Mechanisms of Cell and Tissue Damage

Many infections are associated with damage inflicted either directly or indirectly by invading pathogens. Although some infections do not result in host damage, it is often a natural consequence of the activities of virulence factors produced by the pathogens in order to facilitate survival, and proliferation in the host or onward transmission to another host. The damage often manifests itself as the symptoms of disease which can be useful for diagnosis and for informing appropriate treatments. A wide array of different types of toxins which cause damage to the host are produced by different bacterial pathogens. Here we provide examples of well-characterised toxins and describe their mechanisms of action, and potential function with regard to pathogenesis. In addition we describe indirect damage to the host in the form of inflammation or immunopathology, typically the result of the host's own immune response. Finally, we discuss diarrhoea as a special case and list some of the major pathogens and the toxins associated with this devastating disease.