  Campylobacter jejuni. Its name may not be familiar, but its effects are. It causes the cramping, diarrhea, fever, and nausea usually associated with food-borne gastrointestinal illness. Campylobacter jejuni causes more of this illness in the United States than its more famous cousins, Salmonella or Escherichia coli—somewhere between two and eight million cases of gastrointestinal upsets, and up to 800 deaths, per year. It is also implicated in the pathogenesis of Guillian-Barre syndrome (GBs), a sometimes fatal degenerative neurological disorder. If it's so common, why is Campylobacter so unknown? "It may be because Campylobacter rarely causes outbreaks, as do the other two, or because we haven't been educated about it," says Mike Konkel, assistant professor of microbiology. Most people become infected with Campylobacter by eating undercooked chicken, especially when the barbecue season fires up in the spring. Healthy chickens carry this bacteria in their intestines, and their carcasses often become contaminated during slaughter. When chicken in supermarkets is tested, up to 90 percent is found to be contaminated with Campylobacter. Campylobacter can be transmitted directly from person to person, as can most gastrointestinal bacteria. It can also be transmitted in unchlorinated water and unpasteurized milk. Luckily, resistance to antibiotics is not a big problem with Campylobacter yet. The drug of choice for its treatment is erythromycin, and treatment usually reduces the length of illness from one or two weeks to one or two days. Konkel sees the Campylobacter he studies as a model system for bacteria-host interactions, particularly for bacterial species that cause gastrointestinal problems in humans. Most of these bacteria share mechanisms of infection. After being ingested and spending a half hour or so in the stomach, the bacteria move along the gastrointestinal tract to the small intestine, one part of which is the eight-foot jejunum. During the hour or two the bacteria spend moving through this continually contracting section, they must attach to the cells that line it. There are several different proteins on the surface of bacteria that bind to the intestinal cells. Konkel's lab recently identified the first of these "adhesins." Bacteria always display their adhesins on their surfaces, for there would not be enough time to make and display them after the bacteria are ingested and before they reach the jejunum. But the "invasins," the proteins that mediate the next step in the infection process, are produced by the bacteria only after they bind to the intestinal cell. The invasins help the bacteria enter the intestinal cells. Konkel is working on a number of candidate invasins. "I think invasion into the cell is a much more complicated process than binding to it," says Konkel. Konkel's immediate research goal is to better understand Campylobacter's adhesins and invasins as well as other bacterial molecules that are responsible for its ability to cause illness. Understanding the infection process is a necessary first step to developing new treatments, should the bacteria develop antibiotic resistance on a wide scale. It's also the first step in working to reduce the level of contamination of chicken or becoming better able to detect it when it occurs. Both of these are considered to be the most effective ways to deal with food-borne illness. Although Konkel's focus is on the basic aspects of this goal, he collaborates with the USDA at College Station, Texas. They are trying to determine whether strains of bacteria that do not make the adhesin are less able to colonize chickens. They are also immunizing chickens against the adhesin to see if that helps reduce colonization. Meanwhile, Julia Child gives the best advice for avoiding getting sick from Campylobacter. Cook your chicken until its juices run clear. That means the chicken's interior has reached 190 degrees, a temperature that should kill not only Campylobacter jejuni but most any other bacteria that's hitching a ride on your chicken. —Mary Aegerter |