Identification,molecular Subtyping And Disinfectants As Measures Of Salmonella In Pig Slaughterhouse

Salmonella is one of zoonotic pathogens and one of the most common pathogens of food poisoning.The pig slaughterhouse is the "transfer station" of pork production.Through the collection of samples,isolation and culture of bacteria and microscopic examination of strain morphology,preliminary screening,PCR identification and serotype typing were conducted to find out the contamination status and serotype distribution of salmonella in the slaughterhouse,and the pollution characteristics and laws of salmonella in slaughterhouses were revealed,and then determine the salmonella strain through pathogenicity test.Secondly,molecular typing was performed by pulsed field gel electrophoresis(PFGE)to clarify the internal relationships among different sources of Salmonella strains.Finally,the reduction and prevention measures of common disinfectants were formulated and implemented on site.Effective reduction of Salmonella contamination is of great significance to human food safety.From September 2020 to August 2021,1530 samples were collected from A,B and C(large,medium and small)pig slaughterhouses in Yunnan Province for 9 times.291 Salmonella strains were isolated and identified,the total isolation rate was 19.0%(291/1530),among which,the isolation rates of slaughterhouses A,B and C were 12.9%(66/510)respectively,15.4%(78/507)and 28.7%(147/513).The isolates were classified into 13 serotypes by serum phenotypes.Pathogenicity tests showed that the isolates were consistent with the pathogenic characteristics of Salmonella.Salmonella Derby and salmonella Typhimurium were found in every link of the slaughterhouse,indicating that there was serious cross contamination in the slaughterhouse.Pulsed-field gel electrophoresis(PFGE)was used to draw phylogenetic tree,and60 strains of Salmonella Derby and 30 strains of Salmonella Typhimurium were selected from the identified isolates for PFGE typing.60 strains of Salmonella Derby produced 27 PFGE spectrum types,and 9 homologous clusters were identified.The 30 strains of Salmonella Typhimurium were digested to produce 26 PFGE spectrum types(PF).In general,it was found that the Salmonella PFGE pattern of samples from the same batch and different batches was very similar,indicating that there was serious cross-contamination in the slaughtering process.Seven disinfectants commonly used in slaughterhouse were selected to evaluate the reducing effect of 46 strains of Salmonella.The determination of minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)showed that 50%potassium bisulfate had the best effect 625 μg/m L,followed by 10% povitone 75 μg/m L.Based on this,the prevention,control and reduction plan has been formulated in slaughterhouse B and C,and the effect was obvious.After the implementation of the plan,the pollution level of slaughterhouse B and slaughterhouse C decreased by 15.7%and 30% respectively.There is no great change before and after the A field without implementing the scheme.However,there was no significant change before and after field A without implementing the scheme.It indicates that salmonella contamination in slaughter environment has been controlled and achieved the expected effect.There was no significant change before and after slaughterhouse A without implementing the scheme.The results showed that Salmonella contamination in slaughter environment had been controlled and the expected effect had been achieved.To sum up,as a "transfer station" for pork production,the pig slaughterhouse has caused much more environmental pollution to the carcass surface than to the inside of the pig,and there was serious cross contamination in the slaughter process.Targeted strengthening of disinfection measures and strict standardization of procedures can significantly reduce the cross-contamination of Salmonella in slaughterhouses,thus providing data support for the prevention and control of Salmonella contamination in slaughterhouses in the future and ensuring the safety of pork food.