Study Salmonella Infections in Norway shedding duration. MoMir - Salmonella

Background Non-typhoidal salmonellae (NT-Salmonella) are a major cause of diarrhoea worldwide. Salmonella is generally transmitted through the faecal-oral route. Commonly, this occurs through the improper handling of contaminated foods but also zoonotically. NT-Salmonella gastroenteritis is usually self-limited and generally resolves within 48 to 72 hours. However, in some cases the initial infection can lead to a carrier state in humans, which corresponds to a persistent colonization of the gut and continuous long-term shedding of Salmonella. This study aimed to investigate host and pathogen-specific risk factors associated with long-term shedding of NT-Salmonella post-infection in human salmonellosis cases in Norway, to inform infection control and preventive measures. Methods All salmonellosis cases reported to the national surveillance system in 2019 were invited to participate in the study. Participants were asked to submit a stool sample and a questionnaire five weeks post-initial positive sample. We cultured all samples and sequenced isolates to identify genotype (cgMLST), serotype and antimicrobial resistance. We analysed data by descriptive statistics and measured association for two levels of shedding; i) Long term shedding (LTS): positive sample at ≥ 5 weeks after initial sample, and ≤ 5 allelic differences compared to the initial sample (cgMLST), and ii) Short term shedding (STS): negative sample at ≥ 5 weeks after initial sample. Results The study included data from 273 participants. 23.4% were classified as LTS, and 70.7% as STS. Stratification by serotype found that 45% of S. Agbeni isolates were LTS. In contrast, only 21% of the S. Typhimurium and 19% of S. enteritidis were LTS. We identified a positive association between the length of shedding and persisting diarrhoea (p. 0.02) 5 weeks after initial sample, age group 18- 46 (p. 0.02) and lactose-free diet (p. 0.03).