Pathogenic bacteria have evolved multiple mechanisms aimed to evade host defenses. This review summarizes selected examples
of how bacteria utilize proteolytic enzymes to efficiently establish and spread infection systemically. First, the role of proteases in intracellular
survival and persistence – the primary means used by bacteria to endure phagocytosis and/or avoid the vigilance of the immune
system – is discussed. Second, it is demonstrated how some bacteria escape entanglement in fibrin(ogen) meshes, by inducing their
proteolytic dissolution while other species modify the proteolytic cascade of mesh formation to divert this important innate immune defense
for their own benefit. Third, bacterial proteolytic toxins are introduced, which allow microorganisms to exert and take advantage of
systemic effects already during primary, localized infection. Finally, it is discussed how viruses utilize bacterial proteases by taking advantage
of concurrent infection, and how pathogens may even mutually benefit from the joint presence of other pathogens. The reviewed
adaptations are often essential for pathogen survival in the hostile environment of a host organism. As such, the potential benefits of
pharmacological interference in relevant pathways for the struggle against bacterial pathogens are also discussed.
Keywords: Protease, proteinase, bacteria, intracellular survival, coagulation, fibrinolysis, toxins, viral infection, pathogenesis.
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