Increased Incidence of Antimicrobial-Resistant Nontyphoidal Salmonella Infections, United States, 2004–2016

Felicita Medalla; Weidong Gu; Cindy R. Friedman; Michael Judd; Jason Folster; Patricia M. Griffin; Robert M. Hoekstra


Emerging Infectious Diseases. 2021;27(6):1662-1672. 

In This Article

Abstract and Introduction


Salmonella is a major cause of foodborne illness in the United States, and antimicrobial-resistant strains pose a serious threat to public health. We used Bayesian hierarchical models of culture-confirmed infections during 2004–2016 from 2 Centers for Disease Control and Prevention surveillance systems to estimate changes in the national incidence of resistant nontyphoidal Salmonella infections. Extrapolating to the United States population and accounting for unreported infections, we estimated a 40% increase in the annual incidence of infections with clinically important resistance (resistance to ampicillin or ceftriaxone or nonsusceptibility to ciprofloxacin) during 2015–2016 (≈222,000 infections) compared with 2004–2008 (≈159,000 infections). Changes in the incidence of resistance varied by serotype. Serotypes I 4,[5],12:i:- and Enteritidis were responsible for two thirds of the increased incidence of clinically important resistance during 2015–2016. Ciprofloxacin-nonsusceptible infections accounted for more than half of the increase. These estimates can help in setting targets and priorities for prevention.


Nontyphoidal Salmonella infections cause an estimated 1.2 million illnesses, 23,000 hospitalizations, and 450 deaths each year in the United States.[1] Although most infections result in self-limited illness, antimicrobial treatment is recommended for patients with severe infection or at high risk for complications.[2] Antimicrobial-resistant Salmonella infections can cause adverse clinical outcomes, including increased rates of hospitalization, bloodstream infection, other invasive illnesses, and death.[3–7]

Nontyphoidal Salmonella infections can be acquired during international travel, from contaminated food and water, through animal contact, and from environmental sources (e.g., wetlands and irrigation water).[8–13] Antimicrobial-resistant infections have been linked to various food and animal sources.[3,14,15] In 2015 and previous years, 5 commonly isolated serotypes (Enteritidis, Typhimurium, Newport, I 4,[5],12:i:- and Heidelberg) accounted for more than half of antimicrobial-resistant Salmonella infections in the United States.[16–20] The distribution of antimicrobial-resistant infections caused by some of these common serotypes varied by region.[21,22]

In a previous study, we found that an estimated annual average of 6,200 culture-confirmed infections were resistant to ceftriaxone or ampicillin or nonsusceptible to ciprofloxacin during 2004–2014.[20] For the study described in this article, we used the same modeling approach and data sources to estimate changes in incidence. We estimated the contribution of the 5 major serotypes to changes in incidence and describe differences by geographic region. We extrapolated findings to the United States population to provide estimates to help set targets and priorities for reducing antimicrobial resistance among nontyphoidal Salmonella.