Continuous feeding of antimicrobial growth promoters to commercial swine during the growing/finishing phase does not modify faecal community erythromycin resistance or community structure

Abstract

Aims: To investigate the effect of continuous feeding of antimicrobial growth promoters (tylosin or virginiamycin) on the swine faecal community. Methods and Results: The study consisted of two separate on‐farm feeding trials. Swine were fed rations containing tylosin (44 or 88 mg kg−1 of feed) or virginiamycin (11 or 22 mg kg−1 of feed) continuously over the growing/finishing phases. The temporal impact of continuous antimicrobial feeding on the faecal community was assessed and compared to nondosed control animals through anaerobic cultivation, the analysis of community 16S rRNA gene libraries and faecal volatile fatty acid content. Feeding either antimicrobial had no detectable effect on the faecal community. Conclusions: Erythromycin methylase genes encoding resistance to the macrolide–lincosamide–streptogramin B (MLSB) antimicrobials are present at a high level within the faecal community of intensively raised swine. Continuous antimicrobial feeding over the entire growing/finishing phase had no effect on community erm‐methylase gene copy numbers or faecal community structure. Significance and Impact of the Study: Antimicrobial growth promoters are believed to function by altering gut bacterial communities. However, widespread MLSB resistance within the faecal community of intensively raised swine likely negates any potential effects that these antimicrobials might have on altering the faecal community. These findings suggest that if AGP‐mediated alterations to gut communities are an important mechanism for growth promotion, it is unlikely that these would be associated with the colonic community.

Temporal analysis of the effect of extruded flaxseed on the swine gut microbiota

“…Accordingly, Castillo et al (2007) found no impact on the abundance of lactobacilli and enterobacteria when different fibre concentrations were included in diets starting at 8 weeks of age. In another study, the use of in-feed antibiotics beginning in the growing phase failed to produce a shift in the fecal bacterial community of swine, as measured using a clone library (Kalmokoff et al 2011). Conversely, dietary studies commencing at weaning (16-28 days) have demonstrated notable changes in bacterial DGGE profiles (Konstantinov et al 2003;Namkung et al 2004).…”

Antimicrobial growth promoters modulate host responses in mice with a defined intestinal microbiota

“…Several investigations in broiler chickens indicated that the community structure was altered by AGP treatment concurrent with increased body weight222324. Conversely, other studies in beef cattle, chickens, and pigs concluded that bacterial communities were not altered by AGP treatment252627, although variations in individual taxa were observed in some of these studies2628293031. The differing effects of AGP may be attributed, at least in part, to the complexity of the microbial communities within the GIT in the different animal species and complex interactions between intestinal bacteria and the host.…”

Effects of Chlorophyll-Derived Efflux Pump Inhibitor Pheophorbideaand Pyropheophorbideaon Growth and Macrolide Antibiotic Resistance of Indicator and Anaerobic Swine Manure Bacteria

“…21% and 32%) [73]. However, according to other previous studies [105,106], background levels of erythromycin and macrolide resistance in nonmedicated swine fecal and manure bacterial communities can already be as high as approximately 40% and are enhanced further by the administration of compounds with antimicrobial activities [62][63][64]. In our study, tylosin had last been used 31 days and 4-4.5 months prior to the last pit emptying and days of sampling, respectively, and consequently was not detected by HPLC in the manure.…”