Composition of mucus- and digesta-associated bacteria in growing pigs with and without diarrhea differed according to the presence of colonic inflammation

Abstract

Abstract Background In the pig production, diarrhea can occur during different growth stages including the period 4–16 weeks post weaning, during which diarrhea a diarrheal outbreak also termed as colitis-complex diarrhea (CCD) can occur and it is distinct from post-weaning diarrhea (1–2 weeks post weaning). We hypothesized that CCD in growing pigs is associated with changes in colonic microbiota composition and fermentation patterns, and the aim of the present observational study was to identify changes in digesta-associated bacteria (DAB) and mucus-associated bacteria (MAB) in the colon of growing pigs with and without diarrhea. A total of 30 pigs (8–12 weeks of age) were selected; 20 showed clinical signs of diarrhea and 10 appeared healthy. Based on histological examination of colonic tissue, 21 pigs were selected for further studies and classified as follows: without diarrhea, no colon inflammation (NoDiar; n = 5), with diarrhea, without inflammation (DiarNoInfl; n = 4), and with diarrhea, with inflammation (DiarInfl; n = 12). Composition (16S rRNA gene amplicon sequencing) and fermentation pattern (SCFA profile) of the DAB and MAB communities were characterized. Results The DAB showed higher alpha diversity compared to MAB in all pigs, and both DAB and MAB showed lowest alpha diversity in the DiarNoInfl group. Beta diversity was significantly different between DAB and MAB as well as between diarrheal groups in both DAB and MAB. Compared to NoDiar, DiarInfl showed increased abundance of various taxa, incl. certain pathogens, in both digesta and mucus, as well as decreased digesta butyrate concentration. However, DiarNoInfl showed reduced number of genera compared to NoDiar, but still lower butyrate concentration. Conclusion Diversity and composition of MAB and DAB changed in diarrheal groups dpending on presence/absence of colonic inflammation. We also suggestion that DiarNoInfl group was at the earlier stage of diarrhea compared with DiarInfl and may as well highlight the overall importance of butyrate in relation to gut health. In conclusion, we confirmed that changes in DAB and MAB were associated with CCD and reduced butyrate concentration in digesta. Moreover, DAB might suffice for future community-based studies of CCD.