## 2 Persisters of Foodborne Pathogens
### Common Bacterial Foodborne Pathogens  
_Salmonella_ are Gram-negative, rod-shaped, and facultatively anaerobic bacteria that commonly cause food contamination. According to the European Food Safety Authority, in 2018, almost one in three foodborne outbreaks in Europe was due to _Salmonella_ found in raw or undercooked eggs and meats, contaminated fresh produce, or in dairy products. There are over 2500 identified _Salmonella_ serotypes grouped into two species: _S. bongori_ and _S. enterica_. Clinically, almost all _Salmonella_ populations that cause human and domestic diseases belong to _S. enterica_ subspecies _enteria_. Among that, the most common pathogens are _S. enterica_ serotypes Typhimurium and Enteritidis [20]. The majority of _S. enterica_ servovars are nontypoidal _Salmonella_, which cause milder nontyphoidal salmonellosis with symptoms like diarrhea, fever, vomiting, and abdominal pain [1]. Typhoid fever, a global problem affecting millions of people and causing over 200,000 deaths annually, is caused by the intracellular and human host-restricted pathogen _S. enterica_ serovar Typhi (_S. Typhi_) through the action of a _Salmonella_ cytolethal distending toxin among others [21]. _Escherichia coli_ is a widespread gram-negative, rod-shaped bacterium colonizing the guts of humans and animals. Although most _E. coli_ strains are harmless, several pathogenic species can cause severe illness. These species cause infection primarily through the fecal-oral route, and include (1) enteropathogenic _E. coli_ (EPEC), which is the main cause of infantile diarrhea outbreaks and recurrent diarrheal symptoms [22], (2) enterohemorrhagic _E. coli_ (EHEC), often times cause hemorrhagic colitis and hemolytic uremic syndrome [23], (3) Shiga toxin-producing _E. coli_ (STEC), a human pathogen  
Figure 1: The possible sources of foodborne pathogens. Every step from farm to table can ultimately lead to foodborne diseases, including polluted farming environments, diseased food-producing animals, contaminated raw materials, non-hygienic food processing, and non-hygienic food consumption. In this process, food handlers can cause (post-processing) contamination, which they can also acquire themselves from animals or in the food processing environment even though the latter is less likely. The review focuses on persister-cells of various _Escherichia coli_ (EPEC, EHEC, STEC, EIEC, EAEC, ETEC), _Salmonella_, and _Listeria_ species both in food and upon human infection. For the major bacterial cause of gastroenteritis, _Campylobacter jejuni_, data on persister-cells is emerging but still scarce. _Staphylococcus aureus_ and _Bacillus cereus_ are considered human and animal contaminants of the food chain with the former being present on the skin of food handlers and the latter originating from spores present in the environment. leading to several diseases such as bloody diarrhea and even death (around 25% of cases) [24], (4) enteroinvasive _E. coli_ (EIEC), that are highly invasive to colon epithelial cells causing bacillary dysentery [25], (5) enteroaggregative _E. coli_ (EAEC), which is one of the most prevalent causes of acute and persistent diarrhea due to contaminated foods [26], and (6) enterotoxigenic _E. coli_ (ETEC) that infect travelers and children in developing and semitropical areas and cause diarrhea-associated symptoms [27]. Foodborne _E. coli_ outbreaks are commonly associated with fresh produce, meat products, and unclean water caused by a contaminated environment and/or non-hygienic food processing. _Staphylococcus aureus_ is a Gram-positive, coccoid bacterium. Foodborne _S. aureus_ strains are food intoxication bacteria producing thermal resist toxin, which is responsible for the most prevalent foodborne intoxication worldwide named Staphylococcus Food Poisoning (SFP) [28], leading to nausea, violent vomiting, abdominal cramping, fever, and diarrhea. _S. aureus_ colonizes mostly the human nose but also skin, hair, and mucous membranes. Even though most of the ubiquitous _S.