International Journal of Antimicrobial Agents

Rationale: Infections due to Extended-spectrum {beta}-lactamases-producing Enterobacterales (ESBL-PE) require empirical treatment with carbapenems. ESBL-PE carriage is considered as a risk factor for ESBL-PE involvement during ICU infection. Our aim was to determine factors that may predict the actual involvement of ESBL-PE. Methods: A two-periods bicentric ambispective study including ICU ESBL-PE carriers patients from April 2011 to January 2019. All ESBL-PE carriers who developed an infection were analyzed. Results: 6112 patients and 4902 patients were screened during the two periods. 384 and 232 ESBL-PE carriers were identified. Total number of infectious episodes were 146 and 114, respectively. A total of 144 pneumonias, 42 urinary tract infection and 45 digestive infections were studied. An ESBL-PE was involved in 35 (24.3%) episodes of pneumonia, and 44 (37.9%) of extra-pulmonary infections. The most frequent ESBL-PE involved were K. pneumoniae, E. cloacae and E. coli. Similar species and phenotypes were present in colonisation and infection in 29 (82.8%) of pneumonia and in 40 (90.9%) of extra-respiratory infection. Multivariate analysis identified Klebsiella pneumonia or Enterobacter cloacae carriage as risk factor for ESBL-PE involvement in pneumonia and E. coli carriage and detection of ESBL-PE carriage before ICU admission as protective factors. Conclusion: In our study an ESBL-PE involvement is infrequent in pneumonia. A known carriage before ICU admission and E. coli carriage are factors associated with the absence of ESBL-PE un the episode of respiratory infection. A confirmation of our findings could lead to a reduction in the empirical use of carbapenems in this population.

Background: Antimicrobial resistance poses a major threat to global public health. Large language models (LLMs) offer new possibilities for optimizing antibiotic prescribing decisions, but the capabilities of general-purpose versus domain-specific medical LLMs under different prompting strategies remain to be clarified. Methods: This double-blind, randomized-sequence evaluation used a 2X2 factorial design comparing four AI conditions-the domain-specific model MedGo and the general-purpose model DeepSeek V3.5, each under standard direct prompting and chain-of-thought (CoT) prompting-alongside real physician prescriptions across 59 complex inpatient infection cases. Five parallel regimens were generated per case and independently evaluated by three senior clinicians (1-5 comprehensive score and five domain sub-scores). ChatGPT 5.2 was additionally assessed as an automated evaluation tool. Results: Score ranking: real physicians > MedGo-CoT > DeepSeek-CoT > MedGo> DeepSeek (Friedman test, p<0.001). In base mode, MedGo significantly outperformed DeepSeek (Holm-adjusted p=0.040). CoT improved both models (Holm-adjusted p<0.001 for DeepSeek; p=0.024 for MedGo) and reduced score dispersion. MedGo-CoT significantly outperformed DeepSeek-CoT in individualized adjustment (adjusted p<0.001) and dosing precision (adjusted p=0.005). ChatGPT-expert correlation was negligible (overall Kendall {tau}=0.153, p=0.003; subgroup {tau}=0.06-0.20, all p>0.05). Conclusions: Domain-specific medical LLMs enhanced by CoT approach the antibiotic decision-making level of real physicians, with advantages in individualization and dosing precision. However, notable deficiencies persist in antimicrobial stewardship ecological awareness and automated evaluation reliability, underscoring the continued indispensability of senior clinical expertise.

Background: Rising antibiotic resistance challenges empirical therapies for urinary tract infections (UTIs). This study evaluated the microbial etiology, susceptibility profiles, and multidrug resistance (MDR) patterns of uropathogens among outpatients at the Berekum Holy Family Hospital, Ghana. Methods: This cross-sectional study (February to August 2021) screened 263 symptomatic outpatients. Mid-stream urine samples underwent quantitative culture, biochemical identification, and antimicrobial susceptibility testing via the Kirby-Bauer disc diffusion method following the 2021 CLSI guidelines. Results: Significant bacteriuria prevalence was 22.8% (60/263). UTIs predominated in females (78.3%, 47/60; p = 0.1501) and individuals [&ge;]45 years (33.3%, 20/60). Gram-negative rods accounted for 90.0% of isolates, primarily Escherichia coli (26.7%), Citrobacter spp. (25.0%), and Enterobacter spp. (21.7%); Staphylococcus aureus (10.0%) was the only Gram-positive pathogen. Extreme phenotypic resistance was observed against piperacillin/tazobactam (98.3%), cefotaxime (93.3%), tetracycline (88.3%), and cefoperazone (85.0%). Conversely, highest therapeutic susceptibilities were retained by amikacin (78.3%), levofloxacin (61.7%), and gentamicin (58.3%). Conclusion: The high prevalence of MDR uropathogens against advanced beta-lactamase inhibitor combinations and cephalosporins necessitates an immediate re-evaluation of regional empirical protocols. Amikacin, levofloxacin, and gentamicin remain viable options prior to culture confirmation. These findings establish a crucial phenotypic baseline to guide localized prescribing policies and regional antimicrobial resistance tracking strategies.

Background: Localized skin and soft tissue infections may need systemic antibacterials, but local inflammation can delay symptom recovery. We evaluated whether topical fresh Taraxacum mongolicum wet dressing added to ceftriaxone was associated with short-term benefit in selected clinically stable adults. Methods: In this single-center, assessor-blinded, three-arm randomized trial, 180 adults aged 18-74 years were randomized 1:1:1 to topical T. mongolicum plus intravenous ceftriaxone, topical T. mongolicum alone, or ceftriaxone alone for 7 days. The primary outcome was day-7 clinical response assessed by blinded independent assessors using prespecified global clinical improvement criteria. Analyses followed the intention-to-treat principle; sensitivity analyses assessed robustness. Results: Day-7 clinical response rates were 91.67% (55/60), 76.67% (46/60), and 68.33% (41/60) in the combined, T. mongolicum, and ceftriaxone groups, respectively (overall P = 0.006). Compared with ceftriaxone alone, combined therapy had a higher response rate (risk difference, 23.3 percentage points; 95% CI, 9.6 to 37.0; risk ratio, 1.34; 95% CI, 1.11 to 1.62). Sensitivity analyses were directionally consistent. Secondary outcomes and bacterial clearance favored the combined group. No serious adverse events were reported. Conclusions: In selected clinically stable adults with localized skin and soft tissue infections, adjunctive topical fresh T. mongolicum plus ceftriaxone was associated with improved short-term outcomes compared with ceftriaxone alone. Findings require cautious interpretation because this was a single-center, partially blinded trial without a placebo dressing control. The dressing should not replace antibiotics, drainage, or urgent care when indicated. Trial registration: International Traditional Medicine Clinical Trial Registry, ITMCTR2026000549.

The minimum inhibitory concentration (MIC) assay is the gold standard for evaluating antimicrobial activity1. However, conventional agar-based MIC methods often underestimate the potency of physicochemically complex compounds[1, 2]. Hydrophobic and adhesive molecules, such as lipoglycopeptide antibiotics, exhibit poor diffusion and non-specific binding to agar, leading to artificially elevated MIC values compared to broth-based methods[3]. This issue complicates accurate potency assessment and is particularly an issue when attempting resistance frequency (FOR) studies, which must be conducted on solid media. Here, we developed a modified miniaturised agar MIC assay using 1% agarose, 0.002% Tween 80-supplemented tryptic soy broth (TSB), and a 24-well plate format[4]. These modifications improved compound dispersion, reduced matrix interactions, and lowered compound requirements. The optimised assay was validated with vancomycin, oritavancin, and dalbavancin against Staphylococcus aureus ATCC 43300 (MRSA) and Streptococcus pneumoniae ATCC 700677. This efficient, cost-effective, high-throughput platform overcomes the limitations of traditional agar methods, enhancing reliability in evaluating challenging antimicrobials and supporting next-generation antibiotic development.

Introduction Miltefosine is the only approved oral antileishmanial agent, but its use in women of childbearing potential (WOCBP) is restricted due to preclinical teratogenicity. Current labeling recommends contraception during treatment and for at least five months thereafter, based solely on its long terminal elimination half-life. This study re-evaluated the required contraceptive duration using an exposure margin-based approach. Methods Virtual populations were generated from anthropometric data of 382 Indian, 4,462 Eastern African, and 4,019 Brazilian WOCBP with leishmaniasis. Published population pharmacokinetic models were used to simulate miltefosine exposure following 14-42-day regimens for visceral leishmaniasis (VL), post-kala-azar dermal leishmaniasis (PKDL), and cutaneous leishmaniasis (CL). A developmental safety exposure threshold was derived from the rat no-observed-adverse-effect level (0.6 mg/kg/day for 10 days) and adjusted using a 10-fold safety margin. Contraceptive durations resulting in median residual post-contraception exposure (AUCEOC-{infty}) below this threshold were considered supportive of contraceptive discontinuation. Results The developmental safety exposure threshold was estimated at 2.5 mg{middle dot}day/L. Despite pharmacokinetic differences across geographical regions and disease manifestations, required minimum contraceptive durations were consistent: three months from treatment initiation for the 14-day regimen, four months for 21- and 28-day regimens, and five months for the 42-day regimen. For the 14-day regimen, a single dose of a long-acting injectable contraceptive administered at treatment initiation would provide sufficient coverage. Conclusion An exposure margin-based approach supports shorter contraceptive durations than current recommendations. For the 14-day VL regimen, three months of contraception may provide a practical alternative to current labeling.

The Project to Accelerate New Treatments for Tuberculosis (PAN-TB) aims to accelerate development of shorter, simpler and safer pan-TB combinations. We previously identified 3 out of 25 first-generation novel PAN-TB 4-drug combinations, that cured 90% of mice in less than 3 months, at clinically relevant doses in the relapsing mouse model of TB. These regimens include BPa830Sut, BPa286Sut and BQSut286 (B: bedaquiline; Pa: pretomanid; 830: GSK3211830; 286: GSK2556286; Sut: sutezolid; Q: quabodepistat). Here, we assess the efficacy of these combinations where the original candidates are substituted next-generation or more advanced compounds (ganfeborole (656) for 830, sorfequiline, S for B, TBD09 for Sut and TBD11 for 286) and the individual contributions of specific agents. Six novel regimens demonstrated bactericidal activity more rapid than comparators PHMZ (Rifapentine P, Isoniazid H, Moxifloxacin M, Pyrazinamide Z) and BPaMZ. Modelled cure/relapse data showed that SPa286Sut, SPaSut and SPa656Sut cured 90% of mice in about 1 month, while SPa286, SPaQTBD11 and SPaTBD09 in less than 2 months, faster than PHMZ. Consistent with our previous findings, the fastest-curing regimens centered on a diarylquinoline (S), a nitroimidazole (Pa) and an oxazolidinone (TBD09 or Sut) together with an Rv1625c agonist (TBD11 or 286), DprE1 inhibitor (Q) or a LeuRS inhibitor (656). Notably, significant contributions to sterilizing efficacy were demonstrated for S in all combinations and for Pa, Sut, TBD09, Q and TBD11 or 286 in specific S-containing combinations. These findings suggest potential for these novel agents and combinations to improve treatment of both DS-and DR-TB.

Staphylococcus aureus and Streptococcus pyogenes are major causative bacteria responsible for skin and soft-tissue infections (SSTIs) such as impetigo. Increasing resistance to commonly used topical antibiotics necessitates evaluation of newer agents for the treatment of skin infections. Ozenoxacin, a novel non-fluorinated topical quinolone, has shown promise, exhibiting potent activity against a wide range of pathogens, including methicillin-resistant Staphylococcus (MRSA) and Streptococcus pyogenes. The present study compared the in vitro activity of ozenoxacin and comparator agents against clinical isolates of Staphylococcus aureus and Streptococcus pyogenes from multiple sources including skin and soft-tissue, wound, abscess, and blood. Ozenoxacin was assessed for in vitro antimicrobial activity against 109 methicillin-susceptible (MSSA), methicillin-resistant S. aureus (MRSA), and 24 Streptococcus pyogenes isolates by broth microdilution method recommended by the Clinical and Laboratory Standards Institute (CLSI). Ozenoxacin demonstrated potent in-vitro activity against all 109 S. aureus (MIC50/90= 0.125/0.5 {micro}g/ml) and 24 S. pyogenes (MIC50/90= 0.015/0.03 {micro}g/ml) strains. In contrast, higher MICs were observed for fusidic acid and mupirocin among a subset of S. aureus isolates. A comparison of MIC90values demonstrated that ozenoxacin (0.5 {micro}g/ml) was more active against S. aureus isolates than 8 of the 9 comparator agents tested including vancomycin and linezolid (MIC90= 2 & 4 {micro}g/ml) respectively. In vitro studies of ozenoxacin showed potency against staphylococci and streptococci including resistant S. aureus strains. These findings support its role as an effective first-in-class quinolone topical therapeutic option in the management of various SSTIs.

Nitrofurantoin is commonly prescribed as a first-line treatment for urinary tract infections (UTIs) and is effective against most uropathogens; however, resistance among Klebsiella spp. remains high. In this study, we investigated synergistic drug combinations--defined as pairs of drugs whose combined effect exceeds that of each agent alone--to enhance treatment efficacy against drug-resistant Klebsiella pneumoniae. A high-throughput drug screen identified six and two small molecules that exhibited >50% synergistic activity in tested strains in combination with nitrofurantoin and ciprofloxacin, respectively. We further validated the top three candidates using nitrofurantoin-susceptible and resistant clinical isolates. Notably, the combination of nitrofurantoin and dequalinium demonstrated strong synergistic activity, observed in 68% of susceptible Escherichia coli strains and 94% of resistant Klebsiella pneumoniae strains tested. Combined inhibition of the citric acid cycle by nitrofurantoin and F1-ATPase by dequalinium resulted in a significant reduction in ATP levels compared to either treatment alone. Importantly, decreased ATP levels did not increase persister cell formation, and dequalinium alone reduced persister cell populations more effectively than nitrofurantoin. However, nitrofurantoin is processed into a poorly understood reactive intermediate whose specific metabolic targets have not been fully elucidated. Using metabolomic analyses, we identified aconitase and isocitrate dehydrogenase--key enzymes in the citric acid cycle--as altered in response to nitrofurantoin. Together, these findings demonstrate that dual targeting of bacterial metabolism by nitrofurantoin and dequalinium represents a promising therapeutic strategy for treating drug-resistant Klebsiella spp. in UTIs.

The minimum inhibitory concentration (MIC) is a standard measure for describing the lowest effective dose concentration of an antimicrobial compound in clinical practice; yet, conventional assays often require a substantial amount of antimicrobial compound, limiting their use with scarce, purified agents. Here, we describe a simple and reproducible technique to evaluate the MIC for purified compounds with a limited sample size. The protocol describes the MIC steps against a bacterial strain while minimizing the use of reagents and materials. It is helpful for screening purified natural products as antimicrobial agents and in early-stage drug discovery. The protocol adapts standard microplate-based assays for two-fold dilution of the compound, ensuring their applicability in microbiological studies. The MIC value of the standard antibiotic kanamycin against Staphylococcus aureus, Vibrio fischeri, Klebsiella pneumoniae, and Escherichia coli was determined using our method, and was found to be consistent with the conventional broth microdilution method, validating its reliability. Therefore, this method offers a practical and viable solution for antimicrobial drug discovery, addressing the disparity between limited compound availability and comprehensive microbiological assessment of MIC.

Background: Polymorphisms in the N-acetyltransferase 2 (NAT2) gene explain much of the interindividual variation in isoniazid (INH) metabolism and determine risk of toxicities. However, there is limited evidence to guide INH dose adjustment according to the NAT2 acetylator profile in weekly rifapentine-INH tuberculosis preventive therapy (TPT). Methods: In a prospective, multicenter, within-subject PK trial (NCT05413551), adults initiating 3HP in Brazil were assigned genotype-guided INH doses (slow: 5 mg/kg <=300 mg; intermediate: 15 mg/kg <=900 mg; rapid: 25 mg/kg <=1,500 mg) alongside a standard 900 mg flat dose on an alternate occasion. AUC0-24 and C24 were estimated from serial blood samples; a two-compartment Michaelis-Menten population PK model characterized NAT2 effects on clearance. Results: Among 228 participants, 47.4% (108/228) were intermediate, 43.4% (99/228) slow, and 9.2% (21/228) rapid acetylators. Genotype-guided dosing reduced AUC0-24 variability approximately two-fold versus standard dosing (CV 58.8% vs 76.8%) and increased exposure uniformity (median AUC0-24 27.2 [IQR 18.8-41.3] vs 43.2 [27.3-71.0] mg h/L). Among slow acetylators, C24 >0.15 ug/mL decreased from 27/42 (64%) with standard dosing to 1/42 (2%) with genotype-guided dosing (P<0.0001). In 104 participants with intensive PK sampling, rapid acetylators receiving guided doses had AUC0-24 similar to standard-dose intermediate acetylators (42.8 vs 39.5 mg h/L; P=.63). Monte Carlo simulations supported doses of 600, 900, and 1,200 mg for slow, intermediate, and rapid acetylators, respectively. Conclusions: NAT2-guided isoniazid dosing reduced variation in drug levels, averting very low and high AUC and C24. These findings inform genotype-stratified dosing of INH for TPT, which might reduce toxicities and improve outcomes.

The human opportunistic pathogen Pseudomonas aeruginosa produces copious quantities of the secondary metabolite pyocyanin (PYO). PYO has recently been shown to interact with the aryl hydrocarbon receptor (AhR), a transcription factor controlling expression of a number of genes, including the cytochrome P450 CYP1A family involved in fluoroquinolone antibiotic clearance. In this study, we investigated whether Pseudomonas aeruginosa could influence the metabolism of ciprofloxacin through human CYP1A2 induction. Primary human hepatocytes were exposed to 1-100 M PYO, with high concentrations resulting in apparent cytotoxicity. Treatment with 5 {micro}M PYO led to a 6.2-fold change in CYP1A2 mRNA and a 3.6-fold increase in oxociprofloxacin metabolite formation. Our results suggest that sub-toxic concentrations of PYO induce CYP1A2 expression and increase ciprofloxacin metabolism, which could lead to sub-efficacious antibiotic concentrations and further drive resistance. This finding directs us to a novel mechanism by which Pseudomonas aeruginosa may escape antimicrobial therapy by hijacking host xenobiotic metabolism pathways. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/740721v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1b350forg.highwire.dtl.DTLVardef@388eb7org.highwire.dtl.DTLVardef@121bc9aorg.highwire.dtl.DTLVardef@1e53060_HPS_FORMAT_FIGEXP M_FIG C_FIG

The rapid rise of multidrug-resistant (MDR) bacterial infections has severely limited treatment options, particularly for Gram-negative pathogens such as Klebsiella pneumoniae, a leading contributor to pneumonia, bloodstream, urinary tract, and surgical-site infections. One strategy to restore antibiotic efficacy is the use of resistance-mitigating agents (RMAs), compounds that re-sensitize bacteria to existing antibiotics without displaying independent antibacterial activity. Herein, we report the results of a high-throughput screen of a 3,200-compound fragment-based library against an MDR K. pneumoniae isolate in the presence of subinhibitory ciprofloxacin. This screen identified a tetrahydrocarbazole-containing compound, 1, as a ciprofloxacin potentiator. Subsequent structure-activity relationship studies yielded a difluorinated analog, compound 5, which potentiated multiple antibiotic classes in MDR K. pneumoniae, reducing MICs up to [&ge;]16 fold. Further testing demonstrated synergistic interactions between compound 5 and ciprofloxacin, ceftriaxone, cefoxitin, and tetracycline across four genetically diverse MDR K. pneumoniae strains. These findings suggest that tetrahydrocarbazole-containing compounds constitute a promising new class of RMAs with potential for future development as therapies against MDR K. pneumoniae infections.

SynopsisO_ST_ABSBackgroundC_ST_ABSThe main advantages of Time Kill Curves (TKCs) in antimicrobial drug development are the ability to track bacterial kill and regrowth over time and with varying drug concentrations. Whilst there are guideline documents in place, such as M26-A in CLSI, there remains scope for individual laboratory differences in practice. Here we evaluated several factors which potentially influenced data generated in TKCs. MethodsFirstly, E. coli ATCC 25922 was used to determine optimum sampling volume, culture vessel volume, CFU enumeration variance factors and static versus agitated cultures in a single laboratory. Secondly, a ring test comprising of TKCs was performed by six laboratories focusing on: standardised inoculum, static culture and two culture vessel sizes 10 mL and 200 {micro}L. Data analysis was performed to determine consistency within centres and between them. ResultsConsistently accurate inocula could be achieved by use of: larger sampling volumes between 100 {micro}L > 20 mL; larger culture vessels volumes (10 mL > 100 {micro}L) and higher inocula (10 8 > 1.5x10 5 CFU). Culture agitation during the TKC experiment resulted in reduced killing compared to static cultures. Reproducibility of TKCs was best between centres when they were performed in 10 mL culture vessels. There was more variability per site when performing TKC in 96 well trays. ConclusionsTechnical factors such as preparation of inocula, agitation, vessel size and enumeration of cultures are important variables in performing TKCs that need to be standardised in drug development programmes involving multiple laboratory centres.

Background and objectives Spontaneous bacterial peritonitis (SBP) is a life-threatening complication of cirrhosis with ascites, carrying one- and two-year mortality rates exceeding 70% and 80%, respectively. Fluoroquinolone prophylaxis is the cornerstone of SBP prevention. Real-world longitudinal data on prescribing practices and clinical outcomes from Indian tertiary care centers are sparse. We aimed to evaluate fluoroquinolone prescribing patterns, guideline adherence, and six-month clinical outcomes in SBP patients at a tertiary academic center in North India. Methods This was a pre-specified sub-analysis of a 15-month analytical longitudinal study at AIIMS Rishikesh. Adults (age >/=18 years) admitted with SBP and initiated on fluoroquinolone prophylaxis were enrolled consecutively and followed for six months. Prescribing practices were compared against EASL and AASLD recommendations. The primary outcome was the rate of guideline-directed prescribing. Secondary outcomes included clinical cure at discharge, six-month cure, relapse, regimen modification, adverse drug reactions, and treatment compliance. Categorical variables were compared by Fisher's exact test or chi-squared test (SPSS). Results Forty-eight SBP patients were included (mean age 44.75 +/- 11.94 years; 85.4% male). Guideline-directed fluoroquinolone prophylaxis was prescribed to all patients (100%). Norfloxacin 400 mg once daily was predominant (85.4%), followed by levofloxacin (10.4%) and moxifloxacin (4.2%). Cure at discharge was 85.4%. At six months, 64.6% maintained sustained cure and 22.9% relapsed. Regimen modification occurred in 22.9%, most commonly antimicrobial substitution. Nausea was the only adverse drug reaction (4.8%). Treatment compliance was 73.8%. No patient underwent therapeutic drug monitoring. Conclusions Fluoroquinolone prescribing for SBP prophylaxis at AIIMS Rishikesh was fully concordant with standard guidelines. Despite complete adherence, a relapse rate of 22.9% and frequent regimen modification underscore the limitations of long-term fluoroquinolone prophylaxis, likely reflecting emerging quinolone resistance. Strengthening antimicrobial stewardship is essential to sustain prophylaxis effectiveness in Indian tertiary care settings.

Drug repositioning has emerged as an attractive strategy to accelerate the development of new antimalarial therapies, particularly by evaluating compounds already used against pathologies co-endemic with malaria. This approach offers the advantage of leveraging existing pharmacokinetic, toxicological, and safety data, thereby potentially shortening the drug development pipeline. However, transposing a compound from its original therapeutic indication to an antimalarial use is far from straightforward: differences in target biology, parasite stage specificity, pharmacodynamic requirements, and host-parasite interactions can result in a loss of efficacy despite promising in vitro or structural rationale. Rigorous in vivo validation therefore remains indispensable before any repositioning hypothesis can be considered translationally relevant. In this context, we evaluated the blood-stage antimalarial activity of triclabendazole, an antihelminthic drug used against co-endemic fascioliasis, together with its metabolite triclabendazole sulfoxide, and sutezolide, an oxazolidinone antibiotic, in a murine model of Plasmodium berghei ANKA infection following oral administration. None of the three compounds demonstrated significant antimalarial activity under these experimental conditions, contradicting a previously published repositioning hypothesis. Beyond these specific findings, our study is deliberately framed within the 3Rs principles (Replacement, Reduction, Refinement) governing animal experimentation. We argue that publishing negative in vivo results is not only scientifically legitimate but ethically necessary: sharing such data allows research teams working on similar preclinical models to build on existing knowledge, avoid unnecessary experimental duplication, and ultimately reduce the number of animal procedures performed across the field. We advocate for wider dissemination of negative outcomes in antimalarial drug repositioning research as a concrete contribution to more responsible and efficient use of animal models in preclinical pharmacology. Graphical Abstract

Objective: To consolidate publicly available United States National Antimicrobial Resistance Monitoring System (NARMS) human isolate data spanning 2004-2021 and comprehensively quantify trends in fluoroquinolone resistance, tetracycline resistance, ceftriaxone resistance, and early-stage azithromycin resistance across four NARMS-monitored enteric bacterial pathogens: nontyphoidal Salmonella, Campylobacter jejuni, Campylobacter coli, and Shigella spp. Methods: Annual resistance percentages were compiled from publicly available CDC, FDA, and USDA NARMS Human Isolates Surveillance Reports and Integrated Reports. Multi-year reference-period averages were assigned to their period midpoint years. Ordinary least-squares linear regression was applied to each pathogen-drug series. Slope estimates, 95% confidence intervals, Pearson correlation coefficients, and p-values were computed. A sensitivity analysis was conducted excluding reference-period midpoint years. Results: Ciprofloxacin decreased susceptibility in Salmonella rose from 2.4% to 11% (slope 0.62 pp/year, 95% CI 0.39-0.85; p less than 0.001). Ciprofloxacin resistance in C. jejuni rose from 21% to 34% (slope 1.68 pp/year, 95% CI 1.10-2.25; p=0.001) and in C. coli from 28% to 45% (slope 2.08 pp/year, 95% CI 0.97-3.19; p=0.007). Shigella showed a 5.8-fold increase (underpowered, n=3). Tetracycline resistance in C. jejuni and C. coli rose significantly. Salmonella multidrug resistance declined (slope -0.34 pp/year; p=0.001) while ceftriaxone resistance rose (slope 0.10 pp/year; p=0.028). Azithromycin-resistant Salmonella isolates detected in 2017 equalled the cumulative total from 2011-2016. Discussion: Fluoroquinolone and tetracycline resistance rose significantly across NARMS-monitored Campylobacter species, while Salmonella showed diverging trends: declining classical multidrug resistance but rising fluoroquinolone and ceftriaxone resistance. The emerging azithromycin resistance signal threatens remaining oral treatment options. These trends support sustained investment in harmonized antimicrobial resistance surveillance and stewardship globally.

SynopsisO_ST_ABSBackgroundC_ST_ABSTime kill curve (TKC) assessments are an essential step in the study of an antimicrobials pharmacodynamic characteristics. Surprisingly TKCs have not be formally standardised, therefore there remain concerns that different testing centres/methodologies may produce different results. Six centres participating in Gram-negative-Antibiotics NOW (GNA-NOW) consortium measured a series of TKCs with meropenem against E. coli to establish: Same-day (SD) vs different-day (DD) replication per centre (intra-site), and centre to centre (inter-site) correlations. MethodsMeropenem was tested against three strains of E. coli (ATCC 25922; ESBL producer C1.55; OXA-48 producer C1.62). An inoculum of 1.5x106 CFU was specified with meropenem concentrations of x0, x1 to x16 MIC; and sampling assessment of bacterial density was determined at 0-24h. Experiments were performed in triplicate, aerobically at 37{degrees}C. Centre-specific methodology was collected. Meropenem, media, bacterial strains, were shipped from one central laboratory to participating laboratories. ANOVA and Friedman tests were used to assess SD, DD and between centre replications. ResultsAssessment of the methodologies between centres revealed many differences, including bacterial inoculum, meropenem preparation, volume of TKC vessel, vessel materials, agitation vs static cultures and sampling volumes. Intra-centre SD and DD analysis for all strains were generally associated with P>0.05 suggesting consistency. Inter-centre SD and DD comparisons resulted in P<0.05, indicating variable total bacterial load measurement between centres. ConclusionsTKC methodologies varied between different centres, and while intra-centre comparison of SD and DD were generally consistent, inter-centre comparisons were not. Standardisation of TKC methodologies is required.

Background: Most patients with melioidosis receive prolonged intravenous ceftazidime during the intensive phase of their antibiotic therapy. Contemporary guidelines use weight and renal function to guide dosing, but therapeutic drug monitoring (TDM) might enable further individualisation of therapy. Objective: To examine the potential utility of ceftazidime TDM in the management of melioidosis. Methods: We reviewed consecutive serum free ceftazidime concentrations in patients with culture-confirmed melioidosis at an Australian referral hospital. We documented the minimum inhibitory concentration (MIC) for ceftazidime Burkholderia pseudomallei isolates of the patients. We then recorded the ceftazidime dosing regimen for each patient, their serum free ceftazidime concentration and if any adverse drug reactions occurred during their treatment. Results: Trough concentrations were measured in 31 patients receiving intermittent ceftazidime dosing, while random concentrations were measured in 91 patients receiving a continuous infusion. The median (range) trough concentration:MIC ratio was 37.7 (2.7-156.6) in those receiving intermittent dosing and 47.5 (8.1-181.5) in those receiving a continuous infusion. Serum ceftazidime concentrations correlated with neurotoxicity, which was documented in 5/31 (16%) receiving intermittent dosing and in 4/91 (4%) receiving a continuous infusion. Serum ceftazidime concentrations were also higher in individuals who died from their infection than in those who survived. There was no association between ceftazidime concentrations and subsequent disease recurrence. Conclusion: Current dosing recommendations for the treatment of melioidosis achieve serum ceftazidime concentrations that greatly exceed the MIC of B. pseudomallei in this region of Australia. TDM-guided reductions in the ceftazidime dose and/or dosing frequency may mitigate the risk of ceftazidime toxicity.

Septic shock caused by fungal organisms is characterized by high mortality and diagnostic complexity. We used the Premier Healthcare Database to characterize antifungal use and fungal diagnoses among adults with septic shock requiring vasopressors admitted between October 2022 through July 2024. Among 12.8 million admission at 886 hospitals, 554,948 met septic shock criteria and were included for analysis. A fungal diagnosis was established in 11,405 (2.1%) of encounters; of these, 3,565 (31.3%) received intravenous antifungal therapy within one day of vasopressor initiation. In the overall cohort, antifungal therapy was initiated in 29,824 (5.5%) within one day of vasopressor initiation; of these, 3,656 (12.2%) were ultimately diagnosed with a fungal infection. In the 116 hospitals reporting microbiological data, a subgroup of 489 encounters with septic shock and culture-confirmed candidemia was identified. In this subgroup, intravenous antifungal therapy was initiated in 43.8% within one day, 63.8% within three days, and 78.9% within seven days. These findings highlight a profound decoupling between fungal diagnosis and treatment--few patients receiving antifungals were diagnosed with an infection that would be treated by these agents, while less than half of patients with septic shock and candidemia received timely treatment. Strategies for greater precision in empiric antifungal use in septic shock are needed to improve safety, stewardship, and outcomes.