There continues to be a level of concern about the effects of prudent antimicrobial use in livestock on the development of antimicrobial resistance in both pigs and people. It is important to understand the extent by which antimicrobial interventions affect the pig’s resident microbiota, and their accompanying antimicrobial resistance genes (ARGs). While the antimicrobial resistance profiles of swine pathogens are reasonably well understood there is less known about the ARGs associated with the developing gastrointestinal microbiota. These independent US researchers wanted to assess the impact of a tulathromycin (TUL) (Draxxin) preventive treatment given at birth on the developmental of fecal microbiota and their accompanying antimicrobial resistome in pre-weaned piglets. Sixteen litters were given one of two treatments [control group (CONT; saline 1cc IM) and TUL group (TUL; 2.5 mg/kg IM)] directly after birth. Shotgun metagenomic sequencing was performed on the extracted bacterial DNA, and the fecal microbiota structure and abundance of ARGs were assessed. Across all fecal samples, a total of 127 ARGs related to 19 different classes of antibiotics were identified in the microbiota. The majority of identified ARGs were observed in both experimental groups and at all-time points. The magnitude and extent of differences in microbial composition and abundance of ARGs between the TUL and CONT groups were statistically insignificant. However, both fecal microbiota composition and ARGs abundance changed significantly between different sampling days as the pigs matured.
Take Home Message
In this study, a preventive treatment with tulathromycin at birth had no measurable effect on fecal microbiota structure or the number of antimicrobial resistance genes (ARGs) in pre-weaned piglets.
The researchers hypothesized that the negligible effect on the microbiota may be associated with the rapid absorption and distribution of tulathromycin (TUL) from the injection site and transfer to the target tissues and in particular the respiratory tract.
Even though there is no evidence of a negative effect associated with a preventive treatment with tulathromycin it is important to recognize that this may not necessarily be true of other antimicrobial treatments.
Submitted by Greg Wideman, DVM
Ref: Zeineldin MM, Megahed A, Blair B, Burton B, Aldridge B, Lowe J.Negligible Impact of Perinatal Tulathromycin Metaphylaxis on the Developmental Dynamics of Fecal Microbiota and Their Accompanying Antimicrobial Resistome in Piglets. Front Microbiol. 2019 Apr 5;10:726. doi: 10.3389/fmicb.2019.00726. eCollection 2019