A NEW study has identified key risk factors that may predispose individuals to long-term shedding (LTS) of non-typhoidal Salmonella (NTS), offering insights into why certain patients remain contagious weeks after initial infection. The findings have significant implications for infection control and public health monitoring.
Researchers analyzed cases reported to the Norwegian surveillance system in 2019, focusing on patients who provided a stool sample and health questionnaire five weeks after initial diagnosis. Among 255 respondents, nearly one in four (24%) continued to shed Salmonella bacteria well beyond the acute phase. This persistent colonization may contribute to ongoing transmission risk, especially in high-contact environments like childcare or healthcare.
Children under age 5 were found to be particularly susceptible to long-term carriage, with odds 6.7 times higher than adults aged 18–44. The study also highlighted increased risk in individuals on regular medication (adjusted odds ratio [aOR] 2.17) and those adhering to a lactose-free diet (aOR 7.24). These findings suggest possible links between microbiome-altering factors and gut persistence of the pathogen.
The genetic profile of the Salmonella strain also played a significant role. Carriers infected with less common serotypes such as S. Agbeni or S. Bron were over six times more likely to experience prolonged shedding compared to those infected with S. Typhimurium. This emphasizes the importance of pathogen-specific characteristics in understanding infectious dynamics.
The study used whole-genome sequencing to confirm persistent infection, defining LTS as isolates differing by five alleles or fewer between timepoints. While the sample size was limited, the strength of the associations offers a foundation for further research.
Understanding who remains a carrier of NTS, and why, is critical for tailoring guidelines around isolation, return-to-work policies, and outbreak prevention. These findings underscore the need for more nuanced strategies in managing enteric infections beyond symptom resolution.
Reference:
Rohringer A et al. Risk factors associated with long-term shedding infections of non-typhoidal Salmonella in humans. Eur J Clin Microbiol Infect Dis. 2025. doi: 10.1007/s10096-025-05165-x. [Online ahead of print].
