Increase in Acid Tolerance of Campylobacter jejuni through Coincubation with Amoebae

Abstract

Campylobacter jejuni is a recognized and common gastrointestinal pathogen in most parts of the world. Human infections are often food borne, and the bacterium is frequent among poultry and other food animals. However, much less is known about the epidemiology of C. jejuni in the environment and what mechanisms the bacterium depends on to tolerate low pH. The sensitive nature of C. jejuni stands in contrast to the fact that it is difficult to eradicate from poultry production, and even more contradictory is the fact that the bacterium is able to survive the acidic passage through the human stomach. Here we expand the knowledge on C. jejuni acid tolerance by looking at protozoa as a potential epidemiological pathway of infection. Our results showed that when C. jejuni cells were coincubated with Acanthamoeba polyphaga in acidified phosphate-buffered saline (PBS) or tap water, the bacteria could tolerate pHs far below those in their normal range, even surviving at pH 4 for 20 h and at pH 2 for 5 h. Interestingly, moderately acidic conditions (pH 4 and 5) were shown to trigger C. jejuni motility as well as to increase adhesion/internalization of bacteria into A. polyphaga. Taken together, the results suggest that protozoa may act as protective hosts against harsh conditions and might be a potential risk factor for C. jejuni infections. These findings may be important for our understanding of C. jejuni passage through the gastrointestinal tract and for hygiene practices used in poultry settings.

Acid-shock ofCampylobacter jejuniinduces flagellar gene expression and host cell invasion

“…Acidic conditions may trigger the activation of C. jejuni virulence phenotypes in preparation for host cell invasion. One study investigating co-incubation of C. jejuni with amoebae demonstrated that incubation of C. jejuni under mildly acidic conditions increased its adherence to and invasion of amoebae [37]. The same study also reported that bacterial survival increased after long-term acid exposure and that incubation of C. jejuni with low pH for 1 h increased motility on a swarm plate.…”

The Family Campylobacteraceae

“…are ubiquitous in the environment and have been isolated from soil (Chai et al 2009), mud (Stuart et al 2010), bathing beach sand (Bolton et al 1999), and environmental water (Kemp et al 2005). Campylobacter has been associated with soil amebas that may provide a protected environment for the bacteria (Baré et al 2010;Axelsson-Olsson et al 2010). Campylobacter has also been detected in untreated tap water, consumption of which resulted in outbreaks of campylobacteriosis (Jakopanec et al 2008;Vogt et al 1982).…”

Campylobacter–Acanthamoeba interactions

“…(Axelsson-Olsson et al, 2010b;Baré et al, 2010). Axelsson-Olsson and co-authors investigated whether internalization of C. jejuni by Acanthamoeba affects bacterial tolerance to low pH.…”