Antibiotic resistance characteristics and virulence gene analysis of Escherichia coli in caged Chinese monals （Lophophorus lhuysii）

【Objective】To analyze the antibiotic resistance characteristics and virulence gene carriage status of Escherichia coli in caged Chinese monals （Lophophorus lhuysii）, explore the antibiotic resistance and potential risks of E. coli in caged Chinese monals, which could provide theoretical basis for the rational use of antibiotics and containment of drug resistance in animal-derived bacteria in the breeding process of Chinese monals. 【Method】A total of 116 fresh fecal samples were collected from the artificial breeding ground at the Sichuan Fengtongzhai National Nature Reserve Administration in January, March, April, July and October 2022. Conducted bacterial isolation and identification, determined the antibiotic resistance patterns of E. coli strains obtained through susceptibility testing against 18 types of antibiotics, screened for strains producing extended-spectrum beta-lactamases（ESBLs）, and used PCR amplification to detect 13 types of resistance genes and 9 types of virulence genes. Additionally, performed a correlation analysis between representative resistance phenotypes and associated resistance genes. 【Result】A total of 84 strains of E. coli were isolated from 116 samples, with a detection rate of 72.41%. Among them, 12 strains were sensitive to all tested antibiotics, while 53 strains were resistant to 3 or more tested antibiotics, accounting for 63.10%. The highest number of antibiotic resistance phenotype in the isolates was 12, and a majority of the observed antibiotic resistance phenotype were ampicillin, trimethoprim and gentamicin, with verage resistance rates of 78.57%, 75.00% and 45.24%. The antibiotic resistance gene detection results showed that the average detection rate of the polymyxins resistance gene pmrA was the highest（80.95%）. Other antibiotic resistance genes with a detection rate exceeding 50.00% included β-lactams resistance gene blaTEM（70.24%）, chloramphenicol resistance gene floR（57.14%） and sulfonamides resistance gene sulI（50.00%）. The resistance to gentamicin was significantly associated with the aminoglycoside resistance gene aadA1 （P＜0.01）, while there was no significant correlation between the resistance to ampicillin and the blaTEM gene, nor between the resistance to trimethoprin and the sulI gene, or between the resistance to ciprofloxacin and the qnrS gene（P＞0.05, the same below）. A total of 36 ESBL-producing strains were screened and identified. The resistance rates of ESBL-producing strains to ampicillin and trimethoprim were both 100.00%, but there was no significant correlation between ESBL-producing strains and blaTEM gene. Among the 39 E. coli strains isolated from fecal samples in July and October, the protein secretion regulator gene（escV） had the highest detection rate （17.95%）, followed by the intestinal colonization factor gene（pic） （15.38%）, while the invasion plasmid regulator gene （invE） was not detected. 【Conclusion】The E. coli isolated from the feces of caged Chinese monals exhibits multiple antibiotic resistances and carries certain virulence genes, posing a potential pathogenic risk. The resistance spectrum is primarily characterized by resistance to ampicillin, trimethoprin, and gentamicin. The use of β-lactam, sulfanilamide, aminoglycoside and quinolone antibiotics should be controlled in the prevention and treatment of bacterial diseases in caged Chinese monals.