Molecular insights into the oxidative perturbation of VIM-2 metallo-β-lactamase: Active site remodeling restores imipenem susceptibility in Pseudomonas aeruginosa.

Antimicrobial susceptibility of Clostridioides difficile. An Argentinian multicenter study of isolates from human patients.

Poultry Proteus mirabilis in selected areas of Hunan, China: Resistance profiles and virulence genes.

The current study investigated a detailed account of phytocompounds within Coccinia grandis using GC-MS coupled with high-performance liquid chromatography. An in-silico approach was employed to gain insight into the inhibitory mechanism of Lupeol on Klebsiella pneumoniae. The molecular dynamics simulations were conducted over 100 ns to investigate the stability of metallo-β-lactamase with Lupeol, Imipenem (IPM), and Meropenem (MRP). We meticulously explored the antimicrobial activities of the crude extract of C. grandis leaves (CGL) and Lupeol against carbapenem-resistant K. pneumoniae. Additionally, cellular disruption activity was verified using a scanning electron microscope to better understand the antimicrobial activity of Lupeol. The computed free binding energy evaluated for Lupeol was − 92.380 ± 2.261 kJ/mol. This substantial negative value suggested the robust inhibitory potential of Lupeol, indicating a strong and stable interaction between Lupeol and target protein gold-bound NDM-1. Furthermore, the in-vitro antimicrobial activity of CGL and Lupeol were compared with standard antibiotics; MRP and IPM through the disc diffusion method. The zone of inhibition, and minimum inhibitory concentration, were found to be 23 ± 0.57 and 0.02 ± 0.01 mg/ml for Lupeol, 14.33 ± 0.58 mm and 0.03 ± 0.01 mg/ml for CGL. The ZOI of 12.67 ± 0.58 mm for IPM and 12.33 ± 0.58 mm for MRP was observed whereas 0.13 ± 0.06 mg/ml and 0.17 ± 0.06 mg/ml of MIC was determined for IPM and MRP respectively. Furthermore, the mechanism of action of Lupeol demonstrated significant activity in cell wall disruption assay and NDM-1 enzyme inhibition assay. Moreover, Lupeol also showed apoptotic activity against various cancer cell lines and no cytotoxic effect against healthy cell line. This study suggested Lupeol as an alternative natural therapeutic compound as an inhibitor of β-lactam resistant K. pneumoniae.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-026-41907-3.

Phage therapy is emerging as a promising alternative to antibiotics for treating various infections. However, there have been no prior studies on using bacteriophages for peritonitis in patients undergoing peritoneal dialysis. This report presents the successful treatment of refractory peritonitis in a 71-year-old male peritoneal dialysis patient using bacteriophages combined with antibiotics. The patient has a history of refractory and repeat peritonitis caused by Staphylococcus haemolyticus, which was resolved through simultaneous catheter replacement (SCR). Subsequently, the patient experiences another episode of refractory peritonitis due to Klebsiella pneumoniae. Although this strain is found to be susceptible to amikacin and imipenem, a 14-day course of treatment with these antibiotics in the abdominal cavity fails to resolve the peritonitis. Combined with antibiotic therapy, the patient is successfully treated with intraperitoneal phage therapy targeting his bacterial isolate. We monitor the longitudinal progression of phage loads, phage-neutralizing antibodies, interleukin-6 levels, and lipopolysaccharide concentrations in the dialysate effluent during the bacteriophage therapy. The combination of a phage cocktail and imipenem (IPM) demonstrates a greater effect in killing bacteria than either treatment alone, which indicates that a synergistic effect exists between the phage cocktail and IPM. Intraperitoneal IPM is discontinued after a 3-week course of treatment. At the same time, oral fluconazole is given to prevent fungal infections. The patient is discharged without any antibiotics. After this round of treatment, the patient remains healthy during the one-month follow-up. Our study suggests that personalized phage therapy combined with sensitive antibiotics can play a significant role in managing refractory peritonitis in patients undergoing peritoneal dialysis, showing promise for future applications.

An ID-HPLC-MS/MS based candidate reference measurement procedure for the quantification of imipenem, meropenem and ertapenem in human plasma.

Diagnosis and treatment of chronic infection after internal fixation for long bone fractures in children: a report of 6 cases.

Abstract Background Tebipenem pivoxil hydrobromide (TBP) (formerly SPR994) is in clinical development as the potential first oral broad-spectrum carbapenem agent in the US for the treatment of complicated urinary tract infections (cUTI) and acute pyelonephritis (AP). This study reports on the in vitro activity of TBP and comparator agents against molecularly characterized Enterobacterales isolates recovered from UTI and bloodstream infections (BSI) in the US, including ESBL and carbapenemase (CP) producing isolates. Methods A total of 3,523 Enterobacterales isolates collected from the US in 2023 were included. (UTI, 74.2% (2,614), BSI, 25.8% (909)). Isolates were tested for susceptibility (S) by CLSI reference broth microdilution method. E. coli and K. pneumoniae with aztreonam (ATM), ceftazidime (CAZ), or ceftriaxone (CRO) MICs of ≥2 µg/mL, and P. mirabilis with cefpodoxime (CPD) or CAZ MICs of ≥2 µg/mL were classified as ESBL phenotype. Isolates with MIC ≥2 µg/mL for imipenem (IMI) and/or meropenem (MER), or ≥1 µg/mL for ertapenem (ERT), were categorized as carbapenem-nonsusceptible (CNSE) phenotype. Isolates that met these criteria were screened for plasmid-mediated AmpC (pAmpC), ESBL, and CP genes. Results A total of 14.1% (496/3,523) of isolates were identified with an ESBL phenotype and 13.3% (471/3,523) were ESBL, CSE phenotype (Table). Of the latter, 91.7% (432/471) carried ESBL and/or pAmpC genes. TBP had MIC50/90 of 0.015/0.03 µg/mL against this subset, with those for IMI (MIC50/90, ≤0.12/0.5 µg/mL), MER (MIC50/90, 0.03/0.06 µg/mL) and ERT (MIC50/90, 0.03/0.12 µg/mL). The S to other comparators was below 81%. The CNSE phenotype accounted for only 1.6% (56/3,523) of isolates, and 39.3% (22/56) carried CP. TBP displayed MIC50/90 of 1/ >8 µg/mL. IMI (MIC50/90, 2/ >8 µg/mL), MER (MIC50/90, 1/ >32 µg/mL) and ERT (MIC50/90, 2/ >2 µg/mL) were active against 48%, 61% and 9% of the CNSE subset, respectively, while the S of oral comparators was ≤48%. Conclusion TBP displayed MICs similar to those for overall isolates against ESBL-producing Enterobacterales isolates from UTIs and BSIs in US medical centers. These results indicate that TBP has activity comparable to IV carbapenems and has the potential for use as oral treatment option for cUTI and AP. Disclosures Renuka Kapoor, PhD, GSK: Employee|GSK: Stocks/Bonds (Public Company) Mariana Castanheira, PhD, Melinta Therapeutics: Advisor/Consultant|Melinta Therapeutics: Grant/Research Support Didem Torumkuney, PhD, GSK: Stocks/Bonds (Public Company) Ian A. Critchley, PhD, Spero Therapeutics: Stocks/Bonds (Public Company)

This study presents an eco-friendly method for synthesizing silver nanoparticles (AgNPs) using the supernatant of Candida albicans as a reducing agent. AgNPs were formed via redox reactions and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). XRD analysis confirmed a face-centered cubic structure. The antibacterial activity of AgNPs was evaluated against three Gram-negative bacteria—Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis—using the agar well diffusion method. Their efficacy was compared to four antibiotics: Imipenem (IPM), Amoxicillin/clavulanic acid (AMC), Meropenem (MRP), and Piperacillin/tazobactam (PIT). While antibiotics were effective against K. pneumoniae and P. mirabilis, E. coli showed resistance to PIT and AMC. In contrast, AgNPs exhibited concentration-dependent inhibition, with maximum zones of 16.00 ± 0.58 mm (K. pneumoniae), 27.00 ± 0.57 mm (P. mirabilis), and 22.33 ± 0.33 mm (E. coli). These findings suggest AgNPs as promising antibacterial agents.

This study aimed to investigate the effects of low intensity pulsed ultrasound (LIPUS) combined with imipenem (IMI) on inflammatory responses and organ protection in septic rats. The study involved 230 Sprague-Dawley (SD) rats, with 80 used for survival analysis and 150 for sampling over 72 h. Histological examination (hematoxylin and eosin [H&E] staining) and transmission electron microscopy (TEM) revealed that LIPUS combined with IMI significantly alleviated spleen tissue damage and reduced mitochondrial edema. Key inflammatory cytokines, such as interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and IL-6 were significantly decreased, while IL-10 levels increased in the LIPUS + IMI group (p < 0.05). The combined treatment also reduced the expression of cytokines, such as IL-1 receptor (IL-1R), nuclear factor kappa B p65 (NF-κB p65), transforming growth factor-beta (TGF-β), and high mobility group protein box 1 (HMGB1), indicating a reduction in inflammation (p < 0.05). This study presents a novel approach by integrating LIPUS with IMI, providing a noninvasive and effective strategy to mitigate cytokine storms, optimize antibiotic use, and reduce organ damage in sepsis. The protective effects observed are primarily attributed to the inhibition of the IL-1R/NF-κB signaling pathway, which significantly improves survival outcomes in septic rats. This combined therapy has potential for enhancing sepsis treatment protocols.

Antimicrobial resistance in the Bacteroides fragilis group: National multicenter survey and Bayesian modelling study, France, 2022-2023.

Antibiotics significantly change gut microbiota, leading to dysbiosis and changes in bacterial community composition, which further results in a series of dysfunctions with severe health consequences. This work employed both culture-dependent and -independent methods to examine antibiotic-induced changes in gut microbiota at higher resolution using mouse models. By following bacterial changes and antibiotic resistance daily before antibiotic exposure, after antibiotic exposure, and during recovery, several significant novel findings were made. Ampicillin (AMP) and imipenem (IPM) treatment led to an acute, exponential, but temporary bloom in absolute abundances of live opportunistic pathogens Enterobacteriaceae and Enterococcus, while not affecting potentially beneficial Lactobacillus. The absolute abundances of antibiotic-resistant opportunistic pathogens followed a similar pattern. Impact on antibiotic resistance, on the other hand, is significant and persistent. Nearly, all Enterobacteriaceae performed AMP-resistant at the end of treatment with AMP, and almost 10% of Enterococcus became IPM-resistant following treatment with IPM. Further analysis of the genomes of isolated bacteria suggested that the former was due to replacement of Enterobacteriaceae strains while the latter is not. These studies show that antibiotic exposure led to expansion of gastrointestinal pathogens and their resistance to antibiotics, increasing risks for bacterial infections, contrary to the traditional anti-infection functions of antibiotics.IMPORTANCEThe antibiotic therapy is the primary method for treating and preventing bacterial infections. However, the consumption of antibiotics may also cause collateral damage in the normal microbial flora in human body, leading to dysbiosis with unwanted consequences. This impact was previously studied mostly with sequencing-based methods, which did not distinguish between live and dead cells, and did not provide absolute quantitative data, limiting the physiological relevance of discoveries. This work expands the methods in studying the side effects of antibiotic therapy by including culturing methods that measure absolute quantities of live bacteria. Surprising findings were made that antibiotic uptake can lead to temporary exponential bloom of opportunistic pathogens in mouse gut, and a permanent change of antimicrobial resistance in these pathogens. These findings expand our knowledge on how antibiotic therapy can affect our health and urges caution on casual antibiotic usage.

BackgroundAntimicrobial resistance is a global concern. Tigecycline (TGC) and polymyxin B (PMB) constitute some of the last treatment options remaining for carbapenem-resistant Klebsiella pneumoniae (CRKP). However, heteroresistance to these two drugs has rarely been reported. In this study, we investigated the prevalence of heteroresistance to TGC and PMB among clinically isolated CRKP strains, and assessed the synergistic activity of TGC plus PMB, TGC plus imipenem (IPM), and PMB plus IPM against heteroresistant CRKP.MethodsA total of 90 nonduplicated CRKP clinical isolates were collected from Tianjin Medical University General Hospital, China,from January 2022 to October 2022. PCR was used to detect the resistance genes. Population analysis profile (PAP) was performed to determine the existence of heteroresistance. Checkerboard assay was carried out on ten randomly selected dual-heteroresistant CRKP strains. Additionally, MIC50 (minimum inhibitory concentration) and MIC90 were calculated, and the concentration-cumulative inhibitory percentage curves were plotted. Time-kill assays were conducted with selected CRKP strains.ResultsAmong them, 48 (55.2%) of the 87 TGC-susceptible and TGC-immediate isolates exhibited heteroresistance phenotypes, and 61 (70.9%) of the 86 PMB-susceptible isolates showed heteroresistance phenotypes. Thirty-two isolates (35.6%) were heteroresistant to TGC and PMB simultaneously. PCR results showed that 96.7% (87/90) not only carried carbapenemase genes, but also co-harbored extended-spectrum β-lactamases (ESBLs) genes. Single time-kill curves demonstrated that PMB monotherapy could rapidly eradicate non-heteroresistant strains within 8 h. Conversely, in heteroresistant strains, there was a sharp reduction in cells numbers initially but ensuing a prompt rebound. Intriguingly, further heteroresistance screening decoded the occurrence of heteroresistance phenomenon. Importantly, Checkerboard assay exhibited TGC combined with PMB exert relatively better effect to overcome dual heteroresistance compared with the other two regimes, with MIC50 and MIC90 of them were significantly declined than single drug and the concentration-cumulative inhibitory percentage curves shifted to the left. Moreover, they can early eliminate single heteroresistance in lower dose. Additionally, combined drug time-kill assays proved synergism effect. Overall, combining TGC and PMB may be a therapeutic approach to overcome counterpart heteroresistance in CRKP.ConclusionThis study provides valuable insights and theoretical support for the clinical therapy of relevant heteroresistance.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12866-025-04554-8.

Introduction. In antibiotic chemotherapy, an antimicrobial agent is selected based on MIC, which is determined by a test method using the principle of the broth microdilution. However, it does not provide a viable count in the mutant selection window. In this study, we used turbidimetry and visual judgement to examine the validity of the selection of various antibiotics to treat Pseudomonas aeruginosa based on MIC determination after 24 h of incubation.Methods. The antibiotics used in this study were piperacillin (PIPC), imipenem (IPM), meropenem, ciprofloxacin and amikacin (AMK). The strains used were 30 P. aeruginosa strains clinically isolated that were susceptible to all the antibiotics used, and the standard PAO1 strain. The viable count was measured after exposure for 3 and 24 h to therapeutic concentrations of various antibiotics, at which time turbidity was examined visually or by transmittance. In addition, the MPCs of IPM and PIPC were measured.Results. In this study, 10²-10⁸ c.f.u. ml-1 of P. aeruginosa survived exposure to PIPC, IPM and AMK at concentrations 2.5-80 times the MIC despite high drug concentrations. No turbidity was observed in the culture medium. Furthermore, both IPM and PIPC showed high mutant prevention concentration (MPC), with 64.5% of strains in IPM and 10% of strains in PIPC showing intermediate or resistance after 24 h.Conclusions. Choosing an appropriate antibiotic based on exceeding the MIC may be insufficient. While the PK/PD theory focuses on MIC, measuring MPC alongside MIC is urgent in clinical practice for optimal antibiotic selection.

ObjectiveTo investigate the contribution of blaIMP-45 and its plasmid-borne genetic context in the development of imipenem heteroresistance in Pseudomonas aeruginosa.MethodsSix clinical isolates of P. aeruginosa (HN41, HN66, HN67, HN125, HN148, and HN232) were analyzed. Broth microdilution confirmed imipenem(IMP) resistance in all the strains (MIC ≥8 mg/L). Whole-genome sequencing was performed to identify the presence of blaIMP-45. E-test strips were used to indicate suspected heteroresistance phenotypes, while Population Analysis Profile (PAP) assays were conducted to definitively classify the strains. Complete plasmid sequencing of HN232 (IMP-HR) and HN41 (IMP-NHR) was performed to identify the genetic context of blaIMP-45. Pre-exposure of IMP-HR strain HN232 to sub-inhibitory IMP (1, 4, and 32 mg/L) for 24h was conducted to assess regrowth frequency. Quantitative reverse-transcription PCR (qRT-PCR) and digital PCR (ddPCR) were used to measure blaIMP-45 expression and gene copy number.ResultsWhole-genome sequencing revealed the absence of blaIMP-45 in the HN67 and HN125 strains. E-test strips indicated suspected heteroresistance phenotypes, while Population Analysis Profile (PAP) assays definitively classified HN66, HN148, and HN232 as heteroresistant (heteroresistant subpopulation inhibitory concentration, HIC/HNIC ratio ≥8), with their maximum permissive growth concentrations (256 mg/L) 32-fold higher than non-heteroresistant strains HN67 and HN125 (8 mg/L), implicating blaIMP-45 in driving phenotypic heterogeneity. Complete plasmid sequencing of HN232 (IMP-HR) and HN41 (IMP-NHR) identified blaIMP-45 within the In786 integron, embedded in the Tn7445 transposon (a Tn1403 derivative) on IncP-2 type plasmids. Notably, the blaIMP-45-flanking genetic environment was conserved between HR and NHR strains, excluding promoter region variations (eg, PcH2 and P2 promoters within In786) as drivers of differential expression. Pre-exposure of IMP-HR strain HN232 to sub-inhibitory IMP (1, 4, and 32 mg/L) for 24h induced dose-dependent increases in regrowth frequency at 4 and 8 mg/L IMP. Quantitative reverse-transcription PCR (qRT-PCR) and digital PCR (ddPCR) demonstrated that low-dose IMP exposure (1 mg/L, 24h) upregulated blaIMP-45 expression and increased the gene copy number in HN232, whereas the NHR strain HN41 exhibited stringent plasmid regulation.ConclusionThe study provided critical insights into blaIMP-45-mediated IMP heteroresistance in P. aeruginosa, highlighting plasmid-encoded amplifiable resistance determinants as key modulators of phenotypic adaptability under antibiotic pressure.

Imipenem (IPM) is a broad-spectrum β-lactam antibiotic primarily used to treat bacterial infections. Beyond its antimicrobial properties, it has also been explored as a temporary embolic agent in interventional radiology. This application is due to its ability to form particulate suspensions, leading to transient occlusion of small blood vessels. As an embolic agent, imipenem cilastatin (IPM/CS) induces vessel occlusion and typically recanalizes within 90min to 48h in normal vasculature, though recanalization may take longer in inflamed or hyperemic tissues. As cilastatin may exhibit anti-inflammatory effects, potentially enhancing the therapeutic profile of the compound, this property makes it particularly useful for conditions associated with abnormal neovascularization and inflammation. IPM/CS has been commonly used for temporary embolization in the treatment of musculoskeletal conditions, tumor-related bleeding, and inflammatory hyperemia, and offers a minimally invasive therapeutic approach with rapid resolution. Clinical studies have demonstrated its safety, with minimal complications compared to permanent embolic agents. Unlike permanent embolization materials, its transient nature reduces the risk of long-term ischemic damage while effectively managing pain and inflammation. Given its dual function as both an antibiotic and an embolic agent, IPM/CS represents a promising tool in interventional radiology, warranting further research to optimize its clinical applications. The aim of this review is to summarize the current evidence on the clinical applications, mechanisms, and outcomes of IPM/CS as a temporary embolic agent, and to highlight future directions for its use in interventional radiology.

Entrapping imipenem into poly(methyl methacrylate) assemblies by microfluidic process retains the activity against prosthetic joint infections following thermal treatment.

This study was aimed to evaluate the antimicrobial resistance, biofilm formation and some type 1 fimbriae adhesion genes. A total of 120 urine specimens were obtained from different patients with UTIs during October 2022 to February 2023 from several Baghdad hospitals. Morphological, biochemical and molecular tests were utilized for identifying E. coli isolates. The results were shown that only 80 (66.7%) of isolates were identified as E. coli. Twelve antimicrobial discs were utilized for evaluate the ability of E. coli isolate to resistant these antimicrobials. The results revealed that 98.8% of isolates were resistant to Ampicillin (AMP), followed by 81.3, 77.5, 72.5, 70, 60 and 58.8 of isolates were resistant to Cefepime (FEP), Ceftazidime (CAZ), Tigecycline (TGC), Ciprofloxacin (CIP), Trimethoprim - Sulfamethoxazole (SXT) and Aztreonam (ATM), respectively. All isolates were sensitive to Fosfomycin (FOF) and Amikacin (AMK) as well as the majority of isolates (97.5, 72.5 and 43.8%) were sensitive to Imipenem (IMP), Nitrofurantoin (NIT) and Piperacillin- tazobactam (TZP). A 50 isolates were selected as multi-drug resistant isolates. The biofilm formation of E. coli was measured using microtiter plates. The majority of isolates (55%; n=44) were moderate biofilm producers, while 38.75% (n=31) were strong producers and 5 (6.25%) were weak producers. The molecular detections of fimH and fimA genes were performed with specific primers using PCR technique. The results indicated that all isolates carry both the fimH and fimA genes.

To investigate the antimicrobial efficacy of Melittin (MEL) against carbapenem-resistant Acinetobacter baumannii isolates as a potential alternative treatment option. Minimum Inhibitory Concentrations (MICs) of MEL, imipenem (IMP), and meropenem (MER) were evaluated through the microdilution method in 10 resistant isolates. Synergistic interactions were assessed using checkerboard, time-kill assays, and an in vivo Galleria mellonella model. MEL MICs ranged from 31.25-62.5 mg/L. Only the M5 isolate showed synergy with both combinations. Fractional Inhibitory Concentration Index (FICI) values were 0.375 for MEL+MER and 0.5 for MEL+IMP. Larvae treated with MEL combinations had increased survival rates compared to the infection group. MEL appears to be a promising therapeutic candidate against carbapenem-resistant A. baumannii, and its combination with carbapenems may enhance in vivo efficacy.

ABSTRACTBackground and Aim:Non-typhoidal Salmonella (NTS) is a leading cause of foodborne illness, with poultry products serving as major transmission routes. In sub-Saharan Africa, surveillance of antimicrobial resistance (AMR) and virulence determinants remains limited. This study investigated the prevalence, AMR, and virulence gene profiles of NTS isolated from poultry products retailed in Arusha, Tanzania.Materials and Methods:A cross-sectional study was conducted between August and October 2023. A total of 240 samples (layer eggs and broiler meat) were collected from two wards in Arusha City using systematic random sampling. NTS isolates were confirmed by polymerase chain reaction (PCR) and tested for susceptibility to 11 antimicrobial agents using the Kirby–Bauer method. Virulence (invA and stn) and resistance genes (tetA, tetB, blaTEM, blaCTXM, and blaSHV) were screened by PCR. Statistical associations were analyzed using odds ratios (OR) and 95% confidence intervals (CI).Results:The overall prevalence of NTS was 23.3% (56/240). Layer eggs showed significantly higher contamination (20%) compared with broiler meat (3.3%) (OR = 10.0, 95% CI: 4.4–22.6, p < 0.001). Salmonella Typhimurium was the predominant serotype. All isolates carried invA and stn genes. Alarmingly, 100% of isolates were resistant to imipenem (IMI), while resistance to ampicillin (58.9%) and tetracycline (41.1%) was also common. Multidrug resistance patterns were frequent, although resistance genes were detected at a low prevalence (tetA, 5.3%; blaTEM, 3.5%).Conclusion:The findings demonstrate a high prevalence of virulent and IMI-resistant S. Typhimurium in retail poultry products in Arusha, particularly in eggs. These results highlight critical gaps in food safety regulation and antimicrobial stewardship within the Tanzanian One Health framework. Further genomic studies are warranted to elucidate underlying resistance mechanisms and inform effective surveillance strategies.