Search Results (98)

Background/Objectives: Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are priority antimicrobial-resistant pathogens with significant implications for food safety and public health. Food-producing animals and their derived products represent a key interface for zoonotic transmission, yet prevalence data across Nigeria remain fragmented and unsynthesized. This systematic review and meta-analysis assessed the prevalence, species distribution, geographical patterns, and detection methods of ESBL-producing E. coli in food-producing animals and animal-derived food products across Nigeria. Methods: A comprehensive search of PubMed, Web of Science, Scopus, and African journals online was conducted for studies published between January 2000 and January 2026, following PRISMA 2020 guidelines. Twenty eligible studies collectively analyzed 5104 samples, and 984 ESBL-positive isolates were included in the meta-analysis. Results: The overall pooled prevalence of ESBL-producing E. coli was 17.0% (95% CI: 13.0–21.0%; I² = 89.4%). Subgroup analysis by animal species revealed the highest pooled prevalence among caprine (32.0%, 95% CI: 17.0–52.0%), bovine (24.0%, 95% CI: 17.0–33.0%), porcine (17.0%, 95% CI: 7.0–36.0%) and avian species (13.0%, 95% CI: 9.0–19.0%). Animal-derived food products showed a pooled prevalence of 19.0% (95% CI: 17.0–21.0%). Regional analysis showed the highest pooled prevalence in South-West (19.0%, 95% CI: 13.0–27.0%) and South-South (19.0%, 95% CI: 9.0–34.0%). Studies using combined culture and molecular methods reported higher pooled prevalence (19.0%, 95% CI: 14.0–25.0%) than culture alone (12.0%, 95% CI: 8.0–18.0%). However, the difference between subgroups was not statistically significant (test for subgroup differences: p = 0.0563). Conclusions: These findings confirm extensive ESBL-producing E. coli circulation in Nigerian food-producing animals and highlight critical gaps in antimicrobial stewardship, veterinary surveillance, and food safety infrastructure, underscoring the urgent need for coordinated One Health strategies to contain the spread of resistant strains through the food chain. Full article

To characterize the ecological and genomic architecture of temperate bacteriophages in Escherichia coli isolated from Brazilian broiler chickens, we analyzed 63 femur-derived genomes, most fulfilling molecular avian pathogenic E. coli (APEC) criteria, and tested whether temperate phage regions are enriched for antimicrobial resistance genes (ARGs), virulence factors, plasmid markers, and other mobilome components. Diversity was summarized using incidence-based richness estimators and bootstrap confidence intervals, and positional enrichment was assessed using permutation-based statistical analysis. We detected 1164 phage-like elements, including 188 medium- and high-quality phages, of which 93.6% were temperate. Median temperate diversity per genome was three phage genera and three temperate regions. At the population level, 19 temperate genera were observed, with a Chao2 estimate of 21.2, indicating near-saturated genus-level diversity. Positional mobilome analysis showed significant enrichment of insertion sequences within temperate regions (p < 0.05), while ARGs, virulence factors, and plasmid markers were not significantly enriched inside temperate phage coordinates (p > 0.05). The surrounding genomic neighborhood (±20 kb) accumulated mobile elements but showed no significant enrichment. CRISPR spacer matches further supported ongoing host–phage interactions. Overall, temperate phages are widespread and ecologically structured in Brazilian broiler-associated E. coli, but they are not preferential hotspots for ARG, virulence, or plasmid gene enrichment; instead, they are chiefly associated with insertion-sequence enrichment. Full article

Background/Objectives: Spotty liver disease (SLD), caused by Campylobacter hepaticus, is an emerging disease that leads to substantial production losses in the egg industry. The shift toward antibiotic-free and cage-free production systems has further intensified the impact of SLD. The current control measures largely rely on autogenous killed vaccines; however, their use is constrained by the slow and fastidious growth of C. hepaticus and inconsistent efficacy. To overcome these limitations, this study aimed to identify immunogenic mimotopes as vaccine candidates and express them on the surface of an avian pathogenic Escherichia coli (APEC) vector. Methods: To identify immunogenic mimotopes, Ph.D.-12 phage display peptide library was screened using the hyperimmune serum raised against killed whole-cell C. hepaticus in specific pathogen-free chickens. Subsequently, the outer membrane protein C (OmpC) of E. coli was used as a scaffold for constructing a surface display library. A single restriction site, PstI, located in the seventh external loop of OmpC, was strategically utilized to insert each 12-amino-acid mimotope with a six-histidine (6xHis) tag sequence at its N-terminus, generating ompC + mimotope fusion constructs. These constructs were cloned into the inducible expression vector pTrc and electroporated into an E. coli DH5α ∆ompC strain, which lacked ompC. The surface expression of the mimotopes was confirmed in vitro. The verified ompC + mimotope constructs were subsequently subcloned into the pYA3422 constitutive expression vector and electroporated into the APEC PSUO78 ∆aroA ∆asd vaccine vector strain. A chicken vaccination–challenge trial was conducted using nine groups of chickens, including an unvaccinated challenged control and an unvaccinated–unchallenged negative control. Each experimental group received a mixture of two recombinant E. coli strains carrying different mimotopes at a dose of 1 × 10⁹ CFU, which were administered orally twice at 16 and 18 weeks of age. Results: Fourteen immunogenic mimotopes corresponding to 13 different C. hepaticus proteins were identified as potential vaccine candidates. The expression of these mimotopes on the surface of the E. coli was successfully demonstrated using the OmpC-mediated surface display system. Of the 14 mimotopes tested, two flagellar-related peptides and one major outer membrane protein (MOMP)-derived peptide elicited significant immune responses and conferred protection against the C. hepaticus challenge. Conclusions: We successfully developed a functional E. coli surface display system that was capable of expressing 12-amino-acid mimotopes of C. hepaticus, providing a robust platform for evaluating vaccine candidates against SLD. Immunogenicity and efficacy studies in chickens demonstrated that three identified mimotopes conferred protection against C. hepaticus colonization of the bile and liver. Future in vivo investigations are necessary to develop and evaluate the immunogenicity and protective efficacy of a multivalent mimotope vaccine consisting of three identified mimotopes against both C. hepaticus and APEC, utilizing the ΔaroA Δasd APEC PSU078 strain as the vaccine vector. Full article

Background: Avian pathogenic Escherichia coli (APEC) are significant bacterial pathogens that cause economic losses in the poultry industry and can pose a potential foodborne zoonotic risk. Herein, we examined APEC distribution and antimicrobial resistance in E. coli isolated from slaughtered broiler chickens in northern Thailand. Methods: PCR was used to classify APEC as either virulent or avirulent on 108 stored E. coli strains, as well as to perform Clermont phylotyping. Antimicrobial susceptibility to ciprofloxacin, cefotaxime, ceftazidime, imipenem, and colistin was examined. Results: Of the 108 E. coli strains, 101 (93.5%) isolates were APEC, and the remaining isolates were non-APEC. Among the APEC isolates, 58.4% were classified as virulent APEC; these isolates showed a statistically significant association with phylogroups F and C and (n = 54, 56.8%) more frequently exhibited a ciprofloxacin-resistant phenotype than avirulent APEC (n = 35, 36.8%). Among the ten APEC virulence genes, hlyF, iroC, iroN, iutA, O78, and ompT were significantly associated with virulent APEC. Conclusions: This study reveals a high prevalence of virulent APEC with fluoroquinolone resistance in slaughtered broiler chickens. Almost all virulent APEC strains belong to phylogroups F and C. The prediction of virulent APEC using hlyF, iroC, iroN, iutA, O78, and ompT may be useful. Full article

Chicken respiratory diseases represent multifactorial conditions resulting from viral, bacterial, mycoplasmal pathogens, and environmental factors, causing significant economic losses within the poultry industry. A specific respiratory disease characterized by breathing difficulties and bronchial occlusion due to caseous exudates is termed chicken bronchial obstruction. However, the absence of rapid, precise, and highly sensitive diagnostic methods for differentiation of primary respiratory disease pathogens or opportunistic pathogens, including avian influenza virus (AIV), infectious bronchitis virus (IBV), Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli), constitutes a substantial challenge. This study developed a quadruplex droplet digital polymerase chain reaction (ddPCR) method that targeted the HA gene of H9 subtype AIV, the M gene of IBV, the Pal gene of P. aeruginosa, and the UidA gene of E. coli. Following the optimization of annealing temperature, sensitivity, and repeatability, the minimum detectable concentrations were determined as 3.02 copies/μL for the HA gene of H9 subtype AIV, 3.08 copies/μL for the M gene of IBV, 3.19 copies/μL for the Pal gene of P. aeruginosa, 3.39 copies/μL for the UidA gene of E. coli. No cross-reactivity was observed with Newcastle disease virus (NDV), H5 subtype AIV, H7 subtype AIV, fowl adenovirus serotype 4 (FAdV-4), infectious laryngotracheitis virus (ILTV), Avibacterium paragallinarum, Streptococcus, Salmonella, Pasteurella multocida, and Staphylococcus aureus. The method demonstrated excellent repeatability, with a coefficient of variation (CV) below 9%. The 185 clinical samples collected in Hebei Province China are tested by both quadruplex ddPCR and quadruplex qPCR method and the results compared. The sensitivity of the quadruplex ddPCR method (57.30%; 106/185) slightly exceeded that of the quadruplex qPCR method (49.73%; 92/185). Pathogens or opportunistic pathogens positive rates obtained via the quadruplex ddPCR were 40.00% for H9 subtype AIV, 33.51% for IBV, 24.32% for P. aeruginosa, and 27.57% for E. coli. In comparison, the positive rates of H9 subtypes AIV, IBV, P. aeruginosa, and E. coli from the quadruplex qPCR were 36.22%, 30.81%, 21.62%, and 24.32%, respectively. The coincidence rates between the two methods were 96.22% for H9 AIV, 97.30% for IBV, 97.30% for P. aeruginosa, and 96.76% for E. coli. These results demonstrated that the quadruplex ddPCR method represented a highly sensitive, specific, and rapid technique for identifying H9 subtype AIV, IBV, P. aeruginosa, and E. coli. Full article

Avian pathogenic Escherichia coli (E. coli) impairs poultry production and causes substantial economic losses. This study investigated the effects of Lactobacillus reuteri postbiotics (LR) on growth performance and intestinal health of broiler chickens challenged with E. coli. A total of 180 one-day-old Arbor Acres+ broilers were allocated into three groups (six replicates per group and 10 chicks each replicate): CTR, control group; E. coli-infected group, orally challenged with a mixture of E. coli O₁, O₂, and O₇₈ at a dose of 10⁹ CFU/mL; LR + E. coli-infected group, challenged with E. coli and fed a basal diet supplemented with 100 mg/kg LR. The results showed that dietary LR significantly improved the average daily gain (ADG) in the LR + E. coli group compared to the E. coli-infected group from days 1 to 18 (p < 0.05). However, no significant differences in average daily feed intake (ADFI) or feed conversion ratio (FCR) were observed among the CTR, E. coli, and LR + E. coli groups. Infection with E. coli led to lower total antioxidant capacity in jejunum and activity of total superoxide dismutase in ileum. Moreover, dietary LR significantly alleviated the down-regulation of Mucin2 and Aquaporin-3 gene expression in jejunum and ileum caused by E. coli infection and up-regulated the gene expression of Claudin-1 and Zonula occludens 1 in the ileum. In addition, dietary LR treatment led to the up-regulation of interleukin-10 mRNA transcripts in the jejunum. Further analysis demonstrated that dietary supplementation with LR reshaped the ileal flora of birds challenged with E. coli via elevating the relative abundance of Romboutsia and Bacteroidota, while reducing the abundance of Candidatus_Arthromitus and Escherichia-Shigella. In conclusion, dietary LR supplementation improved the expression of intestinal barrier and anti-inflammatory genes and reshaped the intestinal flora in E. coli-infected broilers. Full article

Bacteriophages, or phages, are viruses that infect and kill specific bacteria, offering a promising alternative to antibiotics in livestock production. With growing concerns over antibiotic resistance, phages have gained renewed interest due to their ability to target harmful pathogens without disturbing beneficial gut microbiota. This review explores the application of dietary phage supplementation in monogastric animals, particularly pigs and poultry. In pigs, phage use has demonstrated beneficial effects such as improved growth performance, enhanced gut health, and reduced infections from Salmonella and E. coli. Various delivery methods, including feed and water supplementation, have been studied, with microencapsulation showing promising results for stability and effectiveness. Similarly, in poultry, phages have been successfully used to control pathogens like Salmonella, Campylobacter, and avian pathogenic E. coli, improving gut health, immunity, and overall performance. Several commercial phage products are already in use, demonstrating both safety and efficacy. Despite these advantages, challenges such as a narrow host range, bacterial resistance, and regulatory limitations remain. Therefore, further research is necessary to understand phage–host interactions, optimize delivery strategies, and evaluate long-term effects under normal and disease-free conditions. This review highlights the potential of bacteriophages as safe, targeted, and sustainable alternatives to antibiotics in monogastric animal production, contributing to improved animal health and reduced antibiotic use. Full article

Background: Escherichia coli strains associated with poultry are increasingly recognized as reservoirs of both virulence and resistance genes, posing significant zoonotic risks throughout the food production chain. However, the genotypic architecture and pathogenic potential of isolates from large-scale turkey farms remain under characterized, particularly in the context of extended-spectrum β-lactamase (ESBL) production. Methods: A total of 160 ESBL-producing E. coli isolates were collected from healthy turkeys on intensive Hungarian farms. Whole genome sequencing (WGS) was performed to characterize virulence factors. Functional annotation included screening for fimbrial adhesins, iron acquisition systems, secretion pathways, and autotransporter toxins, using VirulenceFinder and Prodigal-based genome annotations. Data analysis included assembly quality control with QUAST and BUSCO, and comprehensive virulome profiling. Results: The isolates exhibited a functionally diverse virulence profile encompassing classical ExPEC-associated colonization factors (type I, P, S fimbriae; curli; ECP), multiple iron acquisition systems (enterobactin, salmochelin, aerobactin, yersiniabactin, and heme uptake), and key secretion systems (LEE-associated T3SS and T2SS). Genetic hallmarks of avian pathogenic E. coli (APEC), uropathogenic pathogenic E. coli (UPEC), and enteropathogenic E. coli (EPEC) pathotypes co-occurred in 44% of the isolates, indicating a mosaic virulence landscape. Notably, serine protease autotransporters of Enterobacteriaceae (SPATE) toxins (Vat, Pic) and ColV-type plasmid-associated modules were frequently detected. All isolates were confirmed by ESBL producers, highlighting their antimicrobial resistance potential. Conclusions: This study reveals that E. coli strains isolated from turkeys possess a complex, host-adapted virulence repertoire capable of supporting both enteric and extraintestinal infections. The co-occurence of APEC-, UPEC-, and EPEC-like traits—combined with ESBL production—underscores their One Health relevance. These findings support the need for host-specific surveillance, functional validation, and integrative control strategies in poultry systems. Full article

Avian pathogenic Escherichia coli (APEC) causes avian colibacillosis, a disease responsible for high morbidity and mortality in commercial poultry flocks, leading to devastating economic losses to the poultry industry worldwide. APEC may also act as a source of virulence and antibiotic resistance genes that can be transferred to other Escherichia coli pathotypes. Therefore, this study aimed to determine the serotypes, phylogenetic background, virulence genes, and antibiotic resistance profiles of APEC in Algeria. A total of 98 APEC strains were isolated from chicken samples with characteristic colibacillosis signs between 2019 and 2020. O-serotyping identified O157 (20.41%) and O78 (11.22%) as the predominant serotypes. The isolates were classified into groups B1 (43.87%), C (29.59%), A (12.24%), E (7.14%), F (5.10%), and B2 (2.04%). Virulence gene analysis revealed that among the 31 genes investigated, a high occurrence of mat, crlA (100% each), yijP (98.98%), fimC, ibeB, ompA (97.96% each), iucD (89.80%), iroN (81.63%), iss (80.61%), and eae (79.59%) was observed. The highest resistance rates were found for ampicillin (97.96%), amoxicillin–clavulanic acid (96.94%), nalidixic acid (94.90%), tetracycline (90.82%), and ciprofloxacin (79.59%). Additionally, 92.86% of APEC isolates were resistant to three or more antibiotics, reflecting extensive antimicrobial use in Algerian poultry farms and highlighting a major challenge for animal health management and a potential risk of zoonotic transmission. Our data provide valuable insights into the characteristics of the APEC populations in broiler chickens in Algeria. This may assist in understanding APEC pathogenesis and in developing effective control strategies. Full article

Background: The increasing attention on extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli strains isolated from poultry flocks stems from concerns about their virulence potential and zoonotic risk. Of particular significance is the identification of extraintestinal pathogenic E. coli (ExPEC) pathotypes in poultry, as these strains pose not only animal health concerns but also serious threats to food safety and public health. Mapping the genetic background of pathogenicity and antimicrobial resistance is essential for risk assessment and the development of effective control strategies. Methods: A total of 87 E. coli isolates were isolated from tracheal and cloacal swab samples collected from healthy chickens between 2022 and 2023. Whole-genome sequencing was performed using Illumina and MGI next-generation sequencing platforms. Bioinformatic analyses were conducted to identify virulence-associated genes and pathotype markers using multiple reference databases, including VirulenceFinder. The frequency of virulence genes was summarized both in tabular form and visualized through graphical representations. Results: A substantial proportion of the isolates harbored virulence genes linked to various ExPEC pathotypes, particularly uropathogenic E. coli (UPEC), avian pathogenic E. coli (APEC), and neonatal meningitis-causing E. coli (NMEC). The most frequently detected colonization factors included members of the fim, pap, ecp, and fae gene families. Among fitness-related genes, iron acquisition systems—ent, chu, iro, iuc, fep, and ybt—were especially prevalent. Classic UPEC-associated genes such as pap and fimH, along with the APEC-related iutA and vat, were found at high frequencies. Four isolates exhibited a virulence gene profile characteristic of the NMEC pathotype (ibeA, kpsD/M/T, fimH). In contrast, hallmark genes of enteric pathotypes were absent from all isolates. Conclusions: The predominance of extraintestinal virulence factors in the examined poultry-derived E. coli strains underscores their zoonotic potential. The complete absence of enteric pathotype markers indicates that the studied poultry populations primarily harbor ExPEC-like strains. These findings highlight the critical need for ongoing genomic surveillance and targeted preventive strategies within poultry production systems. Full article

Background/Objectives: Antimicrobial resistance is a critical global health challenge. Among resistant pathogens, the group of bacteria collectively referred to as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) is of particular concern due to their ability to evade multiple classes of antimicrobials. This study aimed to investigate the occurrence and resistance patterns of ESKAPE bacteria in wild birds from Northern and Central Italy sites, and to assess the presence of other bacteria of public health relevance. Methods: Cloacal swabs were collected from 141 wild birds. Samples were processed on selective and differential media, and bacterial identification was performed using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. Antimicrobial susceptibility was evaluated through Minimum Inhibitory Concentration assays and interpreted according to international guidelines. Results: Thirty-seven isolates belonging to the ESKAPE group were identified: E. faecium (n = 10), K. pneumoniae (n = 9), P. aeruginosa (n = 8), Enterobacter spp. (n = 7), S. aureus (n = 2), and A. baumannii (n = 1). Multidrug-resistant isolates were observed among K. pneumoniae and Enterobacter hormaechei. Escherichia coli, although not included in the ESKAPE group, was frequently detected and often co-isolated with clinically relevant bacteria, highlighting its potential role as a reservoir of resistance genes. Conclusions: Wild birds can harbor resistant bacteria of clinical importance, including multidrug-resistant ESKAPE species. Their presence in avian populations underscores the role of wildlife in the environmental dissemination of antimicrobial resistance, with implications for both animal and human health. Full article

The ban on antibiotic growth promoters (AGPs) in poultry farming has prompted the search for effective, natural alternatives. Essential oils (EOs), such as those from oregano (Origanum vulgare: OVEO) and rosemary (Salvia rosmarinus: ROEO), possess antimicrobial and antioxidant properties that may contribute to intestinal health and pathogen control. This study evaluated the antibacterial activity of OVEO and ROEO, individually and combined, against six Escherichia coli and six Salmonella typhimurium strains isolated from healthy poultry via cloacal swabs, as well as E. coli ATCC 25922 and S. typhimurium ATCC 14028 strains. The minimum inhibitory concentrations (MIC) were determined at five pH levels (7.4–5) simulating avian gastrointestinal tract conditions. EO composition was determined by GC-FID-MS. Checkerboard assays revealed partial or full synergistic effects at most pH, especially under acidic environments (pH ≤ 5.5), where the fractional inhibitory concentration (ΣFIC) values often indicated synergy. No antagonistic interactions were observed. These results suggest that OVEO and ROEO combinations are promising candidates to replace AGPs in poultry, particularly because of their enhanced efficacy under gastrointestinal pH. The strategic use of EO blends may reduce pathogen load, support performance, and limit antimicrobial resistance development, suggesting their potential as natural alternatives to AGPs under One Health principles. Full article

Background: Avian pathogenic Escherichia coli (APEC) is a leading cause of colibacillosis in poultry. Piper betle L. is a medicinal plant rich in bioactive compounds including hydroxychavicol that possess potent antibacterial activity. This study aimed to investigate the efficacy of a P. betle L. leaf nanoemulsion (NEPE) and hydroxychavicol against multidrug-resistant APEC isolates. Methods: In vitro and in silico analysis of NEPE and hydroxychavicol against APEC were determined. Results: The nanoemulsion exhibited potent antibacterial activity, with MIC and MBC values of 0.06–0.25% v/v and 0.125–0.25% v/v, respectively. The MIC and MBC values of hydroxychavicol against isolates ranged from 0.25 to 1.0 mg/mL. A time–kill assays revealed rapid bactericidal effects of both compounds, achieving a ≥3-log reduction within 4 h at 4 × MIC. Scanning electron microscopy demonstrated that APEC cells treated with hydroxychavicol exhibited filamentous cells with incomplete septa. Molecular docking and dynamics simulations of hydroxychavicol against APEC cell division proteins were investigated. According to the binding energy, hydroxychavicol exhibited the highest affinity with ZapE, FtsW, FtsX, FtsZ, and FtsA, respectively. However, the FtsA protein showed the least protein conformational change throughout the 5000 ns simulation, reflecting a highly stable conformation. Conclusions: These confirm the potential stability of protein and ligand, as supported by molecular dynamics simulation. The results suggested the potential of NEPE and hydroxychavicol, which may have promising antibacterial potential that can be used to inhibit APEC growth. Full article

Avian pathogenic Escherichia coli (APEC) is highly infective in poultry, causing significant economic losses to the poultry industry. As an extraintestinal pathogenic strain, adherence is a critical step in the infection. The functions of several adhesins, including type I, P, and Curli fimbriae, have been extensively studied. However, the roles of other adhesins, like Sfm, remain largely unexplored. Sfm is widely present in E. coli. Although the Sfm cluster is an ortholog of the fim gene cluster of Salmonella type I fimbriae, the biological function of Sfm in APEC has not yet been elucidated. To investigate whether Sfm in APEC CE129 plays a role in virulence, in this study, we constructed recombinant strains by expressing Sfm in the fimbriae-deficient strain SE5000. Additionally, a CE129 sfmA mutant strain was constructed. The resulting changes in adherence, biofilm formation, resistance to macrophage phagocytosis, and resistance to serum bactericidal ability were observed. The adherence ability of CE129ΔsfmA was reduced by 41%. HD-11 cells demonstrated a 30% increase in the phagocytosis of CE129ΔsfmA, and a 50% reduction in SE5000 (pBR322-sfm). The sfm deletion mutant showed a 23.9% reduction in the resistance to serum bactericidal ability, while SE5000 (pBR322-sfm) displayed a 32% increase. SE5000 (pBR322-sfm) exhibited a 34% increase in biofilm formation, and CE129ΔsfmA demonstrated a 21% decrease. Real-time PCR was employed to examine the impact of Sfm deletion on the transcription level of key virulence factors (fimA, fliC, papC, tsh, ompA, and iss). The results indicated that Sfm in CE129 is closely associated with bacterial adherence and survivability, contributing to biofilm formation and influencing the expression of key virulence factors. This study yields initial insight into the functional roles of Sfm in APEC and provides a foundation for the effective control of E. coli in the poultry industry. Full article

Avian pathogenic Escherichia coli (APEC) poses a global threat to poultry health and public safety due to its high lethality, limited treatment options, and potential for zoonotic transmission via the food chain. However, long-term genomic surveillance remains limited, especially in countries like China where poultry farming is highly intensive. This study aimed to characterize the population structure, virulence traits, and antimicrobial resistance of 81 APEC isolates from diseased chickens collected over 16 years from Shandong and neighboring provinces in eastern China. The isolates were grouped into seven Clermont phylogroups, with A and B1 being dominant. MLST revealed 27 STs, and serotyping identified 29 O and 16 H antigens, showing high genetic diversity. The minor phylogroups (B2, C, D, E, G) encoded more virulence genes and had higher virulence-plasmid ColV carriage, with enrichment for iron-uptake, protectins, and extraintestinal toxins. In contrast, the dominant phylogroups A and B1 primarily carried adhesin and enterotoxin genes. Antimicrobial resistance was widespread: 76.5% of isolates were multidrug-resistant. The minor phylogroups exhibited higher tetracycline resistance (mediated by tet(A)), whereas the major phylogroups showed increased resistance to third- and fourth-generation cephalosporins (due to bla_CTX-M-type ESBL genes). These findings offer crucial data for APEC prevention and control, safeguarding the poultry industry and public health. Full article