Labs investigate food-borne illnesses common during summertime picnics, beach outings

Grace Beahm
The Post and Courier

Erbie Grate spreads bacteria on a blood culture plate to test for salmonella or shigella in the Medical University of South Carolina Hospital's microbiology/immunology lab last week.

Heaps of grilled hamburgers and hot dogs, pasta and potato salads, coleslaw and slow cookers bubbling with family recipes: These Memorial Day staples make for a tasty picnic spread, but sometimes, they pack more than just a boatload of calories and fat. They also can provide a convenient highway for a nasty bug to slide into your digestive system.

Haphazard preparation can spread germs between dishes, a love of rare meat may leave bacteria festering, and dishes that belong on ice might be crawling with bugs after hours baking in the sun. Most people recover in a few days from the tell-tale signs of food-borne illness — crippling stomach pain, vomiting and diarrhea — but some may become dehydrated and need anti- nausea medication, antibiotics or IV fluids.

Summer is prime time for food-borne illness, but doctors say it can strike at any time.

The U.S. Centers for Disease Control and Prevention estimates that these bugs make some 76 million people sick each year. More than 300,000 are hospitalized, and 5,000

Americans — usually small children, the elderly or people whose immune systems are already withered by illnesses — die as a result of food-borne illnesses.

Some of the illnesses have common causes, such as undercooked hamburgers. Others are a little more exotic.

Larry Youngberg, manager for the Medical University of South Carolina's microbiology and immunology lab, recalls an outbreak of E. coli related to chitlins. Still, others seem downright made-for-TV. In 2004, a Summerville woman got ciguatera poisoning, which leads to wacky symptoms such as the sensation that heat is actually cold, after eating a barracuda her husband caught while deep-sea fishing.

When symptoms are severe or hang around for more than a couple of days, proper identification and treatment of these illnesses require that patients provide samples — usually stool — so the bacteria can take a trip to a hospital laboratory.

In Bon Secours-St. Francis Hospital's lab last week, a technician sat in front of a laminar flow hood, a partially covered sterile workstation in which a constant stream of filtered air keeps the sample, culture dish and other equipment clean. Nearby, neat stacks of culture plates (also known as petri dishes) sat at the ready, filled with different types of culture media, each row a different color — red, green, brown, clear — signifying the nutrients found in the dish. The compounds help the bacteria grow in the dish.

To prepare each cell culture, the technician opened a fresh culture plate and used a disposable tool to pick up a bit of the sample.

Slowly, he drew the tool in a straight line across the plate, and then laid down a tight scribble of lines perpendicular to the first mark, all the way across the dish. Next, technicians placed cultures into a body-temperature incubator to grow. In 24 hours or so, the bacteria typically sprout in their characteristic pattern across the dish.

Although physicians may suspect a particular illness based on a patient's symptoms, the truth won't be known until then, after the bacteria have time to grow and be examined, sometimes under a microscope. And if the bug is a pesky one, it may take another 24 hours or more to learn which type of antibiotics it will respond to.

In the culture dish, the bugs look harmless — almost pretty, all speckles and spots across a brightly colored field. But as anyone who's ever spent a night hunkered down in a bathroom after a bad burger or batch of oysters knows, these bacteria are anything but friendly. Most of them won't leave behind any long-term damage, but some types of seafood contamination, such as ciguatera, or botulism from tainted foods and drinks, can cause permanent neurological damage or paralysis.

And food-borne bugs can be sneaky, too: Some of them, such as vibrio vulnificus, a marine bacterium associated with oysters, can even be transmitted through cuts in the skin. And apart from picnicking, other hot-weather activities such as swimming and hot-tub time can leave people vulnerable to digestive illnesses including E. coli and rashes caused by bacteria that dwell in water that hasn't been properly cleaned.

When technicians encounter unusual bugs, in the culture dish or under the microscope, the view may be perplexing enough to leave them wondering how the bacteria found their way into the patient's body. That's why laboratories like to have as much information as possible about the "case history": where the person has been, what they've eaten, what animals or other sick people they might have come in contact with.

"We see all these bugs, and then we hear the case histories and it all makes perfect sense," Youngberg says.

Patients can help by providing details, he says. Was there egg salad on the buffet table? A strange-looking fish their uncle reeled in? Raw-meat juice splattered next to the grill? These clues can help investigators trace the path of the bacteria, and identify other people who may have been infected.

Reach Holly Auer at 937-5560 or hauer@postandcourier.com.