<unk>  infection is typically by ingestion. Depending on the health of the host, fewer than 100 bacterial cells can be enough to cause an infection.<unk>  species generally invade the epithelial lining of the colon, causing severe inflammation and death of the cells lining the colon. This inflammation results in the diarrhea and even dysentery that are the hallmarks of<unk>  infection. Some strains of<unk>  produce toxins which contribute to disease during infection. S. flexneri strains produce ShET1 and ShET2, which may contribute to diarrhea. S. dysenteriae strains produce Shiga toxin, which is hemolytic similar to the verotoxin produced by enterohemorrhagic E. coli. Both Shiga toxin and verotoxin are associated with causing potentially fatal hemolytic-uremic syndrome.<unk>  species invade the host through the M-cells interspersed in the gut epithelia of the small intestine, as they do not interact with the apical surface of epithelial cells, preferring the basolateral side.<unk>  uses a type-III secretion system, which acts as a biological syringe to translocate toxic effector proteins to the target human cell. The effector proteins can alter the metabolism of the target cell, for instance leading to the lysis of vacuolar membranes or reorganization of actin polymerization to facilitate intracellular motility of<unk>  bacteria inside the host cell. For instance, the IcsA effector (which is an autotransporter instead of type III secretion system effector) protein triggers actin reorganization by N-WASP recruitment of Arp2/3 complexes, helping cell-to-cell spread. After infection,<unk>  cells multiply intracellularly and spread to neighboring epithelial cells, resulting in tissue destruction and characteristic pathology of<unk> sis. The most common symptoms are diarrhea, fever, nausea, vomiting, stomach cramps, and flatulence. It is also commonly known to cause large and painful bowel movements. The stool may contain blood, mucus, or pus. Hence,<unk>  cells may cause dysentery. In rare cases, young children may have seizures. Symptoms can take as long as a week to appear, but most often begin two to four days after ingestion. Symptoms usually last for several days, but can last for weeks.<unk>  is implicated as one of the pathogenic causes of reactive arthritis worldwide.
Shigella
Salmonella
Giardia
Vibrio cholerae
Faecalibacterium
Clostridioides difficile 
Escherichia coli
Campylobacter jejuni