Microorganisms Resistant to Free-Living Amoebae

Abstract

Free-living amoebae feed on bacteria, fungi, and algae. However, some microorganisms have evolved to become resistant to these protists. These amoeba-resistant microorganisms include established pathogens, such as Cryptococcus neoformans, Legionella spp., Chlamydophila pneumoniae, Mycobacterium avium, Listeria monocytogenes, Pseudomonas aeruginosa, and Francisella tularensis, and emerging pathogens, such as Bosea spp., Simkania negevensis, Parachlamydia acanthamoebae, and Legionella-like amoebal pathogens. Some of these amoeba-resistant bacteria (ARB) are lytic for their amoebal host, while others are considered endosymbionts, since a stable host-parasite ratio is maintained. Free-living amoebae represent an important reservoir of ARB and may, while encysted, protect the internalized bacteria from chlorine and other biocides. Free-living amoebae may act as a Trojan horse, bringing hidden ARB within the human “Troy,” and may produce vesicles filled with ARB, increasing their transmission potential. Free-living amoebae may also play a role in the selection of virulence traits and in adaptation to survival in macrophages. Thus, intra-amoebal growth was found to enhance virulence, and similar mechanisms seem to be implicated in the survival of ARB in response to both amoebae and macrophages. Moreover, free-living amoebae represent a useful tool for the culture of some intracellular bacteria and new bacterial species that might be potential emerging pathogens

Proteomic aspects of Parachlamydia acanthamoebae infection in Acanthamoeba spp.

“…Besides their role as bacteriovores, acanthamoebae are also facultative human pathogens that can cause keratitis, mainly in contact lens wearers, and granulomatous encephalitis in immunocompromised individuals (Marciano-Cabral and Cabral, 2003). Moreover, Acanthamoeba and other free-living amoebae can act as vectors for bacteria that resist degradation after phagocytosis (Fritsche et al, 1993;Barker and Brown, 1994;Greub and Raoult, 2004). Indeed, as they were found to be associated with Legionella pneumophila (Rowbotham, 1980) and a number of other pathogenic bacteria such as Francisella tularensis (Abd et al, 2003) and Mycobacterium bovis (Taylor et al, 2003), free-living amoebae have been dubbed 'trojan horses of the microbial world' (Barker and Brown, 1994).…”

Cellular Response of the Amoeba Acanthamoeba castellanii to Chlorine, Chlorine Dioxide, and Monochloramine Treatments

“…Some of them are pathogenic, and interest in these microorganisms has recently increased because they might be reservoirs of pathogenic bacteria in the environment (7). Indeed, some bacteria, collectively referred to as amoebaresistant bacteria, resist amoeba phagocytosis (11). Some of them, such as Legionella pneumophila, are even able to multiply within amoeba trophozoites (23,29) and could be found within amoeba cysts (14,27).…”

Effects of Oakmoss and its Components on <i>Acanthamoeba</i><i> castellanii</i> ATCC 30234 and the Uptake of <i>Legionella pneu</i><i>mophila</i> JCM 7571 (ATCC 33152) into <i><i>A. castellanii</i></i>

“…in natural environments Greub and Raoult, 2004Molmeret et al, 2005Rowbotham, 1980Winiecka-Krusnell and Linder, 2001 . In addition, L. pneumophila co-cultured with amoeba is less sensitive to typical chlorine disinfectants Barker et al, 1992Dupuy et al, 2011García et al, 2007Kim et al, 2002 and L. pneumophila multiplied in amoebae possess greater resistance to disinfectants and antibacterial agents than L. pneumophila from cultures in broth Bandyopadhyay et al, 2004Barker et al, 1995 .…”

“…The trophozoite, a metabolically active stage, feeds on bacteria and multiplies by binary fission. In particular, Acanthamoeba are hosts of Legionella pneumophila, a waterborne pathogenic bacterium responsible for Legionnaires disease Greub and Raoult, 2004Molmeret et al, 2005Rowbotham, 1980Winiecka-Krusnell and Linder, 2001 . L. pneumophila is 3-hydroxy-5-methylphenyl 2-hydroxy-4-methoxy-6-methylbenzoate 10 , ethyl 2-hydroxy-4-methoxy-6-methylbenzoate 11 , 6,8-dihydroxy-3-pentyl-1H-isochromen-1-one 12 , ethyl 3-formyl-2,4-dihydroxy-6-methylbenzoate 13 , 8-2,4-dihydroxy-6-pentylphenoxy -6-hydroxy-3-pentyl-1H-isochromen-1-one 14 , isopropyl 3-formyl-2,4-dihydroxy-6-methylbenzoate 15 , 3-methoxy-5-methylphenyl 2-hydroxy-4-methoxy-6-methylbenzoate 16 , 8-2-hydroxy-4-methoxy-6-pentylphenoxy -6-hydroxy-3-pentyl-1H-isochromen-1-one 17 , 2,5-dimethylbenzene-1,3-diol 18 , 3-chloro-2,6-dihydroxy-4-methylbenzaldehyde 19 , 8-2,4-dihydroxy-6-2-oxoheptyl -phenoxy -6-hydroxy-3-pentyl-1H-isochromen-1-one 20 .…”