Transient internalization of Campylobacter jejuni in Amoebae enhances subsequent invasion of human cells

Abstract

The ubiquitous unicellular eukaryote, Acanthamoeba, is known to play a role in the survival and dissemination of Campylobacter jejuni. C. jejuni is the leading cause of bacterial foodborne gastroenteritis world-wide and is a major public health problem. The ability of C. jejuni to interact and potentially invade epithelial cells is thought to be key for disease development in humans. We examined C. jejuni grown under standard laboratory conditions, 11168HCBA with that harvested from within Acanthamoeba castellanii (11168HAC/CBA) or Acanthamoeba polyphaga (11168HAP/CBA), and compared their ability to invade different cell lines. C. jejuni harvested from within amoebae had a ~3.7-fold increase in invasiveness into T84 human epithelial cells and a striking ~11-fold increase for re-entry into A. castellanii cells. We also investigated the invasiveness and survivability of six diverse representative C. jejuni strains within Acanthamoeba spp., our results confirm that invasion and survivability is likely host-cell-dependent. Our survival assay data led us to conclude that Acanthamoeba spp. are a transient host for C. jejuni and that survival within amoebae pre-adapts C. jejuni and enhances subsequent cell invasion. This study provides new insight into C. jejuni interactions with amoebae and its increased invasiveness potential in mammalian hosts.

Survival of Campylobacter jejuni in Acanthamoebae castellanii provides mechanistic insight into host pathogen interactions

“…Invasion and survival assays were performed as previously described [12,25], with minor alterations. Briefly, C. jejuni 11168H, a derivative of the original sequence strain NCTC 11168, and its mutants was incubated with a monolayer of approximately 10 6 A. castellanii at a multiplicity of infection (M.O.I) of 200:1 for 3 hrs at 25 o C in 2 ml PYG media (the M.O.I.…”

“…This study highlights that amoebae and C. jejuni warm-blooded hosts have similar properties which makes A. castellanii a useful model to study C. jejuni-host interactions. which fuse into; 3) larger vacuoles which are emptied through exocytosis; 4) undigested C. jejuni, which are more invasive and more resistant to intracellular stresses [12], are capable of reinvading A. castellanii; 5) and occasionally these more invasive and resistant C. jejuni can withstand encystment of amoebae. CV = contractile vacuole.…”

“…This allows the bacterium to withstand many stresses and remain viable with low metabolic activity for months [7]. Additionally, several studies have investigated C. jejuni environmental survival out-side of the host with free-living protists [8][9][10][11][12], however, the mechanistic understanding of this important niche remains poorly understood.…”

Microbial Musings – Spring 2022

“…Here, the authors discover that passage of C. jejuni through amoebae increased the invasiveness of the bacterium for human cell lines and for reinfection of other amoebae. They suggest some mechanisms of 'priming adaptive response' , which has seen before for adaptation to growth at low pH [9], although they are cautious about the amoebae being long-term hosts, as they cannot detect intra-amoebae multiplication of the bacteria and hence propose that the bacteria reside transiently in the amoebae to potentially increase their chance of transmission to an avian or mammalian host [7].…”

“…Staying with the theme of pathogens adapting to live in environmental amoebae, a paper from Fauzy Nasher and Brenden Wren, at the London School of Hygiene and Tropical Medicine (@LSHTM), UK, also caught my eye, as they report an interesting finding relating to another bacterium, Campylobacter jejuni, which we know as a cause of severe gastroenteritis [7]. While birds are known to be one environmental source of C. jejuni, how they survive and persist more generally in the environment is not well known, although recent studies have reported that C. jejuni can survive inside amoebae [8].…”