Siddiqui Ruqaiyyah, Lakhundi Sahreena, Khan Naveed Ahmed
Department of Biological and Biomedical Sciences, Aga Khan University, Stadium Road, Karachi, Pakistan.
Parasitol Res. 2015 Jun;114(6):2349-56. doi: 10.1007/s00436-015-4432-0. Epub 2015 Mar 21.
Several lines of evidence suggest that Acanthamoeba interact with bacteria, which may aid in pathogenic bacterial transmission to susceptible hosts, and these interactions may have influenced evolution of bacterial pathogenicity. In this study, we tested if Gram-negative Pseudomonas aeruginosa and Gram-positive Corynebacterium spp. can associate/invade and survive inside Acanthamoeba castellanii trophozoites and cysts, as well as non-phagocytic human brain microvascular endothelial cells. The results revealed that both Corynebacterium spp. and P. aeruginosa were able to associate as well as invade and/or taken up by the phagocytic A. castellanii trophozoite. In contrast, P. aeruginosa exhibited higher association as well as invasion of non-phagocytic HBMEC compared with Corynebacterium spp. Notably, P. aeruginosa remained viable during the encystment process and exhibited higher levels of recovery from mature cysts (74.54 bacteria per amoebae) compared with Corynebacterium spp. (2.69 bacteria per amoeba) (P < 0.05). As Acanthamoeba cysts can be airborne, these findings suggest that Acanthamoeba is a potential vector in the transmission of P. aeruginosa to susceptible hosts. When bacterial-ridden amoebae were exposed to favourable (nutrient-rich) conditions, A. castellanii emerged as vegetative trophozoites and remained viable, and likewise viable P. aeruginosa were also observed but rarely any Corynebacterium spp. were observed. Correspondingly, P. aeruginosa but not Corynebacterium spp. exhibited higher cytotoxicity to non-phagocytic HBMEC, producing more than 75% cell death in 24 h, compared to 20% cell death observed with Corynebacterium spp. Additionally, it was observed that the bacterial conditioned medium had no negative effect on A. castellanii growth. Further characterization of amoebal and bacterial interactions will assist in identifying the role of Acanthamoeba in the transmission and evolution of pathogenic bacteria.
多条证据表明，棘阿米巴与细菌相互作用，这可能有助于病原菌向易感宿主传播，并且这些相互作用可能影响了细菌致病性的进化。在本研究中，我们测试了革兰氏阴性菌铜绿假单胞菌和革兰氏阳性菌棒状杆菌属是否能够在卡氏棘阿米巴滋养体和包囊内以及非吞噬性人脑微血管内皮细胞中缔合/侵入并存活。结果显示，棒状杆菌属和铜绿假单胞菌都能够与吞噬性的卡氏棘阿米巴滋养体缔合、侵入和/或被摄取。相比之下，与棒状杆菌属相比，铜绿假单胞菌与非吞噬性人脑微血管内皮细胞的缔合及侵入能力更强。值得注意的是，铜绿假单胞菌在包囊形成过程中仍保持活力，并且与棒状杆菌属（每个变形虫2.69个细菌）相比，从成熟包囊中恢复的水平更高（每个变形虫74.54个细菌）（P < 0.05）。由于棘阿米巴包囊可以通过空气传播，这些发现表明棘阿米巴是铜绿假单胞菌向易感宿主传播的潜在载体。当携带细菌的变形虫暴露于有利（营养丰富）条件下时，卡氏棘阿米巴会形成营养性滋养体并保持活力，同样也观察到了有活力的铜绿假单胞菌，但很少观察到棒状杆菌属。相应地，铜绿假单胞菌而非棒状杆菌属对非吞噬性人脑微血管内皮细胞表现出更高的细胞毒性，在24小时内导致超过75%的细胞死亡，而棒状杆菌属导致20%的细胞死亡。此外，观察到细菌条件培养基对卡氏棘阿米巴的生长没有负面影响。对变形虫和细菌相互作用的进一步表征将有助于确定棘阿米巴在病原菌传播和进化中的作用。
