Non-toxigenic cases of in Spain from 2012 to 2022.

Non-toxigenic non-O1/non-O139 (NVC) isolates are associated with diarrhoeal disease globally. NVC-related infections are on the rise, representing one of the most striking examples of emerging human diseases linked to climate change. This study aims to give a better picture of the evolution of NCV incidence in Spain from 2012 to 2022. In this context, we realized a descriptive analysis and a logistic regression using the isolates submitted to the National Center of Microbiology (NCM) during this period. To elucidate the heterogeneity of sporadic clinical strains of NVC among patients residing in Spain, we conducted whole-genome sequencing (WGS) of a selection of isolates. First, we observed an increase in the number of isolates sent to the NCM after 2019, which was not concomitant to a change in the national surveillance protocol. Furthermore, the number of cases and hospitalizations increased with age. Second, we found a high diversity of NVC strains, which suggested that the usefulness of WGS studies might be limited in waterborne outbreak situations to find the infectious source. Finally, we characterized the genetic determinants responsible for antimicrobial resistance and virulence and found that 21% of the isolates were resistant to -lactamases. To the best of our knowledge, the present study is the first in Spain to report genomic data on non-toxigenic cases at the national level. Because of the high percentage of hospitalization observed for NVC cases (40%), it might be beneficial to test for in all the suspected cases.