Department of Food Safety, Nutrition and Veterinary Public Health, Istituto Superiore di Sanità, Rome, Italy.
Core Facilities, Istituto Superiore di Sanità, Rome, Italy.
Front Cell Infect Microbiol. 2022 Sep 9;12:926127. doi: 10.3389/fcimb.2022.926127. eCollection 2022.
Free-living amoebae (FLA) are widely distributed protozoa in nature, known to cause severe eye infections and central nervous system disorders. There is growing attention to the potential role that these protozoa could act as reservoirs of pathogenic bacteria and, consequently, to the possibility that, the persistence and spread of the latter may be facilitated, by exploiting internalization into amoebae. Shiga toxin-producing strains of (STEC) are zoonotic agents capable of causing serious diseases, such as hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). Cattle represent the main natural reservoir of STEC, which are frequently found also in other domestic and wild ruminants, often without causing any evident symptoms of disease. The aspects related to the ecology of STEC strains in animal reservoirs and the environment are poorly known, including the persistence of these microorganisms within niches unfavorable to survival, such as soils or waters. In this study we investigated the interaction between STEC strains of serotype O157: H7 with different virulence gene profiles, and a genus of a wild free-living amoeba, sp. Our results confirm the ability of STEC strains to survive up to 20 days within a wild sp., in a quiescent state persisting in a non-cultivable form, until they reactivate following some stimulus of an unknown nature. Furthermore, our findings show that during their internalization, the O157 kept the set of the main virulence genes intact, preserving their pathogenetic potential. These observations suggest that the internalization in free-living amoebae may represent a means for STEC to resist in environments with non-permissive growth conditions. Moreover, by staying within the protozoa, STEC could escape their detection in the vehicles of infections and resist to the treatments used for the disinfection of the livestock environment.
自由生活的阿米巴原虫（FLA）是自然界中广泛分布的原生动物，已知会引起严重的眼部感染和中枢神经系统疾病。人们越来越关注这些原生动物可能作为致病菌的储存库的潜在作用，因此，后者的持续存在和传播可能会通过利用内吞作用进入阿米巴原虫而得到促进。产志贺毒素的大肠杆菌（STEC）是一种能够引起严重疾病的人畜共患病原体，如出血性结肠炎（HC）和溶血性尿毒综合征（HUS）。牛是 STEC 的主要天然宿主，这些病原体也经常在其他家养和野生反刍动物中发现，通常不会引起任何明显的疾病症状。关于动物宿主和环境中 STEC 菌株的生态学方面的知识还很匮乏，包括这些微生物在不利于生存的环境中（如土壤或水中）的持久性。在这项研究中，我们研究了不同毒力基因谱的 O157：H7 型 STEC 菌株与一种野生自由生活的阿米巴属 sp.之间的相互作用。我们的结果证实，STEC 菌株能够在一种野生 sp.中存活长达 20 天，处于休眠状态，以非可培养的形式持续存在，直到受到某种未知性质的刺激后重新激活。此外，我们的发现表明，在它们的内化过程中，O157 保持了主要毒力基因的完整集，保持了其致病潜力。这些观察结果表明，在自由生活的阿米巴原虫中的内化可能是 STEC 抵抗非允许生长条件的环境的一种手段。此外，通过停留在原生动物体内，STEC 可以逃避在感染载体中的检测，并抵抗用于消毒家畜环境的处理。
