Immunological and molecular characterization of Leptospira interrogans isolated from a bovine foetus

Abstract

Cattle are commonly infected with pathogenic leptospires, and similarly to rodents, they excrete the bacteria in their urine and can transmit the pathogen from animal to animal or animal to human. Thus, surveillance and monitoring systems for detection of new Leptospira serovars are important for the control of leptospirosis. Here, we report the isolation of a spirochete from a stillborn bovine foetus and its characterization by immunological and molecular techniques. A variable number tandem repeat profile using seven discriminatory primers identified the spirochete as belonging to species Leptospira interrogans serogroup Australis serovar Muenchen. A phenotypic analysis using monoclonal antibodies (mAbs) against leptospiral membrane-associated proteins confirmed the expression of important virulence and pathogenicity factors (LipL32 and LigBrep). Out of 120 reference sera tested, 22 positive (36.66%) and 9 negative (15%) also reacted with the new isolate. Furthermore, the serovar Muenchen isolate was virulent in hamster model. The animal inoculated developed acute lethal infection characterized by hepatic, pulmonary and renal lesions. Local isolates exhibited unique characteristics that differed from those of reference strains; therefore, isolation of leptospires is useful in the surveillance of local pathogenic serovars. In conclusion, the data obtained from this study can contribute to the epidemiological understanding and control of leptospirosis in southern Brazil.

Keywords: Bovine; Leptospira; Serovar Muenchen; Variable number tandem repeat; mAbs.