Isolation, identification, and drug resistance analysis of Salmonella Typhimurium from quails

Abstract:

[Background] The irregular use of antimicrobials and disinfectants in quail breeding has exacerbated the spread of drug-resistant strains between animals, premises, and food. So it is important to understand the drug-resistant status of pathogenic strains of farmed animals. [Objective] To detect the drug resistance characteristics and the prevalence of drug resistance genes in the pathogenic strains derived from quail eggs in the quail farms around Beijing. [Methods] The samples of quail cloacal feces, quail egg surface, breeding environment, and quail drinking water were collected from some quail farms in Wuqing District, Tianjin. A strain was isolated and identified by colony morphology observation, staining microscopy, and biochemical tests. Serotyping and invA sequencing were carried out for this strain. Furthermore, the mouse challenge test was performed to determine the median lethal dose (LD₅₀), and the drug susceptibility test and PCR were employed to detect the drug resistance phenotypes and genes and the virulence genes of the isolates. [Results] The colony color, microscopic morphology, and biochemical properties of the isolates were consistent with those of Salmonella. The invA sequencing results showed that the strain had 99.44% homology with the reference strain of Salmonella Typhimurium, and thus it was identified as S. Typhimurium, with the serotype being 1,4,[5],[12]:i:l,2. The strain had pathogenic effect on mouse, with the LD₅₀ of 2.10×10⁷ CFU/mL. It was resistant to ampicillin, amoxicillin/clavulanate, ceftiofur, streptomycin, sulfamethoxazole, sulfafurazole, norfloxacin, and ciprofloxacin and sensitive to ten antibiotics such as cefazolin. The strain presented enhanced resistance to cationic surfactants and peroxide disinfectants. It carried four resistance genes such as bla_TEM and thirteen virulence genes such as mogA. [Conclusion] A pathogenic Salmonella Typhimurium strain was isolated from a quail farm. It has multi-drug resistance and carries multiple virulence genes. The results provide a reference not only for the hazard assessment but also for the formulation of prevention and control measures of Salmonella from quails.