**7. Pathogenicity of** *E. coli*

The majority of *E. coli* strains in the colon are not harmful, however pathogenic *E. coli* isolates cause intestinal or extraintestinal infections, depending on the array Escherichia coli*: An Overview of Main Characteristics DOI: http://dx.doi.org/10.5772/intechopen.105508*

**Figure 11.** *Growth of* E. coli *on LB liquid medium. (Photo: M. Basavaraju.)*

of virulence-associated genes that they harbor. The intestinal pathogenic *E. coli* (IPEC) strains are divided and classified into several pathotypes (**Table 2**). Diseases associated with various intestinal pathogenic *E. coli* pathotypes in animals are as shown in **Table 3**. *E. coli* is linked also to a number of extraintestinal diseases and is the most prevalent cause of cholecystitis, bacteremia, cholangitis, UTI, traveler's diarrhea, and septicemia as well as neonatal meningitis, etc., [37]. Most infections, with the exception of infant meningitis and gastroenteritis, are endogenous, like *E. coli* from the patient's normal microbiota, cause infection when the patient's defenses are impaired, e.g., through trauma or immune suppression [38]. In order to cause disease *E. coli* to possess several different types of virulence factors: fimbrial and fimbrial adhesins, capsules, toxins (exotoxins, hemolysins, and enterotoxins), iron up-take systems, etc., [39]. Important ExPEC virulence-associated genes, their encoded proteins, function, and connection to different ExPEC pathotypes are given in **Table 4** [41].
