Safety of B. abortus rough mutant strain RB51 administration in Buffalo cows

Abstract

The objective of this study was to determine if B. abortus rough mutant strain RB51 is eliminated in Buffalo milk. Five milk buffaloes were inoculated with the triple of the recommended calfhood dose (3.0 – 10.2 x 1010 cfu/ml) of B. abortus RB51 strain by subcutaneous route in the right axillary region. Milk samples were taken aseptically on a daily basis for the first 30 days and weekly for the second and third months. The samples were inoculated on Brucella Medium Base (BMB) (Oxoid) and Rifampin Brucellae Medium (RBM) and incubated under 10% CO2 at 37°C for 10 days. The suspicious colonies were recultured in BMB and RBM. PCR analysis was also performed on milk samples. There were no isolations of bacteria with characteristics of Brucella from any of the milk samples collected during 90 days of the study. However Brucella RB51 DNA was detected on day 2 and 3 post vaccination in one buffalo cow and on day 21 post vaccination in another buffalo cow. It was concluded that the strain used at this dose wasn’t eliminated by milk in Buffaloes inoculated during lactation, however PCR positive results underline the necessity of milk pasteurization in order to minimize food-chain exposure.