Salmonella Serotyping and Identification

All isolates were serotyped by slide agglutination of O and H antigens according to the instructions provided by the manufacturer of the antiserum that we used (Ningbo Tianrun Bio-technology Co., LTD., China). The serotypes could then be determined according to the Kauffmann–White classification scheme [39 ]. For the identification of S. gallinarum and S. pullorum, dulcitol fermentation and ornithine decarboxylation tests were conducted according to a previous study [40 (link)]. Salmonella biochemical identification tubes were purchased from Hangzhou Microbial Reagent Co., Ltd. (Hangzhou, China). PCR was performed on isolates identified as S. pullorum using a specific IpaJ gene for S. pullorum (Table S1); the standard strain of S. pullorum (CVCC 526) purchased from the China Center for the Preservation and Management of Veterinary Microorganisms was used as a positive control and S. enteritidis (CVCC 3377) was used as a negative control.