Analyses of prevalence and molecular typing of Salmonella in the goose production chain

Abstract

This study investigated the prevalence of Salmonella and the molecular typing of all isolates in a goose production chain including hatchery, farm, slaughterhouse, and market. A total of 350 Salmonella isolates was detected from 1,030 samples, and 13 serotypes were recovered. The highest Salmonella contamination frequency was observed at the hatchery, which 51.8% (188/363) of samples were Salmonella positive. S. Potsdam and S. Typhimurium were the 2 most common serotypes. S. Potsdam was most frequently found in the hatchery, while S. Typhimurium was widely distributed in the goose production chain. In general, the antibiotic resistance of Salmonella isolates is low, which isolates from the market is comparatively higher than from other production links indicating a possibility of Salmonella cross-contamination in the market. By the multilocus sequence typing (MLST) analysis, 7 different ST types were identified. ST2039 was the most common ST type, which was mostly found from S. Potsdam isolates in hatchery indicating that S. Potsdam might have been long existed in hatchery. The pulsed-field gel electrophoresis (PFGE) analysis of S. Potsdam indicated that S. Potsdam could be transmitted along the production chain. The PFGE analysis of S. Typhimurium showed that PFGE pattern 29 (PF29) was distributed in hatchery, and also in farm and from humans indicating the risk of S. Typhimurium transmitting to humans by the food supply chain. Our study provided the evidence of Salmonella cross-contamination in the slaughterhouse and the retail market of goose production chain, and specific serotypes existed for a long time at a particular production link. The spread of Salmonella along the production chain, might cause harm to humans through cross-contamination. Further studies would be needed to control the Salmonella contamination in hatchery and prevent the transmission of the pathogen during the goose production.

Keywords: MLST; PFGE; Salmonella; food safety; goose production chain.

Figure 1

Minimum spanning tree analysis of STs for Salmonella isolated from breeding, hatching, and slaughtering links. Each circle represents 1 ST, and the area of the circle corresponds to the number of isolates. Green stands for hatchery isolates, red represents market isolates, dark blue represents slaughterhouse isolates, yellow represents human isolates of S. Typhimurium, and sky blue represents farm isolates.

Figure 2

Dendrogram of PFGE patterns of S. Potsdam. A total of 5 clusters (A to E) were identified in the “strain” column. There was a total of 22 PFGE patterns (PF1 to PF22). The letter indicates the production link of the source of the strain. The number is the bacteria number. HA is for hatchery, SL is for Slaughterhouse, and FA is for farm. In the “source” column, letters represent samples from different sources. IO is for internal organ samples, and DE is for dead embryo samples. GE is for goose egg samples, and PO is for polished samples.

Figure 3

Dendrogram of PFGE patterns of S. Typhimurium. A total of 9 clusters (F to N) were identified, in the “strain” column. There was a total of 18 PFGE patterns (PF22 to PF40). The letters indicate the production link of the strain source, and the numbers represent the bacterial number. The human isolate is HU, the hatchery is HA, the slaughterhouse is SL, the farm is FA, and the market is MA. The source column, represents different types of samples.