Interaction of Acinetobacter baumannii 19606 and 1656-2 with Acanthamoeba castellanii

Abstract

Acinetobacter baumannii is virtually avirulent for healthy people but maintains a high virulence among critically ill patients or immuno-compromised individuals. The ability of A. baumannii to adhere to cells and persist on surfaces as biofilms could be central to its pathogenicity. In the present study, we compared the virulence of the A. baumannii 1656-2 clinical strain, which is able to form a thick biofilm, with the virulence of the A. baumannii type strain (ATCC 19606(T)). Acanthamoeba castellanii, a single-celled organism, was used as the host model system to study the virulence of A. baumannii. Compared to A. baumannii ATCC 19606(T), A. baumannii 1656-2 exhibited a higher ability to adhere and invade A. castellanii cells and had a higher killing rate of A. castellanii cells. Furthermore, co-incubation of the amoeba cells and the cell-free supernatant of A. baumannii resulted in the cell death of the amoebae. Heat inactivation or proteinase K treatment of the supernatant did not eliminate its cytotoxicity, suggesting heat stable non-protein factors are responsible for its cytotoxicity to A. castellanii cells. In conclusion, this study for the first time has revealed the capacity of the A. baumannii strain and/or its metabolic products to induce cytotoxicity in A. castellanii cells.

A tractableDrosophilacell system enables rapid identification ofAcinetobacter baumanniihost factors

“…1B-D ). Previous studies showed that A. baumannii invasion of mammalian cells can ultimately induce host cell death (Choi et al, 2005; Kim et al, 2008; Smani et al, 2011; Tamang et al, 2011). To determine whether the bacterium similarly killed alveolar cells, we measured the release of LDH, an indicator of host cell death, following infection (Pei and Ficht, 2004; Pei et al, 2008).…”

Acanthamoeba and bacteria produce antimicrobials to target their counterpart

“…However, certain bacteria especially pathogenic bacteria have developed strategies to escape the killing mechanisms of Acanthamoeba and instead use the amoeba as a Trojan horse or reservoir for their own benefit [12,13]. Some bacteria protect themselves from preying amoeba by secreting soluble anti- Acanthamoeba substances in their medium [14-16] or directly injecting such substances into Acanthamoeba through the type III secretory system [15]. These findings suggest that Acanthamoeba and Bacteria encounter each other in the environment routinely.…”

Genomic analysis of a Raoultella ornithinolytica strain causing prosthetic joint infection in an immunocompetent patient

“…have shown that pathogenic bacteria, but not those who are weakly or not pathogenic, can survive within A. castellanii cysts 16 . The ability of R. ornithinolytica to grow and cause cytopathic effect in A. castellanii seems to be correlated with its virulence 14 , 15 . We demonstrated that strain Marseille-P1025 was not only able to survive within amoebae but could also multiply more efficiently than the control strain and kill amoebae, supporting its virulent behavior.…”