Interaction of Pasteurella multocida with Free-Living Amoebae

Abstract

Pasteurella multocida is a highly infectious, facultative intracellular bacterium which causes fowl cholera in birds. This study reports, for the first time, the observed interaction between P. multocida and free-living amoebae. Amoebal trophozoites were coinfected with fowl-cholera-causing P. multocida strain X-73 that expressed the green fluorescent protein (GFP). Using confocal fluorescence microscopy, GFP expressing X-73 was located within the trophozoite. Transmission electron microscopy of coinfection preparations revealed clusters of intact X-73 cells in membrane-bound vacuoles within the trophozoite cytoplasm. A coinfection assay employing gentamicin to kill extracellular bacteria was used to assess the survival and replication of P. multocida within amoebae. In the presence of amoebae, the number of recoverable intracellular X-73 cells increased over a 24-h period; in contrast, X-73 cultured alone in assay medium showed a consistent decline in growth. Cytotoxicity assays and microscopy showed that X-73 was able to lyse and exit the amoebal cells approximately 18 h after coinfection. The observed interaction between P. multocida and amoebae can be considered as an infective process as the bacterium was able to invade, survive, replicate, and lyse the amoebal host. This raises the possibility that similar interactions occur in vivo between P. multocida and host cells. Free-living amoebae are ubiquitous within water and soil environments, and P. multocida has been observed to survive within these same ecosystems. Thus, our findings suggest that the interaction between P. multocida and amoebae may occur within the natural environment.

Interactions between Food-Borne Pathogens and Protozoa Isolated from Lettuce and Spinach

“…Furthermore, bacteria such as E. coli O157:H7 (2) and S. enterica (34) are able to replicate inside the food vacuoles of protozoa. Similar results were reported with Pasteurella multocida (19), Mycobacterium avium (13), and L. pneumophila (18). This implies a complex role for protozoa in the ecology of human pathogens.…”

Survival of Environmental Mycobacteria in Acanthamoeba polyphaga

“…are commonly found in natural aquatic systems, water supplies, and cooling systems (37, 50), usually feeding on bacteria (68). It was shown that amoebae host several intracellular pathogens including Legionella spp., Chlamydia spp., Parachlamydia spp., Listeria spp., Burkholderia spp., Campylobacter jejuni, Helicobacter pylori, Pasteurella multocida, Salmonella enterica, Francisella tularensis, and Simkania negevensis (10,32,38). The association, mentioned above, of Legionella pneumophila with Acanthamoeba spp.…”

Signaling Cascades of Pasteurella multocida Toxin in Immune Evasion

“…The fact that PMT also uses this evasion strategy suggests that it must be useful for the bacteria in some way. Pasteurella multocida is not a typical intracellular pathogen, however, the ability to invade host cells has been described in several publications [44,45,46,47,48,49,50]. However, whether toxigenic strains have an advantage in internalization or intracellular survival has not been studied yet.…”