# The Fate of _Yersinia pseudotuberculosis_ in Raw Fermented Meat Products
## 1 Introduction  
The genus _Yersinia_ includes Gram-negative, facultative anaerobic bacteria that are found worldwide in a variety of environments [1]. The entire genus currently includes 28 species [2], of which only three are pathogenic. The best-known species is _Yersinia (Y.) pestis_ (causative agent of plague), which is very similar to _Y. pseudotuberculosis_s at the genetic level [3]. _Y. pseudotuberculosis_s can also contaminate the food production environment, and its presence has been confirmed in water [4]. In situations of inadequate hygiene, improper sanitation or high primary contamination of raw materials, _Yersinia_ spp. can contaminate meat and meat products and cause foodborne illness. _Y. enterocoltica_ and _Y. pseudotuberculosis_s are significant foodborne pathogens that cause the gastrointestinal illness known as yersiniosis [2, 5]. In humans, yersiniosis can appear in acute or subacute forms, and less commonly as a chronic infection. The acute form of yersiniosis is a typical gastroenteritis with abdominal pain, diarrhea, and fever, sometimes with vomiting, affecting mainly young children. The subacute form of yersiniosis presents similar gastrointestinal symptoms and fatigue. Possible complications include mesenteric lymphadenitis, which mimics appendicitisis, or extra-intestinal manifestations like erythema nodosum and reactive arthritis. Chronic yersiniosis manifests as prolonged enterocolitis or as a post-infectious complication with large joint inflammation, erythema nodosum, thyroiditis, or rarely kidney inflammation. The majority of human yersiniosiscases are sporadic; however, in patients with other comorbidities, immunodeficient patients, the elderly, or young children, yersiniosis may be more severe, and sequelae may occur. _Y. pseudotuberculosis_ infections tend to be more severe and invasive than those caused by _Y. enterocolitica_, with the mesenteric lymph nodes, liver, and spleen being more frequently affected. Infections caused by _Y. pseudotuberculosis_ are underestimated worldwide [5; 6; 7; 8]. Both _Y. enterocolitica_ and _Y. pseudotuberculosis_ also cause diseases in animals with similar symptoms to yersiniosis in humans, i.e., fever, diarrhea, enteritis, and lymphadenitis. Various animals are affected, including livestock, pets, birds, rodents, and wild and zoo animals. Most infections are asymptomatic; therefore, animals can serve as a reservoir of _Yersinia_ spp. _Yersinia_ spp. may be transmitted from pigs and other livestock infected on the farm during slaughter to carcass and organs [3; 6; 8]. The ability of _Yersinia_ to grow at low temperatures is important for food safety. Therefore, in raw meat products, increased attention must be focused on other barriers to growth, such as the pH drop during fermentation or the reduction in water activity (a\({}_{\mathrm{w}}\)) during drying. Raw fermented meat products represent a relatively wide range of products that are very popular in European countries. The principle of processing of raw fermented sausages is that they are aged in air-conditioned chambers without heat treatment. The whole process of aging involves microbial fermentation, which is how this type of salami obtained its name. Raw fermented meat products can be subdivided according to different criteria and countries of origin into further, smaller groups. According to the shelf life and water activity, they can be divided into dry sausages and undried sausages. Dry salami is popular not only in Europe (Hungarian, Italian, German and Greek salamis, Spanish chorizos, Czech Polican, Herkules, etc.) but also in the US (US-style pepperoni). The production process usually consists of several days of fermentation followed by several weeks of ripening and smoking. Their low pH (4.6-5.5) and low a\({}_{\mathrm{w}}\) (<0.9) make them suitable for storage at room temperature (\(\sim\)25 \({}^{\circ}\)C). Undried sausages (e.g., Tewurst, coarse onion Mettwurst) are products that have not undergone significant ripening or drying.