Biotech and Pharma

Drug-resistant intestinal illness Shigellosis spreading in US

CDC warns of new outbreak
CDC warns of new outbreak

An intestinal illness carried by international travelers is spreading across the United States, according to the Centers for Disease Control and Prevention. The culprit bacteria have proven to be resistant to the antibiotic Cipro, most commonly prescribed to treat the infection.

Called Shigella, the bug turned up in 243 cases in 32 states and Puerto Rico between May and February, the CDC said in a statement today. The biggest clusters were reported in California, Massachusetts and Pennsylvania.

Read MoreBiogen Alzheimer's drug shows promise, shares up

"These outbreaks show a troubling trend in Shigella infections in the United States," CDC Director Tom Frieden said in the statement. "Drug-resistant infections are harder to treat and because Shigella spreads so easily between people, the potential for more—and larger—outbreaks is a real concern."

Last week, President Barack Obama unveiled a national action plan to fight antibiotic resistance, a large and growing public health issue, and he designated $1.2 billion to fight drug-resistant bacteria in his most recent budget plan. The CDC says superbugs cause 2 million illnesses and 23,000 deaths each year in the U.S.

Infections with Shigella are not normally fatal, according to the CDC. About a quarter of the cases in the most recent outbreaks were hospitalized, and no deaths were reported. Annually, Shigella causes about 500,000 illnesses, 5,500 hospitalizations, and 40 deaths in the U.S., according to the White House's National Strategy For Combating Antibiotic-Resistant Bacteria. While these strains are predominantly resistant to Cipro, most are still susceptible to at least one other oral antibiotic, the CDC said.

Read MoreUS pharmacist group moves to block execution drugs

Shigella infections often clear on their own, though doctors frequently prescribe antibiotics for even mild illnesses, the CDC said.

Also concerning, physicians frequently prescribe Cipro to international travelers, in case they develop diarrhea outside the U.S. The agency says more study is needed to determine whether that played a role in the most recent outbreaks.