Development of a novel visual isothermal amplification assay for rapid detection of Brucella spp.

Brucellosis is an economically important livestock disease worldwide besides having a noteworthy impact on human health. In this study, a rapid, simple, and ultra-sensitive nuclei-acid diagnostic technique was developed for the detection of brucellosis harnessing saltatory rolling circle amplification (SRCA). The diagnostic method was developed using World Organization for Animal Health (WOAH) approved primers targeting the bcsp31 gene of the Brucella genome. The assay can be accomplished within 90 min at a temperature of 65 degrees C without the requirement of sophisticated instrumentation. The result interpretation can be done with the naked eye with the aid of SYBR green dye. The developed technique displayed 100% specificity by amplifying only 10 reference and field strains of Brucella spp. and there was no cross-reactivity with the other tested pathogens. The lower limit of detections of SRCA and end-point PCR assays were 9.7 fg/mu L (2.7 genome copies of Brucella) and 970 fg/mu L, respectively. Thus, the developed SRCA assay was found to be 100x more sensitive than the end-point PCR assay. To the best of our knowledge, our study is the first one to develop an SRCA-based assay for the detection of brucellosis and it can be a diagnostic tool for resource-constrained laboratories and veterinary hospitals.