One of the most common food-borne pathogens, campylobacter, causes sickness in more than two million people in the United States every year. With funding from USDA's Cooperative State Research, Education, and Extension Service (CSREES), scientists in Iowa are examining how this pathogen develops resistance to antibiotics and is transferred to humans via the food chain causing food-borne illness.

The results of this study will help improve the safety, quality and value of the nation's food supply, particularly through pre-harvest intervention strategies.

Campylobacter jejuni is a species associated mainly with poultry. The pathogen developed resistance to fluroquinolone antibiotics, such as Cipro, after antibiotic treatment of animals. Although the poultry industry banned these antibiotics in 2005, the presence of antibiotic-resistant strains of C. jejuni remained high.

Qijing Zhang and colleagues at Iowa State University found that the antibiotic-resistant strains grow more successfully in the intestinal tract of poultry than the non-resistant strain, even in the absence of antibiotics. The persistence of antibiotic-resistant C. jejuni in poultry highlights the need for new strategies to control it.

To prevent emergence and transmission of the antibiotic-resistant organisms, researchers are targeting the genes involved in the development and persistence.

"We will continue our efforts to understand the antibiotic resistance mechanisms and ecology of antibiotic-resistant campylobacter," Dr Zhang said. "We are also interested in developing intervention strategies to prevent the transmission and colonization."

Researchers tested faecal samples from both poultry and pig farms to isolate campylobacter. They examined the isolates for susceptibility to various antibiotics and used molecular techniques to analyze the resistance-associated genetic mutations.

Antibiotic-resistant campylobacter can infect humans through contaminated poultry meat, water or raw milk, resulting in an infection called campylobacteriosis. C. jejuni is responsible for 95 per cent of campylobacter infections in humans.

Although the consumption of pork is not a major mode of campylobacter transfer, the presence of antibiotic-resistant campylobacter on pig farms makes pork a potential source of horizontal transfer across production systems.