## 2 Persisters of Foodborne Pathogens
### Common Bacterial Foodborne Pathogens
aureus_ populations on the human body are indicated to be harmless [29], they are responsible for high frequency of SFP due to improper food handling. Except for unhygienic food processing, contaminated raw milk and soft cheese that originate from animals suffering _S. aureus_-induced mastitis are also possible inducers of SFP [30]. Note that, upon gaining access to the body through an injury on the skin of mammals, certain _S. aureus_ strains can also cause skin and joint infections, pneumonia, sepsis, endocarditis, and medical device-associated infection [31; 32]. These events are not the central topic of this review. _Listeria monocytogenes_ is a Gram-positive, rod-shaped, facultative intracellular foodborne pathogen and the inducer of a relatively rare disease known as Listeriosis. This food-borne illness is characterized by a high hospitalization and fatality rate (up to 30%) [33]. This potentially lethal infection is associated with symptoms ranging from mild gastroenteritis to fatality cases and the bacteria have higher infectivity and virulence in vulnerable populations like pregnant women, children within five years of birth, the elderly, and patients with deficient immunity [34]. _L. monocytogenes_ can replicate at a wide range of temperatures (2-45 \({}^{\circ}\)C) and divergent environments including mammalian cells, and is able to survive under ubiquitous stresses such as high acidity and high salinity [35]. This makes them extremely resistant to inactivation treatments both in vitro and in vivo. _L. monocytogenes_ is commonly found in processed and cold-stored food such as meat products and dairy products. Recently, fresh produce has also been reported to be a contributor to Listeriosis [33]. _Bacillus cereus_ is a Gram-positive, aerobic facultative, spore-forming bacterium that has been ubiquitously found in soil, water, vegetables, meat, and milk [36]. While certain _B. cereus_ strains are used as a growth promoter or biocontrol against microbial illness, or as probiotics for mammals, other _B. cereus_ strains lead to food poisoning [37]. Pathogenic _B. cereus_ mainly causes two kinds of gastrointestinal diseases: (1) emesis linked to cereulide, a heat-stable and acidic-stable non-ribosomal depsipeptide (pre-) formed in the food matrix, commonly associated with starchy foods like pasta and rice [38], and (2) diarrhea induced by enterotoxins produced in the small intestine, namely hemolysin BL (HBL), non-hemolytic enterotoxin (NHE), and single proteins such as cytotoxin K and enterotoxin T [39]. Although diseases caused by _B. cereus_ are generally mild and self-limiting, severe and lethal cases have been reported [40; 41]. As the third most frequent foodborne outbreak-related pathogen in Europe [42], _B. cereus_ is receiving increasing attention. Finally, as indicated, we now know that _C. jejuni_ strains can also form persister-cells upon ciprofloxacin treatment while such an observation was not made upon exposure to the beta-lactam antibiotic ampicillin [19]. However, the mechanism of _C. jejuni_ persister formation is largely unknown yet. However, recent experiments suggest that _C. jejuni_ cells could undergo a remodeling of the electron transport chain in order to moderate membrane hyperpolarization and intracellular alkalization. These events might jointly reduce the antibiotic efficacy and potentially assist in persister-cell formation [18]. Foodborne pathogens and their persisting forms cause severe food safety and quality challenges to food manufacturing in general and the food industry in particular. The existence of persister cellular forms, which can evade antimicrobial action and regrow after stress removal, makes it difficult to eliminate those pathogens. Although the first discovery of persister-cells dates back 78 years, the contribution of these cells to infection has been underestimated for a long time, until they were clinically isolated from patients who experienced fatal relapse of infection after antibiotic failure [43; 44].