Xiaonan Lu Uncovers Potent Garlic Antibacterial

Xiaonan Lu has shown that a compound contained in garlic is 100 times more effective than two leading commercial antibiotics at fighting the pervasive contamination of food-processing facilities by a bacteria responsible for serious intestinal illnesses.

“This work is very exciting to me because it shows that this compound has the potential to reduce disease-causing bacteria in the environment and in our food supply,” said Xiaonan Lu, a Washington State University postdoctoral researcher and lead author of the paper recently published in the Journal of Antimicrobial Chemotherapy.

Lu and colleagues studied the effectiveness of diallyl sulfide, a compound derived from garlic, in killing the bacterium campylobacter jejuni. Typically campylobacter is protected by a slimy biofilm, making it 1,000 times more resistant to antibiotics than the free-floating bacterial cell. Diallyl sulfide was found to easily penetrate the protective biofilm and kill bacterial cells by combining with a sulfur-containing enzyme, changing the enzyme’s function and effectively shutting down bacterial cell metabolism.

Diallyl sulfide was up to 100 times more effective than the popular commercial antibiotics erythromycin and ciprofloxacin and often worked in a fraction of the time.

Last year by Lu and others in WSU’s department of applied and environmental microbiology and analytical chemistry found diallyl sulfide and other organosulfur compounds are efficient at killing common food-borne pathogens like listeria monocytogenes and Escherichia coli O157:H7.

Infections by campylobacter typically result from eating raw or undercooked poultry or foods that have been cross-contaminated one surfaces used to prepare poultry. The bacterium is also responsible for nearly a third of all cases of a rare paralyzing disorder known as Guillain-Barré syndrome.

“Campylobacter is simply the most common bacterial cause of food-borne illness in the United States and probably the world,” said Lu’s co-author Michael Konkel who has been studying the bacterium for 25 years. It sickens 2.4 million Americans every year with symptoms like diarrhea, cramping, abdominal pain and fever, according to the US Centers for Disease Control and Prevention.

“This is the first step in developing or thinking about new intervention strategies,” said Konkel.

“Diallyl sulfide may be useful in reducing the levels of the Campylobacterin the environment and to clean industrial food processing equipment, as the bacterium is found in a biofilm in both settings,” he said.

“Diallyl sulfide could make many foods safer to eat,” said Barbara Rasco, a co-author on all three recent papers and Lu’s advisor for his doctorate in food science. “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.”

She noted that the compound could improve the shelf life of foods as well as reduce bacterial infections.