May 5, 2006
University of Arkansas, Food Safety Consortium via Newswise
Scientists who look for ways to eliminate foodborne pathogens are up against another obstacle: those pathogens that resist antibiotics. In particular, they want to single out the resistant bacteria for special attention and get rid of them.
That’s the focus occupying Ramakrishna Nannapaneni, a Food Safety Consortium researcher in the University of Arkansas Division of Agriculture food science department working with Michael Johnson. His team is trying to quantify Campylobacter, a pathogen that contaminates nearly all retail raw broiler chicken carcasses, and its emerging ability to resist an important fluoroquinolone antibiotic known as ciprofloxacin.
Surveys have shown that broilers frequently carry large numbers of Campylobacter in their intestinal contents that spread during further processing onto retail raw products. Campylobacter also can occur in raw milk and water and on raw fruits and vegetables. Proper cooking recommended by the U.S. Department of Agriculture will completely kill Campylobacter present on raw poultry.
The problem is that persons who handle raw poultry contaminated by Campylobacter then handle other foods that receive no cooking before consumption such as fresh salads and lightly cooked vegetables. To aid in such risk assessment, scientists are finding better ways to understand the numbers and virulence properties of Campylobacter and those that resist antibiotics.
To better understand ciprofloxacin antibiotic-resistant Campylobacter, “current methods need to be refined for isolating and quantifying the complete diversity of such strains commonly occurring in raw poultry,” Nannapaneni said.
“One of the highest priority research needs on Campylobacter was to develop laboratory methods for quantifying an antibiotic-resistant Campylobacter load persisting on raw poultry products,” Nannapaneni said.
While fluoroquinolone antibiotic-resistant Campylobacter was found to be stable and persistent, there is some good news in the situation. A 30-month study in the Arkansas research showed that chickens often had at least minimally detectable levels of Campylobacter, but only a small percentage of carcasses contained high levels of the pathogen. The good news is that of those chickens with the high levels of Campylobacter, the number of them declined over the 30 months.
Up to 60 percent of chicken carcasses sampled during the study contained the Campylobacter that resist the ciprofloxacin antibiotic. And among those with the higher levels of the resistant Campylobacter, there were reductions each year in the percentage of carcasses carrying such high levels, going from 11 percent down to 0.6 percent.
The Arkansas research is significant for being the first time that trends could be determined by quantifying the total numbers of Campylobacter and the antibiotic-resistant Campylobacter found on chicken carcasses. A report of this new method was published in the scientific journal Applied and Environmental Microbiology.
Among Campylobacter, almost all infections that cause illness in humans are carried by one species of the bacterium — Campylobacter jejuni. Scientists want to be able to narrow down on Campylobacter jejuni from total Campylobacter. The current problem is that a methodology for doing so needs more refining.
“We are trying to come up with probes and methods that can separate antibiotic-resistant Campylobacter jejuni load versus total Campylobacter in raw chicken carcass rinses,” Nannapaneni said. Developing such strategies is on the research agenda for the Food Safety Consortium for the coming year.
While it is currently impossible to completely eliminate antibiotic-resistant Campylobacter occurrence on raw chicken carcass surfaces or in its juices, the organism can be easily destroyed by proper cooking practices at home.