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).