Comparison of PCR assay and bacteriological culture method for the detection of Brucella melitensis in stomach content samples of aborted sheep fetuses.

Abstract

The aim of this study was to evaluate the polymerase chain reaction (PCR) assay for detection of Brucella melitensis in stomach content samples of aborted sheep fetuses and to compare its performance with bacteriological culture method. It was also aimed to determine the agreement between PCR and Rose Bengal plate test (RBPT). Materials were collected from aborted sheep from 109 different sheep flocks in the region of Van during the lambing seasons of 2004-2005 and 2005-2006. Stomach contents from 135 aborted sheep fetuses were examined by bacteriological culture and PCR, and 135 sera from these aborting ewes were tested by RBPT. Identification and typing of Brucella strains were performed using standard classification test. B. melitensis biovar 3 was isolated from 26 (19.2%) of foetal stomach contents. B. melitensis was detected by PCR in 29 (21.4%) stomach content samples. Twenty five sera (18.5%) from aborting ewes tested positive by RBPT. The detection limit of B. melitensis 16 M strain by PCR was 1.7 x 10(3) cfu (colony forming units) /ml in spiked stomach contents. Diagnostic sensitivity and specificity of the PCR were detected as 100% and 97.2%, respectively. The agreement between PCR and RBPT was found to be 97%. In conclusion, PCR assay would have an advantage over conventional bacteriological culture method, but in particular for its ability to meet the specificity requirements for the detection of B. melitensis in stomach content samples of aborted sheep fetuses.