Impact of Pediococcus acidilactici and tylvalosin on porcine Enterobacterales abundance, antimicrobial resistance, and conjugative potential.

2026-02-18
Journal of applied microbiology 137(3)

PubMed: 41707193
DOI: 10.1093/jambio/lxag044

Study Design

Type: Clinical Trial
Population: pigs with ileal cannulas
Methods: Ileal digesta and feces from live pigs with ileal cannulas were collected before and after the administration of Pediococcus acidilactici and/or tylvalosin. Viable antibiotic-resistant enterobacteria were counted on selective media, and the detection of Enterobacterales, Lactobacillaceae, β-lactamase genes, and plasmid replicons was performed using PCR methods. The propagation potential of resistance to cefotaxime and erythromycin was assessed by conjugation.

Animal Study

Aims

Antimicrobial resistance impacts the health of humans, animals, and plants, as well as the metabolic functions supported by environmental microbiomes. Mitigation approaches against this global crisis are being developed to minimize its spread, the associated deaths, and economic burden. This study aims to assess the impact of a macrolide, and of a probiotic adopted by pig producers to support reductions in antimicrobial use.

Methods and results

Ileal digesta and feces from live pigs with ileal cannulas were collected before and after the administration of Pediococcus acidilactici and/or tylvalosin. Viable antibiotic-resistant enterobacteria were counted on selective media. The detection of Enterobacterales, Lactobacillaceae, β-lactamase genes, and plasmid replicons was performed using PCR methods. The propagation potential of resistance to cefotaxime and erythromycin was assessed by conjugation. Pigs receiving P. acidilactici exhibited a significant reduction in the abundances of ileal cefotaxime-resistant Enterobacterales (1.5 logs compared to the control), and a decline in excretion of the blaCMY (3.4-folds) and blaTEM (1.4-folds) genes compared to animals receiving both the probiotic and antibiotic. Still, Enterobacterales from pigs ingesting P. acidilactici exhibited higher transfer frequencies of cefotaxime resistance. These pigs also displayed a significant expansion of the erythromycin-resistant subpopulation in the ileum (1.5 logs), and its decline in feces (2.5 logs). Tylvalosin administration significantly increased the kanamycin-resistant Enterobacterales sub-population (2 logs compared to the control).

Conclusions

This study reveals dynamics of bacterial populations, the flux of antimicrobial resistance genes, and their interplay with conjugative plasmids, highlighting the complexity of evaluating mitigation approaches.

Research Insights

Supplement	Dose	Health Outcome	Effect Type	Effect Size	Source
Pediococcus acidilactici	—	Increased Erythromycin-Resistant Enterobacterales Abundance in the Ileum	Harmful	Moderate	View source These pigs also displayed a significant expansion of the erythromycin-resistant subpopulation in the ileum (1.5 logs)
Pediococcus acidilactici	—	Reduced Beta-Lactam Resistance	Beneficial	Small	View source a decline in excretion of the blaCMY (3.4-folds) and blaTEM (1.4-folds) genes compared to animals receiving both the probiotic and antibiotic.
Pediococcus acidilactici	—	Reduced Cefotaxime-Resistant Enterobacterales Abundance	Beneficial	Moderate	View source Pigs receiving P. acidilactici exhibited a significant reduction in the abundances of ileal cefotaxime-resistant Enterobacterales (1.5 logs compared to the control)
Pediococcus acidilactici	—	Reduced Erythromycin-Resistant Enterobacterales in Feces	Beneficial	Moderate	View source and its decline in feces (2.5 logs).