Multidrug-resistant (MDR) Gram-negative infections represent a growing global health threat with increasingly limited therapeutic options. We report a case of complicated urinary tract infection in a 70-year-old woman with underlying renal cysts complicated by rupture and subsequent formation of left infrarenal and paracolic pelvic abscesses. The initial infection was caused by Escherichia coli; however, following initial prolonged broad-spectrum antimicrobial therapy, a novel New Delhi metallo-β-lactamase (NDM type carbapenemase)-producing Citrobacter species was subsequently isolated from urine cultures. Whole-genome sequencing confirmed identification as a novel Citrobacter species and identified the presence of a blaNDM-4 gene. Antimicrobial susceptibility testing demonstrated resistance to most tested agents, with susceptibility limited to nitrofurantoin, cefiderocol, aztreonam, doxycycline, and tigecycline. Repeat abscess drainage and treatment with cefiderocol resulted in clinical and microbiological resolution of infection. This case underscores the critical role of drainage and access to newer antibiotic agents in management of complex intra-abdominal infections. Genome sequencing aids the detection of novel reservoirs of antibiotic resistance genes in carbapenemase-producing Enterobacterales that may emerge during prolonged antimicrobial exposure.

Treating carbapenem-resistant Klebsiella pneumoniae (CRKP) is challenging, particularly when resistance is mediated by New Delhi metallo-β-lactamase (NDM). Clinical experience with fixed-combination aztreonam-avibactam (ATM-AVI) in young infants remains extremely limited. Here, we report a case of a 2-month-old boy who underwent emergency laparotomy for intestinal obstruction owing to small bowel volvulus with segmental necrosis, followed by bowel resection and reanastomosis. His postoperative course was complicated by respiratory failure, coagulopathy, septic shock, recurrent abdominal distension, and massive ascites. Blood cultures were negative, whereas metagenomic next-generation sequencing of blood detected K. pneumoniae and Enterococcus faecium. Owing to the worsening of his condition, diagnostic paracentesis and repeat laparotomy were performed, revealing an anastomotic leak. Intraoperative pus culture yielded bla NDM -positive CRKP. The isolate was resistant to carbapenems and ceftazidime-AVI but was susceptible to ATM-AVI, with a minimum inhibitory concentration of ≤4 mg/L. ATM-AVI was administered at 30 mg/kg every 8 h, based on the aztreonam component, for 14 days; linezolid and fluconazole were co-administered as part of the broader anti-infective regimen. The combination of definitive surgical source control, targeted antimicrobial therapy, and comprehensive intensive care successfully controlled the infection and stabilized his hemodynamics. The patient defervesced within 24 h of the first ATM-AVI dose. Inflammatory markers declined rapidly, allowing safe extubation. Follow-up abdominal cultures remained negative. No hepatic or renal toxicity was observed during treatment. This case suggests that, when combined with adequate surgical source control, ATM-AVI may represent a valuable mechanism- and susceptibility-guided pharmacological component in a multidisciplinary treatment paradigm for severe bla NDM -positive CRKP infections in selected infants.

Ana Sagar Lake, despite its ecological, public health, and economic importance, has remained largely unexplored with respect to its bacterial diversity and antibiotic resistance. Therefore, the present study aimed to characterize the bacterial diversity of the lake and evaluate the antibiotic resistance profiles of the recovered isolates. Based on 16S rRNA gene sequencing, the bacterial isolates AL-1, AL-5, AL-6, and AL-9 were identified as Priestia sp. (GenBank accession: PX973463), Acinetobacter soli strain AL-5 (PX973464), Pseudomonas sp. AL-6 (PX973465), and Acinetobacter sp. AL-9 (PX973466), respectively. Among these, AL-1 (Priestia sp.) exhibited the highest level of resistance, showing resistance to chloramphenicol, streptomycin, cefepime, aztreonam, and cefoperazone. Interestingly, AL-9 demonstrated an inverse response to antibiotic exposure, with significantly enhanced biofilm formation in the presence of chloramphenicol compared with the untreated control. In addition, AL-1, AL-6, and AL-9 displayed increased intracellular accumulation of ethidium bromide (EtBr), indicating reduced efflux pump activity and a potential increase in antibiotic susceptibility. Chloramphenicol exerted the most pronounced effect on AL-9 cells among the antibiotics tested. To the best of our knowledge, this is the first study to characterize the antibiotic resistance profiles of bacterial isolates recovered from Ana Sagar Lake. These findings provide valuable baseline data for assessing the microbial quality of the lake, understanding the potential public and environmental health risks associated with its use, and supporting future monitoring and management strategies.

Background: The dissemination of extensively drug-resistant Pseudomonas aeruginosa strains across the human-food interface represents a critical threat to global public health, complicating empirical therapeutic choices and challenging traditional nosocomial restriction paradigms. Objective: This study investigated the prevalence, phenotypic resistome landscapes, and underlying integron-mediated mobilization mechanics of P. aeruginosa across the One Health continuum using an optimized real-time quantitative PCR (qPCR) platform. Methods: A total of 116 samples comprising human clinical specimens (n = 61) and retail food matrices (n = 55) were screened. Phenotypic resistance was profiled against 16 antipseudomonal agents, with polymyxin and colistin resistance validated via reference broth microdilution. A novel real-time SYBR Green qPCR assay backed by derivative melting curve analysis was developed to track Class 1 (intI1) and Class 2 (intI2) integrons. Results:Pseudomonas aeruginosa was recovered from 36.2% (n = 42/116) of total samples, exhibiting a homogeneous distribution across clinical (32.8%) and retail food matrices (40.0%, p = 0.445). Antibiogram characterization revealed a critical resistance burden: 100% of isolates fell into extreme epidemiological tiers, with 71.4% (n = 30) exhibiting an extensively drug-resistant (XDR) phenotype and 28.6% (n = 12) reaching absolute pandrug-resistant (PDR) status. Absolute phenotypic resistance (100%) was recorded across both cohorts for meropenem, ceftazidime, aztreonam, tobramycin, polymyxins, and novel combination therapeutics (ceftazidime-avibactam and ceftolozane-tazobactam). Pairwise tracking demonstrated an exceptionally strong positive correlation in resistance distribution patterns between human and food isolates (Spearman's rho = 0.948, p < 0.001). Analytical validation of the qPCR assay demonstrated tight, reproducible specific derivative melting peaks (Tm) at 83.2 °C for intI1 and 83.8 °C for intI2. Genotypic screening revealed universal conservation of plasmid-borne intI1 (100%), whereas plasmidic intI2 was variably distributed (61.9%). Crucially, intI2 carriage served as a definitive marker for the transition to complete pandrug resistance, being detected in 100% (n = 12/12) of PDR isolates compared to 46.7% (n = 14/30) of XDR strains (p = 0.001), supported by a strong positive correlation with the PDR phenotype (rho = 0.496, p = 0.0008). Conclusions: These findings reveal an overlapping, extreme resistome across the food-clinical interface and identify intI2 as a genetic tipping point for absolute pandrug resistance. The validated real-time assay provides a highly sensitive, proactive molecular surveillance framework capable of mapping high-risk mobile genetic platforms before they manifest as catastrophic empirical treatment failures.

Background: Carbapenem-resistant Enterobacterales (CRE) are a major therapeutic challenge, particularly in settings where metallo-β-lactamases are prevalent. Aztreonam-avibactam (AZA) may provide activity against metallo-β-lactamase-producing isolates, whereas ceftazidime-avibactam (CZA) has limited activity against the isolates that harbor these enzymes. This study aimed to evaluate the in vitro activity of aztreonam-avibactam and ceftazidime-avibactam against invasive carbapenem-resistant Enterobacterales isolates and to characterize the distribution of carbapenemase genes in a tertiary-care center in Türkiye. Methods: A total of 100 non-duplicate CRE isolates recovered from blood cultures and sterile body fluids between January 2024 and January 2026 were included. Species identification and routine antimicrobial susceptibility testing were performed using MALDI-TOF MS and an automated system. CZA and AZA MICs were determined by gradient diffusion testing, whereas CZA-aztreonam synergy was assessed separately using a disk/gradient diffusion-based method. Carbapenemase genes were detected by real-time PCR. Whole-genome sequencing was performed for the two AZA-resistant Escherichia coli isolates. Results: The isolate collection was dominated by Klebsiella pneumoniae (87.0%), and most isolates were recovered from blood cultures (80.0%). CZA susceptibility was observed in 31.0% of isolates, with MIC50/90 values of 256/256 mg/L. In contrast, AZA showed high in vitro activity, with 98.0% of isolates categorized as susceptible and MIC50/90 values of 0.25/0.50 mg/L. CZA-aztreonam synergy was detected in 98.0% of isolates. Qualitative CZA-aztreonam synergy testing did not fully concord with direct AZA MIC-based susceptibility categorization: one AZA-resistant isolate showed a positive synergy result, whereas one synergy-negative isolate remained AZA-susceptible. Carbapenemase genes were detected in 99.0% of isolates; blaNDM was the most frequent gene (81.0%), followed by blaOXA-48 (72.0%), blaKPC (14.0%), and blaVIM (4.0%). The most common carbapenemase profile was blaNDM + blaOXA-48 (62.0%). blaNDM carriage was strongly associated with CZA resistance, and CZA MICs were significantly higher among blaNDM-positive isolates. The two AZA-resistant E. coli isolates belonged to ST500 and ST410, and both carried a YRIK insertion in PBP3; one of them additionally showed ompF disruption associated with a 4 bp insertion. Conclusions: AZA demonstrated potent in vitro activity against invasive CRE isolates in this setting, whereas CZA activity was substantially limited, likely reflecting the high prevalence of blaNDM and frequent carbapenemase co-carriage. These findings support the potential value of AZA in regions with emerging metallo-β-lactamase predominance and highlight the importance of local molecular surveillance to guide antimicrobial strategies.

Background:Acinetobacter baumannii is an important opportunistic pathogen responsible for healthcare-associated infections, particularly among critically ill, intensive care unit (ICU), and post-surgical patients. The emergence of carbapenem-resistant A. baumannii (CRAB) has become a major therapeutic challenge worldwide because of its multidrug-resistant nature and limited treatment options. Despite the increasing prevalence of CRAB in Pakistan, information regarding the molecular characterization of carbapenem resistance genes among isolates recovered from surgical site infections (SSIs) remains limited. Methods: A cross-sectional study was conducted from November 2023 to February 2024 at Khalifa Gul Nawaz Hospital, Bannu, Khyber Pakhtunkhwa, Pakistan. A total of (n = 118) surgical wound specimens were collected from patients with clinically diagnosed SSIs. A. baumannii isolates were identified using standard biochemical tests and confirmed by 16S rRNA gene sequencing. In vitro antimicrobial susceptibility was determined by Kirby-Bauer disk diffusion according to CLSI 2024 guidelines. In addition, the concentration-dependent inhibition-zone response of imipenem and meropenem against carbapenem-resistant isolates was evaluated using an agar well diffusion assay. Molecular detection of blaNDM-1 and blaOXA-23 was performed by polymerase chain reaction (PCR), and representative amplicons were subjected to Sanger sequencing for further analysis. Results: In the current study, the total number of (n = 118) wound specimens from healthcare-associated patients were processed, in which A. baumannii-positive isolates (n = 23, 19.5%) were documented. Its prevalence was higher in males (69.6%) compared to females, and was strongly associated (78.2%) with elderly patients (aged 51-68 years). In vitro susceptibility testing revealed that 91.3% of isolates harbored multidrug-resistant (MDR) attributes. Antimicrobial susceptibility profiling revealed high levels of multidrug resistance, with 82.6% of isolates resistant to imipenem and meropenem, as well as 100% resistance to aztreonam and gentamicin. Colistin showed the highest activity, with 87.0% of isolates remaining susceptible. In the agar well diffusion assay, measurable inhibition of the carbapenem-resistant isolates by imipenem and meropenem occurred only at higher concentrations. Molecular screening of resistance genes identified blaOXA-23 in 60.9% and blaNDM-1 in 30.4% of isolates. Co-expression of both genes was detected in some (n = 4) isolates. Among the selected MDR isolates included in the gene resistance analysis, imipenem and meropenem resistance were recorded in 9/14 blaOXA-23-positive isolates and 5/7 blaNDM-1-positive isolates. Conclusions: This study substantiates an escalated incidence of carbapenem-resistant, MDR A. baumannii in post-surgical infections. blaOXA-23 were documented as the predominant carbapenemase gene, with co-expression of blaNDM-1 in a substantial proportion of isolates. These findings provide an important phenotypic and molecular characterization of selected carbapenemase genes in healthcare-associated infections, highlighting the exigency for strengthened antimicrobial stewardship and infection control strategies in the hospitals of the region.

Carbapenem-resistant Pseudomonas aeruginosa (CR-PA) has limited therapeutic options, particularly when metallo-β-lactamases are present. We evaluated aztreonam-avibactam (AZA) against 48 clinical P. aeruginosa isolates, including 44 CR-PA with 18 difficult-to-treat resistant isolates. Class B carbapenemase genes were present in 50.0%, mainly blaNDM-1. AZA MICs ranged from ≤ 0.5 to > 256 µg/mL (MIC50/90, 16/64 µg/mL), and 58.3% of isolates had AZA MICs ≤ 16 µg/mL. Among aztreonam-resistant isolates, AZA restored susceptibility in 33.3%, less frequently than aztreonam plus ceftazidime-avibactam (63.0%).