关键词: 沙门菌; 屠宰场; 血清型; 生物被膜; 多位点序列分型(MLST)

Abstract: 【Objective】 In order to rationally prevent and control Salmonella infection,an experiment was conducted to study the prevalence of Salmonella in livestock and poultry slaughtering and marketing in Gansu province and neighboring areas.【Method】 Bacterial isolation and identification were carried out through bacterial culture,biochemical experiments,and molecular biology methods.The serotype of Salmonella was determined using slide agglutination and multilocus sequence typing (MLST).The quantitative method of crystal violet staining was used to evaluate the biofilm formation ability of the isolated strains.The sensitivity of isolated bacteria to commonly used antibiotics was tested through drug sensitivity tests.The sterilization effect of four commercially available disinfectants on Salmonella was evaluated,and their minimum inhibitory concentration (MIC) was determined. 【Result】 The results of bacterial isolation and culture showed that the suspected Salmonella isolates showed black colonies with metallic luster,tan or gray on BS plates.In XLD plate,the colonies showed glossy and black center,or all black colonies,and the microscopic examination showed that they were Gram-negative short bacilli.The biochemical identification results showed that the isolates reacted positively with hydrogen sulfide,glucose,ornithine,and lysine decarboxylase,and reacted negatively with urease,potassium cyanide,lactose and peptone water.PCR amplification of the Salmonella-specific gene invA yielded a target band of approximately 284 bp in size,confirming that a total of 95 Salmonella strains were isolated.All the isolates belonged to three serotypes of Salmonella enterica: Salmonella Typhimurium, Salmonella Derby and Salmonella Rissen.Multilocus sequence typing identified 3 species,ST34,ST469 and ST40.All the isolates could form biofilm,and drug sensitivity test showed that all strains were completely resistant to minocycline and vancomycin,and antibiotics such as amikacin,ceftriaxone,kanamycin,cefazolin,cefadroxil,and gentamicin were more susceptible to Salmonella isolates,and 75.78% of the strains were multidrug-resistant.The MIC of the four disinfectants against the isolates varied from 0.125 to 0.25 mg/mL for 0.2% formaldehyde solution,0.0625 to 0.125 mg/mL for 0.2% benzalkonium bromide,0.3125 to 0.625 mg/mL for 0.5% iodine solution,1.25 to 2.5 mg/mL for 2% sodium hydroxide.【Conclusion】 Salmonella Typhimurium,Salmonella Derby and Salmonella Rissen were the main serotypes of Salmonella in current slaughterhouses,and they possessd the ability to form biofilms and exhibited multidrug resistance,posing a significant threat to public health.This study provided a scientific basis for strengthening hygiene management in slaughterhouses and agricultural markets in Gansu province and surrounding areas.

Key words: Salmonella; slaughterhouse; serotype; biofilm; multilocus sequence typing (MLST)