Currently, Salmonella enterica serovar Brandenburg is identified serologically on the basis of two surface antigens, somatic (O) polysaccharide and flagellar (H) proteins. This procedure is time-consuming and requires expensive typing reagents. To overcome these problems, a PCR method was developed and validated for the identification of S. Brandenburg. Portions of the invA, rfbJ(B), fliC and fljB genes were targeted for amplification using four pairs of oligonucleotide primers. To validate the assay, genomic DNA from an array of 72 Salmonella strains representing 28 serotypes and 5 non-Salmonella strains from 4 different genera was subjected to PCR. The four targeted genes were correctly amplified only from S. Brandenburg. These results indicate that this PCR assay is a simple, rapid, reliable and reproducible method for the identification of S. Brandenburg that will aid in surveillance, prevention and control of this pathogen.
INTRODUCTIONSince 1996, Salmonella enterica serovar Brandenburg has been a major cause of ovine abortions and mortality, leading to significant economic impact to farmers in New Zealand (Clark, 2000;Clark et al., 2004;Roe, 1999;Smart, 2000). Sheep that have recovered from clinical disease may become carriers and excrete organisms in faeces. S. Brandenburg has also been isolated from humans and other animals, including horses, cattle, goats, deer, pigs and dogs. In New Zealand, human cases occurred through contact with infected animals and not through consumption of animal products (Clark et al., 2004). Therefore, rapid detection of S. Brandenburg would aid in controlling the spread of this pathogen to both animals and humans.The number of Salmonella serotypes reported by 2002 was 2541 (CDC, 2007). The somatic O-antigen, together with phase-1 (H1) and phase-2 (H2) flagellar antigens, forms the basis for Salmonella serotyping. Each Salmonella serotype has a unique combination of O, H1 and H2 antigens. Laboratory methods for the identification of S. Brandenburg include serotyping, which is performed by the identification of O, H1 and H2 antigens according to the Kauffmann-White scheme (Popoff & Le Minor, 2001). This procedure is time-consuming, laborious and costly. Rapid and inexpensive PCR assays for the detection of Salmonella at the genus level have been developed (Rahn et al., 1992), but the number of assays to determine the Salmonella serotype is limited and includes those to detect serotypes Enteriditis (Lampel et al., 1996), Gallinarum (Shah et al., 2005), Typhi (Farrell et al., 2005;Kumar et al., 2006) and Typhimurium (Leon-Velarde et al., 2004). To date, there is no serotype-specific PCR assay for the detection of S. Brandenburg.Somatic O-antigens are polymers of the O-subunit, and the rfb gene clusters are responsible for much of its variation. Variability of O-antigens among serogroups is due to differences in the type and arrangement of sugars in the Osubunit (Fitzgerald et al., 2003; Gillespie et al., 2003). The filament of flagella is a polymer of flagellin monomers that are ...