Real-time detection of Brucella abortus, Brucella melitensis and Brucella suis

Real-time PCR-based assays specific for Brucella abortus, Brucella melitensis and Brucella suis were developed. The assays utilize an upstream primer that is derived from 3' end of the genetic element IS 711, whereas the downstream primers and probes are designed from signature sequences specific to a species or a biovar. The PCR reactions were monitored for fluorescence resonance energy transfer by including two adjacent labeled probes that hybridize to the amplicons as they are formed. The upstream probes were labeled with fluorescein at 3' end while Cy5 was attached to the 5' end of the downstream probes. An increase in the ratio of fluorescein to Cy5 fluorescence during the cycling was indicative of positive amplification event. The assays were accomplished in less than 30 min using a LightCycler in real-time mode. The assays were tested on known strains as well as field isolates and were found to be specific for all known biovars of B. abortus, B. melitensis and biovar 1 of B. suis. Therefore, specificity, sensitivity, speed and real-time detection make these assays attractive for use in epidemiological and ecological studies.