Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy.
J Basic Microbiol. 2012 Jun;52(3):261-8. doi: 10.1002/jobm.201100097. Epub 2011 Sep 23.
The endosymbiotic relationship could represent for many bacteria an important condition favouring their spread in the environment and in foods. For this purpose we studied the behaviour of some food-borne and opportunistic pathogens (Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, Salmonella enterica serovar Enteritidis, Aeromonas hydrophila, Yersinia enterocolitica) when internalized in Acanthamoeba polyphaga. Our results confirm the capability of the bacteria tested to grow within amoebal hosts. We can observe two types of interactions of the bacteria internalized in A. polyphaga. The first type, showed by Y. enterocolitica and A. hydrophila, was characterized by an early replication, probably followed by the killing and digestion of the bacteria. The second type, showed by E. faecalis and S. aureus was characterized by the persistence and grow inside the host without lysis. Lastly, when amoebae were co-cultured with L. monocytogenes and S. Enteritidis, an eclipse phase followed by an active intracellular growth was observed, suggesting a third type of predator-prey trend. The extracellular count in presence of A. polyphaga, as a result of an intracellular multiplication and subsequent release, was characterized by an increase of E. faecalis, S. aureus, L. monocytogenes and S. Enteritidis, and by a low or absent cell count for Y. enterocolitica and A. hydrophila. Our study suggests that the investigated food-borne and opportunistic pathogens are, in most cases, able to interact with A. polyphaga, to intracellularly replicate and, lastly, to be potentially spread in the environment, underlining the possible role of this protozoan in food contamination.
内共生关系可能代表许多细菌在环境和食物中传播的重要条件。为此，我们研究了一些食源性病原体和机会性病原体（单核细胞增生李斯特菌、金黄色葡萄球菌、粪肠球菌、肠炎沙门氏菌血清型肠炎亚种、嗜水气单胞菌、小肠结肠炎耶尔森菌）被内吞入变形虫（棘阿米巴）后的行为。我们的结果证实了所测试的细菌在阿米巴宿主内生长的能力。我们可以观察到细菌内吞入 A. polyphaga 后的两种相互作用类型。第一种类型由小肠结肠炎耶尔森菌和嗜水气单胞菌表现出，其特征是早期复制，可能随后是细菌的杀伤和消化。第二种类型由粪肠球菌和金黄色葡萄球菌表现出，其特征是在没有溶解的情况下在宿主内持续生长。最后，当变形虫与单核细胞增生李斯特菌和肠炎沙门氏菌共培养时，观察到一个潜伏期，随后是一个活跃的细胞内生长，表明存在第三种捕食者-猎物趋势。由于细胞内增殖和随后的释放，在存在棘阿米巴的情况下，粪肠球菌、金黄色葡萄球菌、单核细胞增生李斯特菌和肠炎沙门氏菌的细胞外计数增加，而小肠结肠炎耶尔森菌和嗜水气单胞菌的细胞计数较低或为零。我们的研究表明，所研究的食源性病原体和机会性病原体在大多数情况下能够与棘阿米巴相互作用，进行细胞内复制，最后可能在环境中传播，这突出了这种原生动物在食物污染中的潜在作用。
