Apoptosis as a common bacterial virulence strategy

The comparison of common strategies used by bacterial pathogens to overcome host defenses provides us with the opportunity to analyze the biology of p athogenicity, as well as point out the unique interactions between a partic ular pathogen and its host. Here we compare and contrast apoptosis induced by three enteric pathogens, Salmonella, Shigella, and Yersinia. We point ou t that all three enteric pathogens induce apoptosis in macrophages in vitro , but the proposed mechanisms are quite different. Yersinia induces apoptos is by inhibiting the translocation of the transcriptional activator, NF-kap pa B, into the nucleus, which results in the suppression of TNF alpha produ ction; whereas Salmonella- and Shigella-induced apoptosis depend on the act ivation of caspase-1 (casp-1). The result of casp 1 activation is to induce apoptosis as well as to process the proinflammatory cytokines, pro-IL-1 be ta and pro-IL18 into their mature bioactive forms. Thus, in contrast to Yer sinia, Salmonella and Shigella-induced apoptosis results in a proinflammato ry cascade.