The bacterial strain used in these experiments, B. melitensis 16 M was obtained from ATCC (#23456) and recovered from an aborted goat fetus. Bacterial cultures were prepared as previously described (Pei and Ficht, 2004) . Briefly, B. melitensis 16 M was cultured in TSB for 24 h, pelleted by centrifugation at 20,000 ×g, washed with and resuspended in PBS (pH 7.4) at a density of approximately 5 × 10 9 CFU/ml (Kahl-McDonagh et al., 2007) .