Study on rapid identification of Brucella based on blood culture

Abstract

Objective To explore a rapid and simple method for identifying Brucella, and to provide further evidence for clinical diagnosis. Methods Bact/Alert blood culture system was used to culture whole blood samples, suspicious Brucella positive culture samples were screened by observing growth curve of the positive alarming bottles, and gram staining for blood smears and rapid biochemistry test was performed to identify Brucella initially. Traditional identification methods, including agglutination tests with positive serum and specific single phase serum (A, M and R) and Brucella bacteriophage lytic test, were used to identify suspected isolates to species or type. Clinical specimens from patients identified to be positive with Brucella were further identified and characterized by and PCR method [Brucella surface protein-31 (BSCP31)-PCR and Brucella abortus, Brucella melitensis, Brucella ovis, and Brucella suis species-specific PCR (AMOS-PCR)]. Results The growing curve of the 61 clinical samples showed the following features, including flat lag growth phage, about 72 h of time to positivity, shorter logarithmic growth phase and flat stationary phase. The 64 isolates (3 of them were cultured for 2 times) were further identified to be Brucella with urea hydrolysis tests, gram staining and Kovac's staining. Twenty-seven strains were identified to be Brucella melitensis strains using bacteriological methods. Among the 27 of 64 strains, 21 of which were Brucella melitensis biovar 3 and 6 of them were Brucella melitensis biovar 1; the results of BCSP31-PCR test confirmed that the 27 Brucella strains were identified to be Brucella melitensis, the result of AMOS-PRC test again confirmed that 27 Brucella strains wereBrucella melitensis. Conclusions The rapid Brucella identification method could shorten the identification time. Verified by conventional method and PCR method, the new method could rapidly and reliably identify Brucella strains. Key words: Brucella; Biological assay; Bacterial typing techniques