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CDC: Imported Drug-Resistant Stomach Bugs Spreading in U.S.

Ciprofloxacin resistance rate jumps from 2% to 90%

International travelers are bringing a multidrug-resistant intestinal illness to the U.S. and are spreading it to others who have not traveled, according to a report released April 2 by the Centers for Disease Control and Prevention (CDC).

Shigella sonnei bacteria resistant to the antibiotic ciprofloxacin (Cipro) sickened 243 people in 32 states and Puerto Rico between May 2014 and February 2015. Research by the CDC found that the drug-resistant illness was being repeatedly introduced as ill travelers returned and was then infecting other people in a series of outbreaks around the country.

The CDC and public health partners investigated several recent clusters of shigellosis in Massachusetts, California, and Pennsylvania and found that nearly 90% of the cases tested were resistant to Cipro, the first choice to treat shigellosis among adults in the U.S. Shigellosis can spread quickly in groups such as children in childcare facilities, homeless people, and gay and bisexual men, as occurred in the recent cases.

“These outbreaks show a troubling trend in Shigella infections in the United States,” said CDC Director Tom Frieden, MD, MPH. “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. We’re moving quickly to implement a national strategy to curb antibiotic resistance because we can’t take for granted that we’ll always have the drugs we need to fight common infections.”

In the U.S., most Shigella is already resistant to the antibiotics ampicillin and trimethoprim/sulfamethoxazole. Globally, Shigella resistance to Cipro is increasing. Cipro is often prescribed to people who travel internationally in case they develop diarrhea while out of the U.S. More study is needed to determine what role, if any, the use of antibiotics during travel may have in increasing the risk of antibiotic-resistant diarrhea infections among returned travelers, the CDC says.

“The increase in drug-resistant Shigella makes it even more critical to prevent shigellosis from spreading,” said lead author Anna Bowen, MD, MPH. “Washing your hands with soap and water is important for everyone. Also, international travelers can protect themselves by choosing hot foods and by drinking only from sealed containers.”

The CDC’s PulseNet lab network identified an increase in Shigella sonnei infections with an uncommon genetic fingerprint in December 2014. Further testing at the CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory found that the bacteria were resistant to Cipro. PulseNet detected several large clusters: 45 cases in Massachusetts; 25 cases in California; and 18 cases in Pennsylvania. Approximately half of the PulseNet cases with patient information were associated with international travel, mostly to the Dominican Republic and India. The San Francisco Department of Public Health reported another 95 cases (nine of them among those identified by PulseNet), with almost half occurring among the homeless or people living in single-room occupancy hotels.

Shigella causes an estimated 500,000 cases of diarrhea in the U.S. every year. It spreads easily and rapidly from person to person and through contaminated food and recreational water. It can cause watery or bloody diarrhea, abdominal pain, fever, and malaise. Although diarrhea caused by Shigella typically goes away without treatment, people with mild illnesses are often treated with antibiotics to stop the diarrhea faster. Until recently, Cipro resistance has occurred in only 2% of Shigella infections tested in the U.S., but was found in 90% of samples tested in the recent clusters.

Because Cipro-resistant Shigella is spreading, the CDC recommends that doctors use lab tests to determine which antibiotics will effectively treat shigellosis. Health care providers should test stool samples from patients with symptoms consistent with shigellosis, re-test stool if patients do not improve after taking antibiotics, and test bacteria for antibiotic resistance.

Source: CDC; April 2, 2015.

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