Regarding the order rhizobiales of the class Alphaproteobacteria, the genus that includes human pathogens is Brucella.
Rhizobiales are a type of Alphaproteobacteria, which are a type of Proteobacteria, which are Gram-negative bacteria.
Brucella is also a type of Gram-negative bacteria that can cause brucellosis, which is an infectious disease caused by eating unpasteurized milk or undercooked meat.