The effect of chlortetracycline on faecal microbial populations in growing swine

Authors: Poole, Toni; SUCHODOLSKI, JAN - Texas A&M University; Callaway, Todd; FARROW, RUSSEL - Texas Tech University; LONERAGAN, GUY - Texas Tech University; Nisbet, David

Submitted to: Journal of Global Antimicrobial Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2013
Publication Date: 6/3/2013
Publication URL: https://handle.nal.usda.gov/10113/58270
Citation: Poole, T.L., Suchodolski, J.S., Callaway, T.R., Farrow, R.L., Loneragan, G.H., Nisbet, D.J. 2013. The effect of chlortetracycline on faecal microbial populations in growing swine. Journal of Global Antimicrobial Resistance. 1:171-174.

Interpretive Summary: Bacteria that cause disease in humans and animals are becoming increasingly resistant to antibiotics. This has caused public health concerns because diseases once thought largely eradicated are reappearing. Bacteria are not only becoming resistant to one or two antibiotics they are becoming resistant to many antibiotics; such bacteria are called multi-drug resistant bacteria. Some public health officials blame the food animal industry for the emergence of multi-drug resistant bacteria and down play the role of human medicine. Swine and cattle producers have long been under pressure to limit the presence of disease causing bacteria (pathogens) that are often present on retail meat products. This has required the use of antimicrobials. Because identifying individual animals is difficult, entire herds have been treated. With the emergence of multi-drug resistant pathogens there are new pressures to limit the use of antibiotics. Evidence has shown that reduction of antibiotic use alone is not sufficient to reduce multi-drug resistant bacterial populations. The limitation of antibiotic use in the food animal industry makes it difficult for producers to maintain healthy herds. Subsequently, pathogens carried by these animals may end up on retail meat. There are many aspects to consider in eliminating or minimizing pathogens in swine and beef production environments. This study investigated the use of one growth promoting antibiotic commonly used in swine production, chlortetracycline, on the natural bacteria that reside in the gut of growing swine. The results of this study showed there was no significant difference in the bacterial populations regardless of the antimicrobial used.

Technical Abstract: The effect of antimicrobial use on the gastrointestinal microbiota of food animals is of increasing concern as bacteria accumulate resistance to multiple antimicrobials. Only a small fraction of the gastrointestinal microbiome is culturable, complicating characterization of the swine gastrointestinal ecosystem. The objective of this study was to determine the effect of a growth promotion dose, 50 g ton–1, chlortetracycline on the phylogenetic diversity of bacteria from swine feces using a culture–independent method. Four freshly weaned pigs were provided a grower ration of 80% corn and 20% soybean meal for 21 d. On d 21, the diet of two pigs was medicated with 50 g ton–1 chlortetracycline. Fecal material was collected from each pig on days 0, 14, 23, 28, 35, 42, and 49 for 454-pyrosequencing of the 16S rRNA gene. Unifrac analysis of pyrosequencing data showed no significant difference in bacterial diversity based on diet or among pigs (p < 0.05) fed the low-level dose of chlortetracycline. The most abundant phyla in both treatment groups were Firmicutes, Bacteroidetes, Proteobacteria, and Spirochaetes. Higher concentrations of chlortetracycline (eg. 200 or 400 g/ton) may be required to observe a shift in the gastrointestinal flora in swine feces compared to the low-level dose in this study. Additional studies are needed to understand how growth-promoting antimicrobials influence the gut microflora and benefit food animal growth efficiency.