The compound, diallyl sulphide, is able to pierce a protective "biofilm" employed by the food bug that makes it hard to destroy.
Tests showed diallyl sulphide was as effective as 100 times bigger doses of the antibiotics erythromycin and ciprofloxacin.
It was also able to work in a fraction of the time taken by the drugs.
The discovery is said to open the door to new treatments for raw and processed meats, and food preparation surfaces.
"This is the first step in developing or thinking about new intervention strategies," said researcher Dr Michael Konkel, from Washington State University in the US, who has been investigating Campylobacter for 25 years.
"Campylobacter is simply the most common bacterial cause of food-borne illness in the United States and probably the world."
Symptoms of Campylobacter infection include diarrhoea, cramping, abdominal pain and fever.
The bacteria also trigger nearly a third of cases of a rare paralysing disorder called Guillain-Barre syndrome.
Most Campylobacter infections stem from eating raw or undercooked poultry or foods that have been cross-contaminated via dirty surfaces and utensils.
The research is published in the Journal of Antimicrobial Chemotherapy.
The Washington scientists looked at diallyl sulphide's ability to kill Campylobacter bacteria when they join together to form a slimy biofilm. This makes the bugs 1000 times more resistant to antibiotics than free-floating bacterial cells.
The compound easily penetrated the protective film to kill the microbes by targeting a metabolic enzyme.
Two previous studies published last year showed that the garlic compound was also effective against other food-borne bugs, including Listeria monocytogenes and Escherichia coli O157.
Dr Konkel pointed out that while eating garlic was generally healthy, it was unlikely to prevent Campylobacter food poisoning.
However, he added: "Diallyl sulphide may be useful in reducing the levels of the Campylobacter in the environment and to clean industrial food processing equipment, as the bacterium is found in
a biofilm in both settings."
Colleague Dr Barbara Rasco, another member of the Washington State University team, said: "Diallyl sulphide could make many foods safer to eat.
"It can be used to clean food preparation surfaces and as a preservative in packaged foods like potato and pasta salads, coleslaw and deli meats.
"This would not only extend shelf life but it would also reduce the growth of potentially bad bacteria."
