[Pathogenesis and virulence determinants of the family Legionellaceae].
Legionellae are Gram-negative obligate intracellular parasites of unicellular animal organisms, some of which are sometimes able to cause an acute and sever pneumonia in humans. Legionellae, are capable of surviving for long periods in water when between hosts. Their adaptation to these quite diverse environments seems to be accomplished by morphological and biochemical pathway changes. It has been well established that humans coexisted with these bacteria for a long period of time, and it is only recently that our industrial technology provided these organisms with the means of causing infection. This review describes the invasion process and the life cycle of Legionellae in both protozoan and mammalian cells. Our understanding of the infection cycle of Legionellae is primarily based on observations by transmission and scanning EM and by contrast phase and fluorescence microscopy. The identification of virulence determinants by molecular techniques is also discussed. The bacteria enter the host cell mainly by coiling phagocytosis and reside within unique phagosomes which, during the first hours of infection, are isolated from the endosomal pathway. Within the protected vacuole the mature infectious forms of Legionellae convert to replicative forms that no longer express virulence traits. Evidence is provided on how the biogenesis of the replication niche is determined. The virulence factors that arrest phagosome maturation during intracellular replication are also described. The status of our current knowledge on the means by which Legionellae successfully infect the host cells to cause disease is discussed.
Palusińska-Szysz
Marta
M
Zakład Mikrobiologii Ogólnej, Instytut Mikrobiologii i Biotechnologii, Uniwersytet Marii Curie-Skłodowskiej, Lublin. martasz@biotop.umcs.lublin.pl
Drozański
Wincenty J
WJ
D000818:Animals; D056890:Eukaryota / Q000382:microbiology; D006790:Host-Parasite Interactions; D006801:Humans; D016951:Legionellaceae / Q000472:pathogenicity*; D007877:Legionnaires' Disease / Q000382:microbiology; D014774:Virulence