Prevalence and persistence of Salmonella in broiler chicken flocks

Cecal contents of 2,345 broiler chickens consisting of 28 flocks originated from 12 farms were examined for the prevalence of Salmonella to know the a ctual status of infection with Salmonella in the chicken flocks. Salmonella was isolated from 336 (14.3%) samples. From these isolates, eight serovars were identified. Of the 336 Salmonella isolates, 242 (72.0%) were serotype d as S. Blockley, 60 (17.9%) S. Hadar, 15 (4.5%) S. Bredeney, nine (2.7%) S . Schwarzengrund, four (1.2%) S. Anatum, three (0.9%) S. Enteritidis, two ( 0.6%) S. Ohio, and one (0.3%) S. Livingstone. The same serovars of Salmonel la were repeatedly found in the chickens from the same farms. S. Typhimuriu m and S. Enteritidis were detected in pooled broken eggshell samples collec ted from the hatchery. Analysis of plasmid profiles revealed 11 patterns of S. Blockley and seven patterns of S. Hadar. Strains of the same plasmid pr ofiles of S. Blockley were isolated repeatedly from the same farm over one year after the first isolation.