Effect of thymol on microbial diversity in the porcine jejunum

Thirty two weaned pigs (24 d-old) were fed a diet without or with 1% (w/w) thymol. Pigs from each dietary treatment remained unchallenged or were challenged with Salmonella enterica serovar typhimurium. Jejunal content was collected and molecular microbial diversity was investigated using 16S rRNA gene polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Shannon index analysis showed no differences in diversity but Pearson coefficient analysis showed clear clustering of profiles, which delineated thymol fed and control groups irrespective of Salmonella challenge. Moreover, absence of bands corresponding to Actinobacillus minor (98-99% identity) was observed in thymol groups. A band corresponding to Citrobacter freundii (98% identity) was observed in almost all pigs from thymol groups, and only in 4 samples from pigs fed no thymol in the diet. Supplementation of pig diet with thymol caused clear changes in small intestine microbacterial community. Surprisingly, Salmonella infection caused no major perturbations to the community structure.