A Rapid Screening Method for the Detection of VTEC and Salmonella from Swab Specimens of Flayed Carcasses by Multiplex PCR

Abstract

We investigated the usefulness of a rapid screening method for the detection of VTEC andSalmonellafrom swab specimens of flayed carcasses by detecting the Vero toxin (VT) andSalmonella invAgenes by PCR using multiplex primer sets (MK and SIN primer sets) for the meat inspection at slaughterhouse. Thirteen strains of VTEC and 3 strains ofSalmonellawere examined in the presence of other bacteria (non-VTEC and non-Salmonella) concomitantly present in the swab specimens. The multiplex PCR could detect VT andinuAgenes at a concentration of 2.0×10⁴cfu/ml and 2.1×10³cfu/ml respective1y, even in the presence of other bacteria at a concentration of 10⁹cfu/ml in the broth suspension. Brief shaking-incubation of the swab specimens at 36°Cfor 8 hrs in Tryptic Soy Broth (TSB), during which period both VTEC andSalmonella, if present, grew to 10^6.6-10^8.4cfu/ml, enhanced the detection rate of the multiplex PCR test. Cultivation of the swab specimens in either EEM or N-mEC media showed restricted growth, and subsequent lower detection rates compared with that in TSB. With the combination of brief shaking-culture in TSB and the multiplex PCR, we could detect as little as 1-10cfu/ml of VTEC andSalmonellapresent in the swab specimens. This method can shorten the time and reduce the number of staff needed to perform meat inspection.