ABSTRACT
Bovine tuberculosis (TBB) is a zoonotic disease distributed worldwide and is of great importance for public health and the livestock industry. Several experimental vaccines against this disease have been evaluated in recent years, yielding varying results. An example is the Bacillus Calmette-Guérin (BCG) vaccine, which has been used extensively in humans and tested in cattle showing mixed results related to protection (0-80%) against Mycobacterium bovis. In this study, we used the food-grade bacterium Lactococcus lactis as an expression system for production of mycobacterial protein Hsp65. For this purpose, the construction of a replicable plasmid in strain NZ9000 L. lactis (pVElepr) was conducted, which expressed the Mycobacterium leprae Hsp65 antigen, and was recognized by traded anti-Hsp65 antibodies. The strain NZ9000-pVElepr was applied to calves that were negative to tuberculin test and the immune response was monitored. The results showed that immune response was not significantly increased in calves with NZ9000-pVElepr with respect to control groups, and no injury was observed in any lung or lymph of the calves. Finally, this study suggest that the recombinant NZ9000 strain of L. lactis may protect against the development of M. bovis infection, although studies with longer exposure to this pathogen are necessary to conclude the matter.
ABSTRACT
A commercially available multi-antigen lateral flow assay (LFA) for detection of antibodies to Mycobacterium bovis was evaluated by testing dairy cattle in Baja California, México. Sera and tissue samples were obtained from 268 dairy cattle at a slaughterhouse and were tested by LFA, bacteriological culture, and polymerase chain reaction (PCR). Of 107 culture positive samples, 70 (65.4%) were positive by PCR and 49 (45.8%) were positive by LFA. The PCR and LFA gave positive results with an additional 59 (36.6%) and 77 (47.8%) of the 161 culture negative samples, respectively. The false negative rate for the PCR was 34.6% and 54.2% for the LFA. Due to the high false positive rate for both PCR and LFA observed in this study, the LFA cannot be a useful test, even in combination with PCR.
