Yes the nutribiotic grapefruit seed extract is rather potent. I used to do 30 drops per day inserted into empty gelatin capsules. You don't want this stuff on your tongue, very bitter. I think it's main mode of action is a drastic drop of PH in the body, making a hostile environment for many bacteria.
It is also rumored to break borrelia cysts but i'm not sure how valid that theory is. There is also some controversy to the grapefruit seed extract, some parties claim that it is a chemical(anti infective/preservative) used in the grapefruit skin/seeds extraction process which is actually killing pathogens but i have a snakey suspicion these stories were created by the antibiotic manufactures. who really knows.