Benefits of indirect impediometry, using Rappaport-Vassiliadis broth, for the detection of Salmonella in processed animal protein

Four hundred samples of processed animal protein were analysed for the presence of Salmonella using two impediometric methods. The direct method using both Easter and Gibsonʹs, and Ogdenʹs media, as defined in legislation applying throughout the UK, was less selective and sensitive, detecting 30% fewer positive samples than the indirect method using Rappaport-Vassiliadis broth. The indirect method detected 63 positive samples with a false positive rate of less than 10% and about 87% of positive samples were detected less than 12 h after being loaded onto the impedance equipment. Thus the indirect method was superior in terms of performance as well as being a cheaper and simpler methodology for the detection of Salmonella.