Effect of noradrenaline on the virulence properties of campylobacter species

Abstract

Campylobacter species cause a spectrum of illnesses in humans. The type of illness and the outcome is dependent on the virulence of the infecting pathogen strain and host immune status. Acute stress can seriously compromise host immunity and increase susceptibility to infection. Noradrenaline (NA) is a stress hormone. Several studies have shown that it stimulated growth and increased the pathogenicity of organisms including E. coli and Campylobacter jejuni. However, the effect of NA on other Campylobacter species is unknown. We have examined the effect of NA on growth rate, motility, invasion of T84 epithelial cells, and colonisation of chickens by diverse Campylobacter species. Campylobacter cultures grown with NA had reduced lag phases, increased growth rates, and higher final optical densities than controls. The motility of Campylobacter was also significantly increased in the presence of noradrenaline. Some of the Campylobacter strains tested also showed increased invasion of T84 epithelial cells, greater breakdown of tight junctions, and an enhanced potential to colonise chickens. Our results show that noradrenaline-induced enhancement of virulence of Campylobacter can influence the outcome of infection.

Figure 1

Growth of C. jejuni 81116 (a), C. jejuni M1 (b), C. jejuni 11168 (c), C. coli 1669 (d), C. coli RM2228 (e), and C. fetus fetus (f) species taken over 48 h with readings every hour in the presence and absence of NA at 37°C. Results are the mean of three separate experiments, and bars represent standard error. The control group values are represented by solid squares and noradrenaline-treated group values are represented by solid triangle shape.

Figure 2

Motility of C. jejuni 81116, C. jejuni M1, C. coli 1669, and C. fetus fetus at 37°C. Size of the motility halo after 48 hours in the absence (black) or presence (white) of NA. The diameter of the halo was higher in the presence (white) of NA for all the species of Campylobacter. Star indicates P < 0.05. Results are mean of three separate experiments.

Figure 3

Invasion of T84 epithelial cells by C. jejuni 81116 (a), C. jejuni M1 (b), C. coli 1669 (c), and C. fetus fetus (d) at 37°C was determined by gentamicin protection assay. The percentage of invading cells in the inoculum in the presence (black) or absence (white) of noradrenaline is shown. Results are the mean of three separate experiments, and bars represent standard error. Star indicates P < 0.05.

Figure 4

The effect of noradrenaline on the tight junction integrity of T84 epithelial cells was measured by percentage drop in transepithelial resistance (TER) at 48 hours after infection with Campylobacter species. Results are the mean of three separate experiments, and bars represent standard error. Star indicates P < 0.05. A significantly higher drop in TER was noticed when noradrenaline was added to the transwells infected with C. jejuni M1, C. coli, and C. fetus fetus only.

Figure 5

Effect of Campylobacter on integrity of T84 monolayers. Monolayers were fixed and stained for tight junction protein occludin after 48-hour infection with Campylobacter or Campylobacter with NA and analysed by confocal microscopy. Monolayers exposed to C. jejuni 81116, C. jejuni M1, C. coli, and C. fetus fetus in the absence of noradrenaline shown as control in (b)–(e) (A) (the first figure). Cell monolayers co-infected with Campylobacter in the presence of noradrenaline are shown as treated group in (b)–(e) (B) (the second figure). Ten fields of view were visualised using confocal microscopy with a Hamamatsu camera and digitised using Leica Q fluoro software and analysed by quantitative immunofluorescence using Macros on image J software. The average area of percentage area of occludin staining was measured in ten views and compared by an unpaired test ((a)–(e) (C)). Results shown are from a single experiment; *represents P value <0.05.

Figure 6

The percentage of caeca and livers positive when chickens were inoculated with C. jejuni or C. jejuni pretreated with NA. Notice that higher numbers of birds were positive in caecum in NA pretreated group than when infected with C. jejuni alone. Higher invasion into livers is seen in the NA-treated group only when infected with C. jejuni M1. Results are from a single experiment consisting of ~26 birds in a group. Statistical difference was assessed by a chi-square test and star represents significant P < 0.05.