A Mix-ELISA using lipopolysaccharide antigens from Salmonella enterica serotype Enteritidis
and Typhimurium was evaluated using samples collected over time in the Danish salmonella
surveillance programme for poultry. Serological samples (n = 42813) taken from broiler-breeder
flocks after a year of bacteriological monitoring with negative results were used for calculating
the flock and individual test specificities, which were 0·997 and 0·999, respectively. Layer flocks
from the table egg sector were used for calculation of positive predictive values. In the survey,
flocks were examined for salmonella by Mix-ELISA and by faecal culture, and in case of a
positive result in either of these a repeated, serological testing was performed, and 60 animals
were organ-cultured. If one of these samplings was positive, the flock was declared salmonella
infected. In a period of 3 months, 35 flocks were found to be positive in the routine samples.
Of these, 32 were serologically positive, 2 both serologically and faecally positive and 1 flock
only faecally positive. For flocks serologically positive in the surveillance programme, a
positive-predictive value of 0·62 for organ culture positivity was found, and while considering
serological follow-up samples, the value was 0·95.