Unraveling the causes of Salmonella paratyphi B endemicity in Salta: A clinical-environmental perspective.

Salmonella Paratyphi B (SPB) has become endemic in the city of Salta, Argentina, with a staggering burden of bloodstream infections requiring hospitalization. This study unravels the underlying drivers of this endemicity through an integrated clinical-environmental approach. A novel duplex qPCR system was developed to accurately distinguish SPB from other Salmonella serotypes, enabling precise diagnosis and treatment. Clinical analysis revealed SPB in 98 % of positive blood cultures, confirming its strong association with severe infections. Contrary to initial hypotheses, the public drinking water network -supported by deep wells and systematic chlorination-showed negligible microbial contamination, ruling it out as the primary transmission route. Instead, environmental investigations uncovered widespread SPB in untreated wastewater, river water used for crop irrigation, and in leafy vegetables sold in local markets. SPB was detected in 40 % of lettuce, arugula, and celery samples during the rainy season, with contamination levels exceeding international safety standards by several orders of magnitude. This widespread presence of SPB in fresh produce, coupled with its uniform detection across city districts regardless of socioeconomic level, points to a foodborne route of transmission through contaminated vegetables. Based on these findings, we propose a strategic intervention plan that includes public education, routine screening for chronic carriers, strengthened monitoring of irrigation water, improved vegetable quality control, and upgrades to wastewater treatment infrastructure. This study highlights the importance of targeted, multidisciplinary approaches to address human-restricted pathogens and provides a roadmap for interrupting SPB transmission in endemic urban contexts.