Are all the species of enterococci pathogenic or some of them are.

No. but...: Not all kinds of enterococcus are pathogenic. Your question seems to ask about staph aureus - which as a cause of food poisoning, doesn't make you sick by invading or acting directly as a pathogen. Rather, it grows and makes a toxin (a poison) in improperly stored foods - if one eats it, the toxin is what makes a person sick, not the bacteria itself.