A real-time, genus-specific 5 nuclease PCR assay for amplification of a 322-bp fragment of the per gene was developed for rapid (<2 h) identification of Brucella spp. from agar plates. The assay, including an internal amplification control (116 bp), identified Brucella strains (n ؍ 23) and did not detect non-Brucella strains (n ؍ 174), indicating its usefulness, particularly for laboratories with stringent quality assurance programs.Owing to continuous efforts to control and eradicate brucellosis in domestic animals, the levels of brucellosis have been reduced in many countries (6). However, a natural reservoir of Brucella bacteria in wildlife, e.g., Brucella suis biovar 2 in hares in Denmark, can still pose a threat. Thus, the task of detection and identification remains challenging and requires reliable and sensitive diagnostics tools.The diagnosis of brucellosis is based mainly on serological responses, which can be unspecific owing to cross-reaction or subsensitive reactions in samples from areas with a low or subclinical prevalence of brucellosis (5,7,9,16). Culture-based verification of suspected cases, or pathological findings in clinical cases, can be time-consuming and also can impose a hazard to laboratory personal. Thus, numerous alternative verification methods, based mostly on amplification of universal genes in a conventional PCR, have been reported, although some have produced false-positive results (reviewed in reference 3).The Brucella-specific perosamine synthetase (per) gene is highly conserved and present even in the naturally rough Brucella species B. ovis and B. canis and spontaneously rough strains of B. abortus and B. melitensis (4). The per gene is, with various degrees of similarity, present in a few other bacteria, including Yersinia enterocolitica serotype O:9, Vibrio cholerae O1, Escherichia coli O:157, some serovars of E. hermanni and Stenotrophomonas maltophilia, and Salmonella group N (O:30) (14). To the best of our knowledge, the only real-time PCR work reported is based on hybridization probes used in three different assays for identification of three Brucella species (15). This report describes for the first time the development of a ready-to-go, nonproprietary, open-formula (thus possessing the potential for standardization), 5Ј hydrolysis probe-using real-time PCR assay including an internal amplification control (IAC) for direct verification of suspected Brucella colonies on agar plates.The Brucella-specific primers were designed as previously described (11). The primer combination bruc1-bruc5 was found to be most selective (11). In the present study, three different TaqMan probes (6-carboxyfluorescein [FAM] labeled) were designed and compared in the assay: Bruc1, in close proximity to the 3Ј end of the forward primer; Bruc2, in the middle of the amplified fragment; and Bruc3, within a few nucleotides of the 3Ј end of the reverse primer (Table 1).An artificially created chimerical DNA (12), a second set of primers, and a second TaqMan probe (VIC labeled) (12) were used f...