Core and variable antimicrobial resistance genes in the gut microbiomes of Chinese and European pigs.

Monitoring the prevalence of antimicrobial resistance genes (ARGs) is vital for addressing the global crisis of antibiotic-resistant bacterial infections. Despite its importance, the characterization of ARGs and microbiome structures, as well as the identification of indicators for routine ARG monitoring in pig farms, are still lacking, particularly concerning variations in antimicrobial exposure in different countries or regions. Here, metagenomics and random forest machine learning were used to elucidate the ARG profiles, microbiome structures, and ARG contamination indicators in pig manure under different antimicrobial pressures between China and Europe. Results showed that Chinese pigs exposed to high-level antimicrobials exhibited higher total and plasmid-mediated ARG abundances compared to those in European pigs ( P<0.05). ANT(6)-Ib, APH(3')-IIIa, and tet(40) were identified as shared core ARGs between the two pig populations. Furthermore, the core ARGs identified in pig populations were correlated with those found in human populations within the same geographical regions. Lactobacillus and Prevotella were identified as the dominant genera in the core microbiomes of Chinese and European pigs, respectively. Forty ARG markers and 43 biomarkers were able to differentiate between the Chinese and European pig manure samples with accuracies of 100% and 98.7%, respectively. Indicators for assessing ARG contamination in Chinese and European pigs also achieved high accuracy ( r=0.72-0.88). Escherichia flexneri in both Chinese and European pig populations carried between 21 and 37 ARGs. The results of this study emphasize the importance of global collaboration in reducing antimicrobial resistance risk and provide validated indicators for evaluating the risk of ARG contamination in pig farms.

Sulfite as the substrate of C-sulfonate metabolism of α, ß-unsaturated carbonyl containing andrographolide: analysis of sulfite in rats' intestinal tract and the reaction kinetics of andrographolide with sulfite.

One-sixth of the currently known natural products contain α, ß-unsaturated carbonyl groups. Our previous studies reported a rare C-sulfonate metabolic pathway. Sulfonate groups were linked to the ß-carbon of α, ß-unsaturated carbonyl-based natural compounds through this pathway. However, the mechanism of this type of metabolism is still not fully understood, especially whether it is formed through enzyme-mediated biotransformation or direct sulfite addition. In this work, the enzyme-mediated and non-enzymatic pathways were studied. First, the sulfite content in rat intestine was determined by LC-MS/MS. The results showed that the amount of sulfite in rat intestinal contents was from 41.5 to 383 µg·g-1, whereas the amount of sulfite in rat feed was lower than the lower limit of quantitation (20 µg·g-1). Second, the reaction kinetics of sulfite-andrographolide reactions in phosphate buffer solutions (pH 6-8) was studied. The half-lives of andrographolide ranged from minutes to hours. This was suggested that the C-sulfonate reaction of andrographolide was very fast. Third, the C-sulfonate metabolites of andrographolide were both detected when andrographolide and L-cysteine-S-conjugate andrographolide were incubated with the rat small intestine contents or sulfite, indicating that the sulfite amount in rat intestine contents was high enough to react with andrographolide, which assisted a significant portion of andrographolide metabolism. Finally, the comparison of andrographolide metabolite profiles among liver homogenate (with NADPH), liver S9 (with NADPH), small intestine contents homogenate (with no NADPH), and sulfite solution incubations showed that the C-sulfonate metabolites were predominantly generated in the intestinal tract by non-enzymatic pathway. In summary, sulfite can serve as a substrate for C-sulfonate metabolism, and these results identified non-enzymatically nucleophilic addition as the potential mechanism for C-sulfonate metabolism of compounds containing α, ß-unsaturated carbonyl moiety.