transcription-polymerase chain reaction was used to validate the presence of operon. The contribution of rpoEc-chrR-chrA operon to oxidative stress alleviation and antibiotic susceptibility was evaluated using mutant constructs and stress-tolerance assays. RNA-seq transcriptome assay of wild-type KJ, KJΔChrR (chrR mutant), and KJΔChrRΔRpoEc (chrR/rpoEc double mutant) was performed to reveal the σEc regulon.ResultsThe rpoEc-chrR pair and downstream chrA formed an operon. Inactivation of chrR upregulated the expression of rpoEc-chrR-chrA operon in an σEc- and ChrA-dependent manner. σEc activation contributed to superoxide tolerance and increased β-lactam susceptibility but did not affect the tolerance to singlet oxygen and hydrogen peroxide. Transcriptome analysis revealed that expression of the nine-gene cluster, smlt2375-smlt2367, was significantly upregulated in KJΔChrR and reverted to the wild-type level in KJΔChrRΔRpoEc. smlt2375-smlt2367 cluster was located upstream of the rpoEc-chrR-chrA operon and divergently transcribed, seeming to be involved in membrane lipid modification. Deletion of smlt2375-smlt2367 cluster from the chromosome of KJΔChrR reverted the superoxide tolerance and β-lactam susceptibility to the wild-type level.DiscussionThe rpoEc-chrR pair of S. maltophilia was involved in superoxide tolerance and β-lactam susceptibility. Notably, a novel regulatory circuit involving rpoEc-chrR-chrA operon and smlt2375-smlt2367 cluster was revealed.

Development, Characterization, and Antimicrobial Evaluation of Hybrid Nanoparticles (HNPs) Based on Phospholipids, Cholesterol, Colistin, and Chitosan Against Multidrug-Resistant Gram-Negative Bacteria

Background: Colistin, a lipopeptide antibiotic usually used as a last resort against multidrug-resistant bacterial strains, has also begun to address the challenge of antimicrobial resistance. Objective: this study evaluates whether hybrid nanoparticles (HNPs) composed of Phospholipon® 90G, cholesterol, and colistin can enhance its effectiveness against resistant clinical isolates of Klebsiella pneumoniae, a clinically significant Gram-negative bacterium. Methods: HNPs were developed using the ethanol injection method and coated with chitosan through a layer-by-layer technique. HNP characterization included measurements of particle size, polydispersity index (PDI), and zeta potential, along with thermal (DSC) and spectrophotometric (FT-IR) analyses. Ultrafiltration and ATR-FTIR were employed to assess colistin’s association and release efficiencies. The biological evaluation followed CLSI guidelines. Results: uncoated hybrid nanoparticles (U-HNP) and chitosan-coated hybrid nanoparticles (Ch-HNP) described monodisperse populations, with respective PDI values of ~0.124 and ~0.150, Z-averages of ~249 nm and ~250 nm, and zeta potential values of +17 mV and +20 mV. Colistin’s association and release efficiencies were approximately 79% and 10%, respectively. Regarding antimicrobial activity, results showed that colistin as part of HNPs is poorly effective against this microorganism. However, in the most resistant strain, colistin activity increased slightly when the HNP was coated with chitosan. Conclusions: HNPs described high stability against disaggregation, limiting the colistin release and, therefore, affecting antimicrobial performance.

Synergistic antimicrobial efficacy of glabrol and colistin through micelle-based co-delivery against multidrug-resistant bacterial pathogens.

Widespread bacterial infection and the spread of multidrug resistance (MDR) exhibit increasing threats to the public and thus require new antibacterial strategies. Coupled with the current slow pace of antibiotic development, the use of antibiotic adjuvants to revitalize existing antibiotics offers great potential. We aim to explore the synergistic antimicrobial mechanism of glabrol (GLA) and colistin (COL) while developing an innovative multifunctional micelle-based drug delivery system to enhance therapeutic efficacy. The synergy between GLA and COL was assessed through a combination of high-throughput screening and checkerboard analysis techniques. Moreover, we performed fluorescence-based assays to investigate the underlying mechanisms of action of the GLA and COL combination. We also developed a multifunctional drug delivery platform that integrates GLA and COL into co-loaded composite micelles, aimed at improving antibacterial efficacy against peritoneal sepsis and chronic bacterial wound infections caused by diverse microbial pathogens. We have discovered that natural flavonoids found in plants act synergistically with colistin against MDR bacterial infections, effectively improving its efficacy through a co-delivery strategy. The combination therapy consisting of GLA and COL exhibits enhanced antibacterial efficacy and is capable of clearing 99% of MDR Gram-positive and Gram-negative bacteria in 4 h. Mechanistic studies showed that COL increases the outer membrane permeability, which promotes the adhesion of GLA to the inner membrane, disrupting bacterial metabolism, and ultimately leading to bacterial death. Furthermore, a novel pH-responsive hydrogel system was developed and dispersed with GLA and COL co-loaded composite micelles to mitigate the selective pressure of antibiotics with fewer side effects. Lastly, such a system showed high efficacy in two animal models. Our findings provide a potential therapeutic option using a co-delivery system functionalized with combination therapy, to address the prevalent infections caused by complex bacterial infections and even MDR bacterial infections.

Experimental and computational studies of Schiff bases derived from 4-aminoantipyrine as potential antibacterial and anticancer agents

Schiff bases are organic compounds recognized for their biological activities, including antiviral, antibacterial, antifungal, and anticancer properties, making them promising candidates in medicinal chemistry. In this studio, a series of Schiff bases 3a–h derived from 4-aminoantipyrine and substituted cinnamaldehydes were evaluated in vitro against liver (HepG2) and thyroid (THJ29T) cancer cells, Gram-positive and Gram-negative multidrug-resistant bacteria, and biofilm-forming pathogens. Six compounds demonstrated anticancer activity, though some exhibited toxicity to non-tumor cells. Compounds 3b, 3f, and 3h showed notable anticancer potential, while 3f and 3h also exhibited strong antibacterial effects, with 3f being the most effective against multidrug-resistant bacteria strains. These Schiff bases also inhibit biofilm formation, suggesting their potential for treating biofilm-related infections. In-silico analyses of their ADME properties, global reactivity descriptors, and binding affinities corroborated these findings. The Schiff base 3f has a strong binding affinity for DNA gyrase and vitamin D receptor, suggesting potential mechanisms for its antibacterial and anticancer activities.

Role of glycosylation in bacterial resistance to carbapenems.

Carbapenems are a class of β-lactam antibacterial drugs with a broad antibacterial spectrum and strong activity, commonly used to treat serious bacterial infections. However, improper or excessive use of carbapenems can lead to increased bacterial resistance, which is a significant concern as they are often used as last resort for treating multidrug-resistant (MDR) gram-negative bacteria. Confronted with this challenge, it is crucial to comprehensively understand the mechanism of carbapenem resistance to develop effective therapeutic strategies and innovative drugs. In recent years, emerging research on the glycosylation of bacterial proteins has highlighted the crucial role of glycans in various bacterial processes, including carbapenem resistance. Given the limited understanding of bacterial glycosylation, its role in in carbapenem resistance may be more pivotal than currently acknowledged. In this review, we summarize the direct and multifunctional role of glycosylation in bacterial resistance as well as the classical and recently reported mechanisms of bacterial carbapenem resistance, focusing on illuminating the potential role of glycosylation in carbapenem resistance. We also discuss the potential of leveraging this knowledge to develop more effective strategies for combating clinically resistant bacteria.

P-229. Epidemiology of Catheter-Related Bloodstream Infections in Italian Intensive Care Units: Data from the Italian Network for the Evaluation of ICU Interventions

Abstract Background Intensive care unit (ICU) acquired bloodstream infections (BSIs) are an important cause of morbidity and mortality. The use of invasive devices, such as endovascular catheters is associated with greater risk of developing such infections. Our study focuses on the epidemiology of ICU-acquired catheter-related BSIs (CR-BSIs) in Italy from 2014 to 2022.Table 1.Characteristics of ICU admitted patients from 2014 to 2022.LOS, length of stay; SD, standard deviation; CVC, central venous catheter; BSI, bloodstream infection; CR-BSI, catheter-related bloodstream infection. With intensive care treatment need we mean the number and percentage of patients who were admitted to ICU for intensive care treatment, therefore excluding those admitted for post-surgical monitoring or invasive procedure execution. Methods We retrieved data from the PROSAFE project, a prospective, observational, multicentric study involving 135 Italian ICUs. Clinical data were continuously collected by physicians from January 2014 to December 2022. CR-BSIs episodes were defined in accordance with the National Healthcare Safety Network. Multi-drug resistant Gram-negative bacteria (MDR-GNB) were defined as resistant to at least one carbapenem. Continuous variables were summarized with mean and standard deviation, while categorical data were presented as counts and percentages.Figure 1.Percentage of species isolated from blood cultures of patients with ICU-acquired catheter-related bloodstream infection from 2014 to 2022.S. aureus, Staphylococcus aureus; CoNS, Coagulase negative Staphylococci; GPB, Gram positive bacteria, GNB; Gram negative bacteria. Other GPB include Streptococci and Enterococci. Results A total of 271654 patients were included in our study (Table 1). The number of episodes of CR-BSIs was 3361. The in-ICU mortality of patients with CR-BSIs was 28.5%. The incidence of CR-BSIs slightly increased through the years (1.1% in 2014 vs 1.9% in 2022), peaking in 2020-2021. Regarding the microbiology, most bacteria were Gram positive (GP), representing around half of the involved pathogens (Figure 1). CR-BSIs due to coagulase-negative staphylococci (CoNS) increased over the years (from 28.9% in 2014 to 41.2% in 2022), particularly since the COVID-19 pandemic. More than a third of CR-BSIs were caused by GNB, 22.7% of which were MDR. The most common pathogen was Klebsiella pneumoniae, which represented 13.4% of all CR-BSIs. An overall decrease of MDR-GNB was noted (Figure 2). CR-fungemias represented almost 9% of all CR-BSIs, with a peak at 12% in 2020.Figure 2.Percentage of resistant pathogens isolated from blood cultures of patients with ICU-acquired catheter-related bloodstream infection from 2014 to 2022. Resistant pathogens were defined as resistant to methicillin for Staphylococcus aureus, resistant to vancomycin for Enterococci and resistant to at least one carbapenem for Gram-negative rods. CR-BSI, catheter-related bloodstream infection; MRSA, methicillin-resistant Staphylococcus aureus, E. faecium, Enterococcus faecium; E. faecalis, Enterococcus faecalis; K. pneumoniae, Klebsiella pneumoniae; E. coli, Escherichia coli; P. aeruginosa, Pseudomonas aeruginosa; A. baumannii, Acinetobacter baumannii. Conclusion Our study highlights the significant burden of CR-BSIs in Italian ICUs. Despite efforts to mitigate these infections, the incidence of CR-BSIs has shown a concerning upward trend, particularly driven by the rise in CoNS infections, notably since the onset of the COVID-19 pandemic. These findings underscore the ongoing challenge of combating CR-BSIs and emphasize the importance of continued surveillance and targeted interventions to mitigate their impact on patient outcomes in ICUs. Disclosures All Authors: No reported disclosures

P-1496. Retrospective Study of Ceftazidime-Avibactam Treatment for Multidrug-Resistant Gram-Negative Bacterial Infections in King Chulalongkorn Memorial Hospital

Abstract Background Antimicrobial resistance, particularly among Enterobacterales, poses a significant healthcare threat. With the rise of carbapenem-resistant strains, alternative treatment strategies are necessary. This study explores the clinical experience of using ceftazidime-avibactam (CAZ-AVI) in treating infections caused by multidrug-resistant Gram-negative bacteria (MDR-GNB), including carbapenem-resistant pathogens.Table 1.Baseline characteristics of the patients who received CAZ/AVI Methods A single-center retrospective observational study was conducted at King Chulalongkorn Memorial Hospital, Thailand, from Jan. 2019 to Dec. 2022. The study included adult patients aged ≥18 years, who receiving ≥48 hours of CAZ-AVI for documented MDR-GNB infections. Data on demographics, comorbidities, treatment regimens, and outcomes were extracted from electronic medical records. The primary outcome was all-cause mortality at 14 days. Secondary objectives included clinical and microbiological responses at 14 days, and all-cause mortality at 28 days.Table 2.Clinical outcomes of the patients who received CAZ/AVI Results Among 85 patients receiving CAZ-AVI, 75 met inclusion criteria. The mean age was 65.27 years, with 54.7% being male. Hospital-acquired infections accounted for 82.7%, and 56% were ICU patients. Underlying conditions included chronic kidney diseases/end-stage renal diseases (28%), solid tumors (24%), cirrhosis (13.3%), hematologic malignancies (10.7%), and solid organ transplantation (10.7%). K. pneumoniae was the most common organism (69.3%), followed by P. aeruginosa (20%). All (100%) of K. pneumoniae and E. coli were carbapenem resistance. CAZ-AVI susceptibility was observed in 93.6% of isolates. The 14-day all-cause mortality rate was 25.3%. Clinical and microbiological response rates were 70.7% and 65.3%, respectively. Infection by CAZ-AVI-susceptible organisms correlated with lower mortality rates (p=0.017). No adverse drug effects were reported.Table 3.Clinical outcomes of the patients who received CAZ/AVI Conclusion This study highlights the promising role of CAZ-AVI in treating MDR-GNB infections, offering an alternative to conventional therapies. While challenges remain, including the complexity of empirical therapy and variations in patient outcomes, CAZ-AVI demonstrates efficacy with a favorable safety profile. Disclosures KAMONWAN JUTIVORAKOOL, MD, Msc, Pfizer, Thailand: Grant/Research Support|Pfizer, Thailand: Honoraria Rongpong Reinprayoon, MD, MSc, Pfizer: Grant/Research Support

Colistin antibacterial activity, clinical effectiveness, and mechanisms of intrinsic and acquired resistance.

Following a period of disuse owing to the emergence of multidrug-resistant Gram-negative bacteria, colistin has regained global attention as an antibiotic of last resort. The resurgence in its utilization has led to a concurrent increase in acquired resistance, presenting a significant challenge in clinical treatment. Predominantly, resistance mechanisms involve alterations in the lipid A component of the lipopolysaccharide (LPS) structure. These alterations are facilitated by the addition of cationic phosphoethanolamine (pEtN) or 4-amino-L-arabinose, often driven by the upregulation of two-component regulatory systems such as PmrAB and PhoPQ. Structural components of bacteria, such as capsules and efflux pumps, can also play an important role in the resistance mechanism. In addition to these biochemical modifications, structural components of bacteria like capsules and efflux pumps also play crucial roles in mediating resistance. Another significant mechanism is the acquisition of the plasmid-mediated mobilized colistin resistance (mcr) gene, which poses a global health threat due to its ability to transfer between different bacterial genera. Contemporary strategies to combat colistin resistance include the development and use of novel drugs and inhibitors. To devise effective interventions, it is imperative to first elucidate the precise mechanisms of colistin resistance and determine the roles of various contributing factors.

Risk of Colonization with Multidrug-Resistant Gram-Negative Bacteria Among Travellers and Migrants: A Narrative Review.

Globalization in the 21st century has posed several challenges. In particular, the spread of multidrug-resistant bacterial strains, especially Gram-negative bacteria, which are prevalent in certain regions of the world, is one of the most critical issues. This raises concerns about the risks associated with the booming tourism industry and migratory flows. In fact, even transient colonization with multidrug-resistant strains can present significant challenges to individual, family, and public health. Understanding the epidemiology and mechanisms of resistance, associated risk factors and prevention policies is therefore essential to ensure that strategies are in place to limit the global spread of high-risk bacterial clones and thereby protect public health.

Multidrug Resistant Gram-negative Bacteria in Surgical Site Infections: Antimicrobial Resistance and Preventive Measures

Abstract Multidrug resistant (MDR) gram-negative bacteria (GNB) are responsible for high mortality and morbidity in healthcare settings worldwide. They have been declared as priority pathogens by the WHO for their continuously escalating antimicrobial resistance. Nevertheless, data associated with MDR GNB in healthcare-associated infections are insufficient. Surgical site infections (SSIs) are among the most commonly occurring healthcare-associated infections. Such infections are particularly common when bacteria from the patient's normal microflora are transferred to the surgical sites during surgical procedures. SSIs affect approximately 0.5%-3% of patients undergoing surgery, resulting in prolonged hospital stay compared with patients without SSIs. SSIs result in severe problems and lead to a heavy economic burden. Most SSIs can be avoided if suitable preventive measures are employed. Novel findings support the dedicated usage of oral preoperative surgical antimicrobial prophylaxis for specific surgeries based on sites/organs. Immediate interventions are sought to control the transmission of MDR GNB typically found in hospital settings. The present narrative review aims to describe MDR GNB in SSIs in different sites. Antimicrobial resistance epidemiology and preventive measures for SSIs are also discussed. Different intrinsic and extrinsic factors and control measures are elaborated for curbing SSIs.

Evaluation of multidrug resistance in the Gram-negative microbiome of cancer patients and the adverse effects of their metabolites on albino rats and epithelial or fibroblasts cell lines

BackgroundCancer is a significant global health issue due to its high incidence and mortality rates. In recent years, the relationship between the human microbiota and cancer has garnered attention across various medical fields. This includes research into the microbial communities that influence cancer development, tumor-associated microorganisms, and the interactions between the microbiome and tumor, collectively referred to as the oncobiome.MethodsThe negative effects of secondary metabolites extracted from selected multidrug-resistant Gram-negative bacteria within the cancer microbiota were evaluated. These effects included carcinogenicity, mutagenicity, hepatotoxicity, nephrotoxicity, and sperm deformities observed in albino rats after one month of oral ingestion of these microbial extracts.ResultsOur findings in the present investigation revealed that among the bacterial community derived from the microbiota, Gram-negative bacteria accounted for 74.87% the total microbiota (146 out of 195) and their spectrum including Escherichia sp. (n = 36, 24.66%) followed by Acinetobacter sp. (n = 34, 23.29%), Stenotrophomonas sp. (n = 29, 19.86%), Pseudomonas sp. (n = 26, 17.81%) and Serratia sp. (n = 21, 14.38%), as the most prevalent pathogens. All isolates derived from the cancer microbiome exhibited multidrug resistance to a large number of conventional therapies. Out of them Serratia sp. Esraa 1, Stenotrophomonas sp. Esraa 2, Acinetobacter sp. Esraa 3, Escherichia sp. Esraa 4 and Pseudomonas sp. Esraa 5 strains showed multidrug resistant profile against all antibiotic classes under study including penicillins, cephalosporins, carbapenems, fluoroquinolones, β-lactamase inhibitors combinations, folate synthesis pathway inhibitors, phosphonic, aminoglycosides, polymyxins, tetracyclines, macrolides, and chloramphenicol antibiotics. The adverse effects of oral ingestion of their metabolites were evaluated in albino rats. They induced pronounced carcinogenesis along with severe raise in the inflammatory cytokines, hepatotoxicity, nephrotoxicity, mutagenicity along with sperm deformities in treated animals. Moreover, all metabolites showed marked cytotoxicity against human normal cell lines; human mammary epithelial (MCF10A), human lung fibroblasts (WI38) and human dermal fibroblasts (HDFs).ConclusionThese bacterial strains isolated from the cancer microbiome may play significant roles in inducing cancer, inflammation, mutagenesis, hepatotoxicity, nephrotoxicity, and sperm abnormalities, along with histopathological changes in the treated animal groups by orally administrated metabolites in compared to the untreated group.Graphical

Microbiological Profile of Periprosthetic Joint Infections: A Retrospective Analysis from North India.

With the rise in total joint arthroplasties, prosthetic joint infections (PJIs) have become a significant complication, leading to high morbidity. The causative organisms of PJIs vary by region, and the rates of drug-resistant organisms are growing, thus complicating the initial empiric choice of antibiotics. This retrospective study analyzed records of patients with orthopedic implants and intraoperative tissue samples sent for sonication and culture at a tertiary care hospital in India. The most common organism was Staphylococcus aureus (14 out of 86 bacterial isolates, 16.3%), followed by Pseudomonas aeruginosa (12 out of 86, 13.9%), and both Staphylococcus epidermidis and Klebsiella pneumoniae (11 each out of 86, 12.8%). There was a high prevalence of multidrug-resistant organisms, and 35% of the gram-negative organisms were carbapenem resistant. Our study reveals that in our setting, PJIs are chiefly driven by multidrug resistant gram-negative bacteria.

Increased rate of multidrug-resistant gram-negative bacterial infections in hospitalized immunocompromised pediatric patients.

Multidrug resistant Gram-negative bacterial infections are considered a major public health threat. Immunocompromised pediatric patients are at a great risk of severe or overwhelming infections. The aim of this study was to describe the frequency of infections with multidrug resistant (MDR) Gram-negative bacteria (GNB) in immunocompromised pediatric patients and to determine the risk factors. In addition, we aimed to identify the antimicrobial resistance patterns of these isolates. This was a retrospective observational study conducted at the American University of Beirut Medical Center (AUBMC) from 2009 to 2017. The study included immunocompromised patients 18 years of age or younger with infections caused by Gram-negative bacteria isolated from a sterile site, or nonsterile site in the setting of clinical infection. A total of 381 episodes of infection with GNB in 242 immunocompromised pediatric patients were identified. The mean age was 7.7 years. The most common pathogens were Enterobacterales followed by Pseudomonas and Acinetobacter spp. MDR GNB infections predominated causing 72% of the episodes, with alarming MDR rates among Escherichia coli (95.7%) and Klebsiella pneumoniae (82.7%). The overall rate of MDR GNB isolated increased from 62.7% in 2015 to 90% in 2017. Thrombocytopenia, chemotherapy and previous colonization or infection with the same organism during the past 12 months were found to be independent risk factors for infection with MDR GNB. This study provides data on the epidemiology of infections with MDR GNB in immunocompromised pediatric patients and illustrates the alarmingly high prevalence of these infections. This necessitates the frequent revisiting of treatment guidelines in these high-risk patients and the implementation of judicious antimicrobial stewardship programs and infection control policies to stabilize or decrease the prevalence of these infections.

Efficacy, safety, and therapeutic drug monitoring of polymyxin B sulfate and colistin sulfate in critically ill patients: a real-world retrospective study.

Polymyxin B sulfate (PBS) and colistin sulfate (CS) are the last-line treatments for infections caused by multidrug-resistant Gram-negative bacteria, but their efficacy and safety have not been validated. The aims of the current study were to (1) determine their efficacy and safety among critically ill patients and the influencing factors, and (2) determine the relationships of drug exposure with efficacy and safety, to provide evidence for the precision dosing. This retrospective study included 100 critically ill patients treated with PBS and 80 treated with CS. The efficacy outcomes were clinical efficacy and 30-day mortality, while the safety indicator was acute kidney injury (AKI) incidence. There was no significant difference between the two drugs in clinical efficacy, 30-day mortality, or overall AKI incidence, but the incidence of stage 3 AKI was significantly higher in the PBS cohort than the CS cohort. Therapeutic drug monitoring (TDM) and trough concentration (Cmin) were significantly associated with clinical efficacy and AKI in both cohorts. Classification and regression tree analysis revealed that Cmin values of ≥0.91mg/L for PBS and Cmin ≥ 0.53mg/L for CS were associated with higher clinical efficacy. There is basically no significant difference in the efficacy and safety of PBS and CS. TDM can significantly improve the clinical efficacy of both drugs and reduce the incidence of AKI. TDM is therefore recommended to improve the clinical efficacy while reducing the adverse reactions.

The clinical features and risk factors of coagulopathy associated with cefoperazone/sulbactam: a nomogram prediction model.

Cefoperazone/sulbactam (CPZ/SAM) is an important treatment option for infections caused by multidrug-resistant gram-negative bacteria. However, it is associated with an increased risk of coagulation disorders (CD) and causes severe bleeding in some instances. Early identification of risk factors and prediction of CD related to CPZ/SAM are crucial for prevention and treatment. This study aimed to explore the risk factors and developed a nomogram model for predicting the risk of coagulopathy in patients undergoing CPZ/SAM treatment. A total of 1719 patients who underwent CPZ/SAM in the Affiliated Hospital of Southwest Medical University from August 2018 to August 2022, were recruited as the training cohort. For validation, 1,059 patients treated with CPZ/SAM from September 2022 to August 2024 were enrolled. Patients were divided into the CD and the N-CD groups. The occurrence of CD was designated as the dependent variable. The univariate and multivariate logistic regression analysis was performed to identify the risk factors of CD. A nomogram model was constructed from the multivariate logistic regression analysis and internally validated for model discrimination and calibration. The performance of the nomogram was estimated using the concordance index (C-index) and calibration curve. The multivariate logistic regression analysis resulted in the following independent risk factors for CD: baseline INR level (OR: 5.768, 95% CI: 0.484∼11.372, p = 0.036), nutritional risk (OR:2.711, 95%CI: 1.495∼4.125, p < 0.001), comorbidity of digestive system (OR:1.287, 95%CI: 0.434∼2.215, p = 0.004), poor food intake (OR:1.261, 95%CI: 0.145∼2.473, p = 0.032), ALB level (OR: -0.132, 95%CI: -0.229∼-0.044, p = 0.005) and GFR< 30mL/min (OR: 1.925, 95%CI: 0.704∼3.337, p = 0.004). The internal validation confirmed the model's good performance (C-index, 0.905 [95% CI: 0.864∼0.945]). The calibration plots in the nomogram model were of high quality. Validation further confirmed the reliability of the nomogram, with a C-index of 0.886 (95% CI: 0.832-0.940). The nomogram model facilitated accurate prediction of CD in patients undergoing CPZ/SAM. And this could potentially contribute to reducing the incidence of CPZ/SAM-associated CD and consequently improving patients' outcomes.

Real-world multicentre study of cefiderocol treatment of immunocompromised patients with infections caused by multidrug-resistant Gram-negative bacteria: CEFI-ID.

The increase in the population of immunocompromised patients due to advances in management of end-stage diseases and transplants poses challenges in treating infections caused by multi-drug resistant (MDR) pathogens. Cefiderocol (FDC), a siderophore cephalosporin, has shown efficacy against carbapenem-resistant Gram-negative bacteria. This retrospective multicentre study investigated the real-world use of FDC in 114 immunocompromised adults treated for MDR infections in 12 French hospitals (June 2020-November 2023). Clinical and microbiological outcomes, including infection cure, relapse, as well as mortality, and resistance acquisition, were assessed at days 28 and 90. Antibiotic prescription compliance with current guidelines was investigated. At day 28, clinical success was achieved in 53.3% of cases, and overall mortality was 37.7%, consistent with other studies (33-37%). Infection-related mortality accounted for 25.4%. Relapse occurred in 17.5% of patients by day 28, rising by an additional 9.8% among survivors by day 90. Resistance acquisition was observed in two cases at day 28 (Pseudomonas aeruginosa and Stenotrophomonas maltophilia) and in three additional cases by day 90. FDC was used as monotherapy in 49.1% of cases, with a median treatment duration of 10 days. Nearly 25% of strains collected in FDC-treated patients were susceptible to best-practice alternatives. These findings highlight FDC's utility in difficult-to-treat infections, particularly S. maltophilia, but the high relapse rate and resistance acquisition underscore the need for careful monitoring, adherence to guidelines, and reconsideration of empirical use to prevent resistance and improve outcomes in fragile populations.

Environmental concentrations of antibiotics induced polymyxin B tolerance in Aeromonas hydrophila.

Polymyxin B is one of the last lines of defense in infections caused by multidrug-resistant Gram-negative bacteria. Aeromonas hydrophila are important fish pathogens and the occurrence of polymyxin B-resistant A. hydrophila isolates is increasing. While investigating 14 environmental chemical pollutants that may affect bacterial polymyxin B sensitivity in aquatic bacteria, we discovered that tolerance of A. hydrophila to polymyxin B is increased by short-term (90min) concurrent exposure to tetracyclines, tigecycline or gentamicin at environmentally relevant concentrations (0.0625μg/mL) and persists as long as the inducer is present. The exposure increased the growth of A. hydrophila at an inhibitory concentration of polymyxin B. The increased polymyxin B tolerance was attributed to changes in gene expression, without alterations in genotype and independent of cell surface charge variations. Such changes are relate to six KEGG pathways, including ribosome, nucleotide metabolism, pyrimidine metabolism, glyoxylate and dicarboxylate metabolism, purine metabolism, starch and sucrose metabolism. The dysregulated genes were involved in broad physiological changes, such as cell motility, flagella biosynthesis, quorum sensing, biofilm formation, and chemotaxis. Furthermore, the up-regulation of genes encoding Mg2+ transport, biotin synthesis, lipoprotein, glycerol phospholipid metabolism, phospholipid transport, and the down-regulation of genes, such as ompK, yidD and ompA related to enhanced cell membrane barrier, may contribute to the increased polymyxin B tolerance in A. hydrophila. In summary, the study results revealed the impact of environmental antibiotics in promoting microbial polymyxin B tolerance. Our findings underscore the role of environmental antibiotics in promoting polymyxin B tolerance and provide insights into the mechanisms of polymyxin B tolerance evolution in A. hydrophila.

A novel approach for the synthesis of the cyclic lipopeptide globomycin.

Cyclic lipopeptides (CLiPs) are a highly diverse class of secondary metabolites produced by bacteria and fungi. Examples of CLiPs have been found that possess potent antimicrobial activity against multidrug-resistant Gram-negative bacteria. Globomycin is a 19-membered CLiP that kills both Gram-positive and Gram-negative bacteria through inhibition of lipoprotein signal peptidase II (Lsp). It can only be obtained in small quantities from its Streptomyces producer strain, so there has been much interest in development of synthetic methods to access globomycin and analogues. Globomycin contains an N-terminal anti-α-methyl-β-hydroxy nonanoyl lipid tail, whose hydroxyl group forms an ester with the C-terminal carboxylate. Constructing the anti-arrangement between the α-methyl and β-hydroxy is synthetically challenging and previous globomycin syntheses are not compatible with diversification of the lipid tail after the stereocenters have been installed. Herein, we describe a new approach for the synthesis of globomycin that allows for facile lipid diversification. Using an anti-Evans Aldol condensation, a common intermediate is obtained that allows different "lipid swapping" through Grubbs-catalyzed cross-metathesis. Upon auxiliary cleavage, the resulting lipid can then be utilized in solid-phase peptide synthesis. Given the plethora of lipopeptides that contain β-hydroxy lipids, this method offers a convenient approach for convergent generation of lipopeptide analogues.

Pharmacokinetic/pharmacodynamic analysis of meropenem and fosfomycin combinations in in vitro time-kill and hollow-fibre infection models against multidrug-resistant and carbapenemase-producing Klebsiella pneumoniae.

MDR Gram-negative bacteria, such as ESBL-producing and carbapenemase-producing Klebsiella pneumoniae, represent major global health threats. Treatment options are limited due to increasing resistance and slowed development of novel antimicrobials, making it necessary to apply effective combination therapies based on approved antibiotics. To quantitatively evaluate the synergistic potential of meropenem and fosfomycin against carbapenem-resistant K. pneumoniae strains isolated from clinics. We evaluated four MDR K. pneumoniae strains, each expressing KPC-2 or KPC-3, using static time-kill assays that accounted for measured meropenem degradation. This was followed by pharmacokinetic/pharmacodynamic (PK/PD) interaction modelling, which estimated meropenem degradation rate constants and identified perpetrator-victim relationships in PD interactions. Dynamic hollow-fibre infection model (HFIM) experiments were used to confirm synergy. Static time-kill assays demonstrated high killing effects and suppressed regrowth for the combination of meropenem and fosfomycin, compared with the failure of monotherapy. Meropenem degradation was significantly higher in the presence of bacteria, attributable to carbapenemase activity. Pharmacometric models indicated a synergistic interaction primarily driven by meropenem as the perpetrator, enhancing the potency of fosfomycin. HFIM experiments confirmed in vitro synergy, demonstrating continuous bacterial suppression of the combination therapy. Meropenem and fosfomycin exhibited additive or synergistic potential against carbapenemase-expressing single- or double-resistant K. pneumoniae at clinically achievable concentrations. This combination therapy may offer a strategy against MDR infections, possibly improving clinical treatment outcomes. Further in vivo research is needed to translate these findings into clinical practice, emphasizing the importance of PK/PD modelling in rationalizing antibiotic use.