Why are some strains of E. coli resistant to antibiotics?
Although they’re among the simplest organisms, bacteria are some of the most creative life forms on earth. Just ask molecular biologist Chobi DebRoy, director of Penn State’s Gastroenteric Disease Center. “We receive bacterial samples from all over the world—from veterinary clinics, medical centers, zoos, farms,” DebRoy says. Her lab works to identify disease—causing strains of E. coli and to determine whether they are antibiotic-resistant. Bacteria such as Escherichia coli can alter their genetic makeup with astonishing rapidity. They do this, says DebRoy, “through mutations in normal cellular genes, by acquiring foreign-resistance genes from the environment, or by a combination of those mechanisms.” Consider an animal—a human or a cow, say—with the usual suite of bacteria in the gastroenteric system (the stomach and intestines). If a strain of bacteria starts to overcome the body’s immune system, a doctor or a veterinarian may administer an antibiotic to fight the infection. But if n
