Prevalence, serovars, and antimicrobial resistance of nontyphoidal Salmonella in the swine production chain of the Americas: A systematic review and meta-analysis

Background: Nontyphoidal Salmonella (NTS) represents a public health issue because it causes foodborne disease by consuming contaminated food, including pork products bearing zoonotic serovars, especially those with antimicrobial resistance (AMR). Objectives: We aimed to estimate the prevalence of NTS, assess serovar diversity, and determine the prevalence and profiles of AMR in the swine production chain of the Americas. Methods: A systematic review and meta-analysis were conducted following the PRISMA statement. Electronic searches were performed to identify studies reporting the prevalence of NTS, the diversity and frequency of serovars, and AMR in animals, products and subproducts, and related environmental samples of the swine production chain. A random-effects meta-analysis of proportions was employed to estimate the prevalence of NTS and AMR at the national and sample levels. Results: We identified 242 publications from 13 countries that evaluated 193,896 samples. The pooled prevalence of NTS was 20.1 % (95 % CI: 17.8–22.3), with products and subproducts exhibiting the highest estimate. Mexico had the highest prevalence (39.3 %) and Cuba had the lowest (2.2 %). Among 34,131 isolates, 173 serovars were identified, with Typhimurium, Derby, and Agona being the most common. Among 27,207 isolates, the prevalence of AMR to at least one antimicrobial was 82.8 %, and the prevalence of multidrug resistance (≥3 antimicrobial groups) was 56.4 %. NTS strains exhibited resistance primarily to tetracyclines, aminoglycosides, and beta-lactams. Conclusions: NTS is a significant public health concern in the Americas, given its high prevalence and the diversity of serovars exhibiting AMR across swine samples. However, the disparate number of publications found by country and the contrasting methodological quality across the studies may contribute to the high heterogeneity of the estimates observed. It is essential to reinforce and expand control measures focused on detecting and reducing the transmission of NTS. More stricter policies and regulations are needed to stop indiscriminate antimicrobial use and mitigate the increase of AMR along with the dissemination of NTS-resistant serovars.