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<p>Bacterial pneumonia is a leading cause of mortality in fur-bearing animals, representing a significant challenge for the industry. Bacterial pneumonia is caused by a variety of pathogens, making its prevention and control difficult. This study aims to identify the primary etiological agents of bacterial pneumonia in farmed raccoon dogs in eastern Hebei and southern Liaoning provinces. To this end, we collected 159 pneumonic raccoon dogs between 2022 and 2025 for bacterial isolation and identification. We isolated 109 strains of <i>Escherichia coli</i>, 37 strains of <i>Pseudomonas aeruginosa</i>, and 13 strains of <i>Klebsiella pneumoniae</i>, identifying <i>E. coli</i> as the most frequently isolated bacterium. Further investigations revealed that <i>E. coli</i> caused multisystemic infection in raccoon dogs: the bacterium was detected in the liver, spleen, kidney, and blood, with the most severe lesions observed in the lungs, suggesting potential systemic dissemination. Histopathological examination results revealed multi-organ damage consistent with bacterial infection, which correlates with the isolation of <i>E. coli</i> from affected tissues. Pathogenicity assays demonstrated that the isolated <i>E. coli</i> strains exhibited notable pathogenic potential in a mouse model, capable of reproducing typical pneumonia symptoms via intranasal inoculation. Virulence gene profiling of the isolates showed that all strains harbored at least 5 virulence genes. Among these, the virulence genes <i>ompR</i>, <i>phoU</i>, <i>tonB</i>, <i>fimH</i>, <i>fimC</i>, and <i>Ecs3737</i> exhibited high detection rates, at 94.5%, 94.5%, 93.58%, 84.4%, 77.98%, and 60.55%, respectively. Antimicrobial susceptibility testing (AST) results revealed severe multidrug resistance (MDR) among the clinical <i>E. coli</i> isolates. The isolates showed universal resistance to nalidixic acid and ampicillin, and no single antimicrobial agent was fully effective against all strains. The resistance profiles of the <i>E. coli</i> isolates varied significantly between the two geographic regions studied. Resistance gene detection showed extremely high detection rates (≥ 80%) for quinolone resistance-associated chromosomal target genes and plasmid-mediated quinolone resistance (PMQR) genes, as well as integron-associated mobile elements. The detection rates of aminoglycoside, sulfonamide, and polypeptide resistance genes ranged from 30% to 70%, while those of amphenicol, β-lactam, macrolide, and tetracycline resistance genes were between 3% and 30%. Taken together, these data indicate that <i>E. coli</i> is the most frequently isolated bacterium associated with bacterial pneumonia in sampled farmed raccoon dogs in eastern Hebei and southern Liaoning, with notable pathogenic potential in mouse models and a high prevalence of complex multidrug resistance. These findings provide critical baseline data for guiding clinical antimicrobial use and developing disease control strategies in raccoon dog farming.</p>

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High prevalence of virulent and multidrug-resistant Escherichia coli as the most frequently isolated bacterium associated with bacterial pneumonia in farmed raccoon dogs

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月31日

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  • Hong Li,
  • Chihuan Li,
  • Xintong Zhu,
  • Zhixin Zhu,
  • Guowang Chen,
  • Chao Ren,
  • Siping Zhu,
  • Tonglei Wu,
  • Li Chen,
  • Yonghui Li,
  • Qiumei Shi,
  • Zhiqiang Zhang

摘要

Bacterial pneumonia is a leading cause of mortality in fur-bearing animals, representing a significant challenge for the industry. Bacterial pneumonia is caused by a variety of pathogens, making its prevention and control difficult. This study aims to identify the primary etiological agents of bacterial pneumonia in farmed raccoon dogs in eastern Hebei and southern Liaoning provinces. To this end, we collected 159 pneumonic raccoon dogs between 2022 and 2025 for bacterial isolation and identification. We isolated 109 strains of Escherichia coli, 37 strains of Pseudomonas aeruginosa, and 13 strains of Klebsiella pneumoniae, identifying E. coli as the most frequently isolated bacterium. Further investigations revealed that E. coli caused multisystemic infection in raccoon dogs: the bacterium was detected in the liver, spleen, kidney, and blood, with the most severe lesions observed in the lungs, suggesting potential systemic dissemination. Histopathological examination results revealed multi-organ damage consistent with bacterial infection, which correlates with the isolation of E. coli from affected tissues. Pathogenicity assays demonstrated that the isolated E. coli strains exhibited notable pathogenic potential in a mouse model, capable of reproducing typical pneumonia symptoms via intranasal inoculation. Virulence gene profiling of the isolates showed that all strains harbored at least 5 virulence genes. Among these, the virulence genes ompR, phoU, tonB, fimH, fimC, and Ecs3737 exhibited high detection rates, at 94.5%, 94.5%, 93.58%, 84.4%, 77.98%, and 60.55%, respectively. Antimicrobial susceptibility testing (AST) results revealed severe multidrug resistance (MDR) among the clinical E. coli isolates. The isolates showed universal resistance to nalidixic acid and ampicillin, and no single antimicrobial agent was fully effective against all strains. The resistance profiles of the E. coli isolates varied significantly between the two geographic regions studied. Resistance gene detection showed extremely high detection rates (≥ 80%) for quinolone resistance-associated chromosomal target genes and plasmid-mediated quinolone resistance (PMQR) genes, as well as integron-associated mobile elements. The detection rates of aminoglycoside, sulfonamide, and polypeptide resistance genes ranged from 30% to 70%, while those of amphenicol, β-lactam, macrolide, and tetracycline resistance genes were between 3% and 30%. Taken together, these data indicate that E. coli is the most frequently isolated bacterium associated with bacterial pneumonia in sampled farmed raccoon dogs in eastern Hebei and southern Liaoning, with notable pathogenic potential in mouse models and a high prevalence of complex multidrug resistance. These findings provide critical baseline data for guiding clinical antimicrobial use and developing disease control strategies in raccoon dog farming.