Carrier state of enterotoxigenic Escherichia coli virulence markers in pigs: Effects on gut microbiota modulation and immune markers transcription.

Enterotoxigenic Escherichia coli (ETEC) causes diarrhea in pigs at early age, leading to high mortality rates and significant economic losses in the swine industry. ETEC effect on gut microbiota and immune system is mostly studied in diarrheic model under controlled laboratory conditions, however its impact on asymptomatic carriers remains unknown. Thus, we investigated whether ETEC can modulate gut microbiota or regulate the transcription of immune markers in asymptomatic pigs in farm environment. Stool samples from newborn piglets, nursery and growing pigs, and sows were screened for ETEC markers, then submitted to 16S-rDNA sequencing to explore gut microbiota composition in carriers (ETEC+) and non-carriers (ETEC-) animals. We observed a reduced α-diversity in ETEC+ animals (p < 0.05), while bacterial compositions were mostly driven by ageing (p > 0.05). Prevotella marked ETEC-carrier group, while Rikenellaceae RC9 gut group was a marker for a healthy gut microbiota, suggesting that they might be biomarker candidates for surveillance and supplementation purposes. Furthermore, we observed transcription regulation of il6 and tff2 genes in ETEC+ in newborn and nursery stages, respectively. Our findings indicate that ETEC presence modulate gut microbiota and the immune response in asymptomatic pigs; nevertheless, further studies using a probabilistic design must be performed to assess the effect of ETEC presence on gut imbalance in pigs despite the age bias.