Detection of Brucella abortus DNA in illegal cheese from São Paulo and Minas Gerais and differentiation of B19 vaccinal strain by means of the polymerase chain reaction (PCR)

Abstract

A total of 192 samples of illegal cheese from different regions of the states of Sao Paulo and Minas Gerais, Brazil, were analyzed for the isolation and detection of Brucella spp. DNA by means of microbiological culture and polymerase chain reaction (PCR), respectively. Samples that yielded positive results were submitted to the analysis of the occurrence of Brucella abortus (biovars 1, 2 e 4), as well as to the differentiation of DNA in B19 vaccinal strain or Brucella abortus field strain using PCR. Although the microorganism was not isolated from any sample, PCR detected 37 positive samples (19.27%) using genus-specific primers. From these, all (100%) were Brucella abortus. Differentiation of the strain showed that 30/37 samples (81.08%) were vaccinal strain B19 and seven (18.92%) were Brucella abortus field strains. Results showed that diagnostic sensitivity of PCR was greater than that of microbiological culture. The standardization of the reaction for the differentiation of vaccinal and field strains enabled the analysis of all samples positive for Brucella abortus. It is, therefore, a reliable method, also applicable to natural infections caused by the microrganism.