Porcine circovirus type 2 (PCV2) and Campylobacter infection induce diarrhea in piglets: Microbial dysbiosis and intestinal disorder

Abstract

Diarrhea is considered to be associated with microbial dysbiosis caused by infection of pathogens but poorly understood. We herein characterized the colonic microbiota of diarrheal early-weaning piglets infected with porcine circovirus type 2 (PCV2) and Campylobacter. Campylobacter infection significantly decreased species richness and Shannon diversity index of colonic microbiota together with a significant increase in the proportion of Campylobacter and Enterobacteriaceae, whereas no significant difference on the above indexes was observed in piglets infected with PCV2 compared with healthy piglets. PCV2 and Campylobacter infection could disturb the homeostasis of colonic microbiota through deterioration of ecological network within microbial community, and specially Campylobacter performed as a module hub in ecological networks. The microbial dysbiosis caused metabolic dysfunction and led to a remarkable reduction in production of short chain fatty acids, following by a higher pH level in colon cavity. Campylobacter infection disturbed the function of colonic tract barrier observed in terms of significant lower relative expression of claudin-1, occluding, and zonula occludens protein-1 genes, and PCV2 infection induced intestinal inflammation together with a higher permeability of colon. Generally, these results suggested that PCV2 and Campylobacter infection could induce microbial dysbiosis and metabolic dysfunction, and cause intestinal disorder, all of which finally were associated to contribute to the diarrhea of early-weaning piglets.

Keywords: Inter-species interaction; Intestinal permeability; Metabolic dysfunction; Microbial dysbiosis; Pathogens infection; Short chain fatty acid.

Fig. 1

Relative abundance (A) of different microbial classes (≥a cutoff value of 0.6%) and box plots (B) showing significant variations of relative abundances of microbiota in the colon of piglets. p = phylum; c = class; o = order; f = family; g = genus; s = species. Control group, healthy piglets; VI group, piglets infected with porcine circovirus type 2; PB group, piglets infected with Campylobacter. The median value is shown as a line within the box; +, outlier; ^∗, P < 0.05; **, P < 0.01; ☆, mean value.

Fig. 2

Weight UniFrac principal coordinates (PC) analysis of the microbial communities. Control group, healthy piglets; VI group, piglets infected with porcine circovirus type 2; PB group, piglets infected with Campylobacter.

Fig. 3

Circular plot (A) shows the distribution of OTU at different classification levels. Ecological network (B) describes the sub-modules and the interspecific interaction within the colonic microbial community of piglets. Control group, healthy piglets; VI group, piglets infected with porcine circovirus type 2; PB group, piglets infected with Campylobacter. The taxonomic levels were class, order, family, genera, and species from the outside to the inside of the circle, respectively.

Fig. 4

Zi-Pi plot showing the distribution of operational taxonomic units (OTU) based on their topological roles. Control group, healthy piglets; VI group, piglets infected with porcine circovirus type 2; PB group, piglets infected with Campylobacter.

Fig. 5

Significant changes in bacterial Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using the response ratio method at a 95% confidence interval (CI). (A) Control vs. VI; (B) control vs. PB; (C) VI vs. PB. Control group, healthy piglets; VI group, piglets infected with porcine circovirus type 2; PB group, piglets infected with Campylobacter.

Fig. 6

Relative expression of inflammation-related (A) and tight junction protein genes (B) in colon tissue. IFN-γ = interferon-γ; TNF-α = tumor necrosis factor-α; IL-6 = interleukin-6; ZO-1 = Zonula occludens protein-1; JAM1 = junctional adhesion molecule-1. Control group, healthy piglets; VI group, piglets infected with porcine circovirus type 2; PB group, piglets infected with Campylobacter. ^∗, P < 0.05; ^∗∗, P < 0.01.