Salmonella Typhimurium outbreak associated with frozen tomato cubes at a restaurant in western Finland, January to February 2021.

Several individuals reported gastrointestinal symptoms following meals consumed in late January 2021 at a restaurant in western Finland. We conducted a retrospective cohort study and defined a case as a person who ate at the lunch restaurant between 27 and 29 January 2021 and had stomach pain, vomiting or diarrhoea and/or a laboratory-confirmed Salmonella Typhimurium infection within 2 weeks after the exposure. We collected faecal and food samples for microbiological analysis. Salmonella isolates were characterised in detail using whole genome sequencing (WGS) and cluster analysis by core genome multilocus sequence typing (cgMLST). Altogether, 393 meals were sold and 101 people (who ate 142 meals) participated in the cohort study. There were 49 cases; 23 were laboratory-confirmed infections with a multidrug-resistant S. Typhimurium. The S. Typhimurium isolates from cases and frozen tomato cubes used uncooked in salads were closely related and clustered together in cgMLST comparison. These salads were consumed by 76% of the cases. Based on the cgMLST clustering, they were the suggested source of the outbreak. Statistical association was not significant between eating the salads and being a case. Following the outbreak investigation, the producer decided to recommend cooking of their frozen tomato products before consumption.

Biolistic DNA delivery to leaf tissue of plants with the non-vacuum gene gun (HandyGun).

Non-vacuum gene guns such as HandyGun are flexible tools for bombardment of targets of varying size. Construction of HandyGun is simpler and cheaper than vacuum gene guns and will be described here. The conditions for maximal transient transformation efficiency of plant cells with plasmid DNA using HandyGun will be provided.

HandyGun: An improved custom-designed, non-vacuum gene gun suitable for virus inoculation.

Particle bombardment with a non-vacuum gene gun is an efficient method for transfection of plant cells with cloned viruses and initiation of virus infection. The HandyGun developed in this study is an improved version of a non-vacuum gene gun. Bombardment parameters were studied by inoculating an infectious, 35S promoter-driven cDNA of Potato virus A (PVA; Potyvirus) to the potato clone 'A6', Nicotiana benthamiana and N. tabacum as plasmid DNA coated on microprojectiles (gold particles). The large number of initial infection sites (necrotic local lesions) observed on inoculated 'A6' leaves and the high percentage of Nicotiana plants which were infected systemically with PVA following inoculation with HandyGun were not particularly sensitive to variation in the parameters tested (helium pressure and the amounts of plasmid DNA and gold particles). Data showed that HandyGun is a robust and reliable tool for obtaining high infection rates in plants reproducibly. It is easy and inexpensive to use and can be constructed from parts commonly available.