Alsam Selwa, Jeong Seok Ryoul, Sissons James, Dudley Ricky, Kim Kwang Sik, Khan Naveed Ahmed
School of Biological and Chemical Sciences, Birkbeck College, University of London, London WC1E 7HX, UK.
Pediatric Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
J Med Microbiol. 2006 Jun;55(Pt 6):689-694. doi: 10.1099/jmm.0.46497-0.
The ability of Acanthamoeba to feed on Gram-negative bacteria, as well as to harbour potential pathogens, such as Legionella pneumophila, Coxiella burnetii, Pseudomonas aeruginosa, Vibrio cholerae, Helicobacter pylori, Listeria monocytogenes and Mycobacterium avium, suggest that both amoebae and bacteria are involved in complex interactions, which may play important roles in the environment and in human health. In this study, Acanthamoeba castellanii (a keratitis isolate belonging to the T4 genotype) was used and its interactions with Escherichia coli (strain K1, a cerebrospinal fluid isolate from a meningitis patient, O18 : K1 : H7, and a K-12 laboratory strain, HB101) were studied. The invasive K1 isolate exhibited a significantly higher association with A. castellanii than the non-invasive K-12 isolate. Similarly, K1 showed significantly increased invasion and/or uptake by A. castellanii in gentamicin protection assays than the non-invasive K-12. Using several mutants derived from K1, it was observed that outer-membrane protein A (OmpA) and LPS were crucial bacterial determinants responsible for E. coli K1 interactions with A. castellanii. Once inside the cell, E. coli K1 remained viable and multiplied within A. castellanii, while E. coli K-12 was killed. Again, OmpA and LPS were crucial for E. coli K1 intracellular survival in A. castellanii. In conclusion, these findings suggest that E. coli K1 interactions with A. castellanii are carefully regulated by the virulence of E. coli.
棘阿米巴能够以革兰氏阴性菌为食，还能容纳诸如嗜肺军团菌、伯纳特立克次体、铜绿假单胞菌、霍乱弧菌、幽门螺杆菌、单核细胞增生李斯特菌和鸟分枝杆菌等潜在病原体，这表明变形虫和细菌都参与了复杂的相互作用，这些相互作用可能在环境和人类健康中发挥重要作用。在本研究中，使用了卡氏棘阿米巴（一种属于T4基因型的角膜炎分离株），并研究了它与大肠杆菌（菌株K1，一种从脑膜炎患者脑脊液中分离出的菌株，O18:K1:H7，以及一种K-12实验室菌株HB101）的相互作用。侵袭性K1分离株与卡氏棘阿米巴的关联显著高于非侵袭性K-12分离株。同样，在庆大霉素保护试验中，K1被卡氏棘阿米巴侵袭和/或摄取的程度也显著高于非侵袭性K-12。使用从K1衍生的几个突变体观察到，外膜蛋白A（OmpA）和脂多糖是大肠杆菌K1与卡氏棘阿米巴相互作用的关键细菌决定因素。一旦进入细胞内，大肠杆菌K1在卡氏棘阿米巴内保持存活并繁殖，而大肠杆菌K-12则被杀死。同样，OmpA和脂多糖对大肠杆菌K1在卡氏棘阿米巴内的细胞内存活至关重要。总之，这些发现表明大肠杆菌K1与卡氏棘阿米巴的相互作用受到大肠杆菌毒力的精细调控。
