Capsules that protect the bacteria from phagocytosis and antibodies, and provide a poorly immunogenic surface.
Fimbriae and proteins called adhesins, which enable the bacteria to attach tightly to human cells.
Exotoxins that cause a variety of symptoms such as diarrhea. The genes for exotoxins, fimbriae, and adhesins are frequently located on plasmids, which increases the likelihood that they will be transferred among bacteria.
Iron-binding compounds called siderophores that capture iron and make it available to the bacteria.
Hemolysins, which release nutrients such as iron by lysing red blood cells.