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News From the Centers for Disease Control and Prevention
October 8, 2019

Multidrug-Resistant Salmonella

JAMA. 2019;322(14):1344. doi:10.1001/jama.2019.15309

Researchers have identified a new strain of foodborne multidrug-resistant Salmonella with resistance to ciprofloxacin and reduced susceptibility to azithromycin, warned a recent CDC report.

Centers for Disease Control and Prevention

The CDC first identified the multidrug-resistant strain Salmonella enterica serotype Newport in September 2018 during an outbreak investigation. “Decreased susceptibility to azithromycin has been rare among nontyphoidal Salmonella that cause human infections in the United States,” said the report’s senior author Cindy Friedman, MD, an epidemiologist in the CDC’s Enteric Diseases Branch in an email.

“While most patients with diarrheal illness from Salmonella infection do not require antibiotics, treatment with antibiotics is indicated for patients with severe infections or with risk factors for severe disease,” Friedman said. “Clinicians should consider alternatives to azithromycin and ciprofloxacin, such as ceftriaxone, for treatment of patients who need antibiotics and who are suspected to have this strain of (multidrug-resistant) Newport.”

Between June 2018 and March 2019, 255 patients in 32 states became ill from infections with this newly identified strain of Salmonella, according to the report. Consumption of soft, unpasteurized cheese from Mexico and US beef were linked to the infections, according to the authors. Of the 206 patients who provided travel information, 43% reported recent travel to Mexico. The outbreak strain was detected in a steer and US beef samples from Texas. It was also detected in soft cheese, beef, and steer samples from Mexico.

The genetic similarity between strains isolated from beef and steer suggests the outbreak strain is present in cattle from both countries, according to the authors. A 41% increase in the use of macrolide antibiotics in US cattle between 2016 and 2017 may have selected for the resistant strain, the authors wrote. They recommend people avoid consuming unpasteurized cheese and use a thermometer to ensure that beef reaches recommended cooking temperatures to reduce the likelihood of illness.