Search Results (215)

Background: The spread of extended-spectrum β-lactamase-producing Klebsiella is an emerging public health concern presenting severe clinical impacts. This problem is particularly severe in developing countries where irrational use of antibiotics makes the treatment of such infections more challenging. Methods: In this cross-sectional study, we investigated antibiotic resistance among clinical Klebsiella pneumoniae isolates from 256 patient specimens from Al-Diwaniyah hospitals, using standard microbiological methods followed by PCR. Antimicrobial susceptibility testing identified resistance rates and proportions of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. Carbapenemase genes were detected by multiplex PCR and sequencing. Mutations were characterized, and their functional significance was predicted using in silico prediction tools. Results: Fifty Klebsiella pneumoniae isolates were recovered, exhibiting high resistance rates (42–100%) to penicillins, cephalosporins, fluoroquinolones and carbapenems, with 62% classified as MDR and 38% as XDR. Carbapenemase genes were highly prevalent (blaOXA-48 56%, blaIMP 44%, blaVIM 30%, blaKPC 28%, blaNDM 26%), with 60% of isolates co-harbouring ≥ two genes. Most mutations were predicted to be structurally tolerated, while active-site-proximal substitutions (H120L in NDM-52 and V120L in OXA-48) were predicted to affect enzyme activity. However, docking analysis suggested no significant alteration in carbapenem binding affinity. Conclusions: Our results highlight a very high prevalence of MDR/XDR Klebsiella pneumoniae, associated with diverse carbapenemase genes and resistance-related polymorphisms that may indicate potential functional impacts. To the best of our knowledge, this is the first study in Iraq to combine carbapenemase gene mutation analysis with structural modelling and molecular docking. This study emphasizes the urgent need for effective antimicrobial resistance surveillance in Iraq. Full article

Background/Objectives: Urinary tract infections (UTIs) are common infectious complications in kidney transplant recipients (KTRs) and non-transplant nephrology patients. However, direct culture-based comparisons of urinary isolate distribution and antimicrobial resistance profiles between KTRs and non-transplant nephrology (NTN) patients remain limited. This study compared urinary isolates recovered from urine cultures with significant growth and their in vitro antimicrobial resistance profiles in hospitalized KTRs and NTN patients. Methods: In this retrospective culture-based study, urine culture results from patients hospitalized in the nephrology and kidney transplantation units between 1 January 2024 and 31 December 2025 were reviewed. Urinary isolate distribution, in vitro antimicrobial resistance profiles, and extended-spectrum β-lactamase (ESBL) production were compared between the two. Results: A total of 397 patients with at least one urine culture showing significant growth were included, comprising 220 KTRs and 177 NTN patients. Enterobacterales were significantly more frequent among KTRs than among NTN patients (77.2% vs. 41.1%, p < 0.001). Escherichia coli was the predominant urinary isolate in both groups. In contrast, Candida spp. (26.8% vs. 3.2%, p < 0.001), Enterococcus spp. (15.8% vs. 7.7%, p < 0.001), and non-fermenting Gram-negative bacteria (9.4% vs. 3.4%, p = 0.001) were more frequently recovered from NTN patients. Among E. coli isolates, resistance to gentamicin (p = 0.006) and ertapenem (p = 0.001) was significantly higher in the NTN group. Likewise, Klebsiella pneumoniae isolates from NTN patients showed significantly higher resistance to third-generation cephalosporins, aminoglycosides, and carbapenems (p < 0.05). ESBL production was also more frequent in NTN patients than in KTRs (55.7% vs. 41.9%, p = 0.013). Conclusions: Hospitalized KTRs and NTN patients exhibited distinct urinary isolate distributions and in vitro antimicrobial resistance profiles. These findings should be interpreted as culture-based epidemiological data rather than as differences in clinically confirmed UTI burden. Stratified local surveillance may help contextualize urinary isolate and susceptibility patterns across hospitalized nephrology populations. Full article

Object: Postoperative infection is a severe complication after pediatric cardiac surgery, which is closely associated with sepsis, multiple organ dysfunction, prolonged mechanical ventilation, extended ICU stay and increased mortality. Conventional microbiological tests (CMT) are limited by low sensitivity, long turnaround time, and poor capacity for detecting viruses and polymicrobial infections. This study aimed to compare the diagnostic efficacy of mNGS with that of CMT, and to explore the impact of polymicrobial infection on clinical outcomes in this high-risk pediatric population. Methods: A retrospective cohort study was conducted on 4889 pediatric patients admitted to the PICU after cardiac surgery from January 2025 to March 2026. A total of 510 patients were diagnosed with postoperative infections, including 879 CMT specimens and 86 mNGS specimens enrolled for analysis. Pathogen detection rates, pathogen spectrum and antimicrobial resistance profiles were compared between the two detection methods. Clinical prognostic indicators including mechanical ventilation duration, PICU length of stay and the requirement for continuous renal replacement therapy (CRRT) were further compared between patients with polymicrobial infection and monomicrobial infection. Results: Respiratory tract infection accounted for 87.8% of all postoperative infections, and Gram-negative bacteria were the predominant pathogens, accounting for 65.9%. The overall pathogen detection rate of mNGS was significantly higher than that of CMT (79.1% vs. 56.5%, p < 0.001). Notably, mNGS exhibited significantly better performance in detecting viruses (37.2% vs. 5.8%, p < 0.001), anaerobic pathogens and polymicrobial infections (38.2% vs. 5.4%, p < 0.001). Patients with polymicrobial infections had significantly longer mechanical ventilation time, longer PICU stay, and higher CRRT utilization rate (all p < 0.05), indicating a poorer clinical prognosis. Gram-negative bacteria showed high resistance to penicillins and early-generation cephalosporins, but remained susceptible to carbapenems and β-lactamase inhibitor combination agents. Gram-positive bacteria showed a high resistance rate to penicillin, while maintaining 100% susceptibility to vancomycin and linezolid. Conclusions: mNGS serves as a more sensitive and comprehensive tool for pathogen detection in children with post-cardiac surgery infections, especially for viral and polymicrobial infections. Polymicrobial infection is an independent risk factor for adverse clinical outcomes. Routine application of mNGS in critically ill children may help guide targeted antimicrobial therapy and improve prognosis. Full article

Background/Objectives: Antimicrobial resistance in pediatric infections presents a worsening global public health challenge, with antimicrobial resistance (AMR) accounting for more than one million deaths annually and disproportionately affecting children younger than 5 years of age. Neonates and critically ill children face heightened risk owing to immature immunity, frequent healthcare exposures, and limited therapeutic options. This review synthesizes evidence on the epidemiology, mechanisms of resistance, clinical outcomes, and management of AMR across the full pediatric age range. Methods: PubMed/MEDLINE and Google Scholar were searched for literature from 2014 to 2026 using terms covering antibiotic resistance, pediatric populations, and key pathogens. Approximately 1840 records were screened; 69 sources met all inclusion criteria. A narrative synthesis approach was used, given heterogeneity across study designs and outcomes. Results: Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales, carbapenem-resistant pathogens, and methicillin-resistant Staphylococcus aureus drive substantial morbidity and mortality in children. Approximately one in five pediatric Gram-negative bloodstream isolates are resistant to third-generation cephalosporins, a phenotype independently associated with a roughly three-fold increase in adjusted mortality. Carbapenem-resistant Klebsiella pneumoniae bacteremia carries a 30-day mortality approaching 40%, and isolates in low- and middle-income countries (LMICs) frequently harbor multiple resistance genes. Pneumococcal conjugate vaccine implementation was associated with absolute reductions of 7–11% in the proportion of pediatric pneumococcal isolates that were penicillin-non-susceptible or penicillin-resistant, largely by preventing infections caused by resistant serotypes and by reducing antibiotic selection pressure, rather than through a direct effect on resistance mechanisms; global AMR mortality in children younger than 5 years of age fell by more than 50% between 1990 and 2021. Conclusions: Pediatric AMR reflects intersecting microbiological, clinical, and health-system challenges. Priority actions include scaling antimicrobial stewardship programs, expanding access to rapid molecular diagnostics, integrating whole-genome sequencing into surveillance, conducting pediatric-inclusive randomized trials, and deploying vaccines as primary prevention tools, with particular emphasis on LMICs where the burden is greatest. Full article

Proteus mirabilis is a frequent cause of complicated urinary tract infections (UTIs), in which biofilm formation and antimicrobial resistance contribute to persistence and therapeutic failure. This study investigated the biofilm-forming capacity, antimicrobial resistance profiles, virulence-associated genes, and genetic diversity of P. mirabilis isolates recovered from UTI patients in Isfahan, Iran. A total of 104 non-duplicate clinical isolates were analyzed. Biofilm formation was quantified using a microtiter plate crystal violet assay, and antimicrobial susceptibility testing was performed according to CLSI guidelines. Extended-spectrum β-lactamase (ESBL) production and extended-spectrum cephalosporin resistance (ESCR) were assessed phenotypically and by PCR. Selected virulence- and biofilm-associated genes were detected by PCR, and clonal relatedness was evaluated using ERIC-PCR. Most isolates were capable of biofilm formation, with 51% classified as strong and 45.2% as moderate producers. High carriage rates of virulence- and biofilm-associated genes, including zapA, zapD, ureC, ureR, luxS, rsbA, and acrA, were observed. ESBL production and ESCR phenotypes were detected in 6.7% and 12.5% of isolates, respectively, while multidrug resistance was observed in 30.4% of isolates. ERIC-PCR analysis identified predominant clonal clusters among isolates exhibiting strong biofilm production. These findings highlight the coexistence of biofilm formation, virulence determinants, antimicrobial resistance, and clonal diversity in uropathogenic P. mirabilis in this region. Full article

Background: Colistin- and carbapenem-resistant Acinetobacter baumannii (CRAB) represent a critical threat in intensive care unit (ICU) settings. This study aimed to provide a comprehensive molecular epidemiological characterization of extensively drug-resistant (XDR) A. baumannii clinical isolates from a tertiary-care hospital in Kırşehir, Central Anatolia, a region previously absent from the national surveillance literature. Methods: A total of 43 non-duplicate XDR A. baumannii isolates recovered from ICU patients between November 2021 and December 2023 were included. Antimicrobial susceptibility testing was performed by automated systems and broth microdilution for colistin. Resistance genes, including OXA-type carbapenemases, extended-spectrum β-lactamases (ESBLs), metallo-β-lactamases, plasmid-mediated colistin resistance (mcr-1 to mcr-5), plasmid-mediated quinolone resistance genes (qnr, qepA, oqxAB, aac(6′)-Ib-cr), and class 1 and 2 integrons, were screened by PCR. Integron gene cassettes were characterized by sequencing. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE) using ApaI digestion. Results: All 43 isolates exhibited the XDR phenotype with universal resistance to carbapenems, colistin, fluoroquinolones, aminoglycosides (except amikacin), piperacillin, cephalosporins, and tobramycin. Amikacin susceptibility was retained in 58.1% of isolates. blaOXA-51 was detected in all isolates (100%), and blaOXA-23 was the predominant acquired carbapenemase (90.7%). Notably, blaOXA-48, a carbapenemase typically associated with Enterobacteriaceae, was identified in 3 isolates (7.0%), each belonging to a distinct pulsotype. No blaOXA-24/40, blaOXA-58, or class B metallo-β-lactamase genes were detected. ESBL genes were found in a subset of isolates, with blaCTX-M group 1 being the most prevalent (20.9%). The aac(6′)-Ib-cr gene was detected in 81.4% of isolates, and oqxA/oqxB in 60.5% and 39.5%, respectively. No mcr or classical qnr genes were identified. Class 1 and 2 integrons were detected in 4.7% and 7.0% of isolates, respectively, carrying dfrA12-DUF1010-aadA2 (class 1) and dfrA1-sat-1 (class 2) gene cassettes. PFGE identified 12 pulsotypes among the typeable isolates; PT4 (n = 20, 47.6%) and PT11 (n = 8, 19.0%) were the dominant clonal clusters, together accounting for 65.1% of typeable isolates. Conclusions: This study presents one of the first comprehensive molecular epidemiological analyses of XDR A. baumannii from Central Anatolia. The dominance of OXA-23-carrying clonal lineages, the detection of blaOXA-48 in A. baumannii distributed across three distinct pulsotypes, the high prevalence of aac(6′)-Ib-cr, and the concurrent distribution of resistance determinants across genetically diverse clonal backgrounds indicate that both clonal expansion and possible horizontal gene transfer contribute to resistance dissemination in this setting. These findings underscore the need for systematic molecular surveillance and reinforced infection control strategies in ICU settings, at both the regional and national levels. Full article

Klebsiella pneumoniae is an opportunistic pathogen associated with both community-acquired and nosocomial infections. Multidrug-resistant (MDR) strains are increasingly implicated in urinary tract infections (UTIs), traveller’s diarrhoea, bacteraemia, and sepsis. β-lactam antibiotics are commonly used for treatment; however, antimicrobial resistance has emerged largely due to the production of extended-spectrum β-lactamases (ESBLs), which confer resistance mainly to penicillins, oxyimino-cephalosporins, and monobactams, while cephamycins and carbapenems usually remain stable to ESBL-mediated hydrolysis and compromise therapeutic efficacy. ESBL-producing strains represent a major cause of severe Gram-negative infections. This study aimed to determine the prevalence of ESBL-producing K. pneumoniae among UTI patients in Jordanian hospitals (Al Mafraq, Ma’an, and Islamic Hospitals), evaluate their antimicrobial susceptibility patterns, and detect antimicrobial resistance genes at the molecular level. A total of 450 urine isolates of K. pneumoniae were collected from UTI patients between November 2023 and May 2024. Isolates were identified in hospital laboratories using standard microbiological methods. Antimicrobial susceptibility testing was performed, and molecular characterisation of ESBL-associated genes was conducted using polymerase chain reaction (PCR). Out of 450 K. pneumoniae isolates collected from UTI patients across three Jordanian regions, 72 (16%) were confirmed as ESBL producers. Among the 72 ESBL-positive K. pneumoniae isolates, 34 (47.2%) were recovered from the Central region, 20 (27.8%) from the North, and 18 (25.0%) from the South. Molecular analysis revealed that 41.7% of ESBL-producing isolates carried the blaCTX-M gene, while 33.3% harboured the blaOXA gene. All ESBL-producing isolates demonstrated antimicrobial resistance to third-generation cephalosporins. A significantly higher proportion of ESBL-producing isolates was identified in female patients (84.7%) compared with males (15.3%). A significant association was observed between blaOXA gene distribution and geographic region (p = 0.016), whereas blaCTX-M gene distribution showed no significant regional association. ESBL-producing K. pneumoniae accounted for a substantial proportion of UTI isolates in Jordan, with blaCTX-M identified as the predominant resistance gene. The higher burden observed in the Central region and among female patients highlights notable distribution patterns in this cohort. These findings emphasise the necessity for sustained molecular surveillance and strengthened antimicrobial stewardship strategies to limit the dissemination of ESBL-producing strains in Jordanian healthcare settings. Full article

Hospital wastewater represents a critical hotspot for the dissemination of antibiotic resistance genes (ARGs), serving both as an environmental reservoir and a transmission pathway for multidrug-resistant bacteria into receiving ecosystems. The intense antibiotic selective pressure within healthcare facilities promotes the emergence, persistence and amplification of resistant strains, posing substantial risks to public health and environmental integrity. This study aimed to characterize Escherichia coli (E. coli) isolates recovered from hospital wastewater effluents in multiple cities across Gabon, with emphasis on bacterial loads, antimicrobial resistance patterns and associated genetic determinants. Wastewater samples were aseptically collected from sewer outlets of eleven healthcare facilities distributed across five provinces over a 12-week period, structured into two six-week sampling campaigns to capture temporal variability. A total of 158 bacterial isolates were obtained, among which 49 were confirmed as E. coli. Mean concentrations of presumptive E. coli ranged from 7.1 × 10³ to 1.49 × 10⁹ CFU/mL, indicating substantial microbial contamination of hospital effluents. Antimicrobial susceptibility testing using the Kirby–Bauer disk diffusion method against 19 antibiotics revealed that all isolates exhibited multidrug-resistant phenotypes. Resistance rates were particularly high to β-lactams and third-generation cephalosporins, reaching 90–100% in most facilities, reflecting strong selective pressure and widespread circulation of resistance mechanisms in urban aquatic environments. In contrast, carbapenems and amikacin remained comparatively effective, with resistance levels below 40%, suggesting partial preservation of last-resort therapeutic options. The values of the Multiple Antibiotic Resistance Index (MARI) ranged from 0.21 to 0.84, indicating selection pressure on different classes of antibiotics. Phylogenetic analysis showed a predominance of phylogroup A, traditionally considered commensal but increasingly associated with the spread of resistance. Groups B2, D/E and F proved to be the most resistant. These groups showed marked resistance to first-line antibiotics. The blaCTX-M-1 was the most prevalent resistance determinant (66.6%), occurring twice as frequently as blaSHV (33.3%), a finding that confirms the significant circulation of extended-spectrum β-lactamase-producing E. coli. Overall, these findings highlight hospital wastewater as a major reservoir and dissemination source of multidrug-resistant E. coli, underscoring the urgent need for improved wastewater treatment, strengthened antimicrobial stewardship and integrated One Health-based surveillance strategies. Full article

Background: Public catering is an underexplored One Health interface where structurally complex food-transport equipment may sustain reservoirs of antimicrobial-resistant bacteria. We investigated Escherichia coli from reusable institutional catering food-transport containers, focusing on a difficult-to-clean pressure-relief/ventilation valve compartment. Our objectives were to quantify phenotypic resistance using applied clinical breakpoints, assess inhibitor-synergy outcomes in ESBL confirmatory testing, and contextualize inhibitor-positive isolates by whole-genome sequencing (WGS). Methods: E. coli was isolated from containers sourced from 17 institutions and three central kitchens using ISO 16649-2. Minimum inhibitory concentrations (MICs) were determined by broth microdilution. Extended-spectrum β-lactamase (ESBL) confirmatory testing used cefotaxime/ceftazidime ± clavulanate; inhibitor positivity was defined as a ≥3 two-fold MIC decrease in the presence of clavulanate in isolates meeting CLSI screening thresholds. Inhibitor-positive isolates underwent WGS and CARD-based resistome profiling. Results: Resistance was most frequent to colistin (10, 10.8%), followed by doxycycline (8, 8.6%), florfenicol (7, 7.5%), enrofloxacin (4, 4.3%), and gentamicin (3, 3.2%). Third-generation cephalosporin resistance by clinical breakpoints was uncommon (cefotaxime: 2, 2.2%; ceftazidime: 1, 1.1%). Inhibitor-positive ESBL confirmatory phenotypes occurred in 30 isolates (32.3%), which were sequenced. WGS identified 45 resistance-associated genes across inhibitor-positive isolates but detected no classical ESBL genes; all carried chromosomal ampC/ampH alongside ubiquitous efflux-associated determinants. All WGS isolates belonged to phylogroup A, with serotype O154:H9 (20, 66.7%) and ST5549 (17, 56.7%) predominating. Conclusions: Institutional catering food-transport containers can harbor AMR E. coli, with colistin as the most frequent resistance phenotype and frequent inhibitor-positive ESBL confirmatory profiles that, in this set, were not explained by classical ESBL gene carriage. Integrating phenotype, WGS resistomics, and lineage structure supports targeted hygiene surveillance and risk-informed One Health monitoring in mass catering systems. Full article

Background/Objectives: Antimicrobial resistance (AMR) in companion animals is an emerging public health threat due to zoonotic potential and limited therapeutic options. Dogs with otitis externa may harbor multidrug-resistant (MDR) bacteria, including Escherichia coli (E. coli), Proteus mirabilis (P. mirabilis), and Enterobacter cloacae complex (E. cloacae complex), some producing extended-spectrum beta-lactamase (ESBL) or AmpC β-lactamases. This study aimed to assess the prevalence, AMR patterns, MDR occurrence, β-lactamase production, and co-infection profiles of these pathogens in canine otitis externa. Methods: Ear canal samples were collected from 592 dogs presenting clinical signs of otitis externa, with one sample per dog included in the analysis. Samples were collected from veterinary clinics in Timiș County, Romania, from 2022 to 2025. Samples were cultured on blood agar and MacConkey agar, followed by biochemical testing and MALDI-TOF mass spectrometry for bacterial identification. Antimicrobial susceptibility testing against 15 agents across six classes was performed using the VITEK^® 2 system. MDR and β-lactamase production (ESBL, AmpC) were determined according to CLSI 2018 veterinary guidelines. Co-isolation with bacterial and fungal species were recorded. Results: E. coli, P. mirabilis, and E. cloacae complex were isolated in 9.12%, 6.25%, and 1.2% of cases, respectively. E. coli exhibited the highest resistance to aminoglycosides (tobramycin 72.2%, gentamicin 61.1%) and full susceptibility to carbapenems. P. mirabilis showed the highest resistance to ampicillin (54%) and trimethoprim + sulfamethoxazole (46%), with complete susceptibility to carbapenems and fluoroquinolones. E. cloacae complex displayed universal resistance to cephalosporins but remained susceptible to non-cephalosporin β-lactams (piperacillin–tazobactam), carbapenems and aminoglycosides. MDR prevalence was 35.2% for E. coli, 18.9% for P. mirabilis, and 14.3% for the E. cloacae complex. ESBL production was detected in 13% of E. coli and 8.1% of P. mirabilis isolates, while all E. cloacae complex isolates were AmpC-positive. Co-isolations were common, primarily involving Staphylococcus pseudintermedius (S. pseudintermedius) and Malassezia pachydermatis (M. pachydermatis). Conclusions: MDR and β-lactamase-producing bacteria were identified in dogs with otitis externa, emphasizing the importance of routine antimicrobial susceptibility testing, targeted therapy based on local resistance profiles, and continuous AMR surveillance to prevent treatment failure and mitigate zoonotic risk. Full article

Background: Antimicrobial-resistant Escherichia coli and Klebsiella pneumoniae represent an increasing challenge in community-acquired pediatric diarrheal infections. Understanding the genomic basis and dissemination of resistance in outpatient settings is essential for guiding antimicrobial use. Methods: Eighteen Gram-negative isolates obtained from pediatric outpatients with acute diarrhea were analyzed using selective culture methods, antimicrobial susceptibility testing, and whole-genome sequencing. Multilocus sequence typing, serotyping, virulence profiling, antimicrobial resistance gene detection, plasmid replicon typing, mobile genetic element analysis, and core genome-based phylogenetic analysis were performed. Phenotypic resistance profiles were correlated with genomic resistance determinants. Results: Klebsiella pneumoniae (55.56%) and Escherichia coli (44.44%) were identified, with all isolates exhibiting putative multidrug resistance-associated genomic profiles. Extended-spectrum β-lactamase genes, particularly blaCTX-M variants, were strongly associated with resistance to third-generation cephalosporins. In contrast, fluoroquinolone resistance correlated with gyrA and parC mutations and plasmid-mediated qnr genes. Phylogenetic analysis revealed diverse lineages harboring resistance determinants. In silico plasmid analysis revealed that key resistance genes co-occurred with IncF-type plasmids and mobile genetic elements, including ISEcp1, IS26, and class 1 integrons, suggesting putative plasmid association rather than confirmed localization. Conclusions: These findings highlight the small scale of plasmid-mediated antimicrobial resistance among E. coli and K. pneumoniae causing pediatric community-acquired diarrhea. The integration of phenotypic and genomic analyses underscores the need for continuous resistance surveillance to support rational antibiotic use in outpatient settings. Full article

Background/Objectives: In the broad and current context of antimicrobial resistance, antibiotic management and therapeutic surveillance are essential in hospitals. The present study (five-year retrospective, 2020–2024) aimed to analyze antibiotic consumption in relation to pathogens identified in a multidisciplinary hospital. Results: In terms of antibiotic consumption (overall 2020–2024), although initially Watch antibiotics were predominantly used, a decrease was observed in favor of Access class antibiotics (sharply increase from 2022 to 2023 and maximum in 2024). For Reserve antibiotics, only slight annual fluctuations were observed, but there was an important reduction in colistin consumption. The most used were cephalosporins (cefazolin, cefuroxime and ceftriaxone), carbapenems (meropenem and ertapenem), vancomycin and linezolid. Regarding pathogens, the most notable were: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Enterococcus spp., Pseudomonas aeruginosa. Among the ESKAPE bacteria, Acinetobacter baumannii was the least frequent in our samples. ESKAPE bacteria predominantly colonized specimens from the respiratory tract, digestive tract, skin and soft tissue. Resistant strains were observed, mainly Methicillin-resistant Staphylococcus aureus (MRSA) and Extended-Spectrum Beta-Lactamase (ESBL) Klebsiella spp., but no alarming increases in number were recorded in the analyzed period. Methods: The analysis was carried out using tools recommended by the World Health Organisation (Access Watch Reserve antibiotics classification (AWaRe); Bacterial Priority Pathogen List (BBPL); Defined Daily Dose (DDD)), Average Annual Percent Change (AAPC) calculation and ESKAPE classification (bacteria group: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.). Conclusions: Relatively stable trends in bacterial isolates and resistant strains over five years (2020–2024) are consistent with effective antimicrobial stewardship practices. Full article

The Citrobacter freundii (C. freundii) complex represents an increasingly significant group of opportunistic pathogens within healthcare settings. This bacterial complex demonstrates remarkable genomic plasticity, characterized by extensive horizontal gene transfer capabilities that facilitate rapid acquisition of resistance determinants and virulence factors. Although originally considered environmental organisms with limited pathogenic potential, members of the C. freundii complex have emerged as important nosocomial pathogens responsible for urinary tract infections, bacteremia, wound infections, and neonatal meningitis. Importantly, their clinical significance lies less in unique disease manifestations and more in the moderate risk of resistance emergence during therapy with third-generation cephalosporins, driven by inducible chromosomal AmpC β-lactamase production. Beyond this intrinsic mechanism, the genomic adaptability of the C. freundii complex also enables acquisition of additional resistance determinants, including extended-spectrum β-lactamases (ESBLs) and carbapenemases, further limiting therapeutic options and complicating clinical management. Understanding the molecular mechanisms underlying genomic plasticity, virulence expression, and resistance development in the C. freundii complex is crucial for developing effective diagnostic strategies, infection control measures, and novel therapeutic approaches. This pathogen exemplifies the challenge of emerging multidrug-resistant bacteria in contemporary healthcare and underscores the need for continued surveillance and research. This narrative review provides current insights into the taxonomy, genomic plasticity, virulence, and mechanisms of antibiotic resistance. Full article

Background: Extended-spectrum β-lactamase (ESBL)-producing E. coli are a major One Health concern because they compromise critically important cephalosporins and may spread via mobile genetic elements, including plasmids and transposon-associated modules, within food-animal production systems. Objectives: The aim of this study was to characterize cefotaxime (CTX)/clavulanic acid (CLA) inhibitor-positive phenotype profiles in pig-associated multidrug-resistant (MDR) E. coli and resolve their genetic basis using whole-genome sequencing, with emphasis on ESBL determinants and their predicted mobility context. Methods: MDR E. coli isolates (n = 203) from four large-scale pig farms in Hungary were tested by broth microdilution minimum inhibitory concentration (MIC) determination and Clinical and Laboratory Standards Institute (CLSI) inhibitor-based ESBL confirmation using cefotaxime with/without clavulanic acid. CTX/CLA inhibitor-positive isolates (inhibitor-positive phenotype) were subjected to whole-genome sequencing (WGS; n = 116) and resistome profiling; antimicrobial resistance genes (ARGs) were called against the Comprehensive Antibiotic Resistance Database (CARD) and mobility context was inferred using plasmid-origin and MGE-proximity prediction. Results: Overall, 127/203 isolates (62.6%) showed a CTX/CLA inhibitor-positive phenotype with a pronounced inhibitory effect (median cefotaxime/cefotaxime–clavulanate ratio: 33.3). In the sequenced subset (n = 116), 5427 ARG hits were identified (82 unique ARGs in the export), including frequent acquired determinants affecting tetracyclines, sulfonamides/trimethoprim, aminoglycosides, and phenicols; plasmid-mediated quinolone resistance (qnrB5) and mobilizable colistin resistance (mcr-1) were detected at low frequency. Classical β-lactamase genes were detected, including CTX-M (ESBL genes) and TEM alleles. CTX-M and/or TEM were detected in 47/116 genomes (40.5%), dominated by CTX-M-32 (11.2%) and TEM-1 (23.3%); detected ESBL determinants were predominantly predicted to be located on contigs predicted to be of plasmid origin, with a subset showing signatures consistent with transposition-associated mobilization. Conclusion: The high burden of inhibitor-positive phenotype, together with an inferred plasmid-/MGE-associated context for a subset of ESBL genes, and substantial phenotype–genotype heterogeneity, supports integrated phenotypic–genomic surveillance to refine AMR risk assessment and guide targeted stewardship and biosecurity interventions in pig production. Full article

Background/objectives: A rise in infections associated with carbapenem-resistant Providencia species (CRPS) has been observed worldwide. This study presents a genomic analysis of CRPS isolates from four hospitals in Croatia and the outpatient setting, in order to determine the extent of the spread of CRPS in Croatia. In the present study, we applied a combination of phenotypic characterization and molecular analysis of resistance traits to determine the mechanisms and the routes of spread of CRPS. Material and methods: The antibiotic susceptibility testing was performed using disk-diffusion and broth dilution methods. The nature of extended-spectrum β-lactamases (ESBLs), carbapenemases, and fluoroquinolone resistance determinants was investigated by polymerase chain reaction (PCR). In order to obtain an insight into the whole resistome, selected isolates were subjected to the Interarray Genotyping Kit CarbaResist and whole genome sequencing (WGS). Results: In total, 30 isolates were collected from four centers, located in different geographic regions of Croatia. There was uniform resistance to piperacillin-tazobactam, cefuroxime, expanded-spectrum cephalosporins (ESCs), imipenem, ertapenem, meropenem, and ciprofloxacin. Immunochromatographic testing and PCR revealed OXA-48 and NDM carbapenemase in 15 isolates, respectively. Phenotypic tests for ESBLs were positive in all OXA-48 and one NDM-positive organism (16 isolates). The isolates were categorized as extensively drug-resistant (XDR). OXA-48-producing isolates were susceptible only to ceftazidime-avibactam, whereas NDM producers were susceptible to cefiderocol and, in the majority of cases, also to amikacin. WGS identified a plethora of genes encoding resistance to aminoglycosides, such as aadA1 and aadA2, (aph(3″)-Ib and aph(6)-Id, sulfonamides sul1 and sul2, trimethoprim dfrA1, dfrA10, and dfrA12, tetracyclines tet(A) and tet(B), and chloramphenicol catA3 and catA5. Conclusions: Providencia spp., in spite of being a rare pathogen, should be included in the surveillance studies across the medical centers in Croatia. Full article