Allison C. Brown
The emergence of a multidrug-resistant strain of Salmonella in the United States is cause for concern and health care providers should be aware of the risks it poses to their patients, including the possibility of treatment failure, researchers wrote in Emerging Infectious Diseases.
An analysis showed that the extended-spectrum beta-lactamase (ESBL)-producing Salmonella enterica Infantis strain likely originated in travelers returning to the U.S. from South America, particularly Peru. The FDA found the strain in retail chicken meat in 2014.
“Emergence of this multidrug-resistant Salmonella strain in the United States is concerning because it was associated with a higher patient hospitalization rate and the multidrug resistance eliminates all but one recommended treatment option,” said Allison C. Brown, PhD, MPH, from the CDC’s National Center for Emerging and Zoonotic Infectious Diseases. “Health care providers should consider ordering a culture with antimicrobial susceptibility testing for patients who require treatment, since some common first-line antibiotics may not work for all infections.”
Brown and colleagues analyzed national data to compare patients infected with Salmonella Infantis with those sickened by nontyphoidal Salmonella serotypes. Genetic mapping determined whether Salmonella isolates carried the CTX-M-65 gene, indicating they were from the emergent strain, and further testing showed common ancestors and the geographic location of isolates.
A total of 312 related isolates were reported to PulseNet between June of 2012 and the end of 2017. State health departments submitted 34 isolates, 29 of which had resistance phenotypes consistent with ESBL-conferred resistance to several antibiotics. International travel within 7 days of symptom onset was reported in 12 patients, all of whom reported traveling to South America, with 10 traveling to Peru and two to Ecuador.
A phylogeographic analysis of 32 isolates found that the last shared common ancestor existed around 2006 (probability of 95%) in Peru (probability of 98.7%). Cases among humans in the U.S. shared a common ancestor in or around 2009.
“The spread of CTX-M-65 is concerning because the presence of ESBLs eliminates two recommended treatment options, ceftriaxone and ampicillin, for the management of salmonellosis,” Brown and colleagues wrote. “Given the multidrug-resistant profile of CTX-M-65 Infantis, potential for plasmid-mediated transmission, increased hospitalization rate, and evidence of this strain in domestic poultry, action is needed to prevent widespread dissemination in the United States.”
Brown noted that consumers can protect themselves by following safe handling and cooking guidelines, such as washing hands before and after handling chicken and cooking chicken to an internal temperature of 165F. – by Erin Michael
Disclosure: The authors report no relevant financial disclosures.