# The Fate of _Yersinia pseudotuberculosis_ in Raw Fermented Meat Products
## 4 Discussion  
_Y. pseudotuberculosisis_ is a poorly studied pathogen, and no data on its survival in (fermented) meat products have been published so far. Even data on its viability and growth in raw meat are limited [13,14]. However, multiple authors have studied the fate of _Y. enterocolitica_ in fermented sausages. [PERSON] et al. [15] noted the positive effect of nitrites and starter culture on the inhibition of _Y. enterocolitica_. Starter culture also significantly decreased the relative abundance of _Yersinia_ spp. in Chinese Sichuan sausages [16]. In another study, inoculated _Y. enterocolitica_ (approx. 5 log CFU/g) was completely eliminated in Turkish dry fermented sausage (Sucuk) by _Lactobacillus sakei_ and _Pedicococcus acidlactici_ by the third day of fermentation [17]. [PERSON] and [PERSON] [18] noted that _Y. enterocolitica_ survived poorly in Swedish fermented sausage, with a much higher inactivation rate in comparison with _Listeria monocytogenes_ or _Escherichia coli_. On the other hand, in the study by [PERSON] et al. [19], _Y. enterocolitica_ was eliminated in a dry fermented sausage only after 25 d, with initial counts of 6 log CFU/g. However, despite using a starter culture, the pH values were 4.8 or higher, and water activity was above 0.93 throughout the entire ripening and storage period. Interestingly, _Y. enterocolitica_ was also found in a fermented Sardinian sausage in two from nine samples (22%) with a final pH value of 5.29 [20]. Figure 1: Values of pH (mean \(\pm\) standard error) during manufacture and storage of raw spreadable fermented sausage Teewurst (**a**) and dry fermented sausage (**b**). Figure 2: Values of water activity (mean \(\pm\) standard error) during manufacture and storage of raw spreadable fermented sausage Teewurst (**a**) and dry fermented sausage (**b**). _Y. pseudotuberculosis_ survived much better in raw spreadable sausage compared to dry fermented sausage, which was particularly evident at the highest level of inoculation, with counts dropping during the first 2 d of fermentation by approx. 1.3 and 5.5 log CFU/g in spreadable and dry sausage, respectively. This finding is consistent with results from other studies. [PERSON] et al. [21] reported the good survival of _Y. enterocolitica_ in traditional salsiccia fresca (coarse raw Italian pork sausage) stored at 8 \({}^{\circ}\)C for 7 d, with increasing numbers of the pathogen during prolonged storage (20 d). The German Federal Institute for Risk Assessment (BfR) conducted a study on _Yersinia enterocolitica_ and found that, unlike in salami produced with a starter culture, _Y. enterocolitica_ was detectable throughout the shelf life of spreadable sausages Teewurst and Mettwurst [22]. In the study of [PERSON] et al. [23], inoculated _Mycobacteria_ could be detected in Teewurst during 4 w of storage, but no viable cells were found in dry fermented sausage (final product). [PERSON] et al. [24] reported that Shiga toxin-producing _E. coli_ (STEC) was inhibited during the production of dry fermented salami but not in Teewurst. In general, pathogenic bacteria can be reduced by 2-4 log in semi-dry and dry sausages, but only by 1 log or less in spreadable sausages [25]. This enhanced survival could be related to the higher pH values and higher fat content in Teewurst. It was reported that a low pH and high fermentation temperature improved the inhibition of STEC, while the larger diameter of casing and higher fat content prolonged its survival [26]. Teewurst is a finely cut (meat-in-fat emulsion) meat product, usually containing 35-55% of fat, with a minimum being 25% to keep the product spreadable [27]. The fat may protect the bacteria and enhance their survival. It is also important to note that the term \"Teewurst\" may refer to various products, including \"cooked Teewurst\" in the USA or products without a starter culture characterized by pH-6.0 [28], whereas the German products typically have a final pH of 5.3-5.5 (semi-acidified) or even 4.9-5.0 [24; 27].