Verification of different methods used for isolating <i>Salmonella enterica</i> serovar Dublin from cattle feces

Abstract

Salmonella enterica serovar Dublin is a cattle-adapted serovar, and some infected cattle can become asymptomatic carriers. Identification of carrier animals is important for preventing the spread of infection within a farm, but low diagnostic sensitivity of the fecal culture method is problematic. In this study, we investigated isolation methods of four S . enterica Dublin strains. Selective enrichment using the tetrathionate broth showed better performance than Rappaport-Vassiliadis R10 broth, but one of the strains was not detectable. Since isolation of such strains by selective enrichment can be difficult, we designed a method using immuno-plates that concentrates S . enterica Dublin by antigen-antibody reaction. Our method is able to detect approximately 200 clony-forming units of S . enterica Dublin in 0.1 g of cattle feces. If S . enterica Dublin was isolated from cattle with clinical signs, the method to identify carriers in the farm should be based on the growth kinetics of the target S . enterica Dublin strain.