3.2 Main characteristics of the studies
The 157 publications included in our study were conducted in 15 countries from the Americas, of which 81.5% (128/157) were from the United States of America (USA), Brazil, and Canada. Colombia, Argentina, and Mexico provided 4-6 studies each, whereas Trinidad and Tobago contributed with three studies and Costa Rica, Ecuador, and Paraguay provided two studies each. Finally, we found only one publication from Chile, Guatemala, Puerto Rico, Uruguay, and Venezuela (Fig. 2a ). English was the predominant language of publication with 94.9% (149/157) and according to the study design, cross-sectional studies were the most frequent with 77.7% (122/157) of the publications, followed by surveys, surveillance studies, and experiments (19, 7, and 4 publications, respectively) (Fig. 2b ). The cumulative distribution according to the year of publication showed that 53.3% of the studies were published during the last decade since 2010 (Fig. 2c ). As depicted in Figure 2d , the publications used a mixture of diagnostic techniques to detect NTS in the samples, 43.9% (69/157) of them reported up to three diagnostic tools, whereas 37.6% (59/157) used at least two different diagnostic techniques. Among the publications, bacterial culture was the most frequent diagnostic tool with 95.5% (150/157), followed by serological and biochemical tests (117 and 83). Only 22.3% (35/157) of the publications reported the use of PCR for the molecular confirmation of NTS in the positive samples and used the following genes: inv A, RNAr 16S,bla CMY, bla CMY-2,SpvC , mdh y ompC .
The main characteristics of the 157 publications included in the quantitative synthesis are summarized in Supplementary Table 4 . The publications were characterized by reporting a mixture of the three defined outcomes: 149/157 reported the prevalence of NTS, 94/157 included the serotyping of the isolates, and 46/157 assessed the antimicrobial resistance profiles of the NTS isolates. Besides, the 149 publications that reported the prevalence of NTS included up to three types of samples and we extracted each sample as an independent study within a publication; therefore, there were 194 independent studies that were distributed according to the type of sample in products and subproducts (90), environmental (61), and birds (43).