**2. Transmission of pathogens in the food chain**

Foodborne pathogens are transmitted through the food chain in many ways, such as insect transmission, fecal-oral transmission, food and water transmission, animals transmission, and so on. Some pathogens, such as *E. coli* or *Salmonella enteritidis* can be passed from animal hosts to people, but *Salmonella typhi* has no animal host and is highly harmful to humans.

Insects are considered to be carriers of foodborne pathogens. Their association with degradable substances and their endogenous and coexistence (with humans) are behavioral patterns that are particularly important for the ability of flies, cockroaches, and ants to transmit foodborne diseases. A study conducted in an ant colony in a Brazilian hospital found that several bacteria, including *E. coli* and *Salmonella,* were related to ants. Another study found cockroaches and several cockroach-related bacteria in several buildings in Spain, including *Salmonella* (hospitals), *E. coli* (hospitals, restaurants, companies, and grocery stores), and *Enterobacteria* (shops and food industry factories). In addition, an assessment of cockroaches gathered from hospitals, houses, grocery shops, and restaurants in the South Canary region of southwest India revealed that more than 4% of cockroaches tested positive for several *Salmonella* strains [6]. But existing understanding about the health dangers posed by flies and food is inadequate currently. Flies are at risk of transmitting foodborne pathogens because they have a bowel movement every 4 to 5 minutes during the day [7]. In general, houseflies can promote the spread of pathogens in four different ways: through body hair and surface, through the glandular hair on the feet, through the regurgitant rumen itus, and through the digestive tract [7]. Recently, some researchers have claimed that adult houseflies can spread their eggs and bacteria to food, so that these bacteria could be retransmitted to the first generation of adult flies [8]. Alexandre Lamas studied the bacterial populations of the Australian bush flies in three diverse places: cattle farms parking lots, metropolitan shopping malls, and a barbecue spot [9]. In the agricultural setting, the number of bacterial per fly was highest, whereas, it was lowest in the city [9]. Furthermore, multi-drug resistance was found in 94% of *Salmonella* isolates and 87% of *Shigella* isolates, suggesting that these flies might operate as food carriers for antimicrobial resistance transmission [10].

Water is well-known for its importance in the production, processing, and preparation of food. It is also a medium for the transmission of pathogens during food manufacturing [11]. The quantity of contamination in irrigation water determines pathogen survival, and the higher the degree of contamination, the better. They may survive outside of their human hosts for months to years before being transmitted to humans through water [12]. *E. coli* and *Salmonella* can leach through water or soil to the plant surface [13] and even *E. coli* O157:H7 can be absorbed by lettuce leaves. In

#### *Foodborne Pathogens of Enterobacteriaceae, Their Detection and Control DOI: http://dx.doi.org/10.5772/intechopen.102086*

addition, *E. coli* from livestock manure may persist for at least 5–6 months on soil or grassland, giving pathogens an excellent chance to infect other sources. In another research, *E. coli* O157:H7 could not only attach to the outer surface of radish seeds but also invade the inner tissues and stomata [14].

Many microorganisms that cause foodborne diseases can be transferred directly from animals to people. Mammals such as pigs and cattle are thought to host many foodborne pathogens, which are transmitted to humans either through direct contact with humans or by being processed into food for human consumption. *E. coli* is a typical element of the gut flora of humans and animals, and it is commonly found in poultry and wild animals. As a result, *E. coli* is one of the most likely infections to spread through food. The Shiga toxin-producing *E. coli* (STEC) strain is a serious foodborne pathogen that may be transmitted by consuming pig chow. From 334 pork samples collected from a South Korean slaughterhouse and retail market, 131 strains of *E. coli* were identified [15]. Simultaneously, *E. coli* was discovered in chickens. According to the Daily Mail, a food safety survey conducted in a supermarket in the UK found that 23 out of 99 chicken samples were infected with *E. coli.*

There are many key points where pathogens can infiltrate and jeopardize human food safety, such as the food itself, the surfaces of food preparation tools or food processors [16]. At each food processing or preparation facility location, a variety of factors may impact contamination and transmission. For example, microbial pathogens can be brought into the kitchen environment through commercial foods, cross-contamination of foods via kitchen equipment, or be reused due to inadequate cooking or storage [17, 18].
