title: Serum Bactericidal Assay: New Role in Salmonella Detection.
abstract: While inspecting animal feed for Salmonella contamination, we routinely observed bacterial colonies on selective agars that were similar in appearance to those formed by Salmonella. These were identified as Citrobacter freundii, Proteus mirabilis, and Serratia fonticola using biochemical and serological techniques. Because the presence of these bacterial species confounds identification of Salmonella, we refer to them as "interference bacteria." Polyvalent antisera against these interference bacteria were prepared by immunizing rabbits with a mixture of all three organisms. To minimize or eliminate interference by these bacteria, the polyvalent antisera were introduced between the steps of selective enrichment and Salmonella-selective plating. The antisera raised against the interference bacteria, when combined with neonatal rabbit complement, exhibited specific bactericidal activity against C. freundii, P. mirabilis, and S. fonticola. The respective serum bactericidal assay titers were 2(9), 2(8), and 2(10). In selective broth, polyvalent antisera could also kill the target bacterial cells effectively. We tested 526 samples (186 white fishmeal, 97 red fishmeal, and 243 cattle bone powder) using the polyvalent antisera and found that the rates of contamination of each species of the three respective foods decreased by 58.8, 100, and 83%. Our data indicates that polyvalent sera against C. freundii, P. mirabilis, and S. fonticola can be used as inhibitors to increase the accuracy of Salmonella detection.
authors.affiliation: College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China, 350002.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Da
authors.initials: D
authors.lastname: Wu
authors.forename: Min
authors.initials: M
authors.lastname: Sun
authors.forename: Mingjun
authors.initials: M
authors.lastname: Deng
authors.forename: Shuhua
authors.initials: S
authors.lastname: Cui
authors.forename: Chengzhu
authors.initials: C
authors.lastname: Liang
authors.forename: Juan
authors.initials: J
authors.lastname: Geng
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.forename: Ling
authors.initials: L
authors.lastname: Long
authors.forename: Xizhi
authors.initials: X
authors.lastname: Xiao
mesh_terms: D000821:Animal Feed / Q000382:microbiology; D000818:Animals; D001431:Bacteriological Techniques; D002417:Cattle; D007106:Immune Sera / Q000276:immunology; D011817:Rabbits; D012475:Salmonella / Q000166:cytology / Q000276:immunology / Q000302:isolation & purification*
chemical_list: D007106:Immune Sera